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Constraining the causes, mechanisms and impacts of rapid changes in Greenland's outlet glaciers

The contribution of the Greenland ice sheet to sea level has more than doubled in the last decade. Most of this increase is due to accelerated ice discharge through marine-terminating outlet glaciers to the ocean. These glaciers accelerated as their calving fronts retreated, following a sustained period of ice thinning, and previous studies have shown that the accelerations may be explained by the perturbation to the glacier’s stress field caused by retreat. Furthermore, these changes occurred during a period of rapid climate warming, leading to the possibility that the dynamics of the ice sheet can respond rapidly to changes in climate. If this is the case, the ice sheet may be far more sensitive to warming than currently predicted, as outlet glacier dynamics are not included in numerical ice sheet models used to predict rates of future sea level rise.

These models do not include outlet glacier dynamics because the mechanisms controlling outlet glacier change, including links between glacier dynamics and climate and the response of interior ice sheet, are largely unknown. In order to better understand the controls on outlet glacier behavior and the potential impact on future ice sheet mass-balance we propose 1) a detailed investigation of recent changes in outlet glacier dynamics using a suite of new and existing remote sensing data, including changes in ice velocity and thickness 2) the development of analytical and numerical models, constrained by the observations, to elucidate the physical processes controlling outlet glacier change and 3) the application of these models to the prediction of near-future changes in glacier dynamics and ice sheet mass-balance. By constraining relationships between climate, outlet glacier dynamics and ice sheet mass-balance, this study will provide a detailed quantitative framework upon which future, improved prognostic ice sheet models will be built.

Funded by grant NNX08AQ83G from the National Aeronautics and Space Administration.