HR: 16:15h
AN: PP44A-02 INVITED     [Abstracts]
TI: Global Ocean Sensitivity to Local Geologically Short-Term Variability of Freshwater Fluxes
AU: * Seidov, D
EM: dseidov@psu.edu
AF: Penn State University, 2217 Earth&Enginiring Sci. Bldg., University Park, PA 16802-6813 United States
AU: Haupt, B J
EM: bjhaupt@psu.edu
AF: Penn State University, 2217 Earth&Enginiring Sci. Bldg., University Park, PA 16802-6813 United States
AB: The geologic record and computer modeling indicate that the transitions between cold and warm climates during the last deglaciation , driven by internal climate dynamics, were geologically very fast, lasting for only decades or shorter. The THC is, perhaps, the only viable candidate for driving these kinds of abrupt changes. Current perception of how the THC may become an agent of abrupt climate change is that the THC is rather sensitive to changes in freshwater fluxes in the high-latitudes, also known as major meltwater events. Our recent numerical experiments challenge the idea of the high-latitudinal meltwater events as the only possible cause of THC alteration. These experiments suggest that the inter-basin sea surface salinity contrasts caused by disparity of freshwater fluxes over the world ocean can also be a very potent factor in THC dynamics. To address the role of changes in both high-latitudinal and inter-basin freshwater fluxes in altering the global THC, we performed several simple numerical experiments. First, we ran the atmospheric control experiment using the NCAR Community Climate Model (CCM) with observed sea surface temperature (SST) and salinity to get the present-day control atmospheric state, that is, the wind stress, SST, and freshwater fluxes across the sea surfaces. Next, we ran the oceanic control experiment using the GFDL Modular Ocean Model (MOM) with these sea surface conditions from the CCM. In the first series of experiments, we specified idealized anomalies of freshwater fluxes in the northern North Atlantic, the Southern Ocean, and the subtropical North Atlantic and North Pacific. These experiments gave us insight on the relative importance of high-latitudinal and inter-basin short-term fluctuations in freshwater balance for the THC dynamics. In the second series of experiments, we simulated the disruption of the freshwater regime in the northern North Atlantic caused by freshwater floods from Lake Agassiz (a glacial lake that drained into the Hudson Bay around 8.2 kyr BP). The estimates of freshwater discharged into the northern North Atlantic suggest that these volumes of freshwater could be sufficient for large-scale disturbances of the THC. The results of the two series of experiments will be shown and discussed.
UR: http://www.essc.psu.edu/$\sim$dseidov/
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 1635 Oceans (4203)
DE: 1655 Water cycles (1836)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting