Hydrologic drainage of the Greenland Ice Sheet

Abstract

AbstractA simple hydrologic drainage network for the Greenland Ice Sheet is modelled from available digital elevation models (DEMs) of bedrock, and surface topography and assumptions of hydrostatic water pressure, uniform hydraulic conductivity, and no conduit flow within the ice sheet. As such, it is a first‐order model best suited for broad‐scale hydrological assessment. Results identify 293 distinct hydrologic basins (185–117 000 km2) together with their ‘realized’ (wet) and ‘unrealized’ (dry) drainage patterns. Intersection with 1991–2000 Polar MM5 (PMM5) mesoscale climate model hindcasts of meltwater runoff suggest that these basins route varying amounts of water to the ice edge, ranging from 0 to 16 km3 annually and totalling 242 km3/year for the entire ice sheet. Regionally speaking, average annual volumetric meltwater production (km3/year) is highest in southwest and lowest in northeast Greenland, with greater hydrologic activity in western regions than in eastern regions for a given latitude. The extent to which meltwater truly reaches the ice margin as modelled is difficult to test. However, the simulated flow outlet locations show qualitative agreement with the locations of 460 observed meltwater outlets (proglacial lakes, streams, and rivers; and sediment plumes into fjörds) mapped continuously along the ice sheet perimeter. On average, about 36% of the modelled drainage network was activated (i.e. received water) over the 1991–2000 study period. Remaining areas, barring dynamic changes to ice‐surface topography, would presumably activate if surface melt penetrates deeper into the ice sheet interior. Both new datasets are freely available for scientific use at the National Snow and Ice Data Center (ftp://sidads.colorado.edu/pub/DATASETS/parca/nsidc‐0372‐hydrologic‐outlets; ftp://sidads.colorado.edu/pub/DATASETS/parca/nsidc‐0371‐hydrologic‐sub‐basins). Copyright © 2009 John Wiley & Sons, Ltd.