The ocean is an integral component of the Earth’s climate system. It covers about 70 percent of the Earth’s surface and acts as its primary reservoir of heat and carbon, absorbing over 90 percent of the surplus heat and about 30 percent of the carbon dioxide (CO2) associated with human activities, and receiving close to 100 percent of fresh water lost from land ice. Heat and CO2 are absorbed at the ocean’s surface and transported throughout the ocean depths through the overturning circulation. Although exchange across the ocean’s turbulent surface boundary layer can happen rapidly, in hours or days, and significant exchange of water between the boundary layer and the stratified main thermocline occurs over timescales of years to decades, deep water takes many decades to millennia to return to the surface, acting as long-term storage for heat and CO2 and thereby lessening the near-term impacts of climate change. Because of the long timescales governing the exchange of heat, carbon, and fresh water in the ocean, long-term observational datasets spanning many decades are required to fully document, understand, and predict the climate system, and to detect and attribute changes driven by human activities.
VALUE OF SUSTAINED OBSERVATIONS
With the accumulation of greenhouse gases in the atmosphere, notably CO2 from fossil fuel combustion, the Earth’s climate is now changing more rapidly than at any time since the advent of human societies. Society will increasingly face complex decisions about how to mitigate the adverse impacts of climate change such as droughts, sea-level rise, ocean acidification, species loss, changes to growing seasons, and stronger and possibly more frequent storms. To
make informed decisions, policy makers will need information that depends on understanding the dynamics of the planet’s climate system. Because these dynamics will evolve as the climate warms, the ability to anticipate and predict future climate change will depend on ongoing observations of key climate parameters to tune and enhance models. Observations play a foundational role in documenting the state and variability of components of the climate system and facilitating climate prediction and scenario development. Regular and consistent collection of ocean observations over decades to centuries would monitor the Earth’s main reservoirs of heat, CO2, and water and provides a critical record of long-term change and variability over multiple timescales. Sustained high-quality observations (described in Box S.1) are also needed to test and improve climate models, which provide insights into the future climate system. With knowledge gained through these observations and models, more informed decisions can be made about how to respond and adapt to the impacts of climate change on national security, the economy, and society.
STUDY TASK AND APPROACH
This study committee was charged with considering processes for identifying priority ocean observations that will improve understanding of the Earth’s climate processes, and the challenges associated with sustaining these observations over long time frames (see Box S.2 for the Statement of Task). International bodies, the Global Climate Observing System (GCOS) and the Global Ocean Observing
System (GOOS), established to coordinate observing activities among nations have developed processes for identifying and developing specifications for the highest priority ocean climate observations. The committee reviewed these processes and determined that they represent a robust approach to identifying Essential Climate Variables (ECVs) and Essential Ocean Variables (EOVs) and the requirements for observing these variables. Recognizing the value of this international consensus process, the committee focused its attention on the “challenges to maintaining long-term observations and suggest[ing] avenues for potential improvement.” These challenges are described in this report and conclusions addressing approaches for overcoming these challenges are provided.
The Statement of Task directed the committee to focus on ocean observations for climate; hence the work of the committee considered the priority variables that are most needed to address the ocean’s role in climate. However, the committee recognizes that there are important ocean variables to observe outside of the scope of this study, such as observations of shorter term phenomena and of the impacts of a changing climate on ecosystems.
HEAT, CARBON, AND FRESH WATER BUDGETS
This report identifies three distinct global budgets that help define critical observations for understanding climate: heat, carbon, and fresh water. These were selected because of the central role the ocean plays in each and for their ability to inform climate model projections and detect changes within the climate system. Ocean observations have contributed to vital insights into changes in these budgets and informed understanding of other related ocean changes, such as sea-level rise. Uninterrupted time series of observations are required to distinguish natural variability of ocean processes from changing long-term climate trends. Although ocean general circulation models employ data assimilation methods to estimate the state of the ocean and provide quantitative estimates of how well the observations constrain these budgets, closing these budgets will require extension of ocean climate observations to the full depth of the ocean and into poorly sampled regions such as the polar seas. Additional research will be needed to develop the advanced observing capabilities needed to quantify the full suite of processes contributing to each budget.
