9530684 Takahashi This research project is part of the US Joint Global Ocean Flux Study (JGOFS) Southern Ocean Program aimed at (1) a better understanding of the fluxes of carbon, both organic and inorganic, in the Southern Ocean, (2) identifying the physical, ecological and biogeochemical factors and processes which regulate the magnitude and variability of these fluxes, and (3) placing these fluxes into the context of the contemporary global carbon cycle. Water masses such as Antarctic Bottom Water and Antarctic Intermediate Water which originate in the high latitude Southern Ocean areas spread through the interior of the major ocean basins thus forming a major conduit for exchanges of heat and dissolved gases such as carbon dioxide and oxygen between the atmosphere and the interior of the oceans. Therefore, an improved understanding of the processes governing the physical, and biogeochemical properties of the source waters in the Southern Ocean is important not only for gaining quantitative knowledge of the carbon-nutrient cycle in the global oceans, but also for predicting the future course of atmospheric carbon dioxide and hence the climate of the earth. This research program consists of the following three kinds of field observations. Continuous underway measurements of the total carbon dioxide concentration in surface waters will be made throughout the JGOFS cruises in order to determine the seasonal and geographic variations and the causes of oceanic carbon dioxide sink/source conditions. Measurements of the partial pressure of gaseous carbon dioxide and total carbon dioxide in discrete seawater samples will be conducted to observe depth profiles of the carbon chemistry (especially in the upper 500 meters) at hydrographic stations located at various latitudes during two seasonal cruises. High resolution measurements of the hydrographic structure of the uppermost 250 meters and od nutrients will be conducted in order to document the mesoscal e variability of biogeochemical properties within the Antarctic Polar Front Zone. This will be done with a towed pumping system, designated as SeaSoar, on one of the cruises to the APF. ***
