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Modeling the Pleistocene History of the Greenland Ice Sheet

One of the most profound and immediate consequences of anthropogenic climate change is sea level rise, which in large part is driven by the melting of polar ice sheets. The Greenland Ice Sheet (GrIS) contains enough ice to raise global sea level by ~7 meters. Fluctuations of the GrIS in response to past climate change provide an opportunity to better understanding the stability of the ice sheet during periods of climatic change. In this thesis, we use numerical ice-sheet models to understand the causes and consequences of past fluctuations of the Greenland ice sheet. In Chapters 3 and 4, we examined the last deglaciation (21,000 years ago until present day). The last deglaciation is the most recent time when the ice sheet retreated significantly, shrinking from its advanced state during the Last Glacial Maximum to a minimum configuration slightly smaller than the present-day ice sheet. We evaluate simulations of the deglaciation against a database of observations in order to understand the causes and drivers of ice-sheet retreat around the margin of the ice sheet for different climate scenarios. In Chapter 3, we show how abrupt climate change and changes in seasonality affected different regions of the ice sheet by modulating the timing of deglaciation around the margin. In Chapter 4, we analyze the mass balance processes that drove retreat in each region in order to identify the most salient drivers of retreat for each major drainage of the GrIS. Chapters 3 and 4 are in preparation for publication. In Chapter 5, we studied the initiation of the ice sheet during the warm Pliocene. We show that early fluctuations of the ice sheet can lead to the development of a large proglacial lake, which has major implications for landscape evolution, abrupt climate change, and ice-sheet stability during the Pliocene and Pleistocene. These proglacial lakes have the potential to affect erosional processes, and we argue that they may be responsible for carving Petermann canyon, a geomorphological feature which has important implications for future ice-sheet stability. Chapter 5 has been submitted for publication. In Chapter 6, we used different proxy records from the high Arctic to examine GrIS stability over the last 800,000 years. We show that proxy records from Lake El’gygytgyn (Arctic Siberia) and IODP Site 982 (North Atlantic Ocean) lead to divergent ice sheet histories which are nevertheless consistent with recent sea-level targets and the observation of cosmogenic nuclides in the bedrock below central Greenland. This study demonstrates the potential for numerical ice-sheet models to be used to assist with the identification of locales where additional data constraints could have the largest impact on our understanding of the history of the ice sheet. Chapter 6 is in preparation for publication.