Collaborative Research: Quantifying Heat/Mass Structure and Fluxes Through the Full Thickness of Greenland?s Percolation Zone

覆盖格陵兰冰盖的大部分积雪在夏季融化。融化的水在下面的雪中渗透并重新冻结。随着时间的推移，这种变化的积雪，也就是所谓的降雪，可以达到100米深。降雪结构的这些变化因此改变了冰内以及冰盖和大气之间的热流。然而，到目前为止，降雪层的完整结构尚不清楚，因为观测仅限于浅层。为了解决这一重要的认识不足，研究人员提议进行一项实地研究，重点是钻探一些深冰芯，目的是描述深雪冰的热和物理特性。这些信息对于预测冰盖的体积变化和海平面上升至关重要。该项目涉及研究生和本科生，他们是一名早期的职业科学家，并包括公共宣传活动。该项目将测试以下假设：格陵兰低海拔地区的深层降雪经历了由水渗透/再冻结和热强化压实所控制的致密化。该项目将开发一种新的热水钻井系统，以快速穿透100米，穿过寒冷和潮湿积雪混合的技术挑战条件。现场数据收集将包括数字温度串、视频和岩心测井，以及仪表化钻杆。这项工作将对积雪的厚度、密度、渗透性和热状态进行全面深入的表征。此外，十年前在该地区进行的钻探将使调查人员能够评估冷杉资产随时间的变化。最终，了解格陵兰-S堆积区的融水保留和再冻结过程对于推进冰盖体积变化、流动动力学和海平面变化的预测是至关重要的。该项目将提供实地和实验室研究经验，对大量本科生和研究生产生影响。该项目将支持一名新资助的年轻调查人员，并将包括针对格陵兰和蒙大拿州西部普通公众和中学生的外联活动。

Much of the snow that covers the Greenland Ice Sheet experiences melting during summer months. This meltwater percolates and refreezes within the underlying snow. Over time, this altered snow, which is referred to as firn, can reach to depths of 100 meters. These changes in firn structure consequently alter the heat flow within the ice, and between the ice sheet and the atmosphere. As yet however, the full structure of the firn layer is unclear as observations have been limited to shallow depths. To address this important lack of understanding, the investigators propose a field study focused on drilling a number of deep ice cores, with the goal of characterizing the thermal and physical properties of the deep firn ice. This information is essential to predicting ice sheet changes in volume and sea level rise. The project involves graduate and undergraduate students, an early career scientist, and includes public outreach activities.The project will test the hypothesis that the deep firn in the low elevation regions of Greenland experience densification governed by water infiltration/refreezing and thermally enhanced compaction. The project will develop a novel hot water drilling system to quickly penetrate 100 meters through the technically challenging conditions of intermixed cold and wet firn. In situ data collection will include digital temperature strings, video and core logging, and an instrumented drill stem. This work will yield a full-depth characterization of firn thickness, density, permeability, and thermal status. Moreover, drilling conducted a decade earlier in the region will permit the investigators to assess changes in firn properties over time. Ultimately, understanding meltwater retention and refreezing processes across Greenland?s accumulation area is essential for advancing prediction of ice sheet volume change,flow dynamics, and sea level change. The project will provide field and laboratory research experiences impacting a large number of undergraduate and graduate students. The project will support a newly funded young investigator, and will include outreach activities targeting the general public and middle school students in Greenland and Western Montana.