Oceanic Uptake of Carbon Dioxide and its Transport via the South Atlantic Ventilation

点击翻译按钮获取中文摘要

Two campaigns to measure transient tracers in the Atlantic Ocean (TTO/NAS and TTO/Equatorial) were funded by NSF during the period from 1980 to 1985. A complete data base for modelling this ocean basin would include a South Atlantic Study to: 1.Determine CO2 transports and their influence on world climate, 2.Constrain models of major ocean currents in this area, and 3.Confirm an observed 5-fold increase in the addition rate of new carbon to the thermocline. Eight components of such a study will be performed by investigators from LDGO, Princeton, University of Washington, WHOI, and SIO. The track record of these scientists is well established by successful completion of previous studies in the Equatorial and North Atlantic. They will provide physical and chemical expertise which will be directed toward a cooperative effort to reach the goals of the geochemical study. This component is aimed at improving our understanding of the dynamic transport of CO2 by Antarctic water masses formed in zones of different climates. Previous investigations showed that a prominent circumpolar CO2 sink zone is located in a latitudinal range of 40 degrees S - 50 degrees S, and that it is closely associated with the zone of confluence of the warm Subtropical water with the cold Subantarctic water. This zone accounts for about 40% of the global oceanic uptake flux for CO2. The low pCO2 values in the surface water of this zone are attributed mainly to the effect of cooling of the warm Subtropical gyre waters and to the mixing of the cooled water with the high-pCO. and high-nutrient Antarctic waters. Photosynthetic utilization of CO2 further reduces the surface water pCO2 value. In the vicinity of this confluence zone, an effective overturning of the water column down to about 500 meters is induced mainly by cooling of the high-salinity Subtropical waters. This process would transport the CO2 taken up by the surface water of this CO2 sink zone into the South Atlantic thermocline. One of the major objectives of the proposed investigation is to estimate the rate of this transport using the tracer and CO2 data obtained during the experiment.