The Arctic in the Anthropocene: Emerging Research Questions (2014)

CHAPTER THREE

Emerging Questions

All global climate models forced with increasing greenhouse gases project that the Arctic will continue to warm at a faster rate than that of the rest of the globe, with concomitant losses in the ice and snow (IPCC, 2013) that form the fabric of the Arctic as we have known it (Figure 3.1). In each of the sections that follow, we identify and discuss in detail emerging research questions (those that we are only now able to ask, because they address newly recognized phenomena, use new technology or access, or build on recent results and insights). Research questions emerging from recent change and future projections include understanding the evolving Arctic,

FIGURE 3.1 The Coupled Model Intercomparison Project-5 (CMIP5) produced this multi-model simulated time series from 1950 to 2100 for September sea ice extent in the Northern Hemisphere. The results are displayed as a 5-year running mean. Time series of projections are indicated by a solid line and a measure of uncertainty is indicated by shading. Projections are shown for two Representative Concentration Pathways (RCPs). RCP2.6 (blue) and RCP8.5 (red) represent radiative forcing values in 2100 that are 2.6 and 8.5 W/m² greater, respectively, than preindustrial values. The solid black line (grey shading indicates the uncertainty) is the modeled historical evolution using reconstructed forcings. The mean and associated uncertainties averaged over 2081−2100 are given for all RCP scenarios as colored vertical bars. The number of CMIP5 models used to calculate the multi-model mean is indicated above and below the curves. The projected mean and uncertainty of the subset of models that most closely reproduce the climatological mean state and 1979 to 2012 trend of the Northern Hemisphere sea ice is given (number of models noted in brackets). For completeness, the CMIP5 multi-model mean is also indicated by the dotted lines. The black dashed line represents nearly ice-free conditions (i.e., when sea ice extent is less than 10⁶ km² for at least 5 consecutive years). SOURCE: IPCC (2013), Figure SPM.7, p. 19.

exploring what becomes accessible because of climate change or better technology, investigating the ways Arctic change will affect the rest of the world, finding ways to manage reactions to change, and being prepared to detect and respond to surprises. Box 3.1, below, provides an example of these challenges with regard to the coastal zone, where our understanding depends on considering all parts of the system and on working across geographical and disciplinary boundaries.

We also acknowledge the importance of the ongoing research and high-priority questions that others have identified and continue to study, and we list examples of the

kinds of existing questions that continue to motivate Arctic research. The committee recognizes that the distinction between existing and emerging questions is somewhat arbitrary and that both sets of questions actually fall on a spectrum of research ideas that blend “existing” and “emerging” to varying degrees. Using community input and extensive deliberation, the committee characterized questions as existing or emerging on the basis of the criteria in Box 3.2. The specific emerging research questions presented here are not intended to be comprehensive but are intended to be representative of emerging topics that deserve attention. The committee considered hundreds of potential emerging questions that emerged from community input received through

two workshops, a number of interviews, an online questionnaire, and a review of relevant reports. By their inclusion in this report, the committee considers the high-level topics presented in this chapter (Evolving, Hidden, Connected, Managed, and Undetermined Arctic) to be priorities for IARPC as a whole and leaves individual agencies to prioritize investments in these topics in accordance with their specific mission and goals. The questions in each section are numbered for easier reference, and the numbering does not imply priority or relative significance. Prioritization is a collaborative exercise that requires continuing dialog and reassessment, and will best be achieved through an improved interaction between the scientific and policy communities. This issue is discussed in greater detail at the end of this chapter.

EVOLVING ARCTIC

Emerging Questions for the Evolving Arctic

E1. Will Arctic communities have greater or lesser influence on their futures?

E2. Will the land be wetter or drier, and what are the associated implications for surface water, energy balances, and ecosystems?

E3. How much of the variability of the Arctic system is linked to ocean circulation?

E4. What are the impacts of extreme events in the new ice-reduced system?

E5. How will primary productivity change with decreasing sea ice and snow cover?

E6. How will species distributions and associated ecosystem structure change with the evolving cryosphere?

In this section, we focus on the effects of Arctic change on the Arctic system itself. Already it is evolving at an unprecedented rate, and this is widely seen as just the precur-

sor to what is in store (ACIA, 2005; AMAP, 2012). The most prominent physical change seen thus far is the evolution of the cryosphere, with cascading effects on the biological, chemical, and physical systems of the ocean, land, and atmosphere (Hinzman et al., 2013; Jeffries et al., 2013). These changes will cause large-scale disruption of current systems and infrastructure, offer new challenges and opportunities, and entail potential catastrophes (NRC, 2013).

At the same time, social, cultural, political, and economic changes have been rapid and widespread throughout the Arctic, manifesting themselves in various ways in different regions and at different times (e.g., AHDR, 2004). Cash economies have merged with or overtaken traditional modes of production and distribution. There has been a shift away from colonial relations, and indigenous rights have been recognized in land claims settlements and the creation of new political arrangements such as Nunavut in Canada and Self-Rule Government in Greenland. Languages are being lost while other traditional practices are strengthened by new programs and institutions based in the Arctic. These and related topics are addressed in emerging questions in this section, as well as in the sections on the Connected Arctic and the Managed Arctic.

The rate at which change is occurring may be more important than its magnitude, as both natural and social systems try to match their rate of adaptation to the rate of change. Extreme events and non-linearities, as well as abrupt or unanticipated changes, will challenge both natural and human systems. Many of these changes are immediately obvious, on time scales of days or weeks; however, the longer-term (years to decades) evolution of the system in response to these changes remains unknown. Also, although in many cases the direction of change is known, the critical unknown is the rate of change.

Given both the rate of ongoing change and the profound impact of those changes on all facets of the Arctic system and its connections to other global processes, it is likely that the Arctic region will present some of the greatest challenges to our societies.

The Arctic cryosphere, or “frozen Arctic,” is composed of permanent and seasonal sea ice, ice sheets, glaciers, lake and river ice, snow, and permafrost (Overpeck et al., 2005). During the last decade, changes in extent, thickness, and seasonal timing in all of these components have been observed, with the most prominent being the decline in the extent of summer sea ice in 2012 to a record low of 3.4 million square kilometers (NSIDC¹), dramatic decreases in sea ice age, thickness, and volume (Perovich et al., 2013), and increasing trends of snow-free periods (~11 days/decade in spring and

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¹ See http://nsidc.org/arcticseaicenews/2012/09/arctic-sea-ice-extent-settles-at-record-seasonalminimum/.

FIGURE 3.2 For up to 9 months of the year, snow covers the Arctic land surface. Unlike sea ice and glaciers, most terrestrial snow cover is seasonal, melting and disappearing completely each spring and summer. The timing of this melt, which is influenced largely by surface temperatures, affects the length of the growing season, the timing and dynamics of spring river runoff, permafrost thawing, and wildlife populations. According to the 2013 Arctic Report Card, reductions in Arctic spring snow cover have “direct effects on the global climate system” because snow-free land absorbs much more sunlight. SOURCE: National Oceanic and Atmospheric Administration.

~2 days/decade in autumn) at higher latitudes in North America (Derksen and Brown, 2012). In most regions, permafrost temperatures have increased over the past 30 years, and a general increase in active layer thickness has been observed as well, although there are large regional variations (IPCC, 2013). The rapid loss of permanent Arctic ice and the changing extent and timing of seasonal ice and snow cover (see Figure 3.2) have important ramifications for multiple components of the Arctic system (Overpeck et al., 2005).

Focusing within the Arctic, the most visible manifestations of what the future holds for an evolving Arctic are those connected with human activity. Already, ship traffic in the Arctic is increasing with the expanded access due to decreased summer sea ice, bringing with it a concomitant increase in risks of environmental disaster and threats to human safety (Arctic Council, 2009). Over 400 ships engaged in commerce, tourism, and research transited through the Bering Strait in 2012, a dramatic increase from the just over 200 in 2008 (USCG, 2013). Passages, particularly of cruise ships and small personal vessels, through the still mostly icebound Northwest Passage are becoming commonplace, and the Northern Sea Route is now transited almost routinely by

commercial vessels.² Interests in oil and gas reserves have boomed, accompanied by prospects of financial gain—including local and non-local employment. This development is accompanied by the risks of coastal and terrestrial environmental disturbance and stresses on local communities such as housing in villages (e.g., Lloyd’s, 2012). Permafrost degradation represents another potential impact on local communities and infrastructure. Increasing permafrost temperatures and active layer depth can have serious and costly effects on roads, buildings, and industrial facilities. The projected rise in permafrost temperatures may lead to additional engineering challenges to infrastructure (ACIA, 2005).

With decreased sea ice have come more threats from weather, manifest as more frequent and more intense storms that threaten the now exposed Arctic coast and the human infrastructure on those coasts (Forbes, 2011). In the terrestrial environment, changes in the timing and extent of snow cover have wide-ranging ecological effects on soil, plant, and animal communities, as well as impacts on lakes, rivers, and wetlands and on social and economic infrastructure. Snow also acts as an insulator for Arctic soils, and future increases in snow depth (predicted for the high Arctic during autumn and winter) may result in higher winter soil temperatures, increased biogeochemical processing of organic materials, and increased respiration (Vincent et al., 2011). The timing of snow is also critical; earlier winter snow can have an insulating effect, whereas late spring snow can have a cooling effect (Zhang, 2005). Ecosystems of the northern latitudes are most vulnerable to a changing climate because low temperatures and limited sunlight restrict species diversity, levels of primary productivity, and decomposition rates, and they also affect water and energy exchange processes.

The freshwater cycle plays a central role to every physical and biological process in the Arctic, so we cannot overstate its importance. The Arctic freshwater system is an inherent component of the global hydrological cycle, and as such it plays an essential role in linking Arctic climate dynamics with the global system. The polar regions actually have a net negative annual average radiation balance; that is, more heat is emitted to space as long wave radiation than is absorbed from solar radiation. The total Earth energy balance must of course equal zero, so that energy deficit is made up by heat transported from lower latitudes, through hydrologic processes of moisture advection (latent heat) and dry static energy (sensible heat plus geopotential energy). In recent decades, several of the processes associated with the hydrologic cycle appear to have intensified (Rawlins et al., 2010; White et al., 2007). A major research question has been what has caused the significant increase in discharge of Eurasian rivers in the last

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² See http://www.nytimes.com/2013/09/15/world/europe/russia-preparing-patrols-of-arctic-shippinglanes.html.

century (Peterson et al., 2002), which now appears to be associated with significant increases in atmospheric moisture transport (Zhang et al., 2013b). Other important teleconnections have recently been identified, but characterization of mechanisms remains elusive (Overland, 2014; Tang et al., 2013).

Regionality is as important as seasonality for understanding the evolving Arctic. System-level response will depend on where you are within the Arctic. Basins will respond differently from shelves, and inflow shelves driven by Atlantic and Pacific inflows (like the Barents and Chukchi) will respond differently from interior shelves strongly influenced by river discharge (such as the Siberian Sea). Examining regional differences in the responses of the physical, biological, and social systems of the Arctic will be an important component of addressing the emerging questions presented in this section.

Looking to the future, understanding the evolving Arctic poses multiple research questions and directions. Some of the most compelling questions center on the impacts of diminished ice and snow on the terrestrial and marine systems. A number of questions, such as the impacts of ocean acidification and of the loss of sea ice as a substrate for marine organisms, though extremely important and requiring continued research and funding support, are now so well recognized by both the science community and the general public that they are no longer “emerging.” Some of the existing questions that will not be detailed in this report are listed below.

Examples of existing questions:

• What will be the climatic, ecological, and societal impacts of sea ice loss?
• How will changing seasonality in sea ice and snow cover affect trophic interactions?
• How is the Arctic/Northern Hemisphere hydrologic cycle changing, and how will those changes affect such processes as vegetation change, sea ice formation, sea water stratification, cloud properties, the surface energy balance, and potentially the Atlantic Meridional Overturning Circulation?
• What are the consequences of changing vegetation patterns and resulting responses by wildlife to ecosystem evolution in the tundra and boreal regions of the circumpolar north?
• How do Arctic clouds, aerosols, radiation, and boundary layer processes drive change in the Arctic climate system?
• What will be the impacts of ocean acidification on marine species and ecosystems?

• How will climate-induced natural changes and associated human activities (e.g., shipping, interest in resource development) affect marine mammal populations?
• What are the short- and long-term implications of social, cultural, and economic change among Arctic peoples?
• How will the ecosystem and built infrastructure respond to widespread degradation of permafrost?
• How will rapid Arctic change affect the interactions between scientific discovery and policy making?

Will Arctic Communities Have Greater or Lesser Influence on Their Futures?

As summer sea ice cover decreases and a seasonally nearly ice-free Arctic appears increasingly likely within a few decades, interest in new trade routes and petroleum deposits continue the post-Cold War transformation of the Arctic from a military and hunter-gatherer region to one that embraces a wide range of social and economic aspirations (Åtland, 2009). Such a transformation will expose social-ecological systems to both negative impacts and positive opportunities.

Although national and regional governments remain powerful agents of policy making, global markets, intergovernmental forums, and nongovernmental organizations play an increasing role in determining the attractiveness and viability of economic development in the Arctic. Perhaps more important, though, is the evolving role of Arctic communities and institutions. In particular, the role of indigenous and other local communities, in an era where knowledge networks and consultative processes can play a prominent role in policy formation, is plausibly much greater than ever before.

New and emerging research priorities need to focus on the ways that contemporary Arctic communities navigate and shape their evolving circumstances,³ drawing on a tradition of flexibility, resilience, and adaptive capacity in an environment of high natural variability. The cascading effects of rapid change will stress these traditions in new ways (Hovelsrud et al., 2011; see Box 3.3). The assertion of indigenous rights and the capacity to exercise those rights are increasing in much of the Arctic. Research to date has identified the major institutional and environmental influences on Arctic communities, such as the role of government and the availability of fish and wildlife (AHDR, 2004). More work is needed to understand how these influences function, separately and together; how these relationships are likely to change over time at local, regional,

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³ See http://www.nytimes.com/2012/09/19/science/earth/arctic-resources-exposed-by-warming-setoff-competition.html.

and global scales; and how Arctic communities can best exercise their adaptive capacity (the ability of a system to prepare for stresses and changes so that responses can be developed and implemented to minimize negative impacts in a timely manner). Lessons learned from Arctic communities will also be valuable for other indigenous and remote cultures facing similar stresses due to climate and other changes. At stake is the ability of Arctic communities to determine their own futures, to balance cultural, environmental, and economic needs as they, and not others, see fit. The alternative is that national and global forces dominate, leaving increasingly less room for Arctic communities to shape their own affairs. Reality is likely to include elements of both outcomes.

Will the Land Be Wetter or Drier, and What Are the Associated Implications for Surface Water, Energy Balances, and Ecosystems?

Our ability to predict Arctic watershed and ecosystem evolution remains tenuous at best, yet it is critical to understanding the Arctic’s evolving role in the carbon and hydrologic cycles, in climate, and in energy exchange processes. Most global climate models (GCMs) predict increases in both summer and winter precipitation in high northern latitudes (IPCC, 2013; Knutti and Sedlacek, 2013) although the magnitude

and the rates of change remain uncertain. Most of the uncertainty is due to the ambiguity associated with selection of the correct emission scenario. In Arctic soils, ice-rich permafrost prevents infiltration of rainfall and snow meltwater, often maintaining a surface moist-to-saturated active layer, and can block the lateral movement of groundwater. But, as permafrost degrades, changes in interactions between surface and groundwater occur that affect the surface energy balance and essential ecosystem processes. As permafrost disappears, it will be replaced with seasonally frozen ground, bringing additional scientific and engineering challenges.

