Introduction

During the past decade, the debate about whether Earth's climate is changing has intensified. Global—or even regional—climate shifts will have far-reaching implications for world economics, energy utilization, national defense, and the health of terrestrial and marine ecosystems. The potential significance of climate change has made this topic a major issue in national and international policy. In addition to concern by policymakers, the scientific community continues to search for answers to vital questions about the likelihood of climate change and the predictability of its extent and timing. Scientists are developing capabilities to distinguish actual climate change from "noise" due to natural variation of the global climate system on annual and decadal time scales.

Although the role of the ocean in global climate is not fully understood, there is general agreement that it is significant. For example, the concentration of the greenhouse gas carbon dioxide (CO2) in the atmosphere has been increasing for many decades. However, of the estimated cumulative input of CO2 from human activities, less than 60 percent is now present in the atmosphere. The ocean is believed to be removing much of the remainder, although the extent of uptake by the terrestrial biosphere also remains a question. Climate models predict that increases in greenhouse gases may lead to significant regional and possibly global climate changes.



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The Ocean's Role in Global Change: Progress of Major Research Programs Introduction During the past decade, the debate about whether Earth's climate is changing has intensified. Global—or even regional—climate shifts will have far-reaching implications for world economics, energy utilization, national defense, and the health of terrestrial and marine ecosystems. The potential significance of climate change has made this topic a major issue in national and international policy. In addition to concern by policymakers, the scientific community continues to search for answers to vital questions about the likelihood of climate change and the predictability of its extent and timing. Scientists are developing capabilities to distinguish actual climate change from "noise" due to natural variation of the global climate system on annual and decadal time scales. Although the role of the ocean in global climate is not fully understood, there is general agreement that it is significant. For example, the concentration of the greenhouse gas carbon dioxide (CO2) in the atmosphere has been increasing for many decades. However, of the estimated cumulative input of CO2 from human activities, less than 60 percent is now present in the atmosphere. The ocean is believed to be removing much of the remainder, although the extent of uptake by the terrestrial biosphere also remains a question. Climate models predict that increases in greenhouse gases may lead to significant regional and possibly global climate changes.

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The Ocean's Role in Global Change: Progress of Major Research Programs The scientific community has initiated large-scale research programs based on studies of the ocean and its relation to global climate and climate related processes. This report, which describes the research programs, is divided into two main sections: programs that study processes that occur over periods ranging from days to hundreds of years—the contemporary system; and those that seek to understand long-term variations ranging from thousands to millions of years—the geological perspective (Box 1). Some programs have both long-and short-term elements. A third section discusses crosscutting data collection issues important to all programs. Because of the vastness of the ocean, observations of ocean physical, chemical, biological, and geological characteristics have been relatively sparse. Intense observations are required for process studies, which are focused on the variety of oceanic parameters that interact to produce a set of observed conditions. Processes are sometimes studied by experimentation, for example adding artificial compounds to the ocean to determine how quickly water masses move and mix. Finally, most programs include a modeling component, to attempt to develop predictive relationships between present ocean characteristics and future observations. Models depend on observations and process studies, including information from geological data, in order to assign reasonable values to model parameters and to test model performance. Modeling results can then provide insights to guide further observations and process studies by identifying the variables in the ocean environment that cause the greatest changes in model predictions. In 1990, the Ocean Studies Board published a brief report, The Ocean's Role in Global Change: The Contemporary System—An Overview of Major Research Programs. It described the major research programs that were ongoing or planned at that time, specifically those designed to study the role of the ocean in short-term climate variability. Since that time, many of the programs described have made substantial progress. The chapters that follow are updated summaries of the programs described in the 1990 report, with additional information about new or planned programs that contribute to the study of global change.

