Dramatic changes have been observed in the circulation and physical characteristics of the oceans over the past century. These changes are projected to continue over the next century based on the analyses and summaries recently presented in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). In this Topic, we solicit presentations that address past and future climate variability and change in the ocean, and the role that the ocean plays in these changes. Papers related to changes in forcing mechanisms such as wind fields, air-sea heat exchange, the freshwater budget, and the impact that changes in these forcing fields have had, and will have, on ocean circulation, large-scale sea level, heat and freshwater content and transport, ventilation and upwelling, sea-ice, and surface waves, are all welcome. Presentations using: i) analyses of global and regional data sets arising from observations alone and/or state estimation; ii) idealized and conceptual models of observed climate change; iii) analyses of global climate models projections or results from higher-resolution regional ocean, or coupled atmosphere-ocean, models that are forced by, and take their boundary conditions from, global climate models; iv) uncertainties in model projections and how they might be improved; and v) the ability of models to predict abrupt change and extreme events, are encouraged.

This session will present observations of climate change in the ocean’s physical characteristics, including circulation, water mass properties (heat, salinity, and tracers of water masses), sea level and surface waves; and change in the associated forcings, such as winds, air-sea heat flux, freshwater flux and sea-ice. Papers are encouraged that describe emerging methodologies for observing and quantifying ocean climate change, including new observing networks and state estimation. Model studies that explore the causes of observed climate change in the ocean are also welcome.

This session will extend the observational evidence of oceanic climate change and variability described in Theme 1.1 to future projections. Presentations that summarize or analyze oceanographic characteristics or features simulated by global climate models, as well as those that downscale (statistically or dynamically) results from these models to specific regions, are encouraged. Though the focus will be on change and variability in large scale physical variables, processes, and patterns, talks that draw links to biogeochemistry and impacts are also welcome.

Carbon dioxide is one of the most important “green-house” gases in the atmosphere affecting the heat balance of the earth. As a direct result of the industrial and agricultural activities of humans over the past two centuries, atmospheric CO₂ concentrations have increased by about 100 ppm. The atmospheric concentration of CO₂ is now higher than experienced on Earth for at least the last 650,000 years, and is expected to continue to rise, leading to significant temperature and CO₂ increases in the atmosphere and oceans by the end of this century. The ocean carbon cycle is closely linked to climate because the oceanic uptake of anthropogenic CO₂ helps to regulate atmospheric CO₂ and, furthermore, the rate of uptake of CO₂ is affected by climate-induced changes in biogeochemical and physical processes in the oceans.

Global surveys over the past several decades now allow scientists to examine decadal time-scale variations in ocean biogeochemical processes in unprecedented detail. This session invites observational and modelling papers that describe these changes from many different angles, including physical, biological, biogeochemical and carbon cycle perspectives. Emphasis will be placed on decadal changes in carbon cycling, e.g. anthropogenic carbon, air-sea exchange of carbon dioxide, the biological pump, nutrient and oxygen cycling, impacts of increasing levels of carbon dioxide on carbonate chemistry, and changes in the distribution of natural carbon in mode and deep waters. We encourage submission of contributions that have made use of a broad palette of interdisciplinary tools.

The global oceans are the largest natural long-term reservoir for this excess heat and CO₂, absorbing approximately 85% of the heat and 26% of the combined carbon sources from deforestation and fossil fuel burning. Recent studies have demonstrated that both the temperature increases and the increased concentrations of CO₂ in the oceans are causing significant changes in marine ecosystems. Many marine organisms are already affected by these anthropogenic stresses, including impacts due to coral bleaching and ocean acidification. The goal of this session is to review recent data on the physical, chemical, biological and geological impacts on marine ecosystems due to effects of ocean warming and acidification. Conceptual, experimental and modelling contributions at a variety of spatial and temporal scales are welcome.

Climate change will profoundly shape the global coast. Changes in weather patterns (temperature, rainfall and coastal winds) and extreme events could impact coastal ecosystems as well as societal use of coastal regions. A key factor is likely to be change in availability of fresh water during both flooding and drought periods. Long-term impacts such as sea-level rise and changes in the intensity and frequency of hurricanes and storms could lead to changes in shoreline migration and extent of coastal flooding, salinization of aquifers, and changes in sediment and nutrient transport. Changes in the production and integrity of coastal ecosystems in response to altered climate and physical regimes could decrease the ecosystem goods and services they provide. Because human populations are increasing most rapidly in coastal areas, mitigating the impacts of anticipated climate change is a key determinant in reducing the vulnerability of coastal populations and ecosystems to change and increasing resilience in both urban and rural coastal regions.