Significant changes have already taken place over the past 50 years in response to a warming climate (Lantuit et al., 2012; Soja et al., 2007), including thawing permafrost (IPCC, 2013, and references therein; Romanovsky et al., 2010; Figure 3.3), expanding shrub growth in the Arctic tundra (Sturm et al., 2001), drying of lakes (Carroll et al., 2011), and expanding growing seasons and increasing plant productivity (Walker et al., 2012).

Permafrost soils store almost as much organic carbon (approximately 1,670 Petagrams (Pg) (Tarnocai et al., 2009) as is found in the rest of the world’s soils combined. Tarnocai et al. (2009) have estimated that the soil carbon stocks in the Arctic may account for more than 25 percent of global soil carbon stocks in the top meter and perhaps a

FIGURE 3.3 Stable, cold permafrost (left) is often characterized by low-centered polygons, which form over centuries as massive ice wedges develop, creating the polygonal edges. As climate warms, the permafrost thaws and the massive ice wedges melt, causing subsidence of the surface and enhanced surface drainage networks (right). These disturbed sites are becoming more common and will continue to increase with continued warming and increases in wildfire or other such disturbance. Changes in surface condition affect ecosystems, trace gas fluxes, surface energy and water budgets, and runoff stream chemistry. SOURCE: Larry Hinzman.

third of the carbon stocks in the top 3 meters. Tremendous carbon stocks exist below 3 meters in deep ice-rich deposits of Eurasia and North America (Schirrmeister et al., 2011). Changing active layer and permafrost conditions and increased erosion would promote carbon loss from these huge stores. The short- and long-term impacts to terrestrial and marine ecosystems are unknown. The potential carbon loss to the atmosphere is also largely unknown and of concern.

If warming continues as projected, large-scale changes in surface hydrology are expected as permafrost degrades (Hinzman et al., 2013). Where groundwater gradients are downward (i.e., surface water will infiltrate subsurface groundwater), as in most cases, we may expect improved drainage and drier soils, which would result in reduced evaporation and transpiration (ET). In some special cases, where the groundwater gradient is upward (as in many wetlands or springs), surface soils may become wetter or inundated as permafrost degrades.

Serreze et al. (2002) demonstrated that ~80 percent of high-latitude summer precipitation results from recycled evaporation. A decrease in ET fluxes would therefore lead to a decrease in precipitation, all else being equal. Because GCMs do not currently include realistic treatment of permafrost impacts on surface hydrology, simulations of 21st-century high-latitude climate change are more uncertain, and at this point it is not even possible to quantify the errors. Further, because soil moisture is a primary factor controlling ecosystem processes, interactions between ecosystems, and greenhouse gas emissions, the model predictions of such processes are also considered highly uncertain. These interdependent processes will exert primary controls on several important feedback processes, and they vary across space and time in some as yet unknown way. Important climate feedback processes associated with degrading permafrost include changes in latent, sensible, and radiative heat fluxes as the soils become drier or wetter, as vegetation changes, and as carbon emissions evolve.

Marked changes in surface structure and land-surface evolution are anticipated with continued warming in the Arctic. Numerous surficial landslides have been reported with increased summer thawing (Figure 3.4). Thermokarsts are examples of severe surface subsidence associated with thawing of massive ground ice. They are usually enhanced by fluvial erosion and continued thermal degradation. Such landscape processes are altering drainage networks, usually increasing the density of drainage channels but also increasing the sediment load and altering stream water chemistry, with consequent effects on aquatic and marine ecosystems, as well as human infrastructure and activities.

FIGURE 3.4 Permafrost slump at Yukon River Bridge, adjacent to the Dalton Highway and Trans-Alaska Pipeline System. These slumps have become more common as permafrost thaws and the surface gives way in a landslide. SOURCE: Erik Bachmann, Alaska State Division of Geological and Geophysical Surveys.

How Much of the Variability of the Arctic System Is Linked to Ocean Circulation?

Recently, the National Academy of Sciences addressed the improvements needed in observations and models of both the sea ice and the atmosphere in order to enhance sea ice predictions (NRC, 2012b). A complementary issue is that the ocean also plays a critical role in the Arctic system but it is unclear how the present state of the Arctic and its future evolution are linked to the advection and mixing of oceanic heat and freshwater. In this regard, fundamental questions emerge pertaining to the Arctic Ocean’s circulation, including the mechanisms, rates, and variability of its transport pathways, vertical and horizontal mixing processes, and the fate and dispersal of the waters flowing across its surrounding shelves. These processes span a broad spectrum of time (Bönisch and Schlosser, 1995; Schlosser et al., 1995) and space scales and are intimately linked to one another (Spall, 2013) and to the North Atlantic and North Pa-

cific oceans. Alone and in aggregate, these processes profoundly affect the Arctic’s ice, atmosphere, and marine ecosystems.

There is a negative feedback between vertical mixing of heat and melting ice; an increase in heat flux enhances ice melt but increases vertical stratification, which then suppresses the heat flux shown by Martinson and Steele (2001) in a model for the Weddell Sea in the Antarctic. It is not apparent how this feedback will be modified as ice thickness diminishes and, in the extreme, in a seasonally ice-free Arctic Ocean. For example, Pinkel (2005) has suggested that, with a reduced ice cover, mixing by internal wave energy might increase greatly. On the other hand, even small but sustained changes in the vertical mixing of heat may precondition the ice cover to more rapid melting (Polyakov et al., 2010). Oceanic heat and salt fluxes can occur through a variety of horizontal and vertical mixing processes, each of which varies in time and space (on both the basin and shelves) in response to changes in the Arctic’s ice cover, stratification, boundary currents, and atmospheric forcing (Guthrie et al., 2013). The stratification of the Arctic Ocean also affects the cycling of nutrients and thus exerts important controls on primary production. An increase in stratification will inhibit the mixing of nutrients into the surface layer of the ocean and tend to suppress production. Understanding the factors that affect these turbulent fluxes in the Arctic Ocean is essential for understanding how the Arctic Ocean will evolve.

Over the last two decades, the Arctic has witnessed dramatic and rapid changes in the inflow of Atlantic Water (Polyakov et al., 2012; Schauer et al., 2008) that has resulted in warming in both the Eurasian (Morison et al., 1998; Polyakov et al., 2011; Quadfasel et al., 1991; Steele and Boyd, 1998) and Canada basins (Carmack et al., 1995; McLaughlin et al., 2009; Shimada et al., 2004). There have also been substantial changes in the oceanic accumulation of freshwater and the pathways by which freshwater (Morison et al., 2012; Proshutinsky, 2010) is transported through the Arctic Ocean. These changes are intimately linked to the wind, which forces ocean currents and/or causes changes in the thickness of the upper ocean layer (Yang, 2006). Moreover, the structure of the boundary currents varies in time and location with the local and remote winds and buoyancy forcing (Pickart et al., 2011). There have also been significant changes in the seasonal phasing and volume of river discharge into the Arctic (Shiklomanov and Lammers, 2011) and the fluxes of heat and freshwater through the Bering Strait (Woodgate et al., 2012).

Arctic climate models exhibit substantial differences among themselves and with observations in their ocean temperature and salinity distributions and circulation (Holloway et al., 2007; Holloway et al., 2011). While essential ocean physics may be missing from many models, explicitly capturing the structure of boundary currents,

eddy formation and decay, and mixing represent substantial hurdles for the present generation of Arctic atmosphere-ice-ocean models (Newton et al., 2008). Currently we possess only a rudimentary understanding of the time-varying nature of these processes and then at only a few locations and for limited time periods. It also appears that a major driver of the cyclonic circulation of the Atlantic Water is the salinity contrast between the high-salinity Atlantic Water flowing in the boundary currents and the low-salinity shelf water entering the basin (Spall, 2013). This implies that the response of the Arctic Ocean depends critically on three issues: (1) processes in the North Atlantic Ocean that establish the thermohaline properties and mass transport of the Atlantic Water entering the Arctic Ocean, (2) the fluxes through the Bering Strait (which depend upon North Pacific Ocean processes), and (3) mixing and dispersal of the riverine discharges rimming the basin. The latter two contributions are subsequently modified upon crossing the continental shelves surrounding the basin.

Arctic continental shelves are enormous, occupying 35 percent of the Arctic Ocean area. They support important cultural and subsistence resources for local residents and are the most likely marine regions in which substantial increases in human industrial activities will occur in the near future. The shelves also serve as the Arctic Ocean’s estuaries in regulating the fate and dispersal of both the Arctic’s river discharges (of which many are large and flow year-round) and their dissolved and suspended burdens. They are the site of the largest changes in sea ice extent and seasonality in the Arctic Ocean, but the extent to which changes in winds, air-sea heat fluxes, and shelf currents affect the shelf sea ice environment has hardly been addressed. An unresolved issue is how the estuarine role of shelves will evolve in response to alterations in the terrestrial hydrologic cycle and a changing landfast ice regime.

What Are the Impacts of Extreme Events in the New Ice-Reduced System?

As the Arctic evolves, the potential for unpredictable and extreme events such as storms, wildfires, and anomalous precipitation increases. Increases in storminess and cyclone activity, particularly in the western Arctic, have been documented (McCabe et al., 2001), as have the relationships between Arctic sea ice transport and cyclones (Maslanik et al., 2007). More recent changes in Arctic climate, combined with record reductions in minimum sea ice extent, suggest a qualitative shift in the Arctic atmospheric circulation (Overland et al., 2012).

The complex interplay between Arctic storminess, sea ice cover, and upper-ocean structure poses active and intriguing questions. Increased storminess may contribute to the degradation and reduction in summer sea ice extent, as demonstrated with

a modeling study for the summer of 2012, when a massive cyclone (see Figure 3.5) transited the western Arctic (Zhang et al., 2014). Furthermore, the reduction in summer sea ice and the increasing frequency and severity of storms has direct impacts such as elevated sea state and the accompanying increased flooding, erosion, and incidence of ivu (ice pile-up on shore), with attendant threats to human infrastructure and well-being (Lynch et al., 2008). Severe storms may also have significant impacts on the marine ecosystem. Effects range from loss of sea ice substrate through mechanical disruption to increased primary production in response to increased nutrient availability through vertical mixing, to increased upwelling of high pCO₂ waters into shallower depths (e.g., Mathis et al., 2012; Zhang et al., 2013a). For coastal ecosystems, storm surges of seawater into lakes promote replacement of endemic taxa with brackish-water species (see, e.g., Thienpont et al., 2012).

FIGURE 3.5 The great Arctic cyclone of 2012. This image from August 6, 2012, shows the cyclone centered in the middle of the Arctic Ocean. SOURCE: NASA Earth Observatory.

Greater frequency and severity of storms increases the threat of wildfire ignited by lightning strikes. The potential for wildfire is also associated with soil moisture conditions and the availability of fuel. Climate change scenarios forecasting warmer and drier conditions project greater wildfire frequency, extent, and severity in the high northern latitudes (Balshi et al., 2009; Flannigan et al., 2005). Wildfire was identified as a major emerging issue by the North Slope Science Initiative (NSSI). Recent observations of the wildfire patterns in boreal regions have shown wildfires to be increasing in size and frequency, with the trends attributed to a warming climate (Kasischke and Hoy, 2012; Kasischke and Turetsky, 2006). Tundra fires have been historically rare events on Alaska’s North Slope (Barney and Comiskey, 1973), with only 122 wildfires reported since the state’s record began in 1950. An unprecedented wildfire in terms of size, severity, and duration occurred on Alaska’s North Slope in 2007 (Anaktuvuk fire, 103,600 ha) and burned from July to September in tundra (Jandt et al., 2012). Wildfire in tundra and taiga transition zones has not been thoroughly mapped or recorded. Observations of storms, lightning strikes, and fire frequency, extent, and severity are needed in the tundra to determine whether the fire regime is changing.

On land, heavy rain-on-snow is expected to become increasingly frequent in the Arctic, with potentially large consequences resulting from changes in snowpack properties and ground-icing. Winter rainfall and thaw-refreeze events can form an impenetrable ice layer within the snowpack that restricts grazers’ access to forage plants; however, effects on both plants and animals associated with winter thaw-refreeze events remain unclear (Rennert et al., 2009). There is some evidence that extreme rain-on-snow events can lead to widespread mortality or range displacement of reindeer, caribou, and muskoxen (Stien et al., 2010). However, observations of the frequency, timing, extent, and size of thaw-refreeze events, at relevant scales, remain limited.

Even in the absence of winter rain, extreme winter warming events that subsequently expose plants to cold winter air may lead to the loss of overwintering flower buds that will not produce flowers the following summer (Semenchuk et al., 2013). Although many species are resistant to exposure, exposing flower buds to cold winter air can lead to large population and community changes. There is also evidence of disruption of fish habitat following winter breakup of river ice. The potential for future warming to increase the frequency, extent, and severity of winter rain events, with potentially widespread consequences for plants and animals that depend on access to sheltered subnivean (occurring under the snow) space, will require collaboration across several disciplines and enhanced meteorological monitoring systems at scales appropriate to detect these changes.

Additional potential extreme events include an unprecedented meltback of summer sea ice and a terrestrial or marine anthropogenic environmental disaster such as an oil spill (e.g., the Deepwater Horizon explosion and oil spill in the Gulf of Mexico). There is a need for development of models and other decision-support tools, policies, and strategies for hazard mitigation, including assessing community and ecosystem risks and preparing response strategies.

How Will Primary Productivity Change with Decreasing Sea Ice and Snow Cover?

The concept that increased availability of sunlight to primary producers, either through reduction in sea ice and snow cover in the ocean or through reduction in snow cover on land, will lead to increased primary production seems intuitive. However, primary production is also dependent on the availability of nutrients and, in terrestrial systems, on soil moisture and temperature.

Surprisingly high levels of marine primary production and chlorophyll standing stock have been observed recently at some locations. For example, Arrigo et al. (2012) reported a massive under-ice phytoplankton bloom of unprecedented magnitude and far (100 km) from the ice edge that appears to have been promoted by light penetration through melt ponds in the overlying sea ice. There is increasing awareness of the importance of melt ponds and their potential to become more numerous and ubiquitous, given the thinner seasonal sea ice (Frey et al., 2011). These melt ponds may promote greater primary production by ice algae, potentially at the expense of water-column phytoplankton blooms because of competition for nutrients between the two types of primary producers. The ubiquitous presence of ice-edge blooms is now also recognized, with new analyses of satellite data (Perrette et al., 2011). Whether these increased productivities are new, in response to the changing environment, or are newly recognized because of increased capability or opportunity for study, is at present unknown.

Each summer, the euphotic zone (upper layer that supports photosynthetic activity) of the ocean is depleted of nutrients well before winter sea ice has formed and the Arctic has entered the sunlight-devoid polar night. This would suggest that, unless nutrients are replenished in the euphotic zone from regeneration, vertical mixing, or external inputs, then marine primary production will not increase substantially with increased availability of light. Over much of the Arctic, vertical mixing of nutrients is unlikely, given the strength of the pycnocline, unless that feature is eroded by warming of the deeper Atlantic water below or by mixing (e.g., Rainville and Woodgate, 2009). However, the reduced sea ice extent and greater area of open water may promote

increased inputs of nutrients to the euphotic zone through physical processes such as shelf-break upwelling (e.g., Pickart et al., 2013). Increased riverine input of nutrients, a consequence of permafrost thawing and release of nutrients, as well as increased advective input of nutrient-rich water from outside the Arctic, may increase ocean euphotic zone primary production (e.g., ACIA, 2005; Holmes et al., 2013). By contrast, increased freshwater in the Beaufort Gyre resulting from increased ice melt has deepened the pycnocline and nutricline there to below the bottom of the euphotic zone (McLaughlin and Carmack, 2010). Ultimately, whether marine primary production increases in the future will depend on a complex balance of physical factors that are evolving in response to the changing cryosphere.