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The Ocean's Role in Global Change: Progress of Major Research Programs Box 1—Focus and Goals of the Major Research Programs THE CONTEMPORARY SYSTEM PROGRAMS GLOBAL OCEAN OBSERVING SYSTEM (GOOS) Focus: Observations needed for prediction of El Niño-Southern Oscillation and detection of global change due to greenhouse warming. Goal: To provide the oceanic component of the Global Climate Observing System. TROPICAL OCEAN-GLOBAL ATMOSPHERE (TOGA) PROGRAM Focus: Studies describing the interactions between the tropical oceans and the global atmosphere, especially the El Niño-Southern Oscillation. Goal: To model the ocean-atmosphere system for the purpose of predicting its variations. WORLD OCEAN CIRCULATION EXPERIMENT (WOCE) Focus: Studies of the surface and subsurface circulation of the global ocean. Goal: To understand ocean circulation well enough to model its present state, predict its future state, and predict feedback between climate change and ocean circulation. JOINT GLOBAL OCEAN FLUX STUDY (JGOFS) Focus: Studies investigating the role of marine organisms and chemistry in modulating global climate change. Goal: To gain a better understanding of how carbon dioxide is exchanged between the atmosphere and the surface ocean and how carbon is transferred to the deep-sea. GLOBAL OCEAN ECOSYSTEM DYNAMICS (GLOBEC) PROGRAM Focus: Studies elucidating how changing climate alters the physical environment of the ocean and how this in turn affects marine animals, especially zooplankton and fish. Goal: To predict the effects of changes in the global environment on the abundance, variation in abundance, and production of marine animals.

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The Ocean's Role in Global Change: Progress of Major Research Programs ATLANTIC CLIMATE CHANGE PROGRAM (ACCP) Focus: A combination of studies utilizing historical data, modeling, and direct observation and monitoring of middle and high latitudes of the North Atlantic. Goal: To understand air-sea interactions between the Atlantic Ocean and the global atmosphere. ACOUSTIC THERMOMETRY OF OCEAN CLIMATE (ATOC) PROJECT Focus: Acoustic propagation studies measuring the speed of sound along long distance undersea paths. Goal: To characterize warming trends in the ocean on global scales. GLOBAL OCEAN-ATMOSPHERE-LAND SYSTEM FOR SEASONAL-TO-INTERANNUAL CLIMATE PREDICTION (GOALS) PROGRAM Focus: Studies investigating the variations in sea-surface temperature, soil moisture, sea ice, and snow and the processes that control these conditions. Goal: To gain a better understanding of global climate change variability on seasonal to interannual time scales for the purpose of predicting this variability. LAND-OCEAN INTERACTIONS IN THE COASTAL ZONE (LOICZ) PROGRAM Focus: Studies of fluxes in the coastal zone, how changes in the coastal zone alter the fluxes, and how they will affect the global carbon cycle and trace gas composition of the atmosphere. Goal: To understand the impacts from changes in climate, sea-level, land use, and ecosystem functioning for use in the creation of long-term, sustainable policies for coastal management. ARCTIC SYSTEMS SCIENCE (ARCSS) PROGRAM Focus: Paleoenvironmental multidisciplinary studies to address the physical, chemical, biological, and social processes of the Arctic system. Goal: To understand the processes of the Arctic system in order to predict environmental change on decade-to-century time scales.

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The Ocean's Role in Global Change: Progress of Major Research Programs THE GEOLOGICAL PERSPECTIVE PROGRAMS OCEAN DRILLING PROGRAM (ODP) Focus: Collection and analysis of deep-sea cores from around the world to help reconstruct the paleoceanographic record of past climatic and oceanic conditions. Goal: To reconstruct the Earth's paleoceanography and more importantly to begin to understand the mechanisms that drive changes in climate and oceanic conditions. RIDGE INTER-DISCIPLINARY GLOBAL EXPERIMENTS (RIDGE) Focus: Integrated observational, experimental and theoretical studies to determine the primary processes that have shaped the evolution of our planet, and the long-term temporal variations that may have modified the past climate of Earth. Goal: To understand the causes and predict the consequences of physical, chemical, and biological fluxes within the global spreading center system. THE GLOBAL CHANGE AND CLIMATE HISTORY PROGRAM OF THE U.S. GEOLOGICAL SURVEY Focus: Paleoclimate and current climate processes research addressing environmental change related to increasing human activities Goal: To provide relevant information on global climate change to the government and the research communities. MARINE ASPECTS OF EARTH SYSTEM HISTORY (MESH) Focus: Studies of the paleoceanographic record to address numerous research themes including ocean geochemical and climate change and climate sensitivity and variability. Goal: To determine the sensitivity of the climate system to natural changes in solar radiation.

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