HR: 0800h
AN: PP21B-1559    [Abstracts]
TI: Impact of the Panama Seaway Closure on Ocean Circulation, Marine Productivity and Nutrient Cycling
AU: * Schneider, B
EM: bschneider@ifm-geomar.de
AF: Leibniz Institut fuer Meereswissenschaften, IFM-GEOMAR, Duesternbrooker Weg 20, Kiel, 24103 Germany
AU: Schmittner, A
EM: aschmittner@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, 104 Ocean Admin Bldg, Corvallis, OR 97331 United States
AB: The closure of the Panama Isthmus, ~14-3~Ma, caused large reorganizations of ocean circulation. Here we use a global climate-ocean ecosystem model to investigate the effects of the closing gateway on ocean circulation, marine productivity and nutrient distributions. Several sensitivity experiments with different sill depths and vertical diffusivities are performed. Consistent with previous model studies, we find constricted throughflow due to shallowing of the sill leads to intensification of the North Atlantic thermohaline overturning. The simulated rates of North Atlantic Deep Water formation strongly depend on the vertical diffusion in the model, particularly for a deep sill. For the first time, we document shifts in nutrient distributions associated with reorganisations of ocean circulation with repercussions on marine productivity patterns. Reduced flow of nutrient rich subsurface waters from the Pacific into the Atlantic reduces biological productivity in the North Atlantic. In the eastern tropical Pacific increased upwelling of nutrient rich deep-waters leads to a strong increase in productivity. These results seem to be consistent with the paleo productivity proxy record. Generally, global productivity is found to increase with proceeding gateway closure.
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4928 Global climate models (1626, 3337)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005