Ocean warming accounts for about 90 percent of the net global surface heat gain. Hence, accurate estimates of ocean heat content provide a fundamental index of the present climate system that also will be a determinant of future global surface warming as ocean circulation returns heat stored in the depths to the sea surface. Because heat absorbed by surface ocean waters is transported laterally and vertically through the depth layers and basins of the ocean via mixing and currents, there is no single variable that can be measured to determine ocean warming. On a regional basis, closure of the heat budget requires observations of ocean heat content, air-sea heat exchange, heat transport by ocean currents, and mixing, whereas the global balance is between the global integrals of heat gain and air-sea flux. The challenges for measuring temperature in the ocean (as a measure of heat content) have been to sufficiently sample spatially (across the global extent and full depth of the ocean) and frequently enough to account for the temperature variability induced by global ocean circulation, air-sea fluxes, and mixing.
About 30 percent of the CO2 released by human activities has been absorbed by the ocean, reducing the amount in the atmosphere and the associated greenhouse effect. However, dissolved CO2 becomes a weak acid that lowers the pH of sea water, a phenomenon termed ocean acidification, which will limit the capacity of the ocean to absorb more CO2 in the future and can have negative effects on marine life. Other carbon sinks exist in the ocean, but the dissolution of CO2 from the atmosphere is by far the main ocean carbon sink on a decadal-to-century time frame. Closure of the carbon budget requires measurement of either surface water partial pressure of CO2 (pCO2) or pH, total dissolved CO2 and alkalinity.
Fresh Water Budget
The fresh water budget is important for understanding changes in the salinity of the ocean, a parameter that influences ocean circulation due to stratification, and therefore heat and carbon exchange between the ocean surface and the atmosphere. Ocean salinity is a measure of the salt content of sea water; it is decreased by dilution (through fresh water input from precipitation, river outflows and surface runoff, or ice melt) and increased by evaporation. Evaluation of the fresh water budget requires observations of salinity, temperature, sea ice, velocity, and mixing within the ocean, and the fluxes of fresh water into and out of the ocean in the form of precipitation, continental and ice sheet runoff, and evaporation.
Sea Level Reflects Heat and Budgets
Sea-level rise, one of the leading indicators of a warming climate, will have major impacts on coastal communities and economies, affecting shipping, national and homeland security, tourism, and other valuable societal activities. The ocean heat content provides estimates of rates of thermosteric sea-level rise, the rise in sea level caused by the expansion of the ocean as it absorbs increasing amounts of heat. The net fresh water input to the ocean, which increases when higher temperatures cause land ice to melt and run off into the ocean, is the other major contribution. To assess these components of the heat and fresh water budgets, in situ measurements of temperature and salinity are needed throughout the water column. Moreover, ocean current observations are required to evaluate the transport of heat and salt and their effects on regional sea level. Refining the calculations of these budgets based on a comprehensive set of in situ measurements will advance our understanding of global and regional sea-level change, which is essential for assessing risks to coastal communities and infrastructure in the United States, and to low-lying regions worldwide.
Progress Achieved by Ocean Observations
For each of these budgets and for projections of sea-level change, significant progress has been made through the development of sustained global ocean observing, with synoptic coverage of some ocean properties from satellite remote sensing, and in situ sampling by the global array of profiling floats, repeat sampling from ships along lines that cross the ocean basins, collection of long time series at fixed sites using moorings, and other methods. We do not yet directly measure all the processes involved in the heat, carbon, and fresh water budgets, and full closure of these budgets remains a scientific and technical challenge. The ability to close these budgets will be aided by expansion of observations into poorly sampled regions, by the development of methods to quantify as yet unmeasured processes, and by the deployment of new sensors to sample biogeochemical properties and aid investigation of the carbon budget. Further, it is likely that with time, new scientific targets will mature as drivers for sustained ocean observing and require assessment of new priorities.
Finding: The current ocean observing system has made significant contributions to better understanding the ocean’s role in the Earth system, including its heat, carbon, and fresh water budgets, and to better understanding global and regional sea-level change. Sustaining, optimizing, and increasing ocean observing capability will further improve understanding of the ocean’s role in climate.
BENEFITS OF OCEAN OBSERVATIONS BEYOND CLIMATE
A sustained suite of ocean climate observations will yield a better understanding of future changes in Earth’s climate and also benefit many other shorter term interests of science, commerce, and human safety. Modern weather forecasting relies on the same satellites and in situ measurements used for observing the ocean for climate. Increasingly, observations of ocean temperatures, patterns of sea surface temperature, and even sea-ice extent are used with models to reliably forecast hurricane intensities and tracks as well as seasonal precipitation and storminess. Tide gauges that provide information on sea-level rise are also used to track changes in water level resulting from storms and assess the potential for coastal inundation. Sustained ocean observations are critical for monitoring changes to the environmental conditions that may impact marine life such as coral reefs and commercially important fisheries and aquaculture.
