Using Passive Seismology to Investigate Hydrological Forcing of Fast Glacier Flow in Greenland

Session: Environmental and Near Surface Seismology: From Glaciers and Rivers to Engineered Structures and Beyond
Type: Oral
Date: 4/29/2020
Time: 10:45 AM
Room: 110 + 140
Description: 

Net annual ice loss in Greenland currently contributes 1 mm/year to global sea level rise due to the acceleration of marine-terminating glaciers and steadily increasing surface melting and run-off. Since almost all surface meltwater is transported to the glacier bed, subglacial hydrological conditions are inherently conditioned by changes in surface ablation. To understand the effect of climate change on the contribution of marine-terminating glaciers to global sea-level rise, it is necessary to investigate the interplay between surface run-off, basal hydrology and ice velocity.

By enabling the continuous observation of icequakes, crevassing and tremor related to water transport, passive seismology is ideally suited to studying the links between water input and subglacial hydrological conditions. Here, we present a catalogue of 30,000+ cryoseismic events recorded at Store Glacier, a fast-flowing, marine-terminating glacier in West Greenland. A network of 12 near-surface and 3 deep borehole geophones was deployed alongside 4 GPS receivers and borehole sensor strings, as part of the multidisciplinary RESPONDER project. The seismic network recorded continuously between May-October 2018, capturing the onset and termination of the summer melt season. We found microseismic activity was bimodally distributed in depth, predominantly occurring near the surface and base of the glacier. Basal events were tightly clustered and seasonal changes were observed in the number, magnitude and distribution of events. In particular, basal icequake activity significantly decreased after the start of the melt season, consistent with a transition from basal conditions in which water is produced mainly from frictional heating at the bed to conditions in which much larger quantities of meltwater flow through the subglacial drainage system. Conversely, an increase in basal events was observed in September when surface ablation had ceased. This seasonal pattern is consistent with theoretical changes in sediment pore pressure, highlighting the role of soft sediments in regulating glacier dynamics.

Presenting Author: Charlotte M. Schoonman

Authors