In the Arctic terrestrial environment, earlier snowmelt and longer growing seasons lead to increased vegetation productivity, often referred to as “greening” (Bhatt et al., 2010; Walker et al., 2012; Figure 3.6). Warming soils and deepening active layers pro-

FIGURE 3.6 Land areas adjacent to newly opened water in the Arctic are becoming “greener.” Since observations began in 1982, Arctic-wide tundra vegetation productivity has increased. In the North American Arctic, the rate of greening has accelerated since 2005. SOURCE: NOAA.

vide a more tolerant environment for a greater diversity of plant species and increased productivity, and thus there has been a rapid expansion of woody shrubs into tundra (Myers-Smith and Hik, 2013). This greening of the Arctic is visible from space, and although warming and greening are documented in North America, some areas in northern Russia and along the Bering Sea coast of Alaska are cooling and vegetation productivity is declining (Post et al., 2013), perhaps a consequence of changes in atmospheric circulation patterns over the Eurasian continent in summer (Tang et al., 2013). Gamon et al. (2013) observed that productivity in Alaska was associated primarily with varying precipitation and soil moisture and only secondarily with growing degree days, which can lead to reduced primary productivity in years with earlier snowmelt.

Recent observations, however, call into question the assumption that earlier Arctic growing seasons will lead to greater vegetation productivity, indicating that better calibrated observations will be necessary to adequately forecast future changes in Arctic terrestrial productivity. In situ monitoring of actual vegetation responses using field optical sampling is needed to obtain detailed information on surface conditions that cannot be extracted from satellite observations alone (Gamon et al., 2013).

How Will Species Distributions and Associated Ecosystem Structure Change with the Evolving Cryosphere?

Arctic ecosystems and the biodiversity they support are under increasing pressure from environmental and societal changes occurring at multiple spatial, temporal, and organizational scales. Species-poor Arctic ecosystems tend to lack functional redundancy and so are potentially vulnerable to cascading effects from the loss of a single species. As the Arctic evolves, some organisms will succeed and some will fail. There will likely be poleward shifts in major marine and terrestrial biomes, with the Arctic Ocean geographically limiting the shifts of terrestrial species. The species that succeed will be those that can successfully adapt to and exploit the changing environment by expanding their geographic range and prominence (abundance, dominance) in the ecosystem through more successful recruitment, survival, and competition. The species that fail will be those that cannot successfully adapt because of ecological factors, including physiological intolerance, phenological mismatch with the environment, and inability to compete. These species will decrease in importance in the ecosystem and may become locally or regionally extinct.

Species changes will have significant impacts on food web structures and may result in drastically modified ecosystem function. A shift in the phytoplankton community

of the Canada Basin from larger to smaller species (Li et al., 2009) has already resulted from freshening caused by sea ice melting and increased river discharge. The northern Bering and Chukchi Seas are at present benthically dominated, with much of the ice algal and phytoplankton primary production being used by a rich benthic community (e.g., Campbell et al., 2009; Grebmeier, 2012). With decreased seasonal sea ice, one scenario is that these ecosystems could transition to a pelagically dominated structure, with greater biomass retained in the water column (including the emergence of abundant pelagic fish).

Changes in permafrost are likely to have a large impact on terrestrial ecosystems, particularly forests. The softer soil that results from permafrost thaw interferes with tree root systems, creating “drunken forests” (see, e.g., Figure 3.7). White spruce in Alaska’s tundra have been growing faster in warmer temperatures (Andreu-Hayles et al., 2011),

FIGURE 3.7 Trees in this Alaska forest tilt because the ground beneath them, which was once permanently frozen, has thawed. SOURCE: NOAA.

FIGURE 3.8 Researchers sample a dead spruce at treeline in northeastern Alaska. SOURCE: Susy Ellison.

and further research is needed to understand whether this result will be seen in other forest types or whether trees will instead be stressed by warmer temperatures (Figure 3.8). Warming will likely result in a poleward migration of the northern treeline and the invasion of shrubs into the tundra. The cascading ecological impacts (e.g., on bears, caribou, small mammals, and insects) and potential geographic limitations on shifts in boreal forest cover are unknown. In the tundra, shrubs are replacing lichens and other tundra vegetation (USGCRP, 2009). Recent evidence indicates that coastal permafrost thaw and associated sedimentation has facilitated a shift in Black Brant goose (Branta bernicla nigricans) population distribution from inland lakes to coastal areas (Tape et al., 2013).

Species with value to small local communities may become more available, as already seen with the increased catches of salmon in the northern Chukchi Sea (Carothers et al., 2013). Increasing abundances of commercially important pelagic fish or benthic invertebrates could result in the development of new Arctic fisheries, once sufficient understanding of the ecosystem is available to sustainably regulate that activity. However, new Arctic fisheries may have different social and economic impacts on

different communities and groups, as some may have declining opportunities while the opportunities of others improve. Locally important terrestrial species may decline. For example, caribou are an important food source for some indigenous communities, and they in turn rely on the lichen that is being replaced by shrubs in some parts of the tundra (USGCRP, 2009). The change in ranges of species and populations of species also affects genetic diversity and increases the potential for hybridization between congeneric species, such as between the Calanus glacialis and C. finmarchicus in the eastern Arctic (Parent et al., 2012) and between grizzly (Ursus arctos horriblis) and polar bears (Ursus maritimus) (Kelly et al., 2010).

Trophic interactions modulate ecosystem responses to climate change in the Arctic (Post et al., 2009). For example, herbivory (e.g., grazing by reindeer and musk oxen) shapes plant productivity and community responses to warming, which may, in turn, be mediated by changes in predator or decomposer communities. Such interactions are fundamental in shaping complex feedback processes between consumers and resources. These processes are not easily captured by studies of dynamics at single trophic levels, and more detailed studies are required to determine the role of climate warming in trophic dynamics (e.g., Roslin et al., 2013), especially in aquatic systems, soils, and sediments.

Warming changes the ecology of infectious agents and influences the emergence of disease in humans, domestic animals, plants, and wildlife. For example, warming in the Arctic has altered the transmission, development rates, and distribution of an important parasitic nematode of musk oxen in the Canadian Arctic (Kutz et al., 2005). The potential for new and expanded parasite and disease pressures for wildlife will have ramifications for northern communities, and the subsistence harvest of species that sustains many of these populations. Changing distributions of disease-bearing insects such as ticks (Lyme disease), parasites, or pathogens (e.g., the skin disease affecting seals and walrus observed in the Chukchi and Beaufort Seas) could have both direct and indirect negative impacts on humans. However, there is only a very basic foundation for understanding responses to climate change of other host–parasite systems in the Arctic (Kutz et al., 2005).

Looking ahead, when summer sea ice is gone and light limitations are lessened in spring through summer and autumn, what will be the next rate-limiting factor that will determine the ecology? Perhaps iron? How will the northernmost land fauna adapt to a warming climate, when they are unable to migrate farther north? As the Arctic readjusts to new conditions, what potential trophic flips are in store?

HIDDEN ARCTIC

Emerging Questions for the Hidden Arctic

H1. What surprises are hidden within and beneath the ice?

H2. What is being irretrievably lost as the Arctic changes?

H3. Why does winter matter?

H4. What can “break or brake” glaciers and ice sheets?

H5. How unusual is the current Arctic warmth?

H6. What is the role of the Arctic in abrupt change?

H7. What has been the Cenozoic evolution of the Arctic Ocean Basin?

The Arctic has long been hidden from most of Earth’s inhabitants. Physical access to key geologic and other archives has been limited by sea ice cover, terrestrial ice cover, lack of research icebreakers, lack of terrestrial infrastructure, limited access, and the sporadic nature of international research campaigns. Much of what was previously concealed by logistical challenges is becoming increasingly accessible, aided by reduced sea ice, greatly improved remote sensing, and advances in instrumentation, analytical tools, and observational platforms. This means we can now discover what has long been unseeable.

However, significant logistical, political, and financial challenges to the full realization of these new opportunities will persist. Much of our current research is centered around hypothesis testing, through proposals designed with convincing evidence of feasibility. The rapid changes that are anticipated in the coming decades include the likely threshold behavior and challenges to resilience that are less well understood than steady state processes (see “Investing in Research” section in Chapter 4).

As both sea ice and glacier ice retreat, what surprises will be revealed? How will land ice retreat? How will accelerated melting and glacier dynamics affect ice loss and therefore rates of sea level rise? Now that we will be able to access the Arctic basin more easily, what will we learn about the geologic evolution of sea ice loss?

What will the future Arctic look like? Archives in the sediments beneath the sea and lakes, along with records from within and beneath glacier ice, can tell us a great deal about how the Arctic responded during warm periods in the geologic past. Similarly,

both sediment and ice archives help in understanding the Arctic’s role in abrupt change.

Examples of existing questions:

• What will we learn about the Arctic’s past from sedimentary archives accessed through lake and ocean drilling and proxies contained in ice cores?
• How is the large-scale opening of the Arctic shelves changing interactions among ice, ocean, atmosphere, ecology, and society?
• What surprises will be revealed as we map the Arctic?
• What new perspectives will be revealed through genomic and microbial analyses?

What Surprises Are Hidden Within and Beneath the Ice?

Within the Permafrost

Permafrost holds vast stores of carbon, including gas hydrates (sometimes called methane clathrates). What are the consequences of releasing subsea gas hydrates or terrestrial methane and CO₂ held in permafrost? The potential for rapid release of methane, as may already be occurring from permafrost areas on the shelf of the East Siberian Sea, is a possibility but poorly understood (IPCC, 2007). About 10,400 gigatonnes of methane are currently stored in hydrate deposits, more than 13 times the amount of carbon in the atmosphere (Dickens, 2003; Kennett et al., 2008). The potential for exploitation of gas hydrates is also of great interest in many areas, including the Arctic, but with uncertain prospects for commercial application. Tremendous stores of carbon (over 1.7 gigatonnes) are also trapped in terrestrial permafrost, almost twice the amount of carbon present in the atmosphere (Schuur et al., 2009). The potential consequences of carbon release from these reservoirs remain poorly understood.

The frozen, dark, oxygen-deprived environment beneath ice sheets where there is no basal flow, beneath permanent snowbanks, and within permafrost is ideal for the preservation of organic remains and biomolecules (e.g., DNA) that otherwise have poor preservation potential if subaerially exposed. Unexpected finds of organic human artifacts as snowbanks have melted back in Alaska have offered new revelations about the early human enterprise (Dixon et al., 2007), and ancient mammal DNA in bones recovered from permafrost allow reconstruction of population density changes through time (Shapiro et al., 2004).

Within the Ice

Various physical and chemical proxies preserved in ice cores, particularly from Greenland and Antarctica, have provided some of the most compelling evidence for abrupt climate shifts in the past and for changes in atmospheric composition and circulation on timescales of decades to millennia. It is reasonable to presume that there remain unrealized proxies preserved within the ice that future research may uncover. The unparalleled resolution and age control that make ice cores optimal archives of the past warrant continued searches for new environmental proxies in ice.

Beneath the Ice

In many settings, thin ice caps on low-relief terrain act as preservation agents, rather than erosive agents, preserving intact even the most delicate features of the preglacial landscape, including rooted tundra plants and the soils in which they lived, that are now being revealed as ice caps recede under unusually warm summers. Rooted tundra plants that have been entombed for millennia allow insights into past summer temperatures (Miller et al., 2013), and ancient DNA preserved in sub-ice soils allows greater fidelity in the reconstruction of ancient environments (Willerslev et al., 2007). Within 1 to 3 years of subaerial exposure, these important, widespread climate and environmental archives are lost forever, emphasizing the emerging need for comprehensive sampling as ice caps rapidly recede.

For up to 9 months landfast sea ice mantles the shallow shelves fringing the Arctic coasts of North America and Eurasia that receive the bulk of the river runoff to the Arctic Ocean. The landfast ice zone also encompasses areas of shallow sub-sea permafrost, so thermodynamic perturbations to this zone may have consequences on methane release from the seabed. Much of our understanding of wind- and buoyancy-forced shelf circulation derives from mid-latitude studies, but we cannot readily transfer these lessons to the Arctic when landfast ice shields the underlying shelf waters from the direct influence of the wind. The landfast ice zone dynamically partitions the shelf into two regions, one where winds and drifting ice govern the circulation and one where shorefast ice controls the inner shelf flow. River outflows form shallow, buoyant currents that are typically restricted to within 20 km of the coast (Chant, 2011) so that their natural trapping scale is within the width of landfast ice zones. Models suggest sluggish alongshore, under-ice flows, ice-edge jets, and complicated secondary cross-shelf circulation cells that inhibit mass and material exchanges with the outer shelf (Kasper and Weingartner, 2012). These dynamical differences have implications for the transport of contaminants introduced into shelf waters, and they suggest that

biogeochemical processes might evolve quite differently between the two portions of the shelf. Understanding these issues has implications for the formation of dense shelf waters in winter, the seasonal evolution of shelf stratification, and the fate of materials borne by the plume. It also has implications pertaining to the biological “connectivity” of adjacent shelves, since buoyancy-forced coastal currents are potentially capable of flowing along vast shore distances.

What Is Being Irretrievably Lost as the Arctic Changes?

The loss of snow and ice is uncovering parts of the Arctic, but at the same time much is being lost. Coastal and riverbank erosion threatens villages and archeological sites (Brunner and Lynch, 2010; GAO, 2003; Lochner, 2012) (see, e.g., Figure 3.9). Nearly all coastal sites are being impacted by erosion due to changing sea levels, and stronger

FIGURE 3.9 A nearly century-old whaling boat in July 2007 along the Beaufort Sea coast near Lonely, Alaska. The boat washed away to sea just a few months later as a result of erosion. SOURCE: Benjamin Jones, USGS.

storms that are destroying archeological sites that have never been documented because of the vast extent of the coastline. Archeological sites are also at risk from a rising water table due to sea level rise (e.g., Coffrey and Beavers, 2013). Well-preserved organic artifacts previously protected within the cryosphere are being exposed by retreating ice (e.g., Andrews and MacKay, 2012). The least understood and documented loss is that of riparian sites due to ice-jam floods and riverbank erosion (e.g., Ott et al., 2001). This loss of information affects future excavations and our understanding of how people adapted and lived in the past. This record is now recognized to have major value to bioscience (aDNA, stable isotopes, etc.), paleoclimatology, and culture, and it has huge potential for expanded joint investigation. Iceland and Greenland, for example, offer the rare combination of archeological sites and contemporaneous written records, but many are threatened by thawing and decomposition. This threat is urgent and widespread. There is a great need for coordinated logistics, combined international resource application, and well-designed response strategies that will combine mitigation with a coherent interdisciplinary science program.

Ecological communities, too, are at risk. Unique freshwater ecosystems on the ice shelves of Ward Hunt and Ellesmere Islands in the Canadian Arctic have been lost as the ice shelves disintegrate (Mueller et al., 2003), and freshwater drains to the ocean or mixes with seawater in the absence of ice barriers. The loss of Arctic features and phenomena that are poorly understood or even unknown is a major challenge, especially if they are in remote areas where access is difficult, reducing the chances of discovery and hindering any research efforts even if discoveries are made.

