A Strategic Vision for NSF Investments in Antarctic and Southern Ocean Research (2015)

CHAPTER TWO

Opportunities and Challenges of Antarctic and Southern Ocean Research

OVERVIEW OF THE BREADTH OF ANTARCTIC AND SOUTHERN OCEAN SCIENCE

Scientific research in the Antarctic and the Southern Ocean has always been, and remains, a challenging endeavor. Access to the major research bases requires specialized ships runways prepared on ice and aircraft equipped with skis. The information connectivity that one takes for granted in the United States remains very limited at Antarctic research bases. Working safely in the extreme environment of the deep field, or in the often stormy waters of the open ocean, remains challenging for both people and technology. Yet despite the difficulties and expense of working in these extreme environments, the research supported by NSF produces a wide array of important and exciting scientific advances. The unique nature of Antarctic and Southern Ocean research can be appreciated through many different disciplinary perspectives—from oceanographic to tectonic to microbial to astrophysical. Highlighted here are some examples of the exciting developments and new scientific questions that have emerged from the U.S. Antarctic Program (USAP) research in recent years.

An ice-covered continent. Ice covers all but about 2 percent of Antarctica, and in places it is over 4 km thick. The ice sheets first grew in Antarctica over 34 million years ago as the Drake Passage opened and global atmospheric carbon dioxide (CO₂) levels dropped below ~1,000 ppm (as a result of erosion and weathering of the huge area of raw rock emerging as the Himalaya Mountains). Together, the ice sheets in East and West Antarctica hold the largest reserve of freshwater on the planet that if fully melted is capable of raising sea level globally by nearly 60 m. While continental in scale, ice sheet flow speed and thickness are affected by the underlying rock and sediment, the temperature of the surrounding oceans, and input of new snow from the polar atmosphere. Advances in our understanding of this integrated system have come from both individual studies and major international collaborative programs. For instance, individual investigator analysis of records from seismometers and exposed landscapes led to an understanding of how large ice streams and outlet glaciers drain the ice from

the ice sheet interior toward the oceans, and how the movement of large icebergs is controlled by ocean tides. The large multinational collaborative framework provided by the International Polar Year led to the discovery of major subglacial water networks beneath Antarctica and their contributions to ice sheet dynamics. (See Figure 2.1.)

A tectonic keystone. Understanding the tectonics and geologic history of Antarctica is key to understanding continental assembly, to decoding how major species dispersed across the planet, to deciphering how the ice sheets have grown and collapsed in the past, and to understanding what controls the temperature of the base of the ice sheet and where it begins to flow fast. Twice the Antarctic continent has been at the center of a “supercontinent”—Rodinia over 1.2 billion years ago and Pangea 260 million years ago. The age and geochemistry of a boulder stranded at the edge of the ice (glacially transported from along the edge of the Transantarctic Mountains), provided strong evidence that Antarctica was adjacent to North America 1.2 billion years ago (Goodge et al., 2008). Marine sediments contain the record of how and when the ice sheet grew and have demonstrated how the ice sheet has collapsed many times in the past. Dating of the exposed rock and ancient deposits high in the Transantarctic Mountains have offered insights into past changes in atmospheric temperature and how the ice sheets and alpine glaciers responded to these changes. A large collaborative program that instrumented much of Antarctica with GPS instruments and seismometers (POLENET) found evidence for active volcanic systems beneath the West Antarctic Ice

FIGURE 2.1 Subglacial aquatic system. SOURCE: Zina Deretsky, NSF.

Sheet, and observed vertical motion of the Earth’s crust. Together with precise gravity measurements from the GRACE satellite, this has been crucial for quantifying the current rate of ice loss from Antarctica.

A frontier for exploration and discovery. Many of the places, processes, and ecosystems in Antarctica remain as unknown as other planets. The surface of Mars is known better than the topography beneath the Antarctic ice sheet and its floating ice shelves. The ocean cavities beneath Antarctica’s peripheral ice shelves in particular are critical environments where warming ocean water and ice meet, and yet are almost completely unmapped and unmeasured. However, a few well-framed hypothesis-driven expeditions to study and sample new locations have resulted in major scientific advances. A U.S.-led multinational program discovered that rapid changes occurred in the seafloor ecosystem along the east and west coasts of the Antarctic Peninsula following ice-shelf and fjord-ice collapse, thus demonstrating how sensitive polar ecosystems are to change. The Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) program has recently recovered the first samples from a subglacial lake and from the grounding zone beneath the Ross Ice Shelf (Christner et al., 2014).

