GCM response to late precambrian (similar to 590 Ma) ice-covered continents

Recent coupled energy balance/ice sheet modeling studies indicate that ice- covered continents can be simulated for the Late Precambrian with 6% solar constant reduction. We examine the ocean mixed layer response to such an ic e sheet with the GENESIS 2 general circulation model and CO2 levels varying from 0.5-2.5 times present. The ocean ices over completely at 0.5-1.0X pre sent levels, with the final phase of sea ice growth occurring within a sing le model year. A qualitatively different 2.5X CO2 solution is close to equi librium and yields open water between similar to 25 degreesN and similar to 25 degreesS paleolatitude. The prevailing wind patterns suggest that an eq uatorial Pacific-type circulation may have developed in part of the Neoprot erozoic ocean.