Feedbacks between Arctic climate change and glacial ice discharge: Using seismic observations to constrain water transport to the bed of the Greenland Ice Sheet
OCCI/Arctic Research Initiative
2007 Funded Project
Some of the most dramatic predicted effects of climate change, including global sea level rise and the alteration of ocean circulation patterns, result from the response of polar ice sheets to rising global temperature. Until recently it was believed that the response of thick (> 1 km) ice sheets to climate change would be relatively slow due to the long time scales (~1000 yr) needed for temperature variations at the surface to reach the bed via thermal conduction and diffusion. Recent observations from the Greenland Ice Sheet, however, suggest that ice sheets have the potential to respond much more rapidly and dramatically to climate change than was previously believed. Specifically, new data show ice-flow acceleration on time scales of days to weeks following the onset of surficial melting, suggesting that meltwater drains advectively through the ice sheet, rapidly lubricating and warming the bed. Understanding the mechanisms of meltwater transport is thus critical for incorporating these feedbacks into models of ice-sheet evolution and for estimating the rates and magnitudes of past and future ice sheet drawdown and sea level change.
One mechanism that has been proposed to rapidly transport meltwater from the surface to the bed of an ice sheet is the propagation of water-filled fractures that initiated beneath supraglacial lakes that form annually at the surface. However, while theoretical models suggest this is a plausible transport mechanism, water-filled crack propagation has never been observed in thick subfreezing ice sheets. As part of the WHOI Arctic Initiative we propose to deploy a new network of seismometers around two supraglacial lakes on the Greenland Ice Sheet. These lakes are currently being monitored by as part of a 3-year NSF project and have been observed to drain seasonally. The proposed seismic network will enable us to constrain seismicity (i.e., icequakes) associated with lake drainage and determine 1) whether crack propagation coincides with drainage and 2) the maximum depth extent of crack penetration. These measurements would provide the first direct evidence for rapid meltwater transport from supraglacial lakes to the bed of Greenland Ice Sheet.