Novel records of past change. Sediments under the Southern Ocean and the Antarctic ice sheets preserve unique records of how the climate and the ice sheets have changed in the past. Scientists studying sediment cores drilled from beneath the Ross Sea (see Box 2.1) discovered that in the past, the ice sheets have been highly sensitive to rapid melting when atmospheric CO₂ concentrations are close to present-day values (Naish et al., 2009). They also found evidence of a remarkably warm period in Antarctica 15.7 million years ago. The marine algae and woody plants whose fossils and pollens were recovered indicate summer land temperatures up to 10°C (50°F) and sea surface temperatures as warm as 11.5°C (53°F) (Warny et al., 2009). Even more remarkable is the discovery that coastal East Antarctica 50 million years ago supported dense near-tropical forests, wherein winters were warm enough to be frost-free (Pross et al., 2012). A deep ice core recovered from the center of the West Antarctic Ice Sheet has provided a high-resolution record of abrupt climate change. And evidence of dramatic changes in atmospheric composition, gathered from air bubbles recovered from the ice core points to rapid, widespread changes in climate that occurred as the Northern Hemisphere ice sheets collapsed.

Ecosystems at the edge. The opening of the Drake Passage initiated unrestricted circumpolar oceanic flow over 30 million years ago, and this Antarctic Circumpolar Current (ACC) formed a nearly impenetrable barrier that organisms could not cross. The sequestered Antarctic biotic survivors confronted subsequent episodes of major climatic transitions over the next several million years. Unable to flee elsewhere,

Antarctic organisms have had to contend with continual environmental challenges and extreme conditions. Microbial organisms living in Antarctic ice, rocks, soil, sediments, ocean waters, sea ice, lakes, meltwater ponds, and subglacial environments must adapt to extreme freezing and/or arid conditions, prolonged dark-light cycles, or complete absence of light. While the pace of evolution of most all Antarctic life is poorly understood, complex multicellular organisms are thought to be particularly vulnerable, thus limiting their diversity in Antarctica. At sea, the rich diversity of fish species present in earlier eras is survived today by a single predominant group, the Antarctic notothenioid fishes. Their ancestors evolved antifreeze proteins, discovered by U.S. polar biologists, that allow them to survive in the freezing Southern Ocean. More recent studies demonstrated that this protein is both an antifreeze and an antimelt protein, meaning that the lives of high-latitude fishes are a balancing act of avoiding freezing and avoiding tissue damage from internalized ice crystals that do not melt (see Box 2.2).

Land of weather extremes. Antarctica is the highest, coldest, windiest, and driest continent on Earth, and is linked with weather events elsewhere on the planet, over a variety of timescales. The highly reflective ice surface and long, dark winter lead to the formation of a cold, dense air layer adjacent to the surface, creating a continent-wide, gravity-driven airflow pattern known as katabatic winds. In some coastal regions this airflow layer converges to generate extremely persistent and intense winds, for example, at Cape Denison in Adélie Land, considered the windiest place on Earth (Wendler et al., 1997). The influence of the katabatic airflow reaches deep into the overlying atmosphere, anchoring a clockwise cyclonic circulation high above the ice sheet. Air rising from Southern Ocean storms close to Antarctica moves up and toward the center of this cyclone. As it cools radiatively, it sinks, sustaining the northward katabatic flow from the central plateau. This “polar direct cell” is a major feature of the large-scale atmospheric circulation of the Southern Hemisphere. As air moves upward and poleward, nearly all of its moisture is lost, leaving the high interior with little precipitation and few clouds, which intensifies cold air production. The temperature contrast between the cold Antarctic atmosphere and warmer regions to the north generates westerly winds over the Southern Ocean, whose variations have a profound impact on the formation of sea ice, generation of bottom water, air–sea exchange of CO₂, and climate variability across the Southern Hemisphere and many parts of the Northern Hemisphere.

