Orbital and CO2 forcing of late Paleozoic continental ice sheets

Abstract

Contrasting views of the size, duration, and history of the Gondwanan continental ice sheets have been proposed from late Palcozoic glaciological and sedimentological evidence. To evaluate these differing views, a coupled ice sheet-climate model is used to simulate continental ice sheets under a wide range of late Paleozoic orbital and pCO2 conditions. The model experiments indicate that orbital variations at PCO2 concentrations below 2X pre-industrial atmospheric levels (PAL; 280 ppm) produce large changes in late Paleozoic ice volume (∼ 1.3 x 108 km3) and sea level (∼20 to 245 m). Between 2 and 8X PAL Gondwana continental ice is simulated only under the most extreme Southern Hemisphere cold summer orbit, but still produces significant ice volumes (∼8-12 x 107 km3). Our results highlight the important role of atmospheric CO2 in determining the distribution, volume, and stability of late Paleozoic ice sheets, factors that ultimately impacted sea level, cyclothem deposition, and global climate, and reconcile disparate views of the Late Paleozoic Ice Age. Copyright 2007 by the American Geophysical Union.