Researchers discover a meltwater aquifer beneath the southern Greenland ice sheet
The aquifer, representing a previously unknown storage mode for water within the ice sheet, was discovered in 2011, when researchers drilled deep beneath the ice layer and found water flowing back to the surface despite the freezing air temperatures of -15ºC.
The aquifer covers an area of about 70,000 km², an area the size of Ireland, with depth to the top of the water table of 5 to 50m.
The liquid water is held in firn—partially compacted snow—which has the “capacity to store significant amounts of meltwater in liquid or frozen form,” researchers said, “and thus delay its contribution to sea level. Here we present direct observations from ground and airborne radar, as well as ice cores, of liquid water within firn in the southern Greenland ice sheet.”
Meltwater from the Greenland ice sheet significantly contributes to the rise in sea levels. About half of Greenland’s mass loss has been attributed to meltwater runoff.
“Surface melt has been spreading and intensifying in Greenland, with the highest ever surface area melt and runoff recorded in 2012,” say the researchers.
A Surprise Discovery
“This discovery was a surprise,” said Prof Rick Forster the lead author from the University of Utah.
“Instead of the water being stored in the air space between subsurface rock particles, the water is stored in the air space between the ice particles, like the juice in a snow cone.”
Scientists are puzzled about the speed, direction and final destination of the meltwater.
“It depends on whether it is currently connected to a system that is draining into the ocean or if it is a bit isolated and completely acting as a storage source without a current connection,” said Forster.
“We don’t know the answer to this right now. It’s massive, it’s a new system we haven’t seen before – we need to understand it more completely if we are to predict sea level rise.”
The research is published in the journal, Nature Geoscience, Published online 22 December 2013.
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Greenland’s Surface Ice Melt
An all-time record high temperature for Greenland may have been set in 2013, according to NSIDC.
The graph above shows the daily percent of the Greenland Ice Sheet surface that has shown melt, as of August 19, 2013 (red), along with the daily surface melt extent for 2012 (blue) and the average melt extent for 1981 to 2010 (dashed line). Two peak extent days are noted. Credit: National Snow and Ice Data Center/Thomas Mote, University of Georgia – High-resolution image
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Title: Extensive liquid meltwater storage in firn within the Greenland ice sheet
Authors: Richard R. Forster et al.
Abstract:
Mass loss from the Greenland ice sheet contributes significantly to present sea level rise. High meltwater runoff is responsible for half of Greenland’s mass loss. Surface melt has been spreading and intensifying in Greenland, with the highest ever surface area melt and runoff recorded in 2012. However, how surface melt water reaches the ocean, and how fast it does so, is poorly understood. Firn—partially compacted snow from previous years—potentially has the capacity to store significant amounts of melt water in liquid or frozen form, and thus delay its contribution to sea level. Here we present direct observations from ground and airborne radar, as well as ice cores, of liquid water within firn in the southern Greenland ice sheet. We find a substantial amount of water in this firn aquifer that persists throughout the winter, when snow accumulation and melt rates are high. This represents a previously unknown storage mode for water within the ice sheet. We estimate, using a regional climate model, aquifer area at about 70,000 km2 and the depth to the top of the water table as 5–50 m. The perennial firn aquifer could be important for estimates of ice sheet mass and energy budget.
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