HR: 13:55h
AN: C53A-02    [Abstracts]
TI: Direct Observations of Melt-Water Lake Drainage and the Establishment of an Efficient Surface to Basal Water Connection on the Greenland Ice Sheet
AU: * Das, S B
EM: sdas@whoi.edu
AF: Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole Road, Woods Hole, MA 02543, United States
AU: Joughin, I
EM: ian@apl.washington.edu
AF: Polar Science Center, Applied Physics Lab, University of Washington, 1013 NE 40th Street, Seattle, WA 98105, United States
AU: Behn, M D
EM: mbehn@whoi.edu
AF: Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole Road, Woods Hole, MA 02543, United States
AU: Howat, I
EM: ihowat@apl.washington.edu
AF: Polar Science Center, Applied Physics Lab, University of Washington, 1013 NE 40th Street, Seattle, WA 98105, United States
AU: King, M A
EM: m.a.king@newcastle.ac.uk
AF: School of Civil Engineering and Geosciences, University of Newcastle, Cassie Building, Newcastle Upon Tyne, NE1 7RU, United Kingdom
AU: Lizarralde, D
EM: danl@whoi.edu
AF: Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole Road, Woods Hole, MA 02543, United States
AU: Bhatia, M P
EM: maya.bhatia@gmail.com
AF: Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole Road, Woods Hole, MA 02543, United States
AB: Melt water lakes are recurrent features on the surface of the Greenland Ice Sheet margin that collect a large fraction of the annual surface melt across the ablation region. Many of these lakes fill and drain seasonally and are hypothesized to be a significant source of surface melt water to the ice sheet bed. We present results from field campaigns during the summers of 2006 and 2007 to investigate the filling and draining of two lakes, and the dynamic response of the ice sheet to drainage events. Measurements include air temperature, lake-water level, seismicity and local ice motion. One of the instrumented lakes was observed to be actively discharging water through a meltwater-cut channel in the side of the lake basin, which followed a deeply incised (5-10 m) supraglacial stream for nearly a kilometer before cascading into a moulin. The second instrumented lake drained catastrophically through a series of fractures and moulins that opened beneath the lake and that were subsequently mapped in the field following drainage. At this site, the 2.7-km-diameter lake, holding on the order of 0.03 km³ of water, drained entirely through 1 km of ice thickness in less than 2 hours. The peak rate of water flow during this event exceeds the average flow over Niagara Falls. This drainage event coincided with increased seismicity as well as rapid glacier uplift (1.2 m) and horizontal acceleration to nearly 8 km/yr as measured on the ice surface near the lake shoreline. Subsequent subsidence and deceleration of the ice sheet occurred over the following 24 hours. These observations provide evidence for the injection of surface melt water directly to the ice sheet bed, and also indicate the presence of an efficient basal drainage system that can quickly disperse large inputs of surface melt water.
DE: 0720 Glaciers
DE: 0726 Ice sheets
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: 2007 Fall Meeting