Climate and environmental change is not the only cause of loss in the Arctic. Arctic languages are also being lost rapidly (Barry et al., 2013) as a result of social and other changes. A wealth of cultural practice and traditional knowledge is lost as languages diminish and disappear. Although not a new trend, language loss may be increasing in the face of modern media and telecommunications. At the same time, however, information technology and education reforms have provided new ways to support and perpetuate the use of languages spoken by relatively few people, providing hope for a change in the overall trend.

Difficult decisions may be necessary concerning what can be saved and what cannot. The ability to respond rapidly in cases of imminent disappearance depends on funding, logistics, cooperation, and other planning (see Chapter 4). Awareness of what is being lost is only a first step, but it is a critical one.

Why Does Winter Matter?

Winter occupies the bulk of the Arctic year. Winter conditions and processes, including ice formation and snow buildup, determine the timing and patterns of snow and ice melt in spring, thus affecting physical and biological environments as well as climate feedbacks. With the observed changes in seasonality, it is increasingly important to understand what happens in the winter and how winter processes affect conditions for the rest of the year.

Only a few studies to date have focused on this period of the annual cycle, especially in the biological sciences, in part because of a misplaced perception that the systems are essentially dormant during winter and in part because of difficulty in accessing those ecosystems, given the harsh winter conditions and the barrier of sea ice or of deep snow. This relative lack of knowledge has compromised our ability to understand the winter ecology of many organisms and to model these systems over the full annual cycle, ultimately limiting our ability to predict the ecosystems’ response to ongoing climate change.

Hidden beneath sea ice and snow, the ecology of the winter biota of the Arctic marine and terrestrial systems remains elusive. We now understand that, rather than being dormant or dead during winter, the biota of the marine and terrestrial ecosystems retain some activity during the cold, dark winter months (e.g., Darnis et al., 2012; Sturm et al., 2005). We also now have the technology to better study aspects of these systems during this forbidding period of the year. The reduction of thick, multiyear ice over a significant portion of the Arctic Ocean also may permit better access by research vessels during winter.

In the ocean, winter conditions are critical to the present-day density stratification that defines much of Arctic oceanography, and changing stratification is key to heat storage and energy release. Process studies are needed to understand how future winters may differ from today. If summer is ice free and the halocline breaks down through strong wind mixing and other processes, what will be the impact on winter ice formation in the central Arctic Ocean (see Chapter 3, Emerging Question E3)? Wind mixing is usually only significant down to 10 m, thus it is not likely that wind alone will destroy stratification. But with changing conditions in the shelf seas, stratification may be weakened enough to allow large polynyas to develop where deep convection could occur within the Arctic Ocean. An Antarctic analog for this is the Weddell Sea (Gordon et al., 2007). How could such a change impact local changes in marine ecosystems, as well as global redistribution of heat through the Atlantic Meridional Overturning Circulation (AMOC; see Chapter 3, Emerging Question C3)?

What Can “Break or Brake” Glaciers and Ice Sheets?

Over the last decade, Arctic ice masses, in particular the Greenland Ice Sheet (GrIS), have continued to offer new surprises. Supraglacial lake water has been shown to hydrofracture through more than a kilometer of ice to reach the bed, causing localized acceleration of ice flow (Das et al., 2008; Joughin et al., 2013; Zwally et al., 2002), with local effects propagating inland through stress coupling (Price et al., 2008). Meltwater and subglacial hydrology has been shown to be an important, yet poorly understood, control on sliding dynamics (Schoof, 2010; Shepherd et al., 2009). Water produced from surface melting may refreeze at depth, resulting in englacial (within the glacier) warming from latent heat release (Phillips et al., 2013) and/or it may persist in storage, both englacially and subglacially (Rennermalm et al., 2012) as well as in saturated zones of glacial firn (ice that is in the intermediate stage between snow and glacial ice) (Forster et al., 2014; Humphrey et al., 2012). Outlet glaciers from the GrIS have undergone rapid fluctuations in flow speed and calving rate (Howat et al., 2005; Howat et al., 2007; Joughin et al., 2004; Joughin et al., 2008). Increases in flow velocity have propagated to the north (Khan et al., 2014; Rignot and Kanagaratnam, 2006). Large “Antarctic scale” calving events have begun in North Greenland outlet glaciers (Falkner et al., 2011) (see Figure 3.10). Beneath the ice, new subglacial topography mapping has revealed extensive, never before seen subglacial canyons comparable in scale to the Grand Canyon (Bamber et al., 2013). On the surface, a confluence of factors combined in the summer of 2012 to produce surface melting on 97 percent of the GrIS, the scale of which, while not unprecedented in the climate history reconstructed from ice cores, has not been observed since systematic satellite observations began in the 1970s (Nghiem et al., 2012). Although they are not large reservoirs of stored fresh water, smaller glaciers and ice caps are losing mass at a much faster rate than the GrIS, and as such are currently the dominant cryospheric contributor to sea level rise (IPCC, 2013; Meier et al., 2007).

These new observations and discoveries highlight the need for persistent and pervasive observation and process studies on land ice in the cryosphere, for both small glaciers and the GrIS. Many of the findings cited above were made possible through remote-sensing campaigns, both satellite and airborne. In particular, the intensive Operation IceBridge air campaigns have enabled change detection in particularly fast-changing regions. Field instrumentation campaigns have also been critical in developing these observations and findings, underscoring the need for continued field research. Finally, model-based process studies of ice sheet behavior in a warming climate have helped shed light on the causes of positive and negative feedbacks, and such studies need to be continued and strengthened.

FIGURE 3.10 The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite observed Petermann Glacier and an iceberg calving and drifting downstream, July 16–17, 2012. At 1025 UTC on July 16 (top image), the iceberg was still close to the glacier. At 1200 UTC that same day (middle), the iceberg had started moving northward down the fjord. Thin clouds partially obscure the downstream view. One day later, at 09:30 UTC on July 17 (bottom), a larger opening between the glacier and the iceberg, as well as some breakup of the thinner, downstream ice, was clearly visible. SOURCE: NASA Earth Observatory.

“Breaking”Glaciers and Ice Sheets

Are there positive feedback mechanisms hidden at the ice-bed interface that we have yet to appreciate and understand? Is there a threshold at which the coupling between ice and bed will become weaker? How is inland ice deformed internally by warming through latent heat transported by percolating meltwater from events such as the widespread surface melt of Greenland in summer 2012? What effect will warming ocean water have on sea-terminating outlet glaciers and ice shelves? What is the interplay among surface melt, basal hydrology, and enhanced ice motion? These are currently among the most pressing questions in glaciology because of the strong influence Greenland could have on the rate of future sea level rise.

“Braking” the Current Decline of Land Ice Cover

Is there any potential negativefeedback mechanism that would slow the rates of sliding and internal deformation that carry ice to low-elevation ablation areas (areas where loss of snow and ice occurs)? For example, the thinning of the GrIS results in a lower basal shear stress . Is there a threshold where the coupling between ice and bed will become stronger, resisting further change? Will evolving subglacial hydrological systems in a warming climate reduce the accelerating effect of meltwater at the bed?

The search for new, unanticipated feedback mechanisms requires innovative measures: new process-based modeling studies, in particular of the ice/bed interface in the presence of liquid water; new technologies to determine the location and characterization of liquid water at the ice/bed interface; and new means for making observations at the difficult-to-access calving fronts of fjord-terminating glaciers. Ongoing observations of ice topography and flow rates would help assess the evolution of negative feedback mechanisms, as indicated by changes in flow rates and driving stresses. Finally, new remote-sensing platforms on multiple scales (e.g., unmanned aerial vehicles [UAVs], aircraft, spacecraft) will enable a sharper focus on “current events” in glacier and ice sheet motion, allowing us to identify these new feedbacks as and when they begin to take effect.

How Unusual Is the Current Arctic Warmth?

Arctic Ocean sea ice loss during recent decades has exceeded most model projections, leading to an emerging recognition that sea ice may be more sensitive to climate forcing than previously anticipated. In this context, understanding the paleo-record

of both the appearance and the loss of sea ice is especially important now, given the increasing accessibility of archives and new geochemical and paleoenvironmental tools to track the evolution of sea ice from sedimentary archives. Focused research into quantifying the dimensions and distribution of sea ice and on the status of land ice during known past warm times in Earth’s history, when continental configurations were similar to present, will inform our understanding of the sensitivity of Arctic ice to changing radiative forcing and ocean circulation patterns (Polyakov et al., 2010) and thereby improve our projections of the future Arctic.

Key warm periods in the past, when Arctic summer temperatures were higher than the 20th-century average, are given in Table 3.1.

Analyses of previous warm periods in the geological record indicate that there have been several extended time periods when sea ice was absent or only present in winter, or when there was less extensive summer ice than the 20th-century average, in the Arctic Ocean (e.g., Backman and Moran, 2009; Ballantyne et al., 2013; Brigham-Grette et al., 2013; St John, 2008), and when the GrIS was much reduced. In the early Cenozoic, the pole-equator temperature difference was much less than it currently is, and mean annual temperatures were at least 20 °C warmer than present at 71 °N (Markwick, 1998; Tarduno et al., 1998; Vandermark et al., 2007). Arctic Ocean surface waters reached ~20 °C during the warm Paleocene–Eocene Thermal Maximum, ~55 Ma ago (Sluijs et al., 2006), precluding permanent sea ice (Moran et al., 2006). Grains sand-sized and coarser found in marine sediment far from land (ice-rafted debris [IRD]) likely required ice-transport, either by calving glaciers or sea ice, although floating trees and other debris may also contribute to the delivery of coarse material far from shore. Rare IRD and sea-ice diatoms first appear in Arctic Ocean sediment ~47 Ma (St John, 2008; Stickley et al., 2009), and suggest seasonal sea ice may have been initiated then, although the conditions necessary to sustain persistent ice in the Arctic Ocean remain poorly understood.

A continuous high-resolution lacustrine record, supported by fragmentary paleontological data, suggests that during the mid-Pliocene (~3.5 Ma) summer temperatures were ~8°C warmer than today, when the partial pressure of CO₂ was ~400 ppmv (Brigham-Grette et al., 2013). Alley et al. (2010) summarized the Cenozoic history of the GrIS. Based on IRD distributions, calving glaciers may have been present on Greenland as early as 16 Ma (Moran et al., 2006), but establishment of a GrIS probably occurred after the mid-Pliocene, when large increases in IRD flux occurred throughout the northern North Atlantic. However, warm intervals, including one or more intervals of reforested Greenland, occurred after initial formation of a GrIS (Funder et al., 2001; Willerslev et al., 2007). Particularly warm intervals of the mid-to-late Quaternary are

TABLE 3.1 Past Warm Periods

Marine Isotope Stage (MIS) 31 (~1.1 Ma), when summers were up to 4 to 5 °C higher than the Holocene (Melles et al., 2012); MIS 11c (~0.4 Ma), when summers were also 4 to 5 °C higher than the Holocene (Melles et al., 2012) and CO₂ was ~285 ppmv, less than in MIS 5e but of much longer duration (30 ka) (Siegenthaler et al., 2005); the GrIS was much smaller than present (Willerslev et al., 2007); and sea level was 6 to 13 m higher than today (Raymo and Mitrovica, 2012). During the last Interglaciation, MIS 5e (~125 ka), summers were similarly warm (Miller et al., 2010, and references therein), the GrIS was about a third smaller than present, and sea level was +5 m (Overpeck et al., 2006). MIS 5e and 31 also had strong insolation forcing, with coincidence of high obliquity, eccentricity, and precession resulting in perihelion coinciding with boreal summer. During the Holocene, the present interglaciation (the past 12 ka), the Arctic was warmest between 9 and 6 ka, with summers 1.7 ± 0.8 °C above the 20th-century average (Kaufman et al., 2004; Miller et al., 2010, and references therein). As Greenland has been steadily losing mass in recent years (Svendsen et al., 2013), an emerging realization is that more complete Arctic-wide environmental reconstructions for intervals when the GrIS was substantially smaller than present may provide important constraints on the future state of the Arctic.

Understanding the local and global conditions associated with these times will help us to better anticipate future changes. How sensitive is sea ice to warming? How might biota respond? How much of the GrIS could be lost and at what rate? How might precipitation, freshwater discharge, and ocean circulation patterns shift? Is the mid-Pliocene a realistic analog for a future Earth equilibrated with current greenhouse gas concentrations and other forcings?

Increased access to the central Arctic Ocean offers opportunities to extract marine sediment cores that are expected to provide a more complete history of Arctic Ocean circulation and surface conditions through the late Cenozoic. A substantial challenge is the development of improved proxies that are directly linked to specific concentrations of sea ice. Emerging tools in organic geochemistry are the arena where new sea-ice proxies are most likely to be developed.

What Is the Role of the Arctic in Abrupt Change?

From a human perspective (as from that of much of the rest of the biosphere), the rate of change is more important than the magnitude of change, and both extreme events and nonlinearities (abrupt change) are likely to be our greatest future challenges.

Abrupt change refers to changes in the physical climate system and abrupt impacts in physical, biological, or social systems triggered by a gradually changing climate over a timescale of years to decades. Rapid change is more problematic for societal adaptation than regular, gradual change because it is unpredicted and unexpected and hence unprepared for, forcing reactive rather than proactive behavior. These changes may propagate systemically, rapidly affecting multiple interconnected areas within and beyond the Arctic (NRC, 2013).

Because of strong positive feedbacks and teleconnections to the global system, the Arctic may be the region most likely to face these challenges, which may in turn result in abrupt change in distant regions. A recent NRC report, Abrupt Impacts of Climate Change: Anticipating Surprises, identified the disappearance of late-summer Arctic sea ice as an abrupt climate change that is already happening, and outlined the potential climate surprises that could occur as a result of methane release from permafrost and methane hydrates (NRC, 2013). As access to key climate archives increases, we will gain a better understanding of how abrupt changes have occurred in the past, to shed light on how they may happen in the future.

Naturally Forced Abrupt Climate Change in the Holocene

The increasing distance of Earth from the Sun during Northern Hemisphere summer sincev ~11 ka, caused by Earth’s orbital irregularities, led to a decay of Northern Hemisphere incoming solar radiation in the summer, especially across the Arctic. Earth is currently close to its Northern Hemisphere summer insolation minimum, after which summer insolation will begin to slowly increase again. An emerging realization is that, as Northern Hemisphere summer insolation decayed, the high latitudes cooled irregularly (Wanner et al., 2011), with local to regional evidence for abrupt, step-wise, environmental change (Geirsdottir et al., 2013). Evidence of, and an explanation for, abrupt shifts under uniform, hemispherically symmetric insolation forcing are emerging research questions.

Volcanism

Sulfur-rich explosive volcanism can inject SO₂ into the stratosphere, where it rapidly converts to sulfuric acid aerosols that cool Earth’s surface but warm the stratosphere for 1 to 3 years (Robock, 2004). A series of decadally-spaced eruptions may have a more sustained climate impact (Schneider et al., 2009). What remains hidden is whether explosive volcanism served as a trigger for abrupt climate change during the

Holocene that persisted for decades to centuries, and whether the sensitivity of the Arctic system to explosive volcanism is dependent on the background state (Zanchettin et al., 2013).

Solar Irradiance

There is an extensive literature evaluating the role of solar irradiance variability on the climate evolution of the past millennium (e.g., Mann et al., 2009), although the likely range of solar irradiance variability on centennial timescales has been reduced in recent years (Schmidt et al., 2011). The largest remaining uncertainty is likely whether changes in the UV spectral strength of solar radiation impact stratospheric circulation through ozone formation in such a way that it strongly impacts the Arctic system.

