资源环境科技发展态势分析平台

Subglacial drainage systems are known to critically control ice flows, but their spatial configuration and temporal evolution are poorly constrained due to inaccessibility. Here we report a 12-year-long monitoring of the drainage underneath Bering Glacier, Alaska, by correlating ambient noise recorded at two seismic stations on the sides of the glacier. We find that the seismic surface waves traveling across Bering Glacier slowed down by 1-2% during its latest 2008-2011 surge, likely due to the switch of the subglacial drainage from a channelized system to a distributed system. In contrast to current models, the relative amplitude of velocity reductions for Rayleigh and Love waves requires the distributed drainage to be highly anisotropic and aligned perpendicular to the ice flow direction. We infer that the subglacial water flow is mainly through a network of transverse basal crevasses during surges and thus can sustain the high water pressure and ice flow speed.

Plain Language Summary Water underneath glaciers strongly controls how ice flows. However, it is difficult to map how water flows under the cover of hundreds or thousands of meters of ice. Here we propose a new approach to image and monitor water in glaciers, by using seismic waves continuously excited by the ocean and atmosphere. With sensors on both sides, we can measure the time seismic waves take to travel across a glacier. More water in glacier can slow down the seismic waves. For Bering Glacier, Alaska, we detected a substantial slowdown of seismic waves from 2008 to 2010, which coincides with a period when the ice flow accelerated by a factor of 10. We interpret the observed seismic slowdown as caused by water flowing through a network of crevasses near the base of the glacier.