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

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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.