Wind and currents in the Southern Ocean. The Antarctic Circumpolar Current (ACC), which is driven by the circumpolar westerly winds, plays a unique role in linking the Atlantic, Pacific, and Indian oceans (see Figure 2.2). Around Antarctica, Upper Circumpolar Deep Water derived from the ACC penetrates and interacts with the ice sheet margins, initiating more melt and rapid ice flow. The ACC itself is an important region for ocean mixing and air–sea exchange of heat and gases, including fluxes of CO₂ and dimethylsulfide. The ocean eddies and currents play a role in the formation and modification of many different water masses that link the region to the global thermohaline circulation. Antarctic Bottom Water forms close to the Antarctic coast, becoming a well-defined dense and cold water mass that fills the deepest basins of the global ocean. Studies indicate that because of climate change, this Antarctic Bottom Water has been warming and decreasing in volume over the past few decades, which could have major implications across the world’s oceans (Purkey and Johnson, 2012). With near-zero primary production on the Antarctic continent, the entire Southern Ocean ecosystem depends on nutrient- and sunlit-driven food production within sea ice and upper ocean waters, which are shaded by sea ice and mixed by currents and winds. Rapidly changing physical conditions are impacting Southern Ocean biogeochemistry and food supply, but the actual processes underlying these impacts remain mostly

FIGURE 2.2 Illustration of how Southern Ocean circulation is linked to global oceanic dynamics.
NADW = North Atlantic Deep Water; CDW = Circumpolar Deep Water; AABW = Antarctic Bottom Water.
SOURCE: Lumpkin and Speer (2007).

unstudied. New NSF-sponsored initiatives such as the Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project will greatly expand our understanding of such issues (see Box 2.3).

A world-class astrophysical laboratory. The South Pole offers an unparalled ground-based platform for studying the evolution and structure of the universe. The region’s dry and stable atmospheric conditions and uniformity of weather provide a critical advantage for astrophysics research that involves deep, large-scale observations at infrared, submillimeter, and millimeter wavelengths. For instance, the 10-m South Pole Telescope (SPT) and the BICEP and Keck telescopes are designed for observing the faint, diffuse emission from the cosmic microwave background, which provides a wealth of information about the origin and evolution of the universe. In 2002 the first detection of the polarization of the cosmic microwave background was made from

the South Pole (Kovac et al., 2002), and in 2013, the SPT made the first detection of B-mode polarization of the cosmic microwave background (Hanson et al., 2013). The IceCube Neutrino Observatory at the South Pole, encompassing a cubic kilometer of ice, searches for nearly massless subatomic particles called neutrinos. The IceCube team recently observed the first astrophysical high-energy neutrino detections (see Box 2.4).

INTRA- AND INTERAGENCY CONTEXT FOR NSF’S ANTARCTIC AND SOUTHERN OCEAN RESEARCH

Many of the research topics and activities carried out through NSF’s Antarctic and Southern Ocean research programs are inextricably linked to broader global-scale research questions. Several examples illustrate these linkages:

• The Southern Ocean waters surrounding Antarctica play a critical role in global oceanic circulation and in uptake of heat and CO₂ from the global atmosphere. Better quantifying atmosphere–ocean exchanges across the Southern Ocean will help us better understand global energy, heat, and chemical constituent budgets. Southern Ocean mixing processes also play critical roles in ocean biology, for instance, in the Antarctic Convergence Zone where cool Antarctic water encounters warmer subpolar waters. This is a region of mixing and upwelling, where high nutrient levels yield a rich ecosystem with bacterioplankton, phytoplankton krill, and other organisms that support higher trophic levels.
• Antarctic climate changes observed in recent decades, especially warming of the Antarctic Peninsula and across West Antarctica (e.g., Nicolas and Bromwich, 2014) are influenced by a number of long-distance atmospheric linkages known as “teleconnections” (see Figure 2.3). One major teleconnection is the interplay between the strengthening and poleward migration of the westerly winds over the Southern Ocean (which happens in the positive phase of a periodic variation known as the Southern Annular Mode [SAM]), and the El Niño-Southern Oscillation (ENSO) which arises in the tropical Pacific. The strengthening and migration of the winds has caused a slight cooling over most of the continent and warming of the northern Antarctic Peninsula. Over West Antarctica the influence of the shifting winds weakens, and the remote atmospheric effects of tropical atmospheric variations predominate. The tropical ENSO impact on West Antarctica is amplified when the SAM and ENSO oscillations are in phase with each other, and the impact is damped when the two oscillations are out of phase.
• Solar-terrestrial research informs scientific understanding of how short-term and longer-term variations in solar output affect Earth’s “space weather”

FIGURE 2.3 Map showing a deep low pressure system centered over the eastern Ross Sea on October 19, 2014. The system brought large amounts of warm marine air, clouds, and precipitation into West Antarctica. Arrows show wind flow and colors show wind speed in the middle part of the atmosphere. Data from ERA-Interim reanalysis. SOURCE: Julien Nicolas, Ohio State University.

and its climate variations over scales of decades to millennia. Because these solar influences affect the entire globe in complex patterns, monitoring such impacts requires globally distributed networks of observational equipment. (See Figure 2.4.) For instance, arrays of magnetic observatories are deployed at dozens of locations around the world, to investigate the dynamic variations of the field produced by the changing electrical current systems in the magnetosphere and ionosphere. The polar regions, and Antarctica in particular, are particularly critical nodes in these networks, and these Antarctic-based observational sites would be much less valuable if not planned and utilized as part of the broader global networks.

