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PUBLISHED ONLINE: 22 DECEMBER 2013 | DOI: http://www.nature.com/doifinder/10.1038/ngeo2043
Web End =10.1038/NGEO2043
Extensive liquid meltwater storage in rn within the Greenland ice sheet
Richard R. Forster1*, Jason E. Box2,3, Michiel R. van den Broeke4, Clment Mige1, Evan W. Burgess1, Jan H. van Angelen4, Jan T. M. Lenaerts4, Lora S. Koenig5, John Paden6, Cameron Lewis6,
S. Prasad Gogineni6, Carl Leuschen6 and Joseph R. McConnell7
Mass loss from the Greenland ice sheet contributes signicantly to present sea level rise1. High meltwater runoff is responsible for half of Greenlands mass loss2. Surface melt has been spreading and intensifying in Greenland, with the highest ever surface area melt and runoff recorded in 20123. However, how surface melt water reaches the ocean, and how fast it does so, is poorly understood. Firnpartially compacted snow from previous yearspotentially has the capacity to store signicant amounts of melt water in liquid or frozen form4, 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 rn in the southern Greenland ice sheet. We nd a substantial amount of water in this rn 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 550 m. The perennial rn aquifer could be important for estimates of ice sheet mass and energy budget.
The mass of liquid or refrozen melt water that could be stored in firn pore space throughout the percolation zone of the entire ice sheet is estimated to be between 322 and 1,289 Gt (ref. 4). In the western part of the ice sheet, the possibility of liquid water persisting within the upper 10 m of the snow/firn5 or in moulins6
during winter is suspected. Discharge measurements at ice marginal streams indicate winter water release, suggesting that some melt water may be stored englacially or at the bed and is released months after the end of the melt season7. However, there has been no account of directly observed liquid water in the firn persisting through...