Many coastal areas around the world are experiencing an increased impact of natural hazards. The impact of climate change to the coastal systems, resulting from increasing sea level rise, storms surges and wave heights can cause severe coastal erosion and flooding with further consequences on infrastructure and human life, especially in underdeveloped countries. A precise knowledge on the magnitude of these impacts and the factors controlling them is a prerequisite to perform any decision making process related to mitigation and adaptation policies. We invite papers exploring linkages between climate change and coastal natural hazards. Studies may also address climate change impacts on the coast including altered hydrology and sea-level rise, changes in surface waves, storm surges, altered ocean-meteorological weather patterns and frequency of extreme events. In particular, research that improve our understanding of sea-level rise and variability, including the different factors influencing the observed sea level, observational systems and requirements needed to refine this, and future projections and uncertainties, are especially welcome.

Climate change will potentially result in dramatic alterations for coastal ecosystems—affecting fluxes of water, sediments and nutrients; geomorphology; and societal use and management of coastal regions. Particularly sensitive are sea-level controlled wetlands and enclosed water bodies, such as estuaries and coastal lagoons. Manifestations of climate change include altered hydrology and sea-level rise, altered weather patterns and frequency of extreme events. The ability of coastal ecosystems to remain productive and functional within the complex interactions of landscape and human dependence relies on continued ecosystem processing of materials and energy. Human activities influence these functions and will modify the coastal ecosystem’s ability to respond to (or even survive) climate change. Human impacts on ecosystem function are being addressed widely for natural resource management, and the effects of climate change on ecosystem functioning are receiving more attention. The challenge is to understand how the two interplay in management and sustainability of ecosystems that support the viable integration of humans and future coastal landscapes. This session invites papers that explore how the consequences of climate change may result in altered material fluxes, geomorphology, hydrology, habitats, ecosystem functioning, and societal functioning within coastal ecosystems.

Recent studies have documented the impacts of climate variability and change, on a range of ecosystems, over a range of time scales. While we can now begin to identify and monitor some of these impacts, many questions remain. These include how ocean processes will change in the future, the mechanisms involved, what effects such changes may have on ecosystems, and whether we can develop indicators for early detection of changes. This Topic will particularly encourage comparative studies of relations between climate variability, climate change and marine ecosystems, as well as presentations which consider mechanisms that link physical forcing with ecosystem change. Central themes are: What are the key processes of ecosystem change and how might they be monitored? Can we predict shifts in species distributions and changes in productivity? Are there other limits that will constrain such global movements? What is the status of our knowledge of the ability of organisms to adapt to climate change? What are the options for managing marine ecosystems to sustain goods essential to societies? Such understanding is essential if we are to effectively manage global marine living resources such as fisheries and marine protected areas during this period of increased human impact. Studies from both shelf and open ocean areas are encouraged.

Physiological processes of planktonic organisms, such as nutrient uptake, photosynthesis, respiration, and reproductive development are highly sensitive to temperature as well as other environmental factors such as UV and CO₂. Most plankton species are short lived, resulting in tight coupling between environmental effects and plankton dynamics. In contrast to higher trophic levels such as fish, few plankton species are commercially exploited so changes at lower trophic levels may be more easily be attributed to climate variability and change. These characteristics make lower trophic levels good potential indicators of the global impacts of climate change. Impacts may include changes in distribution of individual species and communities, in the timing of important lifecycle events or phenology, in abundance and community structure, and through feed-backs to the climate system. In turn these climate impacts on plankton may have consequences for higher trophic levels and ecosystem structure and dynamics. In this session contributions on the impacts of climate change on all lower food-web components of the plankton, from bacteria to mesozooplankton, are particularly encouraged.