What Has Been the Cenozoic Evolution of the Arctic Ocean Basin?

Our understanding of the geologic history of the Arctic Ocean has been inhibited by our inability to recover key sedimentary archives and underlying crustal rocks from the central Arctic Ocean. Instead, the history of the region has been derived from extrapolation of geophysical data and incomplete industry well data and land-based outcrops. With the exception of a single long record from the Lomonsov Ridge that extends back to the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) with several hiatuses, there is a serious lack of direct evidence to reconstruct the evolution of the Arctic Ocean Basin and its climate history. Understanding the tectonic evolution of the Arctic Basin can in turn inform our understanding of ocean circulation and biogeography, topics that were discussed in greater detail in the previous section on the Evolving Arctic. As it becomes possible to drill into the Arctic Basin seafloor, it becomes practical for the first time to study these important research topics.

Ridges, sediment-filled basins, stranded extended crustal blocks, and seamounts of unknown origins dominate the complex bathymetry of the Arctic Ocean Basin (Figure 3.11). These features, which are still not well studied, record the tectonic and magmatic evolution of this ocean basin. The Lomonosov Ridge is thought to be an extended crustal block that rifted off the Kara Shelf in northern Russia. The Lomonosov Ridge divides the Arctic Ocean into two basins—an eastern part referred to as the Eurasian Basin and a western part known as the Amerasian Basin. The Gakkel Ridge in the middle of the Eurasian Basin is the northernmost extension of the Mid-Atlantic Ridge and has the characteristics of a typical mid-ocean ridge. The Gakkel Ridge divides the Eurasian Basin into two smaller basins—Nansen and Amundsen. The Alpha Ridge and

FIGURE 3.11 Bathymetric features of the Arctic Ocean Basin. SOURCE: Mike Norton, Premier Oil.

Mendeleev Ridge divide the Amerasian Basin into the Makarov Basin and Canada Basin. The Alpha and Mendeleev Ridges may represent, at least in part, hotspot volcanic tracks, although data remain rather scarce for a definitive assessment.

Development of the Amerasian Basin

As year-round sea ice continues to retreat in the Arctic Ocean, large areas of the Amerasian Basin are made accessible to a variety of studies, including the ocean floor for its bathymetric features, geological structures, volcanic eruption history, and sedimentation. The geological development and evolution of this basin remains poorly

understood because until only recently many important submarine structures, such as faults, ridges, and volcanic lineaments, have been inaccessible because of sea ice and therefore have remained unmapped. The Canada Basin is bordered by North America on the southeast and the Chuckchi Plateau—a block of extended continental crust—on the northwest. Based on limited data, it has been proposed that the Canada Basin opened by counterclockwise rotation of this crustal block and its collision with the Siberian margin. This is known as the “windshield wiper” model for basin opening, and its verification hinges on whether future studies definitively identify magnetic anomalies in the central Canada Basin.

High Arctic Large Igneous Province

Large igneous provinces (LIPs) that have erupted in both marine and terrestrial environments throughout Earth’s history are thought to cause environmental devastation, and perhaps even mass extinctions, because of the massive volumes of material erupted onto Earth’s surface in what is presumed to be a short amount of time (~ 1 million years). This hypothesis notwithstanding, there has never been a satisfactory demonstration that indeed LIPs are emplaced in only ~ 1 million years. This is because they are too thick (up to 35 km) to drill through to obtain samples for dating of the entire volcanic sequence. The High Arctic Large Igneous Province (HALIP) centered on the Alpha and Mendeleev Ridges of the western Arctic Ocean offers a unique opportunity to test the model about its emplacement inasmuch as its eruptive history is recorded in the sedimentary record of Canada Basin. Drilling through a few kilometers of sediments is a much easier proposition than drilling through tens of kilometers of volcanic material in relatively deep water.

CONNECTED ARCTIC

Emerging Questions for the Connected Arctic

C1. How will rapid Arctic warming change the jet stream and affect weather patterns in lower latitudes?

C2. What is the potential for a trajectory of irreversible loss of Arctic land ice, and how will its impact vary regionally?

C3. How will climate change affect exchanges between the Arctic Ocean and subpolar basins?

C4. How will Arctic change affect the long-range transport and persistence of biota?

C5. How will changing societal connections between the Arctic and the rest of the world affect Arctic communities?

The Arctic is connected with the global system through a variety of mechanisms, both direct and indirect (Figure 3.12). These linkages span physical, biological, social, and economic realms. Thus, as the Arctic undergoes a profound physical transformation to what has been described as a “new normal” of the Anthropocene and residents

FIGURE 3.12 The Arctic system is made up of various components, including a complex network of process interactions, interdependent feedbacks, thresholds, and linkages with lower latitudes (e.g., warm water inflows/cold water outflows). There are many interconnections among system components, and important changes in one component may influence numerous other parts of both the Arctic and global systems. SOURCE: Roberts et al., 2010.

begin to experience the effects of globalization, profound changes in the entire global system are expected.

The Arctic is warming at least twice as fast as the rest of the Northern Hemisphere, resulting in the loss of approximately 75 percent of the volume of summer sea ice in only 3 decades, greatly increased surface melting on Greenland, unprecedented thinning and retreat of glaciers, thawing of permafrost, and marked warming of the Arctic Ocean surface (Blunden and Arndt, 2013). Because of the Arctic’s essential role in Earth’s heat engine that drives global-scale air currents, it is unlikely that changes of this magnitude would not have an impact on the large-scale atmospheric circulation. Those responses may become more widespread as greenhouse gases continue to accumulate. Conversely, changes in tropical and mid-latitude temperature patterns will also affect wind patterns, which, in turn, will influence Arctic change. A variety of positive feedbacks amplify these effects. Great uncertainty revolves around the linkages among changes in the Arctic freshwater system (e.g., increased precipitation and river runoff, decreased sea ice, earlier snow melt in spring) and potential impacts on physical and biological systems within and beyond the Arctic (Francis et al., 2009). Understanding the details of these interactions is in its infancy, but its importance is difficult to overstate.

People living in temperate latitudes are beginning to care about the impact of Arctic changes on their way of life. According to a recent polling study by Hamilton and Lemcke-Stampone (2013), the public generally accepts that the widely publicized disintegrating sea ice in the Arctic is affecting mid-latitude weather patterns. Further, an individual’s responses to poll questions are tempered by the weather conditions prevailing just prior to being interviewed, among other factors (Figure 3.13). The potential for a causal linkage between Arctic amplification (enhanced warming in the Arctic compared to the rest of the Northern Hemisphere) (see, e.g., Pistone et al., 2014) and mid-latitude weather resonates with the public in terms of recognizing the immediacy of climate change.

Connections are also apparent in considering how the Arctic will respond to climate change, including mitigation and learning from others’ experiences. Anthropogenic carbon emissions are predominantly from mid-latitudes, and thus addressing the major driver of Arctic climate change will require action outside the Arctic. The cost of adaptation measures in the Arctic, such as erosion control, is likely to be much higher than what Arctic residents or societies can afford, and mitigation therefore will require funding from sources largely outside the Arctic (e.g., Huntington et al., 2012). As the impacts of climate change are felt throughout the world, successful responses can be shared with other societies and regions, and collective actions can be considered.

FIGURE 3.13 Predicted probability of “major effects” response as a function of a 2-day temperature anomaly. SOURCE: Hamilton and Lemcke-Stampone (2013).

Many ongoing research efforts are focused on these changes (see existing questions below). This section highlights emerging questions related to interactions between the rapidly warming and thawing cryosphere and the physical, biological, and social systems south of Arctic boundaries.

Examples of existing questions:

• Which factors are most important in driving seasonal variability of sea ice, ice sheets, snow cover, and the active layer over permafrost?
• Why do global climate models underestimate the loss of Arctic ice?
• How can we quantify the role of climate feedbacks, their variability in space and time, and their impact on both climatic and environmental variables?
• How will changes in atmospheric circulation affect pollutant sources, pathways, and processes in Arctic ecosystems and communities?
• How will northern communities be affected by societal and environmental change, both internally and environmentally forced?

How Will Rapid Arctic Warming Change the Jet Stream and Affect Weather Patterns in Lower Latitudes?

Several studies based on theory, observations, and models have explored various mechanisms that may link Arctic amplification with changes in the large-scale atmospheric circulation of the Northern Hemisphere. Some of these proposed mechanisms include slowing the mid-latitude upper-level westerlies and increasing the amplitude of planetary waves, with enhanced potential for blocking and more persistent and/or extreme weather events (e.g., Francis and Vavrus, 2012; Petoukhov et al., 2013; Tang et al., 2013). Some of these studies provide robust evidence for linkages and some do not (e.g., Barnes, 2013; Screen et al., 2013; Screen and Simmonds, 2013). This is a rapidly evolving avenue of research (Palmer, 2013; Vihma, 2014).

What we know about the depletion of the Arctic cryosphere (sea ice, glaciers, snow, and permafrost), combined with new studies implicating Arctic amplification as a driver of more frequent extreme weather, has reignited discussions of weather as a manifestation of climate change (Jeffries et al., 2013; Lynch et al., 2008). Climate model projections of future Arctic amplification vary widely (Holland and Bitz, 2003), leading to uncertainty in estimating the response of large-scale circulation as well as weather patterns. The capability of models to simulate extreme weather events related to the changing jet stream is also in question. A better understanding of the details of the response will enable decision makers to prepare for changes ahead. However, predicting these extremes in the short term with numerical weather prediction models and projecting their variability in the long term with GCMs both present a substantial challenge. Recent studies suggest that the changing character of the jet stream includes an increase in blocking patterns and highly amplified flows, demanding realistic simulations of nonlinear dynamics at mesoscales that at present appear to stymie the relatively coarse dynamical models used for global weather forecasting and climate projection (Masato et al., 2013). High-resolution models are generally more successful in simulating these mechanisms.

Climate models vary in their simulations of past and future Arctic amplification, leading to uncertainty in the projections of dry static energy transport (Hwang et al., 2011). Meanwhile, as global temperatures increase, so does the maximum physical limit of water vapor concentration in the atmosphere. The dependence of water-vapor concentration on temperature is not linear, as 1 degree of warming at high temperatures results in a larger increase in water vapor than at low temperatures. This delicate interplay adds complexity to projections of changing poleward moisture transport, as a more rapidly warming Arctic partially offsets the nonlinearity in the temperature/water-vapor dependence. The importance of knowing future changes in moisture

cannot be overstated, as it affects the amount of latent heat energy that fuels storms, the magnitude of its greenhouse effect, and moisture availability for cloud formation (which affects the surface radiation budget) and precipitation intensity.

The thermal responses to increasing greenhouse gases in the troposphere and stratosphere differ. As vertical atmospheric stratification changes, the exchange of wave energy between the troposphere and stratosphere is modified (e.g., Cohen et al., 2007). The impacts of these changes on the large-scale circulation are poorly understood, but they are likely to affect weather patterns around the Northern Hemisphere.

Modes of natural variability within the coupled ocean-atmosphere system have been identified and studied (El Niño-Southern Oscillation, Pacific Decadal Oscillation, Northern Annular Mode, Quasi-biennial oscillation, etc.), each with its distinctive influence on the large-scale circulation. Dramatic reduction of sea ice and early-summer snow on high-latitude land areas, along with increasing atmospheric water vapor, have led to an emergence of the signal of Arctic amplification from the noise of natural variability only within the past decade or two, and most strongly in the autumn and winter. Because a rapidly warming Arctic is a new driver in the system, little is known about how natural oscillations and large-scale patterns will interact with its thermodynamic and dynamic effects.

Arctic vegetation change, too, can contribute to hemispheric weather patterns. Models suggest that the greening of the tundra has led to greater predominance of high-pressure systems during the Arctic summer (Jeong et al., 2012). Greener tundra has a lower albedo than snow-covered tundra, resulting in more absorption of solar radiation. The resulting warming of Eurasia may affect the strength of the Indian summer monsoon, although current understanding of the combined effects of tundra greening and snow cover changes is incomplete and warrants further investigation.

What Is the Potential for a Trajectory of Irreversible Loss of Arctic Land Ice, and How Will Its Impact Vary Regionally?

A direct and crucial linkage between the Arctic and global physical systems is the loss of land-based ice to the ocean and the effect on global sea levels, which will affect billions of people living in coastal cities around the world. The IPCC AR5 (2013) reports that the rate of sea level rise has accelerated over the 20th century to an average of ~3.2 mm per year from 1993 to 2010. Assessments of contributions from various sources have become more accurate, but large uncertainties remain, especially with

regard to future projections. Sea level rise from 1993 to 2010 was caused by thermal expansion of the ocean (~39 percent), glacial changes (~27 percent), land water storage (~13 percent), Greenland (~12 percent), and Antarctica (~9 percent) (IPCC, 2013). Sea level rise projections for the 21st century vary widely (0.26 to 0.82 m) (IPCC, 2013). Land-based ice in the Northern Hemisphere (e.g., glaciers, ice caps, and the GrIS) will contribute to future sea level rise. Future loss from the GrIS is the most serious concern, because of its large ice volume, its potential for a sustained long-term impact on sea level rise, and uncertainty regarding the sensitivity of the mechanisms that maintain the ice sheet’s stability.

The greatest uncertainty in making reliable predictions comes from the inability to project future ice sheet responses to warmer air and ocean temperatures, the possibility of outlet glacier destabilization, and even the unlikely but possible rapid collapse of marine-based sectors of Antarctica (e.g., Pine Island Embayment).

It is now recognized that ocean heat plays an important role in forcing increased ice discharge via processes such as circulation of the water near the ice, rapid melting of floating glacier tongues, calving at the glacier terminus, and the glacier’s response (changing terminus position, elevation, and velocity field). Assessing the magnitude and sensitivity of these various controls (including outlet glacier discharge) on GrIS stability is essential and requires comprehensive in situ and remotely sensed observations coupled with advanced modeling studies. Without observational and modeling improvements, it will be impossible to assess the likelihood and characteristics of a trajectory (how much and how fast) for irreversible GrIS melt.

Three factors will prevent sea-level rise from being spatially uniform: land subsidence, differential ocean warming that changes the distribution of water across the planet, and the huge mass of frozen water on Antarctica and Greenland that exerts a gravitational pull on the surrounding liquid water. As ice sheets lose mass, regions in close proximity to the major ice sheets will experience lower rates of sea level rise, while regions farther afield, particularly the tropical Pacific Ocean, will experience higher rates of sea level rise (Spada et al., 2013). Other factors affecting regional rates of sea level rise include varying thermal expansion and changes in ocean circulation. Much uncertainty surrounds the relative roles of these various factors affecting local rates of sea level rise, including shifting ocean currents in response to changes in wind patterns and ocean density profiles, the thinning rate of the GrIS, and differential rates of land subsidence, to name just a few.

How Will Climate Change Affect Exchanges between the Arctic Ocean and Subpolar Basins?

