Can Milankovitch orbital variations initiate the growth of ice sheets in a general circulation model?

摘要: The Goddard Institute for Space Studies climate model is used to investigate whether the growth of ice sheets could have been initiated by solar insolation variations. Three different orbital configurations are used, corresponding 116 and 106 kyr B.P., a modified field with greater reductions in summer at high northern latitudes. time periods chosen those which geophysical evidence suggests may growing rapidly. reduced characteristic all experiments thought be necessary condition allowing snow last through summer, build. results show that fails maintain cover locations suspected initiation major sheets, despite fall insolation. When 10-m-thick was inserted where continental existed during Last Glacial Maximum, failed it as well, producing energy mass imbalances would remove within 5 years. Only when ocean surface temperatures were adjusted their peak age values able keep any additional ice, then only very restricted region Baffin Island. indicate there wide discrepancy between model's response Milankovitch perturbations sheet initiation. As grow or sustain low-altitude high-latitude maximum radiation reduction (120–110 B.P.), unlikely done so other several hundred thousand If correct, indicates occurred an extremely ablative environment, thus demanded some complicated strategy, else forcing addition variation influence (and CO2 reduction), imply we do not really understand cause ages connection. nearly sensitive enough forcing, implications projections future change.