Abstract ATM-9618025 Najjar, Raymond G. Pennsylvania State University Title: Assessment of the Response of the Ocean-Atmosphere System to the Evolution of the Southern Ocean During the Cenozoic This award supports a study of the role of southern hemisphere ocean bathymetry and continental configuration in the evolution of global ocean circulation, climate and the cryosphere during much of the Cenozoic (14 to 55 million years ago) using general circulation models of the ocean and atmosphere. In particular, by conducting a series of numerical experiments of varying complexity (with idealized and realistic ocean bathymetry and with uncoupled models) this work will evaluate the effects on ocean circulation and climate of (1) the separation of Australia from Antarctica, (2) the opening of Drake Passage, (3) the progressive increase in the surface area of the ocean in the southern hemisphere, and (4) the Antarctica ice cap. An important component of this study will be the evolution of the models using paleoceanographic data on ocean circulation and thermal structure for the Cenozoic. This model- data comparison will also provide a framework for the interpretation of paleoceanographic data and model-data comparison will help to constrain the possible causes of the dramatic changes in the earth system that occurred during this time period. The proposed simulations will also allow the evaluation of previously proposed hypotheses regarding the development of an extensive Antarctic ice-sheet.