Finding: The ocean observing system contributes not only to our understanding of climate variability and change, but also to a wide variety of other services including weather and seasonal-to-interannual forecasting, living marine resource management, and marine navigation. This understanding of climate variability and change and other services underpins national defense, economic, and social policy decisions.
PRIORITY OCEAN OBSERVATIONS
The Global Climate Observing System
Due to the global nature of climate observations, international frameworks have been developed through GCOS that establish observing requirements for adequate sampling resolution, long-term coordination, data sharing, and capacity building. This vital early step in global climate observing was established with the goal of providing comprehensive information on the total climate system, involving a multidisciplinary range of physical, chemical, and biological properties, and atmospheric, oceanic, hydrological, cryospheric, and terrestrial processes. GCOS has a process for developing implementation plans to articulate and address what have been identified as the ECVs to measure across the entire Earth system.
The Global Ocean Observing System
The GOOS program arose to meet research and operational requirements for internationally coordinated networks of both in situ and remote ocean observing platforms. Similar to GCOS’s ECVs, expert panels have developed the EOVs, which are judged by the international community to be the priority variables to be observed in the ocean, with overlap between the ECVs and EOVs in the area of ocean climate. There is a rigorous structure in place for these expert panels to develop technical standards for the sampling requirements of the EOVs. The process of identifying EOVs is ongoing; as scientific and societal needs evolve and as the readiness and feasibility of observing specific variables advances, the expert panels will update their assessments and EOV lists will change. GOOS developed the Framework for Ocean Observing, which articulates the requirements and technical readiness of a multidisciplinary ocean observing system to meet both scientific and societal needs. GOOS utilizes this framework to guide implementation of an integrated and sustained ocean observing system by identifying the science requirements for addressing societal issues, the types of observations they require, and deployment and maintenance needed for the production of impactful and relevant information to address those issues.
Finding: The GOOS efforts are effective at promoting international cooperation to sustain the ocean climate observing system. Its guiding document, the Framework for Ocean Observing, and the associated procedures for establishing priority observation—the Essential Ocean Variables—are constructive for defining ongoing requirements (precision, frequency, spatial resolution) for sustained ocean observations and provide a solid foundation for selecting and prioritizing ocean variables for sustained observing.
The GOOS is coordinated internationally, with significant contributions from the United States. There have been agreements with other nations for specific contributions, such as for the Tropical Pacific Observing System. The Joint Technical Commission on Oceanography and Marine Meteorology provides coordination to both oversee and guide global ocean observing and to provide a forum for increasing observing capacity through enrollment of new nations and capacity building.
Finding: Opportunities exist to increase the spatial coverage and multidisciplinary nature of sustained ocean observations through U.S./international (either bilateral or multilateral) coordination and sharing of resources.
Finding: Capacity building enhances international support for the sustained ocean observing system and is valuable for increasing international use of the information and sharing of observing responsibilities.
During the course of its work, the committee identified many challenges to building and sustaining the essential elements of an ocean observing system for climate. These challenges encompass coordination among both intergovernmental organizations and U.S. federal agencies, national priority setting and planning, provision of stable funding, workforce support and training, and observing infrastructure and technology development. A description of the current status and the remaining challenges is summarized below.
INTERNATIONAL COORDINATION CHALLENGE
GOOS provides the framework under which nations can plan and prioritize their ocean observing activities. Although GOOS does not provide a mechanism for sustaining national commitments, this international coordination and cooperation for ocean observing is generally considered to be effective. However, the issue of access within Exclusive Economic Zones (EEZs) for deploying observing system elements, or for the drift of mobile platforms such as Argo floats, remains a challenge and can act as a disincentive to deploy in some regions of the global ocean. About 30 percent of the area of the global ocean lies inside the EEZs of coastal nations or within other maritime zones such as the region governed by the Antarctic Treaty System, and it is critical for a global ocean observing system to maintain instruments deployed inside EEZ boundaries and those drifting across them.
Conclusion on International Cooperation: The Global Ocean Observing System organization has effectively engaged countries and built capacity for this global enterprise for ocean climate observing. A challenge remains in obtaining
global access to national EEZs for drifting platforms which could be addressed by the National Ocean Research Leadership Council.
