The shallow coastal ocean, representing approximately 8% of the modern global surface ocean area and 19% of the land area, is a domain that exercises poorly understood controls of the global carbon cycle and the air-sea CO2 exchange that are of unquestionable importance to climate change since the Last Glacial Maximum (LGM) and into the future. At present, 10 to 30% of total oceanic biological production occurs in the coastal ocean, near 80% of the terrigenous material mass reaching the ocean is deposited there, and as much as 50% of total calcium carbonate and 80% of total organic carbon accumulation in the ocean occur in this region. At the end of pre-industrial time, nearly 200 years ago, biological calcification and remineralization of organic carbon produced in situ and imported from land might have been responsible for 30% to 50% of the CO2 emission from the surface ocean to the atmosphere. At the millennial to centurial time scale since the LGM near 18,000 years before present and into the next two centuries of the Anthropocene, the coastal ocean, because of its relatively small size, is particularly susceptible to environmental changes in its bigger neighboring reservoirs of atmosphere, land, open ocean, and sediments. For the same reason, it transmits and modulates rapidly the external and internal forcings of the past and the near future.
In this project, researchers at the University of Hawaii - Manoa and Northwestern University will address four important, but not well understood, issues of the role of the coastal ocean in the global carbon cycle and air-sea CO2 exchange in the time period since near the LGM to the end of pre-industrial time and into the future two centuries of the Industrial Age. The role of the coastal ocean is a global role and the research accordingly focuses on obtaining global or world-average answers. These will be handled by model analysis developed from the investogators? dynamic process models that have been successfully applied to the shorter time periods of the Industrial Age and the future two to three centuries. Success of the models? application is in their agreement with the results of others? estimates for the industrial past and future. The model analysis will produce estimates of the major processes that interact with the CO2 transfer: the removal of carbon and other nutrients from land, sedimentary storage of organic and inorganic carbon as affected by seawater chemistry and surface water acidification, biological production on land and in the coastal zone, the CO2 and temperature role in mineral weathering, and the CO2 air-sea exchange of the coastal ocean.
The broader impacts of this proposal are its relevance to the societal issues and policy decisions involved in the understanding of the biogeochemical fundamentals of global change and, particularly, of the role of the heavily human-impacted coastal ocean in the global carbon cycle in the past and on into the future. Additional impacts involve undergraduate and graduate education, and dissemination of information by means of a web site allowing the community access to the models and results, and presentations at professional meetings. Finally, the behavior of the coastal ocean domain in the past and future is critical to any analysis of the Earth system undergoing both natural and human-induced environmental change.