The Arctic Ocean, like the Arctic atmosphere, is connected to its lower-latitude complement (Carmack et al., 2010), although the oceanic connections or pathways are more physically constrained. The Arctic Ocean affects deep water convection through control on the volume and pathways by which freshwater is exported into the North Atlantic Ocean through the Canadian Arctic Archipelago and through Fram Strait (Dickson et al., 2002; Serreze et al., 2006). The North Atlantic Ocean is the formation site for deep water that feeds the meridional overturning circulation. At present the North Atlantic’s deep water formation sites are delicately structured in their ability to sustain deep convection (Aagaard and Carmack, 1989; Schlosser et al., 1991). The reviews of Alley (2007) and Srokosz et al. (2012) underscore the numerous paleoclimatic and modeling studies indicating that variations in the strength of the Atlantic Meridional Overturning Circulation (AMOC) have far-reaching effects on global winds, temperatures, and precipitation patterns. These studies also show that changes in the strength of the AMOC occurred on decadal (abrupt) or centennial to millennial (slow) timescales in the past. Rates may change in a warmer world.

Better understanding is needed of the constraints on Arctic freshwater production and its influence on the AMOC. River runoff feeds a large amount of freshwater into the Arctic Ocean surface, most of which is exported southward by sea ice and upper-ocean flux. Increasingly, freshwater discharged from the retreat of the GrIS will play a role. Understanding the controls on the outflow of freshwater, and hence improving its predictability, is essential because of its influence on the stratification of the water column in the Greenland, Icelandic, Norwegian, and Labrador seas, which are important regions of deep water formation (Aagaard and Carmack, 1989; Jahn et al., 2010). Massive increases in freshwater export from ice sheet meltwater in the Arctic, such as occurred during the Younger-Dryas event ~12,000 years ago, are believed to have caused a shutdown of the AMOC and a major reorganization of Earth’s climate (Broecker et al., 1989). The current generation of IPCC models predicts a slowing, but not an abrupt shutdown, of the AMOC through the 21st century in response to greenhouse gas warming (IPCC, 2007). Nevertheless, these forecasts remain uncertain, given the large scatter among models in the predicted strength of the AMOC, particularly in their dispersal of liquid freshwater export in narrow boundary currents. There are large differences among models in their ability to capture interannual variability in the liquid freshwater export.

The low-salinity upper-ocean waters exported from the Arctic Ocean may have important effects on the carbon cycle and ocean acidification processes in the North Atlan-

tic from changes in stratification, chemical buffering capacity, and the biological uptake of CO₂. For example, an increase in haline stratification, associated with enhanced freshwater export, will inhibit deep convection and consequently reduce the efficacy by which atmospheric CO₂ is sequestered in the deep ocean. In addition, the total alkalinity of the freshwater export (either in ice or liquid form) is low and therefore exerts a diluting effect on carbonate mineral saturation states at the surface.

At present the Arctic Ocean is a sink for anthropogenic CO₂ (Anderson et al., 1998) and accounts for 5 to 14 percent of the global balance of CO₂ sources and sinks (Bates and Mathis, 2009). A continued reduction in sea ice cover and a concomitant enhancement in phytoplankton production (assuming no nutrient limitation) is expected to further increase CO₂ uptake in Arctic surface waters (Bates, 2006; Fransson et al., 2001). However, the increased production will also enhance organic matter remineralization in subsurface waters that will exacerbate ocean acidification. Indeed this appears to be occurring at present insofar as acidification rates in the Arctic Ocean are substantially greater than elsewhere in the global ocean (IGBP, 2013). These subsurface waters, having a low pH, high dissolved inorganic carbon, and low total alkalinity, are eventually exported into the North Atlantic (Shadwick et al., 2009; Shadwick et al., 2013), potentially expanding ocean acidification effects there as well.

Outflows from the Arctic Ocean may impact North Atlantic marine communities and biological production. For example, the freshening associated with the Great Salinity Anomaly (Dickson et al., 1988) appears to have contributed to a reorganization of the plankton and fish communities of the North Sea (Edwards et al., 2002). Greene and Pershing (2007) showed that an increase in low-salinity, Arctic-derived shelf waters into the Gulf of Maine and Georges Bank in the mid-1990s led to a major decadal-scale shift in zooplankton communities that, together with the vulnerability of the already overfished stocks, subsequently altered the commercially important cod and haddock fisheries.

How Will Arctic Change Affect the Long-Range Transport and Persistence of Biota?

Marine and terrestrial biota in the Arctic are affected by changes in, and transport from, lower latitudes, and changes in the Arctic may influence areas beyond the Arctic. Transport of expatriate organisms (invasive species) into the Arctic, by natural processes and by human activity, for example, has long been recognized⁴

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⁴ See http://www.sciencedaily.com/releases/2013/11/131104112713.htm.

(Lassuy and Lewis, 2013). In the western Arctic Ocean, copepod species (Figure 3.14) characteristic of the northern Pacific/Bering Sea have been observed in low but detectable numbers throughout the Chukchi Sea and extending into the Arctic Basin, associated with water types of Pacific Ocean origin (e.g., Ashjian et al., 2003; Hopcroft et al., 2010; Matsuno et al., 2011). During the last decade, transport of a number of additional species spanning the benthic and pelagic environments and across multiple trophic levels (e.g., phytoplankton to seabirds) has been recognized (e.g., Hollowed et al., 2013; Post et al., 2013; Wassmann et al., 2011). For example, Alaskan salmon are now much more common, and increasingly utilized as subsistence food, along the Alaskan north coast in Barrow and Nuiqsut (Carothers et al., 2013). Atlantic cod are abundant around Svalbard, displacing the endemic polar cod (AWI, 2013; Renaud et al., 2012).

FIGURE 3.14 Researchers deploy a bongo net to sample zooplankton at the ice edge in the Bering Sea aboard the Research Vessel Thomas G. Thompson. SOURCE: NOAA.

Transport into a region by itself does not predict that a species can become established in that region and persist, potentially permanently displacing endemic species. The expatriate species may be able to survive in the short term but, because their life histories and physiology are not adapted to the environmental conditions (e.g., temperature, phenology of production, light cycles), they may not reproduce. For example, it has been hypothesized that Alaskan salmon cannot reproduce along the north coast of Alaska (Carothers et al., 2013) and that Bering Sea pollock will not experience a northward shift in distribution because of persistence of very cold water (<0 °C) at depth in the northern Bering Sea (the “cold pool”) and further north (Sigler et al., 2010).

If, on the other hand, subarctic species can adapt to and successfully reproduce in Arctic conditions, then their biogeographic ranges can expand. In the future, with warmer temperatures and earlier and potentially higher primary production with a longer productive season, temperate organisms transported into the Arctic may be able to persist—that is, to reproduce and maintain populations in the Arctic. It also has been suggested that temperate species may have better resistance to ocean acidification (AWI, 2013). Changes in persistence of expatriate species can result in changes in community composition, displacement of endemic Arctic species, changes in pelagic-benthic coupling, changes in the size composition of planktonic and benthic organisms, and thus the availability of prey for forage fish and seabirds and, ultimately, marine mammals.

Recognizing colonization by expatriate marine species is difficult because few long-term records exist (Wassmann et al., 2011). The situation is better for terrestrial ecosystems, for which there are some long-term records (e.g., Jeffries et al., 2012; Post et al., 2013). Lack of understanding of physiological tolerances, temperature-dependent rate processes, and species phenologies also hampers our ability to predict northward expansion of marine and terrestrial organisms. Studies focusing on the potential for expatriate species to survive and persist, including modeling, observations, and experimentation to determine species-specific responses and vital rates under varying environmental conditions, are necessary to gain this predictive capability.

A by-product of many types of phytoplankton is dimethyl sulfide (DMS), which serves as effective condensation nuclei for the formation of clouds. As the Arctic Ocean transitions to a seasonally ice-free state, the resulting shifts in distributions and abundance of phytoplankton are likely to influence DMS production. Large uncertainty surrounds the magnitude of this change on cloud production within and beyond the Arctic.

How Will Changing Societal Connections between the Arctic and the Rest of the World Affect Arctic Communities?

In social and political terms, the Arctic functions less as a circumpolar unit and more as a series of northward extensions of individual countries and regions. It is difficult, for example, to travel from Arctic Canada to Alaska or Greenland without first going south. Similarly, trade and supply routes typically run north-south rather than east-west (Box 3.4). Organizations such as the Inuit Circumpolar Council, the Northern Forum, and the University of the Arctic work against this pattern, making connections

within the Arctic based on common language and interests. For the most part, Arctic regions have been the beneficiaries of government spending and subsidies. Fisheries and, more recently, petroleum and mineral exploration have helped change that pattern of dependence to some extent, and interests in development are increasing. Thus, some parts of the Arctic may reach economic self-sufficiency, at least to some degree. The appeal of Arctic resources, however, will also attract many more people, greater outside influence, and the attention of more countries (e.g., the application of several countries for observer status at the Arctic Council⁵).

A seasonally ice-free Arctic Ocean will open new trade routes and facilitate access to untapped oil and natural gas reserves (Gautier et al., 2009), repositioning the Arctic from a post-Cold War periphery to a region central to national and international economic interests (Åtland, 2009). Although Arctic states and Arctic residents anticipate financial benefits from increased development of fossil fuels and minerals, shipping routes, tourism opportunities, and fisheries, the region is also exposed to the ongoing environmental and infrastructural risks associated with global climate and environmental change, potential oil spills, and other hazards. Economic development can bolster local adaptive capacity relative to climate change and climate mitigation policies by encouraging local investments, while at the same time encouraging stronger links to the global society, along with an enhanced appreciation by outsiders of their unique surroundings and relationships with nature. That said, many developments also contribute to local vulnerability by contributing to global climatic changes.

Arctic communities are attempting to ensure their participation in policy processes such as the Arctic Council (Sejersen, 2004). Arctic indigenous communities, many of whom have corporate and constitutional rights, are part of consultative processes that can delay proposed developments that threaten traditional land and resource use or can shift the way benefits from economic development are distributed (see also Chapter 3, Emerging Question E1). Different groups are not always cohesive and do not necessarily share the same views, and hence anticipating how consultative processes will shape decision making is never straightforward. At the same time, they have their own perspectives on security and risk that often run counter to state-centric definitions. Whereas states may emphasize the significance of energy security, for example, indigenous communities may place more significance on food security (Hansen et al., 2013).

The increase in resource exploration has also led to greater interest from, and presence of, non-Arctic countries. China is working with Iceland and Greenland to help develop

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⁵ See http://www.economist.com/news/international/21578040-arctic-council-admits-its-firstpermanent-asian-observers-warmer-welcome.

minerals. South Korea and Singapore are developing Arctic shipping capability with an eye to the Northern Sea Route. These activities will influence international relations in the Arctic Council and beyond (see Chapter 3, Emerging Question M2). They will also affect Arctic communities, through the influx of new people, new cultures, new ideas, and new problems as well as new opportunities. Modern telecommunications and transport have also spurred the development of connections between Arctic peoples and indigenous peoples elsewhere in the world, as they discover common experiences of colonization and common challenges of maintaining cultures in the face of social and environmental change. In short, even as east-west interactions remain challenging in some ways, north-south connections to and from the Arctic are growing stronger and more influential in both directions.

MANAGED ARCTIC

Emerging Questions for the Managed Arctic

M1. How will decreasing populations in rural villages and increasing urbanization affect Arctic peoples and societies?

M2. Will local, regional, and international relations in the Arctic move toward cooperation or conflict?

M3. How can 21st-century development in the Arctic occur without compromising the environment or indigenous cultures while still benefiting global and Arctic inhabitants?

M4. How can we prepare forecasts and scenarios to meet emerging management needs?

M5. What benefits and risks are presented by geoengineering and other large-scale technological interventions to prevent or reduce climate change and associated impacts in the Arctic?

The Arctic has been managed, to one degree or another, intentionally or otherwise, since the first humans arrived in the region tens of thousands of years ago (e.g., Fitzhugh et al., 1988; Pavlov et al., 2001). Early hunters affected animal populations, altered vegetation in and around their camps and settlements, and used the resources they found to support themselves and to trade with their neighbors (e.g., Krupnik, 1993). Over time, humans spread throughout most of the Arctic (e.g., McGhee, 2007), excepting only a few remote island groups. And they spread again, as new technologies supplanted old, as one group supplanted or blended with another, as people found new ways to use resources and new resources to use.

The beginnings of the modern era followed the same pattern, with whalers and seal hunters voyaging north (e.g., Bockstoce, 1986), with explorers seeking new lands and new trading routes (e.g., Berton, 2000), and with inevitable clashes and blendings of cultures and people (e.g., Slezkine, 1994). In the 19th and 20th centuries, the idea that the Arctic has intrinsic value started to develop, leading in time to the recognition of indigenous rights (e.g., Hensley, 2010) and a need to conserve Arctic places and species (e.g., Nash, 2001). Nations claimed sovereignty over the lands of the Arctic, and then over increasing areas of the sea, and now out to the extended continental shelves. The commerce and colonization of the emerging Anthropocene brought further technological advances and cultural change, as well as the introduction of disease and other detriments to health and well-being (Bockstoce, 1986). These patterns continue today, as globalization reaches remote communities, as national and international policies affect traditional practices, and as interest in resource development increases (e.g., GAO, 2003). Material well-being has advanced substantially throughout the Arctic, life expectancy has increased, and much is now possible that never was before.

At the same time, the impacts of climate and environmental change pose new challenges (e.g., ACIA, 2005; see Box 3.5). Permafrost degradation and coastal erosion threaten the structures and viability of many communities (GAO, 2003). Changing weather and ice conditions increase the hazards faced by those traveling on land and sea (e.g., Pearce et al., 2011). Changes in vegetation and wildlife bring new opportunities (e.g., Noongwook et al., 2007) but also undermine established patterns of hunting, fishing, and gathering (e.g., Gearheard et al., 2006). These changes occur within a wider context of continuing economic, cultural, and political change. Many reindeer herders and small-scale fishermen find their livelihoods less and less able to support them (e.g., Helander and Mustonen, 2004). Many indigenous languages are endangered and some have disappeared (Barry et al., 2013). New modes of governance, through the settlement of land claims or the evolution of political relationships with nation-states, allow greater self-determination (AHDR, 2004), while the Arctic Council provides a new way for nations to cooperate with each other and with indigenous peoples (Axworthy et al., 2012).

All of these topics have been, and continue to be, studied in depth and in many places, deepening our understanding of the ways people affect the Arctic environment and the Arctic environment affects people, there and throughout the world. Indigenous peoples are taking an ever-greater role in designing and carrying out research in their areas. As noted in Chapter 2, this research has never been more important, as countries and companies look north and as Arctic communities do more and more to shape their own futures. Identifying ways to achieve sustainability for communities and

for economic development activities, finding successful adaptations to a changing environment and the underpinnings of preparedness and resilience, and enhancing food security and well-being are among the areas vital to the future of the Arctic, areas where research can offer a great deal.

Examples of existing questions:

• What are the impacts of climate and environmental change on Arctic communities and how can communities adapt effectively?
• How can Arctic indigenous languages be sustained?
• How can food security be improved in the Arctic?
• How can the well-being of Arctic peoples be improved, for example, to reduce suicide rates?
• How do the distinctive features of Arctic climate change (long time horizon, uncertainty, variable spatial scale, complexity of natural systems, interdependence of actors) shape human perception and response?
• How will changing government policies, with regard to economic support and resource use, affect the sustainability of Arctic communities?

In addition to these established research areas, several themes are emerging as the Arctic and its societies change, as the impacts of climate change grow greater, and as those with stakes in the Arctic become more numerous and widespread. We highlight five such emerging areas of research, not as an exhaustive list of what can and should be done but as examples of the ways in which research can and should adapt, in recognition of new trends and patterns in the way the Arctic is managed, locally, regionally, and globally.

How Will Decreasing Populations in Rural Villages and Increasing Urbanization Affect Arctic Peoples and Societies?