NATIONAL PRIORITY SETTING
Within the United States, federal agencies engage in the intergovernmental negotiations at the international level, and are the primary supporters of ocean observing activities through funding for research, technology, and operations. This includes building and maintaining the research fleet needed for equipment deployment, maintenance, and operations; conducting research through federal laboratories and operational programs; and serving as coordinators on the international stage. These U.S. investments contribute to the international program, but with the knowledge gained through ocean observing, national issues related to the economy, society, and national security can also be addressed. Oceanographic institutions also operate a significant portion of the observing system with support from federal grants, and conduct research that contributes to the state of knowledge of the ocean and its role in climate change. Some philanthropic and nonprofit organizations provide funding for ocean conservation research and technological development.
Finding: Raising awareness of the importance and value of sustained ocean climate observations could increase support for the observing system from multiple sectors, including philanthropic organizations.
The primary U.S. federal agencies that contribute to ocean observing are the National Oceanic and Atmospheric Administration (NOAA), the National Science Foundation (NSF), and the National Aeronautics and Space Administration, with additional support for technology development from the Office of Naval Research (ONR). Federal activities among these agencies and others are coordinated through an array of interagency working groups under the National Science and Technology Council. The National Ocean Research Leadership Council (NORLC), established by the National Oceanographic Partnership Act in 1996 (P.L. 104-201), is organized within this structure and is charged with promoting partnerships to strengthen ocean observing, research, and education. The Subcommittee on Ocean Science and Technology, co-chaired by representatives from NOAA, NSF, and the White House Office of Science and Technology Policy, oversees the Interagency Ocean Observation Committee (IOOC), which was established under the Integrated Coastal and Ocean Observation System (ICOOS) Act of 2009 (P.L. 111-11) to “advise, assist and make recommendations on matters related to ocean observations.”
NATIONAL COORDINATION, PLANNING, AND FUNDING CHALLENGE
Although the interagency bodies described above have responsibilities to coordinate activities associated with ocean climate observing, the committee has not been able to identify a clear national leadership position for this intersection of ocean, climate, and observing. Neither has the committee been able to identify a national plan to sustain and expand this critical ocean observing system for climate change. Although Congress recognized the need for sustained ocean observations in the ICOOS Act, the annual budgets have not matched the costs of sustaining the current system in terms of workforce, infrastructure, and data management. The absence of an overarching long-term (e.g., 10-year) national plan with associated resource commitments and lack of strong leadership presents a challenge for sustaining U.S. contributions to ocean observing, by inhibiting effective coordination and multiyear investments in the many components of the observing system.
Finding: The continuity of ocean observations is essential for gaining an accurate understanding of the climate. Funding mechanisms that rely on annual budget approval or short-term grants may result in discontinuity of ocean climate measurements, reducing the value of the observations made to date and in the future.
Conclusion on Planning: Because of the extended time frame required for climate observations, a decadal plan for the U.S. ocean observing system would be the most effective approach for ensuring that critical ocean information is available to understand future climate. Consistency of the decadal plan with the Framework for Ocean Observing would optimize U.S. investments relative to contributions of the international community, with plan updates likely required to align with international activities during the 10-year period. Elements of a decadal plan include identification of requirements, assessment of the adequacy of the current system, components to be deployed over the 10-year period, potential for technological advancements, and an estimate of resources necessary to implement the plan. The National Ocean Research Leadership Council (NORLC) has the mandate under the ICOOS Act to oversee development and adoption of a long-term plan and NORLC could be responsible for its periodic assessment and update, possibly utilizing the IOOC and the Ocean Research Advisory Panel. Progress in implementing the plan would depend on the engagement of the broader stakeholder community and coordination with international partners in the global ocean observing system.
Conclusion on Partnership: An Ocean–Climate Partnership (OCP) organization described further in Chapter 5 would be an effective mechanism to increase engagement and coordination of the ocean observation science community with
nonprofits, philanthropic organizations, academia, U.S. federal agencies, and the commercial sector. Through their shared interests in the observational data and associated products, the OCP members could work together toward the goal of sustaining the ocean climate observing system.
Much of the in situ ocean observing system is operated by academic and government research institutions and the experts they employ. Research institutions and their funding sources place a high priority on peer-reviewed, original research, with consequent attention to the value and quality of the observations. The observing system elements that have deep roots in research laboratories and that are led by scientists who are also supported to utilize the data from the observing system have demonstrably high success.
