GCM SENSITIVITY TEST USING INCREASED ROTATION RATE, REDUCED SOLAR FORCING AND OROGRAPHY TO EXAMINE LOW-LATITUDE GLACIATION IN THE NEOPROTEROZOIC

During the Neoproterozoic period, most landmasses were assembled into the super-continent, Rodinia, and parts experienced glaciation in low paleolatitudes. We examine possible causes of glaciation by increasing rotation rate, reducing the solar constant and carbon dioxide concent rations for an idealized super-continent that is centered in the North ern Hemisphere tropics-subtropics. Further, we introduce a 2 km north- south mountain chain in the western regions of this super-continent. A mixed layer ocean or prescribed time varying sea surface temperatures are used in these simulations. Our results show that neither an indiv idual factor or a combination of these factors can cool temperatures e nough to bring about glaciation on the tropical super-continent. We co nclude that other factors would be needed to initiate glaciation.