Impact of the Greenland Ice Sheet on Northern Hemispheric Glacial-Interglacial Cycles

The cryosphere is considered to be one of the major influences on global climate change through the Cenozoic and into the future. Climate-ocean-cryosphere feedback mechanisms influence rapid transitions from glacial to interglacial states and vice versa. However, much of the sensitivity of the system and the dynamics involved in these abrupt transitions remain poorly understood. Here, we investigate the climatic sensitivity of the Northern Hemisphere to the removal of the Greenland ice sheet by applying a coupled GCM-ice sheet model. The focus of the study lies in analyzing the role of Greenland in the inception of continental ice sheets. Interglacial to glacial transitions are modeled using boundary conditions representative of Pliocene and late Pleistocene conditions. We use the latest (2008) version of the GENESIS GCM (version 3.0) asynchronously coupled to a standard thermomechanical ice-sheet model. Four simulations and a modern preindustrial control run are performed. A modern sensitivity test is run to investigate the effects of deglaciation on preindustrial climate conditions. The paleoclimate simulations use both modern and ice-free Greenland topography and vegetation, modern and 116ka orbits, and 250 and 400 ppmv CO2. The impact of the melted Greenland ice sheet reaches beyond the local-regional scale, with significant effects on Arctic sea ice, radiation budgets, snowfall, atmospheric circulation patterns, and moisture availability. This has an impact on internal feedback mechanisms vital for continental ice sheet inception. The effect of Greenland's interglacial survivability on Northern Hemisphere glacial cycles will be explored in a long, time continuous simulation using asynchronous GCM-ice sheet model coupling.