Modeling the Effects of an Ice Sheet on the Climate of a Supercontinent

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The Gondwanan ice sheets were approximately as large as those in the Pleistocene, but differed in one important respect, they were located on a supercontinent. The interaction of the ice sheet with the large seasonal cycle simulated in previous energy balance model experiments for a supercontinent configuration suggests a response of significant climatic interest. Extremely cold temperatures over the ice-covered supercontinent of Gondwanan coupled to warm tropical latitudes should result in extreme baroclinicity and suggest significant melting. This award will focus research on the climate system response during the time period of maximum Gondwanan glaciation, with a general circulation model and five different scenarios of glacial ice extent and Milankovitch orbital configurations. The influence of Milankovitch orbital variations will be explored in a matrix of simulations using a present tilt-symmetric orbit, a cool summer-warm winter orbit for the Southern Hemisphere, and a hot summer-cold winter orbit for the Southern Hemisphere. Analysis of global patterns of circulation, temperature, and the hydrologic cycle will provide data to understand the global climate during glacial periods. Attention to the regional ice-sheet aspects of the simulations (e.g. surface heat budget, hydrologic cycle) will clarify the debate on the compatibility of a glacial ice sheet on a supercontinent with the large seasonal temperature ranges suggested for large land masses. Results will be validated against available geologic data.