Sensitivity Studies of Northern Hemisphere Glaciation Using an Atmospheric General Circulation Model

Abstract

Abstract The U.K. University Global Atmospheric Modeling Programme GCM is used to investigate whether the growth of Northern Hemisphere ice sheets could have been initiated by changes of orbital parameters and sea surface temperature. Two different orbital configurations, corresponding to the present day and 115 kyr BP are used. The reduced summer solar insulation in the Northern Hemisphere results in a decrease of the surface temperature by 4° to 10°C in the northern continents and to perennial snow in some high-latitude regions. Therefore, the model results support the hypothesis that a deficit of summer insulation can create conditions favorable for initiation of ice sheet growth in the Northern Hemisphere. A decreased sea surface temperature northward of 65°N during the Northern Hemisphere summer may contribute to the maintenance of ice sheets. A simple mixed-layer ocean model coupled to the GCM indicates that the changes of sea surface temperature and extension of sea ice due to insulation changes pl...