MRI: Development of a Thermal Melt Probe System for Extensive, Low-Cost Instrument Deployment at the Bed of the Greenland Ice Sheet

这项核磁共振成像建议的目的是开发一套低成本的仪器，用于研究冰川和冰盖底部的水文系统。估计格陵兰冰盖(地理信息系统)未来对海平面上升的贡献，关键取决于对动态冰下水文学的定量理解。冰下水文网络中的加压水强烈地调节着冰盖在其床上的滑动，即使这些网络在时间和空间的大范围尺度上随着输入速率和地表融水的数量而演变。因此，冰盖下的水压力是系统中唯一最重要的动态和诊断变量。尽管这很重要，但由于现有方法的实际局限性，目前很少有现场测量冰盖下的压力(或任何其他冰下变量)。现有的能够到达这些深度的冰钻和取心钻机包括数以吨计的设备和燃料，由几个或几个人的工作人员操作。因此，在不大幅增加后勤负荷的情况下，许多项目无法获得基本水压的测量，尽管这些数据与它们的调查直接相关。研究人员提议开发热融化探测器，这种探测器将以每小时几米的速度自动融化冰。在小型化仪器、固态电源控制电子设备和高压布线方面的进步，现在可以使用小型、逻辑轻便的熔融探头对基础水压和其他变量进行可靠、可靠和复杂的测量。该提议是基于一个小规模的原型，该原型已经在海冰和山脉冰川中建造和测试。调查人员计划在格陵兰岛西部600-1000米的冰层下安放至少一个探测器，并获取基本水压数据，以作为一系列进一步提案的概念验证，从而使新系统投入使用。本科生和研究生将在这个项目的过程中接受培训。

The aim of this MRI proposal is to develop a low-cost instrumentation package for studying the hydrologic system at the bases of glaciers and ice sheets. Estimating future contributions of the Greenland Ice Sheet (GIS) to sea level rise depends critically on a quantitative understanding of dynamic subglacial hydrology. Pressurized water in subglacial hydrological networks strongly modulates sliding of the ice sheet over its bed, even as those networks evolve in response to input rates and quantities of surface melt water, on a wide range of scales in time and space. The pressure of water beneath the ice sheet is thus the single most important dynamic and diagnostic variable in the system. Despite this importance there are presently very few field measurements of pressure (or any other subglacial variable) beneath ice sheets, because of the practical limitations of existing methods. Existing ice drilling and coring rigs capable of reaching those depths comprise tons of equipment and fuel, and are operated by crews of several or more people. Without dramatically increasing their logistics loads, many projects are therefore unable to acquire measurements of basal water pressure, despite direct relevance of such data to their investigations. The investigators propose to develop thermal melt probes, that would melt their way autonomously down through the ice at speeds of meters per hour. Advances in miniaturized instrumentation, solid-state power-control electronics, and high-voltage cabling now enable reliable, robust and sophisticated measurements of basal water pressure and other variables with small, logistically light melt probes. The proposal is based on a subscale prototype that has been built and tested in sea ice and a mountain glacier. The investigators plan to commission the new system by emplacing at least one probe beneath 600-1000 m of ice in western Greenland and acquiring basal water pressure data to serve as a proof-of-concept for a wide range of further proposals. Undergraduate and graduate students will be trained in the course of this project.