FIGURE 2.4 Illustration of the coupled atmosphere–ionosphere–magnetosphere system and processes that control dynamics across the system. SOURCE: J. Grebowsky, NASA/GSFC.

• Cosmic microwave background studies and the IceCube Neutrino Observatory at the South Pole are key experiments in multiagency, multinational efforts to understand the fundamental workings of time and space, and the origin and evolution of the universe. These experiments complement work being done around the world, in high-energy physics collider experiments, dark matter searches, large surveys of the sky across the electromagnetic and particle spectra using ground-based, balloon-based, and satellite platforms.

NSF/PLR research focuses on the region poleward of 60°S latitude, but the ocean, the atmosphere, and the energetic particles reaching Earth from outer space do not recognize such boundaries, as the examples listed above help illustrate. For this reason, PLR research overlaps with key topics of interest to other divisions in NSF’s Directorates for Geosciences, Biological Sciences, and Mathematical and Physical Sciences. A variety of cross-divisional research support opportunities do exist, but there are some contexts in which bureaucratic divisions within NSF can act as a barrier to advancing

critical integrative research and observations. Some key opportunities to overcome these barriers are discussed in Chapter 4.

Collaboration with other U.S. federal agencies is likewise critical for advancing Antarctic and Southern Ocean research, given the costs and challenges of gaining logistical access to the region, and NSF’s essential role in facilitating this access. Although the Committee was tasked to advise strategic priorities just for NSF, there are, of course, other U.S. federal agencies that play important roles in the USAP. Some examples include:

• NASA’s Operation IceBridge utilizes research aircraft equipped with monitoring instruments to characterize annual changes in thickness of sea ice, glaciers, and ice sheets. IceBridge fills a gap in polar observing needs until launch of the ICESat-2 satellite.
• NASA’s Long-Duration Balloon Program (with logistical support from NSF) uses large unmanned helium balloons to provide an inexpensive means to place payloads into a space environment, taking advantage of the unique atmospheric circulation over Antarctica. This helps in the development of new technologies for NASA’s spaceflight missions and enables important scientific observations in fields such as x-ray/gamma-ray, infrared, and submillimeter-wave astronomy; cosmic rays; and upper atmospheric studies.
• NOAA’s Global Monitoring Division operates an Atmospheric Research Observatory at the South Pole, as part of an extensive global network of sites where air samples are collected weekly and analyzed for greenhouse gases, halo-carbons, stable isotope tracers, and volatile organic compounds. The South Pole site also collects in situ observations of aerosols, radiation, and surface and column ozone. These data help us understand long-term trends, seasonal variability, and spatial distribution of key atmospheric constituents.
• NOAA’s Antarctic Ecosystem Research Division oversees the Antarctic Marine Living Resources Program, which does research that contributes to ecosystem-based management of fisheries that impact krill, finfishes, krill-dependent predators, and other components of the Antarctic ecosystem. This program supports the U.S. contribution to the Commission for the Conservation of Antarctic Marine Living Resources.
• DOE’s Climate–Ocean–Sea Ice Modeling project develops high-performance, multiscale models of the ocean, sea ice, ice sheets, and the ocean and cryosphere components of the Community Earth System Model and Accelerated Climate Model for Energy. The goal is to improve modeling of high-latitude climate change and its impacts on ice sheets, sea level rise, sea ice changes, Southern Ocean circulation, and high-latitude ocean–ice ecosystems.

