LATE PLEISTOCENE ICE-AGE SCENARIOS BASED ON OBSERVATIONAL EVIDENCE

Ice age scenarios for the last glacial-interglacial cycle, based on ob servations of Boyle and Keigwin concerning the North Atlantic thermoha line circulation and of Bamola et al. concerning atmospheric CO2 varia tions derived from the Vostok ice cores, are herein analyzed. Northern Hemisphere continental ice sheets are simulated with an energy balanc e model (EBM) that is asynchronously coupled to vertically integrated ice sheet models based on the Glen flow law. The EBM includes both a r ealistic land-sea distribution and temperature-albedo feedback and is driven with orbital variations of effective solar insolation. With the addition of atmospheric CO2 and ocean heat flux variations, but not i n their absence, a complete collapse is obtained for the Eurasian ice sheet but not for the North American ice sheet. We therefore suggest t hat further feedback mechanisms, perhaps involving more accurate model ing of the dynamics of the mostly marine-based Laurentide complex appe ars necessary to explain termination I.