Collaborative Research: Using seismic tremor to constrain seasonal variations in subglacial hydrology at the bed of the Greenland ice sheet

据估计，格陵兰冰盖在下一个世纪对海平面上升的影响从几厘米到一米多不等。在地势低洼、人口稠密的沿海地区，每年几毫米的差异可能很大，因为在这些地区，规划具有如此大的不确定性，对政府、社区和企业来说，经济和社会成本很高。这项研究将提高我们对地表径流增加如何影响冰流以及随后从格陵兰冰盖到海洋的水量损失的理解。研究人员将采用一种新的方法，利用地震震颤来量化格陵兰冰盖上冰下水文系统和冰面速度的季节性变化。该项目将支持两名研究生，一名博士后科学家和一名早期职业科学家。 此外，一名记者将陪同科学小组前往研究地点，为普通观众制作一系列媒体，包括每日广播日记，在国家公共广播电台和其他媒体上播出。 在这项研究中，研究人员将同时部署位于同一地点的地震和GPS阵列，以监测格陵兰冰盖西缘一个经过充分研究的地点的冰下融水流动和冰面速度。该网站有很强的季节性速度变化，经历了显着的加速在初夏（100%大于冬季速度）和显着放缓在夏末。该团队将使用冰下流体流动和表面速度的共同定位测量来评估地震震颤是否可以解决厚（#8805; 1公里）冰区域冰下水文的季节性变化。 具体而言，这些数据将限制冰下水流的渠化是否以及何时发生，以及冰下水道的特征（如密度和间距）如何随时间变化。 最后，冰面速度将与冰下渠化，以确定这一过程是否符合现有的模型，在该地区观察到的特征季节性速度变化。这种方法有可能提供一个强大的新技术，研究冰下融水流动的地区是很难访问的。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

Estimates of the Greenland ice sheet's contribution to sea level rise over the next century range from a few centimeters to over one meter. Differences of a few millimeters per year may be significant in low-lying, populous coastal areas where planning with such a large range of uncertainty has high economic and social costs for governments, communities, and businesses. This study will improve our understanding of how increases in surface runoff will influence ice flow and subsequent loss of water mass from the Greenland ice sheet to the oceans. The investigators will employ a novel approach that uses seismic tremor to quantify seasonal changes in the subglacial hydrologic system and ice surface velocities on the Greenland ice sheet. The project will support two graduate students, a postdoctoral scientist, and an early career scientist. In addition, a reporter will accompany the science team to the study site to produce a range of media for general audiences, including a daily radio diary to air on National Public Radio stations other outlets. In this study, the investigators will deploy co-located seismic and GPS arrays simultaneously to monitor subglacial meltwater flow and ice surface velocities at a well-studied site on the western margin of the Greenland ice sheet. The site has strong seasonal velocity variability, experiencing dramatic acceleration in the early summer (100% greater than winter velocities) and pronounced slow-down in the late summer. The team will use co-located measurements of subglacial fluid flow and surface velocities to assess whether seismic tremor can resolve seasonal changes in subglacial hydrology in regions of thick (≥ 1 km) ice. Specifically, the data will constrain if and when channelization of sub-glacial flow occurs and how characteristics of subglacial channels, such as density and spacing, vary with time. Finally, ice surface velocities will be correlated with sub-glacial channelization to determine whether this process is consistent with existing models for the characteristic seasonal velocity variations observed in this region. This approach has the potential to provide a powerful new technique to study subglacial meltwater flow in regions that are difficult to access.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.