HR: 14:55h
AN: PP42C-05    [PDF]
TI: The Role of Paleogeography on the Evolution of Mesozoic Ocean Circulation: Sensitivity Experiments Using a Fully Coupled Ocean-Atmosphere Model
AU: * Huynh, T T
EM: tranhu@umich.edu
AF: Department of Geological Sciences, University of Michigan, 425 E. University Ave., Ann Arbor, MI 48109-1063 United States
AU: Poulsen, C J
EM: poulsen@umich.edu
AF: Department of Geological Sciences, University of Michigan, 425 E. University Ave., Ann Arbor, MI 48109-1063 United States
AB: Geography has long been recognized as one of the primary controls on climate. Many studies have assessed the response of paleoclimate to paleogeography by examining the impact of continental configuration, land area, and the opening/closing of gateways on oceanic circulation patterns in the past. Most of these modeling studies have employed ocean-only general circulation models (GCMs) using restoring boundary conditions derived from atmosphere-only GCM experiments. The lack of ocean-atmosphere feedbacks may have serious consequences for the predicted circulation, and would tend to prohibit changes in ocean heat transport and water-mass formation. In this study, we use a fully coupled ocean-atmosphere GCM, the Fast Ocean Atmosphere Model (FOAM), to examine the role of geography on Mesozoic ocean dynamics. Triassic and Cretaceous paleogeographic reconstructions were chosen because these time slices represent the extremes of geographic evolution during the Mesozoic. All experiments include identical boundary conditions (e.g. land surface characteristics, solar luminosity, atmospheric pCO$_{2}$) except for paleogeography. All simulations were integrated until the ocean component of FOAM reached equilibrium. In addition, we compared the relative impact of geography to atmospheric CO$_{2}$ on ocean circulation by running experiments with high and low pCO$_{2}$ values for the Triassic and Cretaceous. Initial results demonstrate that changes in the continental configuration during the Mesozoic will affect the location, as well as the number of sites, of water-mass formation. More sites of deep and intermediate water formation existed during the Triassic than Cretaceous. The simulations suggest that while the sites of water-mass formation are determined by continental configuration, it is atmospheric CO$_{2}$ that controls the strength of oceanic overturning. The simulations also show that ocean heat transport is higher during the Mesozoic than the modern day, and that the total heat transported poleward by the oceans decreases between the Triassic to Cretaceous experiments. Thus it appears that paleogeography exhibits primary control in the patterns of oceanic circulation during the Mesozoic by determining the sites of water-mass formation and ocean heat transport. However, other factors (such as atmospheric CO$_{2}$) can also have significant impact on ocean dynamics of the time.
DE: 4255 Numerical modeling
DE: 4267 Paleoceanography
DE: 4532 General circulation
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting