氷床モデルSICOPOLISを用いたハインリッヒ・イベントの数値実験およびモデル間相互比較

Heinrich events (HEs) are large scale surges of the Laurentide Ice Sheet (LIS) over Hudson Bay and Hudson Strait. These surges are thought to be triggered by the internal dynamics of the ice sheet. Therefore it is important to investigate HEs in order to estimate the effect on climate variability. It will be tested whether the 3D ice sheet model SICOPOLIS is able to simulate such large scale surges, and what is their sensitivity to change in surface and basal boundary conditions. The model domain is a flat horizontal square. The ice sheet is built up from zero ice thickness over 200 ka, with atemporally constant glacial-climate forcing. The bedrock elevation remains flat throughout the simulations. Further, the geothermal heat flux is applied directly at the bottom of the ice sheet. We could generate many saw-shape oscillations of the ice sheet expressing a series of growth phases and HEs from the standard run. The growth time is about 7 ka, whereas the subsequent HE collapse lasts only for several hundred years. Parameter studies showed that surface temperature affects the ice volume, and surface accumulation affects the periodicity of HEs. Further, the strength of the subglacial sediment affects the amplitude of ice-volume changes. Therefore, surface and basal conditions of the LIS are crucial elements for HEs