Doctoral Dissertation Research: Modeling the Influence of Surface Meltwater on the Ice Dynamics of the Greenland Ice Sheet

观测表明，格陵兰冰盖西坡夏季冰速增加与多年来融水产量增加之间存在关系。 这个博士论文研究项目将映射的空间分布的moulins（垂直管道，传输表面融水到冰盖的床）基于高分辨率的卫星图像在1,100平方公里的区域内的内陆冰东北部的雅各布港/伊卢利萨特，西格陵兰岛（在纬度约70度N）。 博士生将比较观察到的冰臼位置与历史上的冰臼位置，根据1985年的航空摄影地形图确定，以确定随着时间的推移，冰臼分布的变化。 一个多元回归模型将被推导出来，以解释整个研究区域的冰臼密度。 冰下水的压力，从冰臼密度确定，将被转换为基础的滑动速度使用以前验证的高山冰川滑动定律。 季节性融化加速现象，然后将使用一个耦合的热力学冰盖模型在今天和未来的气候条件下，后者包括模拟增加表面融水生产。 该项目的主要目标是模拟观测到的融化引起的冰流加速的物理基础，并预测这种机制将如何影响未来的冰盖动力学。 该项目的第二个目标是确定随着时间的推移，冰臼分布的变化。 将通过从高分辨率（大约一米像素）商业卫星图像中提取特征来确定冰川冰川泥隙的分布。 目前，冰川和冰盖对海平面上升的估计主要基于表面质量平衡，忽略了冰速变化的可能影响，冰山崩解增加导致冰损失增加。 因此，该项目将直接解决需要提高对格陵兰冰盖冰流加速可能造成海平面上升的基本认识的问题。 该项目的成果将是研究区域内冰臼密度图和基底滑坡的规模和空间分布图。 该项目将通过提供新的表面水文学模型（即冰臼密度）以及基底滑动（冰下水压力和冰-基岩界面处冰速度之间的关系），提供有关融水对冰盖冰动力学影响的新见解。 在这个项目中的参数化和概念上的进步可能将是有用的高山冰川社区以及。 该项目将应用这些理论进展来探索格陵兰冰盖西侧冰面速度与夏季融化持续时间之间观测到的相关性的物理基础。 作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。

Observations have shown a relationship between increased summer ice velocity and increased meltwater production over several years on the western slope of the Greenland Ice Sheet. This doctoral dissertation research project will map the spatial distribution of moulins (vertical conduits that transmit surface meltwater to the bed of the ice sheet) based on high-resolution satellite imagery within a 1,100 square-km area of the inland ice northeast of Jakobshavn/Ilulissat, West Greenland (at a latitude of roughly 70-degrees N). The doctoral student will compare observed moulin locations to historical moulin locations as identified on a topographical map based on 1985 aerial photography in order to identify changes in moulin distribution over time. A multivariate regression model will be derived to explain moulin density across the study area. Subglacial water pressures, determined from moulin density, will be translated into basal sliding speed using sliding laws previously validated for alpine glaciers. The seasonal melt-acceleration phenomenon then will be modeled using a coupled thermodynamic ice sheet model under both present day and future climatic conditions, with the latter including a simulated increase in surface meltwater production. The primary goal of this project is to model the physical basis of the observed melt-induced acceleration of ice flow and predict how this mechanism will influence ice sheet dynamics in the future. The secondary goal of the project is to identify changes in moulin distribution over time. Moulin distribution will be determined via feature extraction from high resolution (with roughly one meter pixels) commercial satellite imagery.Sea-level rise is a highly relevant societal concern. The estimated sea-level rise contribution from glaciers and ice sheets currently is based primarily on surface mass balance and ignores the possible influence of changing ice velocity, with increased ice loss related to increased iceberg calving. This project therefore will directly address the need to improve basic understanding of the potential sea-level rise contribution due to accelerated ice flow in the Greenland Ice Sheet. The products of this project will be maps of moulin density and of the magnitude and spatial distribution of basal slide within the study area. This project will provide new insights regarding the influence of meltwater on the ice dynamics of ice sheets by contributing novel models of surface hydrology (i.e moulin density) as well as basal slide (the relation between subglacial water pressure and ice velocity at the ice-bedrock interface). The parameterizations and conceptual advances made in this project likely will be useful for the alpine glacier community as well. This project will apply these theoretical advances to probe the physical basis of the observed correlation between ice surface velocity and duration of summer melt on the western flank of the Greenland Ice Sheet. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.