MILANKOVITCH CYCLES AND CARBONIFEROUS CLIMATE

Cyclical Permo-Carboniferous sea level fluctuations have long been linked to glacial-interglacial fluctuations on Gondwanaland. Similar to the Pleistocene, such fluctuations may in turn have been driven by variations in orbital insolation forcing. Herein we report results from climate model simulations that examine the effect of Milankovitch insolation variations on the climate of the Gondwanan supercontinent. Utilizing maximum summer insolation values typical of interglacials, we simulate completely snow-free conditions, with summer temperatures at the South Pole >20-degrees-C. Modifying orbital configuration to minimum summer insolation receipt results in a large area of below freezing temperatures. Comparison of model-generated summer snow cover for the latter run with reconstructions of glacial ice extent indicates a good first-order agreement. These calculations support the cyclothem model and suggest that the entire glacial-interglacial couplet for the Carboniferous can be simulated with a minimum number of adjustable parameters.