Finding: Direct scientific involvement in sustained observing programs, from design to implementation to analysis, synthesis, and publication, ensures that the ocean observing system will be robust in terms of data quality, incorporation of new methods and technologies, and scientific analyses; all are essential elements for realizing the value of long-term, sustained observations.
For individual scientists, starting up and implementing an ocean observation activity is time-consuming and may be difficult without substantial institutional support and guarantees of long-term funding. By its very nature, observational science typically requires years of data collection before results are publishable. This acts as a disincentive for early-career scientists contemplating participation in ocean observing activities beyond utilization of existing datasets. The long-term investment required to develop and sustain the necessary expert workforce of the future is a challenge due to limited professional rewards or career incentives at research institutions and laboratories to ensure intergenerational succession of scientists, engineers, and technical staff. Success to date in the development, deployment, and operation of ocean observing infrastructure has been enabled by a relatively small but dedicated group of scientists and other professionals who have devoted their careers to this activity, even though the long-term nature of the research is typically not rewarded in the academic community.
Conclusion on Workforce: Direct scientific involvement in sustained observing programs, from design to implementation to analysis, synthesis, and publication, ensures that the ocean observing system will be robust in terms of data quality, incorporation of new methods and technologies, and scientific analyses. Thus, intergenerational succession of scientists is critical for sustaining the
observations on climate timescales. The OCP could focus on improving career incentives for the scientific workforce as a priority.
THE END-TO-END SYSTEM
The ocean observing enterprise is an end-to-end system that not only relies on ocean climate observing scientists, but also on the development of technologies by engineers, deployment and maintenance of observing platforms from ships, and the management and application of the processed data.
Finding: To avoid data gaps and ensure the required data quality and the accessibility of the data for monitoring climate over decades, ocean observing initiatives will need to plan for the end-to-end scope of expenses associated with observing programs, including appropriate logistical planning and all processing including data analysis, data management, and scientific involvement.
New Technology Challenge
The ocean is a challenging environment for making sustained observations, driving the need for ongoing technological advances in the platforms and sensors. New technological developments can increase the effectiveness and efficiency of ocean observing instruments to collect data in harsh environments for several years, thus avoiding the high costs of maintenance which often requires a substantial amount of ship time. The maturation of sustained ocean observing has benefited from the investments of U.S. agencies, such as ONR and NSF, in the development of ocean observing platforms and sensors. Declining and flat budgets have reduced funding available for investments in new technology and improvements to existing technology. The limited investment in advancing technological capabilities is a challenge that, if addressed, will yield significant returns over the lifetime of sustained observing platforms through development of more robust and efficient sensors and platforms and through the maturation of observing methods to address existing and new scientific challenges.
Conclusion on Technology: Declining investments have slowed the development of new technology, which is proven to expand the capability, the efficiency, and therefore the capacity of the observing system. Some philanthropic efforts have in part filled this gap and the OCP could encourage more support there.
Research Fleet Challenge
While new technologies such as autonomous ocean-going vehicles hold promise, ships, and in particular global- and ocean-class vessels, still will be re-
quired to deploy and maintain ocean observing platforms. Establishment of ocean observing sites, such as moored observatories or repeat ship-occupied sampling lines, which require regular visits by ships every year or every decade (and may require long transits) introduce significant demands on the days at sea available each year from the U.S. research fleet. The decreasing number of global- and ocean-class research vessels is creating a shortfall in the infrastructure required for sampling the global ocean and expanding collection into poorly sampled regions such as the polar seas. Ships require long-term planning and investment, and maintenance of a capable fleet of research vessels is an essential component of the U.S. effort to sustain ocean observing.
Conclusion on the Research Fleet: While new technology holds promise for access to the ocean, a capable fleet of research vessels, including those with global reach, is essential to sustaining the U.S. contribution to ocean observing.
POTENTIAL NEW MODELS OF SUPPORT FOR SUSTAINED OCEAN OBSERVING
This report identifies the many benefits of sustaining and growing the capabilities of the global ocean observing system to advance climate science and improve capabilities to anticipate changes critical for decisions on mitigating and adapting to climate change. Because ocean climate data are needed to inform national security, economic, and societal decisions on climate change and other ocean-related issues and given the intergovernmental negotiations required for participating in a global system, responsibility for supporting the ocean observing system falls predominantly on the federal government in the United States. However, limited funding means there is a need to prioritize efforts and increase the efficiency of existing operations. In addition to prioritizing limited government spending, there is also an opportunity to create new models for partnerships of the government with the private and nonprofit sectors in order to accomplish shared goals for ocean observing and research.