Modeling the Dynamics of Surface-slope Reversals and their Role in the Formation and Stability of Subglacial Lakes

该奖项支持一项为期三年的建模工作，以了解围绕冰流和冰架上冰-空气表面坡度逆转的动态，以及对冰下湖泊的形成和稳定性的影响。冰-空气表面坡度的局部反转可能会通过水力梯度的反转导致基水和地表水的滞留，分别产生冰下和冰上湖泊。就冰下湖泊而言，一旦形成了这样一个相当大的加压水蓄水池，就有可能以大洪水的形式或以较小但持续的冰下水流增加的时间段的形式进行排水。这项研究试图扩展已做的一些初步工作，以包括时间相关性和更广泛的参数和几何阵列。这些方法将涉及一套模型的使用，所有这些模型都将包括纵向偏差应力和底部剪切应力，其中一些还考虑了横向阻力和内部垂直剪切。拟议活动的学术价值包括更好地了解在冰流/冰架系统中形成地表-坡度反转的过程和参数，以及洞察由于坡度反转而形成的冰下湖泊的稳定性。这项活动产生的更广泛的影响包括提供研究冰流/冰架系统动态的工具，更好地了解暴发洪水背后的物理原理，以及深入了解冰流与其冰下水系统的耦合情况。这项研究将支持开始博士后研究的研究。研究结果将被纳入课程和公共宣传，每年为数百到数千人提供服务。

This award supports a three-year modeling effort to understand the dynamics surrounding ice-air surface slope reversals on ice streams and ice shelves, with implications for the creation and stability of subglacial lakes. Local reversal of the ice-air surface slope may lead, through a reversal of the hydraulic gradient, to the trapping of basal and surface water, producing subglacial and supraglacial lakes, respectively. In the case of subglacial lakes, once such a sizable reservoir of pressurized water is created the potential exists for drainage, in the form of large outburst floods or as smaller, but sustained, periods of increased subglacial water flow. The research seeks to extend some initial work that has been done to include time-dependence and a wider array of parameters and geometries. The methods will involve the use of a suite of models, all of which will include longitudinal deviatoric and basal-shear stresses, with some also taking account of lateral drag and internal vertical shear. The intellectual merit of the proposed activity includes an improved understanding of the processes and parameters involved in the formation of surface-slope reversals in ice-stream/ice-shelf systems, as well as insight into the stability of subglacial lakes formed as a consequence of slope reversals. The broader impacts resulting from this activity include the provision of tools to study the dynamics of ice-stream/ice-shelf systems, an improved understanding of the physics behind outburst floods, and insights into the coupling of ice streams with their subglacial water systems. The research will support the studies of a beginning postdoctoral researcher. Results of the research will be incorporated into courses and public outreach serving anywhere from hundreds to thousands of people per year.