Collaborative Research: Testing the Impact of Climate Change on the Greenland Ice Sheet: Combining Past Climate Records with a Coupled Climate and Ice-Sheet Model

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This project is aimed at understanding the response of the Greenland Ice Sheet to past climate changes, with the ultimate goal of improving predictions of its response to future change. The investigators will compile all available data on the size of the ice sheet at times in the past 20,000 years. They will also gather data on the history of surface air temperatures, the accumulation rate of ice, and surrounding ocean temperatures from ice- and sediment core records. The climate records will be used as inputs to a numerical model of the regional climate and the Greenland Ice Sheet to investigate the response of the ice sheet to changes in climate conditions. Direct observations of changes in the Greenland Ice Sheet only span the past few decades, making it difficult to identify a trend and distinguish it from natural variability. The relative roles of oceanic and atmospheric warming in driving Greenland Ice Sheet retreat also remain poorly constrained and debated. Ascertaining past Greenland Ice Sheet response to a warming climate can provide important bounds on the rates at which the ice sheet can retreat and lose mass. The last deglaciation (20 to 6 thousand years ago) provides a natural experiment for assessing large-scale Greenland Ice Sheet response to changing conditions including rising atmospheric carbon dioxide.Three fundamental questions will be addressed by this project. 1) What drove the disparate behavior between west-east margins and southern margins of the ice sheet during the last deglaciation and how does this relate to abrupt deglacial climate change? 2) What is the relative importance of atmospheric versus oceanic warming in causing rapid ice margin retreat during the last deglaciation? 3) Given the large, sustained deglacial climate warming, what is the maximum rate that the Greenland Ice Sheet has delivered ice to the ocean as constrained by the geologic record and how do those rates compare with ice-sheet model simulations? Addressing these questions will 1) provide essential insight into how the broader Greenland Ice Sheet behaves in a warming world, 2) test the sensitivity of terrestrial versus marine ice-margin settings to warming, and 3) test the fidelity of a Greenland Ice Sheet model that can be applied to future simulations. The investigators will disseminate scientific results to the public through lectures and publications in popular science magazines, and to museums with movies and animations on the Magic Planet visualization system. The project will train a postdoc and Ph.D. student (geochronology-data analysis and numerical modeling) in a multi-disciplinary approach to paleoclimatology, glaciology, glacial geology, and paleoceanography. Undergraduates will work on the project, with a goal of recruiting under-represented groups in the geosciences.