A growing shift in Arctic populations is that indigenous people are moving into urban settings (AHDR, 2004). Whether because their home communities are disappearing or for economic reasons, those making such moves are facing major life decisions that will affect generations to come. The people will have to adapt their ways of life, and at the same time they will bring their values and culture with them into a new environment. Based on the 2010 U.S. Census, Alaska Natives compose 14.8 percent of Alaska’s population, and over half of Alaska Natives live in Anchorage.⁶ Many questions remain about how indigenous peoples are adapting to the urban setting (Voorhees, 2010).

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⁶ See http://quickfacts.census.gov/qfd/states/02000.html.

Will they sustain their cultural traditions, lose them in the urban melting pot, or create new ways of living and being?

Such decisions will affect not just their social and economic well-being as indigenous peoples but also their culture, place, and the larger society of which they are part. Indigenous people such as the Yupik, Iñupiat, and Inuit are synonymous with the Arctic, yet major portions of their populations have already moved out of rural settings and often out of the Arctic entirely. These moves bring a gamut of social and cultural challenges and issues, including many negative ones that attract the majority of attention. Success stories, however, seem to happen with far less fanfare. How have these individuals made the transition, and what have they kept with them in the way of language, food, stories, dances, and other cultural practices? One obstacle is that discussions of being indigenous in an urban setting appear to be taboo in many circles, with the implication that one is less “indigenous” for living in a city.

The flip side of urbanization is the loss of small communities in the Arctic, from outmigration or from loss of the physical site of the community. For centuries indigenous peoples living in the Arctic adapted readily to an ever-changing environment (Krupnik, 1993). They built sod homes near resources, and if things changed they were able to move easily, without regulations or restrictions. Today is a different story. The homes, water and sewer, power grids, schools, runways, and roads of modern Arctic communities have grown through time, and now they impede the ability to respond to a changing landscape. When indigenous people in Alaska move to larger cities, they may give up their hunting rights, such as with the Migratory Bird Treaty Act. It may be legally difficult for people living in urban areas to return to their home village to hunt migratory birds. Similarly, if someone moved to Fairbanks, he or she probably would not be called a “coastal native” and thus probably could not hunt marine mammals. Coastal communities threatened by erosion face difficult decisions regarding relocation. What happens when a community is no longer physically viable or is too expensive to maintain (e.g., Huntington et al., 2012)?

The lack of opportunities, resources, and services in small communities, especially for those who have left to pursue higher education or training, leads to outmigration, the second major challenge for remote communities. Often, young women leave and do not return, creating a gender imbalance (e.g., Hamilton, 2010). Today, many young men are also leaving, resulting in a dearth of young people in most rural communities. Although many move back as they grow older, many remain in cities. How will outmigration affect rural communities, not just in terms of raw numbers but also the loss of those with valuable skills and aspirations? What rights, to subsistence and to gover-

nance, do those who have left retain in their home communities, and how will these be recognized and allocated?

A great deal of research effort has been focused on various aspects of these questions, but a complete look at the various factors in migration, urbanization, and sustainability of individuals, communities, and cultures has rarely been attempted. Yet these trends will help define the indigenous experience through the 21st century, and thus deserve careful study and open discussion that can help indigenous peoples chart their own futures in a rapidly changing social and natural world.

Will Local, Regional, and International Relations in the Arctic Move toward Cooperation or Conflict?

During the Cold War, the Iron Curtain extended through the middle of the Bering Strait and also along the Norwegian-Soviet border, separating nations and also indigenous peoples from their relatives and areas of travel and use. The demise of the Soviet Union and the creation of the Arctic Council have helped promote communication and cooperation, and Norway and Russia recently resolved a disputed maritime boundary in the Barents Sea. But claims to extended continental shelves, access through the Northern Sea Route and the Northwest Passage, and divergent policies for wildlife management or resource development offer many sources of potential conflict. Growing interest in the Arctic by non-Arctic countries raises the stakes higher with greater uncertainty (e.g., Wall, 2013). Locally and regionally, similar divergent paths can be seen, for example, between local governments and large corporations as to the conditions under which industrial activity will take place. A recent election in Greenland hinged on the way the Self-Rule Government should approach mining and oil development.

Throughout human history, mankind has raced to discover the next frontier. And time after time, discovery was swiftly followed by conflict. We cannot erase this history. But we can assure that history does not repeat itself in the Arctic.

—Chuck Hagel, U.S. Secretary of Defense, November 2013, regarding his department’s newly released Arctic Strategy.

This question of cooperation or conflict leads to additional lines of inquiry, about the role of indigenous peoples within nations and internationally, for example, through the Arctic Council and the United Nations; about the respective ambitions and policies of Arctic and non-Arctic countries; about the distribution of risks and rewards from resource development; and more. The aspirations of Arctic peoples to achieve greater

self-determination are particularly noteworthy (see Chapter 3, Emerging Question E1), with different approaches being taken in various regions, and work being done toward a common voice through organizations such as the Inuit Circumpolar Council and the Saami Council.

As exploration, economic development, and political assertion increase, the potential for conflicting pathways increases, but so do many incentives for cooperation. Rules for Arctic shipping are under discussion as the IMO develops its Polar Code, and regional arrangements are also under development. Various scenarios for the future of international relations in the Arctic have been proposed, but these remain speculation at present (e.g., Arctic Council, 2009). Local patterns may differ from national ones, as, for example, the United States and Russia cooperate on marine safety and related issues in the Bering Strait area even as Washington and Moscow spar over larger geopolitical differences. Canada and Russia are pursuing extended continental shelf claims in the Arctic Ocean.

Non-Arctic countries take a greater interest in Arctic affairs, raising concerns over their level of influence. For example, China is pursuing development opportunities in Greenland and Iceland, and South Korea is building ice-capable ships. They both seek engagement in the Arctic Council and other forums for joining forces with Arctic countries. The Arctic Council, in turn, has shown greater willingness to extend observer status to non-Arctic countries, although so far not to the European Union as its own entity.

The newly formed Arctic Circle, a group established to facilitate dialogue between businesses and Arctic governments and organizations, is attempting to establish itself as a business-friendly alternative to the Arctic Council. Many corporations are producing or exploring for natural resources such as oil, gas, lead, zinc, gold, and diamonds, providing employment opportunities and tax revenues as well as potential impacts on the environment and local communities.

Indigenous communities collaborate with one another to a greater degree than ever before, including working beyond the Arctic directly and through international working groups and forums for indigenous rights, though there are often differences between and within communities over whether and how resource development should take place.

Research has been done in all these areas, enhancing our understanding of the relationships among the various entities as well as the factors that influence those relationships. It is important that such research continue, from simply tracking the activities of the Arctic Council, to documenting the ways that indigenous communities

interact with and learn from another; from evaluating the effectiveness of community consultations by industry or governments, to exploring the potential role of indigenous communities in exploration and development activities.

Little is known, however, about the trajectories of these forms of interaction and how cooperation or conflict in one region or sector will affect cooperation or conflict elsewhere. These trajectories and their interactions will determine the overall course of human relations in the Arctic in the decades to come. A better understanding of their direction may allow intervention to reduce conflict or enable better planning for infrastructure, policies, governance, and other human arrangements that are likely to operate for decades, well into an uncertain future.

How Can 21st-Century Development in the Arctic Occur Without Compromising the Environment or Indigenous Cultures While Still Benefiting Global and Arctic Inhabitants?

Whether spurred by new opportunities for access, by global economic factors (such as energy supply and cost), or by the aspirations of local populations, increasing exploration and development in the Arctic will bring both opportunity and risk (e.g., Gautier et al., 2009; see Box 3.6). In recent remarks to the inaugural Arctic Circle forum, Scott Minerd, Global Chief Investment Officer, Guggenheim Partners, likened the physical and economic opening of the Arctic to the “discovery” of the Americas. He highlighted the potential for economic benefits as well as the potential for environmental degradation and for detrimental impacts on indigenous people. In the United States, for example, the Outer Continental Shelf Lands Act specifically mandates expeditious and orderly development, subject to environmental safeguards. Billions of barrels of oil are expected to be found (e.g., Gautier et al., 2009), but operating in remote regions is hazardous. Under the Law of the Sea Treaty, Arctic nations have the potential to extend territorial claims (Exclusive Economic Zones; see Figure 3.15) to the seabed of extended continental shelves. This potential has fostered a rapid exploration of the geology of the continental-basin margin, a clear indication of interest in capitalizing on resource development opportunities in these areas.

The effort to bring about sustainable exploration and development will require an enhanced understanding of Arctic physical, ecological, social, political, and economic systems. The management of these Arctic systems will be accomplished through a matrix of local and national regulatory frameworks, international agreements and standards, and private sector technical operating standards that either currently exist or are to be developed (e.g., Holland-Bartels and Pierce, 2011). A common theme of these manage-

ment structures is that successful implementation is contingent upon the strength of the science upon which decisions and requirements are based.

Basing policies and practices on science then raises a debate as to the adequacy of information available to support certain development decisions. Conversely, it also raises a debate as to the adequacy and capability of policy frameworks to respond to the available information to support development decisions. A great deal has been done to obtain scientific knowledge about the various components of the Arctic system. As the utilization of the Arctic by indigenous peoples has formed a strong base of traditional knowledge, repeated waves of Arctic development, including commercial whaling in the 1800s, militarization in the mid to late 1900s, and oil and gas exploration of the late 1900s to early 2000s, have each driven associated expansion of research and knowledge of the Arctic (see Table 3.2). This research has helped industry to design operations for safety and environmental protection, government agencies to develop appropriate regulations to meet national expectations for careful practices, and Arctic communities to enhance self-determination and to determine how to harness economic development for lasting benefit.

At the same time, there is much yet to be learned about the Arctic in relation to economic development. The functioning of Arctic ecosystem and social-ecological systems lags behind our understanding of the components of those systems (Holland-Bartels and Pierce, 2011), limiting our ability to project how further changes will affect people and the environment. Resource development in the Arctic is occurring in a context of rapid and large-scale environmental (ABA, 2013; ACIA, 2005) and social change (AHDR, 2004), and assessing the extent, rate, and trajectories of such changes is essential to being able to evaluate how locally driven changes interact with globally driven ones. Increasing understanding of the cumulative impacts from resource development, including subtle impacts and those that increase over time, needs to be matched by a better understanding of the options for avoiding or mitigating those impacts. Finally, the use of scientific knowledge to achieve effective governance needs to be examined, to determine how science can best support sound decisions in recognition both of what we know and of what we do not know.

A number of key issues that may be related to development of the Arctic deserve specific mention. Whether it is related to increased shipping, increased size and development of communities, or oil and gas development, the potential for oil and other hazardous material spills is increasing in the Arctic. Oil-spill-related research ranges from the technical engineering side of strengthening prevention and intervention and the design of effective recovery technologies, to understanding the potential interplay between oil and Arctic biological resources and ecosystems and potential mitigation

and restoration measures. A carefully developed suite of research initiatives is needed to address each of these oil-spill-related topics from prevention to restoration. The NRC Committee on Responding to Oil Spills in Arctic Marine Environments recently covered this topic in much greater detail (NRC, 2014b).

The introduction of increased vessel traffic and industrial activities has the potential to produce sound-related impacts in an area that has heretofore been largely isolated from the general increase of sound in the world’s oceans. The relative increase

of sound levels above baseline and the implications to marine species and the use of these resources by subsistence communities is a key question of concern.

How Can We Prepare Forecasts and Scenarios to Meet Emerging Management Needs?

The Arctic environment—including its weather, snow conditions, and ice conditions—is changing rapidly. In addition, the scope and scale of human activity in the region

FIGURE 3.15 Exclusive Economic Zones in the Arctic Ocean.

TABLE 3.2 Historical Timeline Depicting the Evolution of U.S. Arctic Research Programs (Westlien, 2010).

are increasing. The result is that past experiences are not as reliable in predicting the future as they once were, at a time with an ever greater need for forecasts and scenarios from daily to decadal time frames. Development of both physical and economic forecasts and scenarios in collaboration with those who will use them can help meet the needs of those living and working in the Arctic. For example, improved forecasting capabilities can help save lives in rural communities. Many coastal communities in Alaska are dealing with changing weather patterns, and this has already impacted their ability to harvest traditional foods for themselves. Communities and their members have to take more risks in trying to provide food⁷ due to unpredictable weather, abnormal sea ice conditions, and animals shifting migration routes. Knowing the weather patterns is critical in this case for a community’s survival.

Specific forecast and scenario needs, including time frame and region, will vary by user. For example, hunters and fishers may want reliable daily to 3-day wind and visibility forecasts, whereas vessel captains or offshore oil rig managers may need ocean, weather, and ice forecasting over a 3-to-10-day time frame so that they can reroute a vessel or shut down an oil rig and evacuate the crew. Seasonal to annual forecasts are increasingly important for longer-term planning of logistics and personnel, and par-

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⁷ See http://aksik.org/village/savoonga.

ticularly important for staging of wildfire crews and supplies. As operations push into the shoulder seasons, forecasts are especially critical because the phase change from liquid to solid, and vice versa, impacts the viability of tundra travel and oil exploration, ice roads, ice platforms, shipping lanes, and more. In addition to projections of the natural Arctic system, longer-term community planning requires decadal projections and scenarios of key social indicators. Because of the implications for sea level rise and teleconnections to Northern Hemisphere weather, Arctic scenarios spanning 20, 50, and 100 years are of global interest to a wide range of users.

As the Arctic transitions toward less snow and ice, conditions are becoming more variable and harder to predict (Krupnik and Jolly, 2002). The improvement of operational weather forecasting will rely on an enhancement of the automated weather observation network, addition of Doppler radar (NEXRAD) stations, and improvements in forecast models. Training for weather forecasters needs to include Arctic phenomena. Open pack ice moves more quickly than consolidated sea ice, and there are shifts in the direction of ice movement as well (Pfirman et al., 2010a,b). Increased calving of marine glaciers produces increased iceberg hazards: 22 percent of the GrIS drains through marine-terminating glaciers (Nick et al., 2009). More traffic, and traffic in new regions, places more people and infrastructure at risk.

Better observations and models are also important to improve predictability for specific locations for explicit forecast lead times and seasons. Location-specific forecasts of sea ice distribution, thickness, and/or age are essential. Improving forecast skill will require a coordinated network of upper air, land, and ocean surface measurements, as well as model inter-comparison and sensitivity studies. Beyond the atmosphere and ice, forecasts for the ocean, permafrost, hydrology, and ecosystems, as well as warnings for storm surges and other hazards and extreme events (See Chapter 3, Emerging Question E4) are essential. Also needed are integrated ensemble forecast systems designed specifically for application to the Arctic, with high-resolution products that can be used for risk management and other decision making.

Turning to longer time frames, consideration of scenarios for the next 20, 50, and 100 years allows exploration of causes and effects. The IPCC (2013) and AMSA (Arctic Council, 2009) assessments have shown the value of scenario development in assessing trade-offs between proactive versus reactive choices and responses. Scenarios for the next 20 years may focus on potential resource development, and conflict/cooperation issues (see Chapter 3, Emerging Question M3). Industries and land/resource management agencies that need a 50- to 100-year planning horizon would need to address a new Arctic normal of changed plant and animal species, a mostly open Arctic Ocean, and changed Northern Hemisphere circulation patterns. Additionally, scenario analy-

ses will permit the consideration that the global community may act to address the causes of the current warming and recovery/restoration may be an emerging issue (see Chapter 3, Emerging Question M2). Just as with the shorter-term forecasts, different stakeholders with diverse perspectives will have a range of needs over the next century, and new unknowns will emerge from this analysis.