Marine species, including many commercially-exploited stocks, have evolved species-specific life histories through adaptation to complex environmental conditions. They also clearly respond to ocean variability over a wide range of spatial and temporal scales and through various pathways. These responses are both direct, through regulating metabolic factors such as swimming speeds, activity rates, feeding rates and reproduction, and indirect, primarily through effects on the food web. They can result in changes in growth, recruitment, abundance, age of maturity, distribution, etc. The effects of fishing can also make populations more vulnerable to climate change and changes in higher trophic levels, in turn, can affect ecosystems through, for example, “top-down” or “wasp-waist” controls. In this session we encourage contributions on the impacts of climate variability and change (either direct or indirect) on trophic levels above mesozooplankton; ecosystem modeling that includes higher trophic levels; mechanistic linkages between climate change and population dynamics; the interaction between climate and fishing; and indicators that are useful for earlier detection of ecosystem changes. Contributions addressing perspectives on management of ecosystems and commercially-exploited stocks in the face of future climate change are also invited.

Marine ecosystems worldwide are changing as a result of climate variability and climate change. This session will consider potential impacts on and perturbations of ecosystem structure, function, goods and services using our current knowledge of ecosystem response to climate variability and the prognosis for future climate change. At present, our ability to make (even simple) predictions about coastal and oceanic ecosystem response to climate change may be hampered by an incomplete understanding of the linkages between them. We know that ecosystems in the Arctic are changing rapidly due to ice melting and resultant changes in habitat, thus we are interested in examples of scenarios for physical forcing and ecosystem change in the Arctic as well as in other geographical regions. Does our current knowledge of climate change allow us to predict shifts in distributions of organisms and/or changes in productivity? What do we know about the ability of organisms to adapt to climate change? What are the options for managing marine ecosystems to sustain goods and services essential to societies? We seek presentations that address these questions as well as regional examples of physical climate change scenarios and the resultant ecosystem responses. We expect that the information presented in this Topic will lead to discussion of projected future changes and options for adaptation and mitigation.

There are serious gaps in our understanding of the potential impacts of climate change on the marine ecosystems, and predicting ecosystem responses may prove challenging. Large, long- lived species tend to have very stable populations, so even dramatic changes in juvenile survivorship may not easily be detected for a considerable period of time. At the other end of the size range of organisms, natural variation in population size of phytoplankton is generally large and can mask detection of longer-term trends in abundance. This requires urgent attention in order to make significant progress toward predicting and understanding the impacts of climate change on the marine environment. This session will describe future changes in the marine ecosystem, including distribution, production and biodiversity due to changing climate. We seek papers that focus on ocean currents and transport pathways, vertical stratification and impact on nutrient distribution and phytoplankton production, identification of species sensitivity to climate change (sentinel species), indirect and non-linear effects on biological processes, match/mismatch between predators and prey, and competition when/if new species are introduced into the ecosystem. Ecosystem responses to the common, large scale climatic forcing could vary in respective latitudinal regions due to regionally-specific environmental/ecological characteristics. We hope to contrast especially the mechanisms of ecosystem changes in the polar, mid-latitude, sub-tropical, and tropical regions.

The recent reports of the Millennium Ecosystem Assessment and the IPCC Working Groups II and III included only a minimal discussion of climate impacts on marine ecosystems. This session invites papers that will expand our understanding of climate impacts on marine ecosystems, and on ecosystem services produced. We seek papers that discuss adaptation, vulnerability, mitigation and the potential for reduction of impacts on coastal and oceanic ecosystems. What are our options for managing marine ecosystems to sustain critical services within both a climate change and an ecosystem management perspective? Will organisms be able to adapt to climate change? What tools are available to increase the likelihood that organisms will adapt and to enhance the resilience of ecosystems to detrimental impacts of changes? Coastal ecosystems such as wetlands, estuaries, intertidal and nearshore habitats, kelp forests, coral reefs and ecosystems surrounding small islands are particularly vulnerable to climate change due to global warming, sea level rise, increased freshwater runoff and storms, and influence of coastal winds. Changes in fish production are expected but may be mitigated by avoiding other ecological stressors such as overfishing and coastal pollution. Networks of marine protected areas and no-take marine reserves may enhance resilience of ecosystems. They may also counter selection pressures for reproduction at smaller size. Fishing practices may need to change to mitigate social and economic impacts of shifting availability of fishes as well as evolutionary changes. Aquaculture ventures will find that rising water temperatures are likely to increase growth rates of some species, but may be detrimental to others. What are the gaps in our knowledge that prevent us from making better assessments of likely outcomes under various climate change scenarios? Is it feasible and wise to consider the ocean as a depository for carbon dioxide either through pumping CO₂ into the deep sea or through massive iron fertilization experiments?