• DOE’s Lawrence Berkeley National Laboratory has been an essential contributor in designing and developing the neutrino detectors used in IceCube. Berkeley Lab’s National Energy Research Scientific Computing Center also contributes its supercomputing power to filtering the signals and analyzing the data from IceCube as well as processing the data from the 10-m South Pole Telescope.
• DOE, NASA, and the National Institute of Standards and Technology have contributed to the development of the superconducting bolometric detector arrays used on cosmic microwave background cameras deployed to the South Pole. DOE Office of Science will likely be a major contributor with NSF to the next-generation ground-based cosmic microwave background program.
• DOE’S Atmospheric Radiation and Monitoring (ARM) program is supporting, in conjunction with NSF, the ARM West Antarctic Radiation Experiment to study Antarctic clouds, which are poorly characterized in climate and weather prediction models. The effort will operate at McMurdo Station for 1 year and for a few summer months in West Antarctica, and related efforts may later be carried out over the Southern Ocean.
• The U.S. Geological Survey (USGS) has worked in Antarctica for over 60 years, starting in 1947 with geophysical and geologic surveys and in 1957 with topographic mapping. More recently, the USGS has been involved in marine, airborne, and satellite studies, as well as mapping and coring of the ice sheet; and, working jointly with NSF, the USGS oversaw the U.S. Antarctic Resource Center—the nation’s most comprehensive international collection of Antarctic aerial photography, maps, charts, satellite imagery, and technical reports.

The research and monitoring efforts of these other agencies are often linked to, and sometimes directly contribute to, NSF-sponsored research. As discussed in Chapter 4, the community engagement discussions point to a variety of ways in which interagency cooperative efforts could be expanded to better leverage resources toward reaching USAP research goals.

INTERNATIONAL COLLABORATION IN ANTARCTIC AND SOUTHERN OCEAN RESEARCH

Antarctica is the only continent on Earth set aside just for international cooperative science, and international cooperation in scientific research is a cornerstone of the Antarctic Treaty System. At present, 30 nations have Antarctic-based research facilities (see Figure 2.5). The NSF has a long history of leading, engaging in, and supporting international collaborative research in Antarctica. A few illustrative examples are:

FIGURE 2.5 Top: Countries that have one or more research stations in Antarctica. SOURCE: Wikipedia. Bottom: All countries’ Antarctic research stations. SOURCE: Australian Antarctic Data Centre.

• International research dating back to the International Geophysical Year 1957-1958 led to the remarkable discovery that the Antarctic ice sheet is more than 2 miles thick.
• Our fundamental understanding that global climate change, temperature, and pCO₂ levels have moved together over the past 800,000 years was a result of pioneering ice core research at Vostok Station, jointly supported by the United States, Russia, and France, and of the European Project for Ice Coring in Antarctica (EPICA).
• NSF collaborated closely with New Zealand, Italy, and Germany in the ANDRILL project to recover cores that demonstrated the rapid collapse of the West Antarctic Ice Sheet many times in the past 5 million years.
• During the 2007-2008 International Polar Year, a seven-nation team of scientists led by the United States surveyed the largest unexplored mountain range on the planet (hidden by the ice) and discovered new dynamical processes at the base of the ice sheet.
• The Polar Earth Observing Network (POLENET), which collects GPS and seismic data from autonomous observing systems across the Antarctic ice sheets, has been supported by participation by or contributions from 28 nations.
• The IceCube detector that recently made groundbreaking observations of astrophysical neutrinos involves collaborators from institutions in 12 countries, with significant additions to U.S. funding support coming from Belgium, Germany, Japan, and Sweden.

NSF and the U.S. research community have also been participating in recent international efforts to improve observations and understanding of the Southern Ocean. For instance:

• The Southern Ocean Observing System seeks to coordinate and expand the efforts of all nations that gather data from the Southern Ocean, with the specific aim of developing a coherent and efficient observing system that will deliver the observations required to address key scientific and societal challenges.
• The World Climate Research Program’s Climate and Ocean: Variability, Predictability and Change (CLIVAR) Program hopes to expand the Argo profiling float program with additional sensors and floats capable of working under the ice, and enhancing observations such as subsurface moored arrays, mobile platforms such as gliders and wave gliders, biogeochemical floats, moored biogeochemical observations, and the establishment of crucial under-ice acoustic tracking of floats, gliders, and other autonomous underwater vehicles.
• The Global Ocean Ship-Based Hydrographic Investigations Program (GO-SHIP) is an international program that reoccupies basinwide ocean sections on

decadal timescales for hydrographic and biochemical studies. A number of GO-SHIP transects go through the Southern Ocean and/or terminate at the Antarctic coast. Several nations use their ships that resupply Antarctic bases to also collect temperature and salinity profiles and observations of ocean currents and surface meteorology and air–sea fluxes.