Forecasting and scenario development present opportunities for exploring public-private partnerships and for international cooperation. Currently, Arctic forecasting is occurring largely within the United States, Canada, Russia, and the European Union, with many inconsistencies in data-sharing protocols, data and forecast formatting, and forecast and warning language. Collaboration could provide mutual benefits to advance the field in general, while providing more valuable products to users throughout the world. Key research topics in this area include probing the limits of forecasting ability and connecting user needs with specific forecast products.

What Benefits and Risks Are Presented by Geoengineering and Other Large-Scale Technological Interventions to Prevent or Reduce Climate Change and Associated Impacts in the Arctic?

With the Arctic headed for long-term declines in glacier and sea ice, some have proposed turning toward geoengineering activities that would reduce ice loss or potentially even allow ice to be restored (MacCracken et al., 2013). Indeed, the Arctic may even be the impetus that sparks a global discussion of geoengineering. An emerging aspect of geoengineering is whether there are any strategies that could be applied to the Arctic alone. Further research would help us understand the implications of geoengineering in the Arctic.

Historically, two categories of activities have been discussed as geoengineering approaches (Figure 3.16): (1) carbon dioxide removal (CDR) techniques that aim to enhance the escape of longwave (thermal infrared) radiation and (2) albedo modification (commonly referred to in the literature as solar radiation management [SRM]) that seeks to counter indirectly the heating effects of anthropogenic climate change by deflecting shortwave (solar) radiation from entering the Earth system (Boucher and Randall, 2013; NRC, 2010). This second category is considered indirect because it does not seek to address the primary cause of anthropogenic climate change—increasing concentrations of carbon dioxide in the atmosphere—and thus does not address the biogeochemical effects of that carbon dioxide, such as ocean acidification.

Geoengineering has the potential for delivering both large societal benefits and significant natural and societal risks. Some CDR methods are well established and have

FIGURE 3.16 Summary of various carbon dioxide removal and solar radiation management geoengineering approaches. SOURCE: IPCC (2013), FAQ 7.3, Figure 1.

been commercialized on a small scale, such as afforestation and biofuel approaches. However, only limited research has been conducted to assess the technical feasibility and ecological impacts of many of the potential approaches in either category, particularly those that act on shorter timescales or larger spatial scales. Further, approaches that address regional problems, such as seeding clouds with sea salt to increase their brightness over Arctic ice (e.g., Caldeira and Wood, 2008; Wood and Ackerman, 2013), face limitations in our ability to understand and model key phenomena (Fyfe et al., 2013). Also, Tilmes et al. (2014) conclude that regional dimming has challenges in preserving sea ice under global warming, because the impact is largely counteracted by increasing northward heat transport as well as changes in Arctic clouds. Research that improves our understanding of the phenomena and interactions in this complex system, in the context of natural variability and a variety of forcings, is a critical compo-

nent of our ability to address key gaps in our understanding of the benefits and risks of geoengineering approaches.

A landmark study by the Royal Society of the United Kingdom made the recommendation to develop a code of practice for geoengineering research (Gardiner, 2011; Royal Society, 2009). A key contribution to the governance of research (including field testing), development, and any eventual deployment of geoengineering technologies was the “Oxford Principles” (Rayner et al., 2013). These principles state, in short, that geoengineering is a public good, which implies that public participation, open publication, and independent assessment are key elements of appropriate governance.

The NRC Committee on Geoengineering Climate: Technical Evaluation and Discussion of Impacts is currently conducting a technical evaluation of selected geoengineering techniques. This committee will be examining feasibility and potential environmental, economic, and national security impacts, as well as identifying future research needs. The committee will briefly explore societal and ethical considerations related to geoengineering. In this context, Arctic research would be useful in three areas of knowledge gaps in geoengineering approaches: (1) understanding of Arctic climate systems, particularly in the areas of cloud–radiation interactions, biogeochemistry, and Arctic teleconnections; (2) Arctic social, environmental, and economic studies that address technological effectiveness in the context of both actual and perceived risks to Arctic natural systems and peoples; and (3) the pragmatic implementation of ethics and governance principles under which research is conducted.

UNDETERMINED ARCTIC

Other important elements of the Arctic system remain hidden, not because they are physically inaccessible but because of our incomplete understanding of the system. These are the intriguing things we don’t know we don’t know.

Providing openings for “to be determined” questions is often implied in strategic assessments, acknowledging our inability to predict the future. Given the rapid pace of change in the Arctic, and the surprises encountered thus far, it is appropriate in this report to treat this category explicitly. As noted in Chapter 2, the only ways to prepare for what we do not know are to understand the system as best we can and to be positioned to detect and prepare to respond to changes and events.

This set of uncertainties requires at the same time that (1) we invest in the most fundamental and basic research, including exploration as well as hypothesis-driven research; comparison of models with observations; cross-scale experiments; research

at the interfaces of disciplines; understanding feedbacks and nonlinearities; investigation of outliers and extremes in the paleoclimate record; and creative, non-traditional approaches; (2) we invest in comprehensive monitoring systems; and (3) international funding, logistics, and governance frameworks are flexible enough to deploy resources on rapid timescales and appropriate locations. A research question in and of itself is how governments will structure their responses to the abrupt transitions, changes, and surprises that are sure to come in the future. These three elements are also questions related to the things we know we know and the things we know we don’t know.

The committee was tasked with exploring “how agency decision makers might balance their research programs and associated investments (e.g., balancing work done to respond to urgent global change concerns versus work to advance fundamental knowledge and discovery). In other words, what are some of the challenges of trying to do both problem-driven research and curiosity-driven research?” We do not see fundamental knowledge and discovery as a trade-off versus urgent global change research but, rather, as an investment in better preparing us for what the next urgent issue might be.

Similarly, although many view monitoring and long-term observations as a technical issue or something that can be cobbled together, the committee sees it as worth high-profile and comprehensive investment: monitoring and long-term observations are at the frontline of detecting the next big thing (Figure 3.17). As one example, the satellite record has been essential to the Arctic community because it provides a circumpolar perspective and a clear record of change, even over the short duration of the satellite era. Without investment in satellites, their sensors, and the technical and scientific capacity to make use of the resulting data, our understanding of the Arctic would be far poorer. The committee’s Statement of Task (see Box 1.1) requested that attention “be given to assessing needs where there may be a mismatch between rates of change and the pace of scientific research.” It is only by maintaining long-term observations that we have an ongoing way to know where to deploy resources on short notice, so that we can implement our research programs with this year’s situation in hand, not dependent on information from the last time a field program may have been in the area, which could have been as much as a decade ago.

Because much of the Arctic has been difficult to access, research has tended in the past to focus on the regions surrounding logistics hubs, with the result that scientific findings are concentrated in these areas. Logistics coordination and sharing can help overcome this obstacle. For example, the Fleet Arctic Operation Game report (Gray et al., 2011) analysis concluded, “In order to mitigate these challenges in the short term, the United States Navy should leverage DOD, industry and multinational logistics hubs

FIGURE 3.17 North Pole webcam image. SOURCE: NOAA.

and platforms. In the long term, the development of permanent infrastructure at the mid-point of a NWP transit capable of providing fuel to maritime assets was recommended.” (P. 18)

Creative new ways to crowd-source Arctic monitoring also need support,⁸ along the model of Google working with the Centers for Disease Control to collect information on the locations of people conducting online searches for flu symptoms, to give hospitals warnings for where the next flu outbreak is likely to be.⁹ For example, working with commercial interests, ground truthing data for satellite observations of sea ice conditions in marginal ice zones could be tracked with cruise ships and other ships of opportunity.

Ultimately, the ability to address questions that are as yet unknown will depend on a responsive community, from those identifying priority topics, to those conducting research, to those making funding decisions, to those setting research policies and investing in infrastructure. Trendy new ideas do not diminish the importance of crucial,

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⁸ See http://www.nature.com/news/crowdsourcing-may-open-up-ocean-science-1.13341.

⁹ See http://www.google.org/flutrends/us/#US.

established research needs. But neither should past practices limit the exploration of what is new or blind us to the possibility of surprise. This chapter presents many compelling and emerging research questions, but it cannot claim to provide a complete guide for new research areas for the next decade or two. Instead, it is a vivid demonstration of how much remains to be learned and of how often we need to look at the Arctic in a new way.

PRIORITY SETTING

Assigning priorities among the emerging research questions identified in this report inevitably involves a degree of subjectivity. Agencies have specific missions, which will align differently with the questions depending on their particular responsibilities. Depending on one’s location in the Arctic, priorities may differ according to specific local economic, environmental, cultural, political, and other conditions. Furthermore, the committee is unwilling to suggest that any of the emerging questions in this report is “low priority,” as all have come from extensive input from the research community and lengthy committee discussion. Addressing each question offers the promise of useful information or significant advances in knowledge. The committee was tasked “not to provide a literal ranking of research priorities but to provide some scale by which recipients of the report can better judge importance or time-relevance among the identified questions.” The committee therefore cannot assign priorities with confidence or rigor, and it instead suggests that such work be undertaken as part of a discussion among agency personnel, researchers, and (where appropriate) policy makers and other stakeholders.

The committee was also asked to “[e]xplore how agency decision makers might balance their research programs and associated investments (e.g., balancing work done to respond to urgent global change concerns versus work to advance fundamental knowledge and discovery). In other words, what are some of the challenges of trying to do both problem-driven research and curiosity-driven research?” Curiosity-driven research and problem-oriented research are often considered to be competing and even mutually exclusive approaches. This dichotomy is more a reflection of agency funding priorities and mechanisms than a fundamental property of the research enterprise itself.

In practice, our understanding of the Arctic benefits from both approaches, and the ability to act on Arctic matters requires insights from all points on the research spectrum. To demonstrate this, we plotted the emerging questions along time and basic versus applied axes (Figure 3.18a). The time-relevance axis (x-axis) is the degree to

which answers to each question could guide decisions being made now versus those likely to be made later. The other axis (y-axis) is the degree to which the answers will improve our basic understanding of the Arctic versus those that will have direct application to decisions and actions. The result is a fairly even distribution along both time and applications spectra, with questions largely falling along a line from “direct application, short-term” to “basic understanding, long-term.” This no doubt stems largely from the fact that we know what today’s pressing issues are, so we can ask pertinent questions to address short-term needs. For the longer term, it is easier to identify key areas of basic understanding that we expect will be relevant to tomorrow’s pressing issues.

Because this dichotomy between research on fundamental questions versus that on specific, urgent problems is misleading, we should not seek to identify an “optimal balance.” Nor are short-term questions necessarily more pressing than long-term ones, as addressing long-term needs often requires long-term action. It is more productive to think about the ways in which decision makers and communities can draw on the results of all types of research to find appropriate paths for action, and the innovative research that emerges when researchers direct their inquiry toward what decision makers need to know. Both approaches are necessary, and their respective importance is likely to vary by agency.

Similarly, the Arctic in the Anthropocene requires both natural and social scientific study in order to understand the phenomena and processes that define and shape it, as well as the “sustainability science” called for in the Statement of Task, which informs the decisions that lie ahead. Plotting the emerging questions along time-relevance (x-axis) and natural versus social science emphasis (y-axis) again reveals a relatively even spectrum in both directions (Figure 3.18b). Many short and medium term questions have a social science component, in part because of the rate of change and in part because investments have not been made in the social sciences to the same degree as the natural sciences. Social science research, including economic, cultural, and behavioral analysis, is clearly needed to provide lines of evidence for making decisions at individual and organizational levels about preparedness and how to live and work in the Arctic. Using the best available information can help improve wellbeing now and enhance our resilience to future shocks.

The emerging questions can also be arranged by spatial scale (y-axis) to highlight geographic scope (Figure 3.18c). As the section on the Connected Arctic demonstrated, what happens in the Arctic does not stay in the Arctic. The reverse is also true. The Arctic is interconnected with global social and economic systems as well as through atmospheric and oceanic transfers and terrestrial migration patterns. And within the

FIGURE 3.18 The emerging research questions are plotted with time relevance on the x-axis and (a) potential for contribution to basic knowledge versus direct application; (b) natural versus social science emphasis; and (c) local versus regional versus global geographic scope on the y-axis.

E1: Community futures. Will Arctic communities have greater or lesser influence on their futures?

E2: Wetter or drier. Will the land be wetter or drier, and what are the associated implications for surface water, energy balances, and ecosystems?

E3: Ocean variability. How much of the variability of the Arctic system is linked to ocean circulation?

E4: Arctic extremes. What are the impacts of extreme events in the new ice-reduced system?

E5: Primary productivity. How will primary productivity change with decreasing sea ice and snow cover?

E6: Species distribution. How will species distributions and associated ecosystem structure change with the evolving cryosphere?

H1: Icy surprises. What surprises are hidden within and beneath the ice?

H2: What is lost. What is being irretrievably lost as the Arctic changes?

H3: Winter. Why does winter matter?

H4: Break or brake. What can “break or brake” glaciers and ice sheets?

H5: Unusual warmth. How unusual is the current Arctic warmth?

H6: Abrupt change. What is the role of the Arctic in abrupt change?

H7: Cenozoic. What has been the Cenozoic evolution of the Arctic Ocean Basin?

C1: Jet stream. How will rapid Arctic warming change the jet stream and affect weather patterns in lower latitudes?

C2: Irreversible ice loss. What is the potential for a trajectory of irreversible loss of Arctic land ice, and how will its impact vary regionally?

C3: Ocean exchange. How will climate change affect exchanges between the Arctic Ocean and subpolar basins?

C4: Biota transport. How will Arctic change affect the long-range transport and persistence of biota?

C5: Social connections. How will changing societal connections between the Arctic and the rest of the world affect Arctic communities?

M1: Urbanization. How will decreasing populations in rural villages and increasing urbanization affect Arctic peoples and societies?

M2: Cooperation/Conflict. Will local, regional, and international relations in the Arctic move toward cooperation or conflict?

M3: 21st-century development. How can 21st-century development in the Arctic occur without compromising the environment or indigenous cultures while still benefiting global and Arctic inhabitants?

M4: Forecasts. How can we prepare forecasts and scenarios to meet emerging management needs?

M5: Geoengineering. What benefits and risks are presented by geoengineering and other large-scale technological interventions to prevent or reduce climate change and associated impacts in the Arctic?

Arctic, conditions are not uniform, both in terms of natural and social settings and also with respect to vulnerability to change. As highlighted in the first finding of the Polar Regions chapter of the 2014 IPCC report on Impacts, Adaptation, and Vulnerability, “The impacts of climate change, and the adaptations to it, exhibit strong spatial heterogeneity in the Polar Regions because of the high diversity of social systems, biophysical regions and associated drivers of change” (IPCC, 2014, p.2). Therefore priorities vary by location, discipline, and stakeholder representation.

A failure to address emerging questions in a timely fashion and with an appropriate suite of expertise may undermine our ability to mitigate and adapt to change by increasing the risk of:

(1)  making decisions based on faulty and/or outdated information (especially for those questions that have direct applications in the short term; Figure 3.18a),

(2)  pursuing inadequate understanding of important phenomena (especially for questions in the middle areas of Figure 3.18), and

(3)  laying an insufficient foundation for future research (especially for questions that lead to new basic understanding over the long term; Figure 3.18c).

Remaining open to questions and surprises that will emerge in the future enables crucial new insights to the way the Arctic physical, biological, and social systems work, enhancing society’s ability to attain the most benefit from Arctic research.

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Southeast coastline of Greenland between 62.5 and 65.5 degrees north. Photo credit: Perry Spector