Greenland Ice Sheet dynamic response to inland expansion of a hydrologically-active ice-sheet bed

格陵兰冰盖对水文活跃冰盖床内陆扩张的动态响应

• 批准号: 2003464
• 负责人: Meredith Nettles
• 金额: $ 72.26万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-10-01 至 2024-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2003464&HistoricalAwards=false
• 关键词: Greenland; Ice; Sheet; dynamic; response

The Greenland Ice Sheet’s contribution to sea-level rise is accelerating, partly due to the acceleration of ice-sheet flow. Melt from the ice-sheet surface can reach the base of the ice and change ice flow, but this effect is complex and poorly understood. As the climate warms and the area of the ice surface undergoing surface melting expands inland, important questions include whether a larger area of the ice-sheet bed will receive injections of meltwater, and whether this will lead to faster flow. This 3-year project will make measurements of ice-sheet velocity and deformation along a transect of supraglacial lakes and moulins, which provide surface-to-bed meltwater pathways, on the Greenland Ice Sheet. These on-ice measurements will allow improved understanding of the processes controlling water access to the ice-sheet bed in regions of new supraglacial lake formation, with a focus on the process of hydro-fracture (water-driven fracture). The project will support an educational partnership between Lamont-Doherty Earth Observatory scientists and the New York City Department of Education to develop and implement a series of classroom sessions focused on geophysics applied to the Greenland Ice Sheet and New York City environments. This project will train one graduate student and support a postdoctoral scientist and an early career scientist.The current inland migration of surface melt is unprecedented in the observational era. A fundamental challenge in predicting the ice sheet’s dynamic flow response to the injection of surface meltwater at the ice-sheet bed is quantifying stresses in areas of nascent supraglacial lake formation in the mid- to upper-ablation zone of the ice sheet. In this project, Global Positioning System (GPS) and autonomous phase-sensitive radar units will be deployed over a 16-month period to measure ice-sheet surface velocity, surface and englacial strain, and stress transients around supraglacial lakes and moulins in the mid- to upper-ablation zone. These field data will be used in conjunction with geophysical inverse modeling techniques to compute surface and englacial stress and deformation patterns and to quantify the processes controlling water access to the ice-sheet bed. A major goal of the research is to address fundamental questions that will move us towards being able to describe the dynamic impact of surface-to-bed meltwater transit in prognostic ice-sheet models for both the Greenland Ice Sheet and Antarctic Ice Sheet. Quantifying the stresses necessary to initiate hydro-fracture or moulin formation over a range of ice thicknesses and viscous strain rates allows for the extension of these findings to thousands of existing and forthcoming lakes on grounded regions of these ice sheets. Moreover, combining observations of englacial strain and surface deformation has the potential to transform our understanding of ice-sheet deformation, by allowing an empirical test of the assumption that an elastic model is appropriate for inverting observations of surface deformation of glacial ice on short timescales. Answering the question of whether, and when, the Greenland Ice Sheet interior will respond dynamically to surface melt is vital for predicting sea-level rise. The engagement of school students and doctoral and postdoctoral trainees will broaden participation in the Earth Sciences and help train the next generation of interdisciplinary geoscientists.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

格陵兰冰盖对海平面上升的贡献正在加速，部分原因是冰盖流动的加速。冰盖表面的融化可以到达冰的底部并改变冰的流动，但这种影响是复杂的，人们对它的了解很少。随着气候变暖，冰面融化的区域向内陆扩展，重要的问题包括冰盖床的更大区域是否会接受融水的注入，以及这是否会导致更快的流动。这个为期3年的项目将测量格陵兰冰盖上沿沿着一条冰上湖泊和冰臼断面的冰盖速度和变形，这些湖泊和冰臼提供了从表面到冰床的融水通道。这些冰上测量将使人们更好地了解控制水进入新的冰上湖形成地区冰盖床的过程，重点是水力压裂（水驱动断裂）过程。该项目将支持拉蒙特-多尔蒂地球观测站科学家与纽约市教育部之间的教育伙伴关系，以制定和实施一系列课堂课程，重点是应用于格陵兰冰盖和纽约市环境的地球物理学。该项目将培养一名研究生，并支持一名博士后科学家和一名早期职业科学家。在预测冰盖的动态流动响应注入表面融水在冰盖床的一个基本挑战是量化应力新生的冰上湖形成的地区中，到上消融区的冰盖。在这个项目中，全球定位系统（GPS）和自主相敏雷达装置将在16个月的时间内部署，以测量冰盖表面速度，表面和冰内应变，以及在中到上消融区的冰上湖泊和冰臼周围的应力瞬变。这些实地数据将与地球物理逆向建模技术结合使用，以计算表面和冰内应力和变形模式，并量化控制水进入冰盖床的过程。这项研究的一个主要目标是解决基本问题，使我们能够描述格陵兰冰盖和南极冰盖的预测冰盖模型中地表到河床融水过境的动态影响。量化必要的应力，以启动水力压裂或冰臼形成在一系列的冰厚度和粘性应变率允许扩展这些研究结果的数千个现有的和即将到来的湖泊接地这些冰盖的地区。此外，结合观测的englacial应变和表面变形有可能改变我们的理解冰盖变形，允许一个弹性模型是适当的反演观测冰川冰表面变形的短时间尺度的假设进行实证检验。格陵兰冰盖内部是否以及何时会对表面融化做出动态反应，这一问题对于预测海平面上升至关重要。学校学生和博士及博士后学员的参与将扩大对地球科学的参与，并有助于培养下一代跨学科的地球科学家。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。