• The NSF’s Ocean Observatories Initiative has deployed two Southern Hemisphere ocean observatories, at 55°S/90°W and at 42°S/42°W. Each site has four moorings, including a surface mooring and up to five ocean gliders, multidisciplinary instrumentation, and capacity to add more sensors. These observatories provide opportunities for collaborative studies with observatories being established by other nations (e.g., the Australian Integrated Marine Observing System’s surface mooring south of Tasmania; the Japanese Science and Technology Agency surface mooring near the Antarctic coast). They also provide important contributions to the Global Climate Observing System, the Global Ocean Observing System, and other international efforts to develop a global array of sustained ocean observing sites.

The specific mode of international cooperation supported by NSF varies widely—from informal collaboration between individual scientists, to formal proposal calls that specifically outline the need for international partnerships. For instance, during the International Polar Year 2007-2008 the NSF funding call required international collaboration and robust scientific partnerships. For some large programs, NSF program managers led the process of convening international peer review panels and negotiating subsequent cost-sharing and proportional scientific participation.

U.S. marine scientists have long enjoyed opportunities to sail on other nations’ Antarctic research vessels either as part of official joint projects, or as “ships of opportunity” when individual scientists work with international collaborators. For instance, numerous U.S. scientists have pursued NSF-funded research on board the German research icebreaker Polarstern. Some countries, such as South Korea, fund U.S. scientists to join their sponsored programs. In turn, U.S. Southern Ocean projects often include overseas participants. For instance, International Ocean Discovery Program drilling proposals for the Southern Ocean are always reviewed by an international panel of experts, and U.S. funding to operate the vessel is comingled with contributions from over 25 nations. There is potential for expanding coordination in use of the various national ships for underway meteorological and oceanographic sampling, for deployment of drifters, floats, and gliders; and possibly for establishing mooring sites along ship transits.

The United States also has a long history of international collaboration in logistical support for Antarctic and Southern Ocean research. NSF has worked extensively with New Zealand and Italy in the western Ross Sea, has collaborated on several occasions with Argentina and Chile in studies along the Antarctic Peninsula, and is developing relationships with South Korea and China as these nations establish new bases in Terra Nova Bay close to McMurdo. The British Antarctic Survey has been a close partner with NSF in projects from the difficult-to-access Amundsen Sea and deep interior of East Antarctica, to the western Antarctic Peninsula where they are a formal partner in NSF’s Palmer LTER (Long Term Ecological Research) program.

The United States was a driving force behind the creation of the Antarctic Treaty and continues to support Treaty System activities, including COMNAP (Council of Managers of National Antarctic Programs) and SCAR (Scientific Committee for Antarctic Research). A large number of U.S. scientists participate and play leadership roles in SCAR activities and projects. These activities, as well as the relationships that have developed through alliances in SCAR, mean the United States is well positioned to play a leadership role in further developing international scientific and logistical cooperation.

Antarctica remains one of the most challenging places on Earth to work, and many research efforts remain beyond the scope of any single nation. International collaboration will continue to be critical for making new advances, and sharing expenses across multiple national funding entities increases the probability of implementing large programs. Specific needs and opportunities for expanding international cooperation are discussed further in the following chapters.

STRATEGIC FRAMEWORK FOR NSF INVESTMENTS IN ANTARCTIC AND SOUTHERN OCEAN RESEARCH

In considering all the factors that make research in the Antarctic and Southern Ocean such a unique and challenging endeavor, the Committee developed a conceptual vision of the major components that make up a robust U.S. Antarctic Program. It includes three major components:

• A broad-based program that supports curiosity-based research driven by proposals from Principal Investigators (PIs) across all major areas of Antarctic and Southern Ocean science—currently organized under six main PLR Antarctic science programs.
• A small number of high-priority larger-scale research initiatives that address particularly compelling scientific questions poised for significant advance within the next decade, but which are beyond the scope of a single PI-led

project. These require a coordinated effort, resource commitment, and targeted, upgraded logistical support.

• A set of foundational elements that enable, support, and add value to all research activities. These include, for example,
  • — Core logistical infrastructure needs (e.g., vessels and aircraft) in support of access to research sites; and continued maintenance and improvement of science support items such as laboratory facilities and data transmission capacities;
  • — Maintenance of strategic observational efforts, including NSF leadership in coordinating and expanding international and interagency activities;
  • — Comprehensive management of Antarctic research data, and active education and public outreach efforts—both of which can significantly expand the return on investment for all PLR research activities.

The next chapter discusses the first two of these components, including our recommendations for the high-priority, large-scale research initiatives. Chapter 4 addresses the last component (the foundational elements), with recommendations for what is most needed to support the priority research areas, and to be well positioned to respond to innovative new directions in any aspect of Antarctic and Southern Ocean science.

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