The impact of rapid human development on coastal regions and shallow water systems is not fully understood and remains a research priority. Results of the proposed planning meeting will be expanded U.S. – China research collaborations on interrelated research themes of coastal and ocean environments that are heavily impacted by human activity and climate variability and change, and that, in turn, have the potential to create widespread societal and environmental changes. Human development activities will both affect and be affected by these changes. Resolving (through research) uncertainties about how such changes occur would provide knowledge needed to support national and international policy decisions about sustainable human development and environmental protection.
Numerous research parallels exist between, for example, the impacts of outflow from the Changjiang and Mississippi Rivers on the East China Sea and Gulf of Mexico, respectively. Both basins are heavily populated and the natural processes have been disrupted by dam construction, land use and land cover change, and other factors. The outflow of the rivers carries large amounts of sediment and nutrients, which profoundly affect the biogeochemical conditions on the continental shelf. This can lead to a variety of processes that can cause environmental and economic damage such as hypoxia (low oxygen concentrations in sea water which adversely affect marine life) or shifts in coastal productivity. Large rivers are also a primary source of carbon to the ocean and therefore directly contribute to the global carbon cycle and climate change. Inversely, climate variability and change affect river discharge through changes in precipitation patterns. Comprehensive and long-term observations of riverine fluxes to the ocean are virtually non-existent; therefore, many of the processes and their variability are poorly understood. The Changjiang and Mississippi Rivers rank fifth and seventh in water discharge and fourth and seventh in sediment discharge. While these systems are being studied independently, both would benefit from combined and comparative research. Joint observations and modeling of both systems will allow for intercomparisons and knowledge sharing that will lead to improved protection and management of riverine, estuarine, coastal, and ocean resources.
Similarly, mounting evidence suggests that sea-surface temperature (SST) variability in the tropical oceans has a dramatic influence on regional and global weather patterns. Over the North American continent, fluctuations in seasonal rainfall are known to be linked to the El Niño-Southern Oscillation, while decadal or longer time scale fluctuations are linked to SST anomalies in both the tropical Pacific and tropical Atlantic. Over the Asian continent, the prime climatic phenomena controlling the rainfall fluctuations are the Asian Monsoons and El Niño-Southern Oscillation, which tie closely to SST variability in the Indo-Pacific. Positive trends in heavy precipitation have been observed over the U.S. and the southern part of China over the past decades, while significant negative trends are observed in northern China. Are these changes in the precipitation patterns caused by changes in ocean circulation in the Indo-Pacific and tropical Atlantic, respectively? If so, the coastal and continental shelf ecosystem processes in the Changjiang and Mississippi river basins must be remotely connected to these ocean circulation changes, because variation in river discharge is affected by precipitation and snow melt, which in turn are affected by climate variability and change. However, how climate information flows from global through regional to local scales is not clear, nor is it clear what aspects of the ocean circulation changes are most critical for driving the regional climate and local ecosystems. Given the many commonalities between the two systems and the unique features that each system possesses, a comparative study of the Indo-Pacific and Atlantic climate systems and their respective impacts on the coastal and continental shelf ecosystem processes in the Changjiang and Mississippi River basins is an ideal area for bilateral collaborations.
This joint research proposals that will result from this planning meeting will be relevant to societal issues shared by the U.S. and China and beyond, ranging from local and regional fisheries economies to permanent changes in global climate. They will also form the basis for important research advances, and for the training of coastal, ocean, and climate scientists capable of addressing critical environmental concerns related to our coastal and ocean environments at all scales in space and time. Collaborators and students from both countries will benefit from this program through increased access to multiple, parallel study regions, including both observational and modeling activities and results. Shared results can inform the development and refinement of comprehensive models of both the Changjiang and Mississippi basins and respective coastal environments and receiving waters. Three specific proposal ideas that were identified during the Washington, D.C. meetings are presented below.