S.M. Lewis & L.C. Smith, Hydrologic Processes, 23 (2009), Hydrologic drainage of the Greenland Ice Sheet

Hydrologic Processes, (May 2009), Vol. 23, No. 14, pp. 2004-2011; DOI: 10.1002/hyp.7343

Hydrologic drainage of the Greenland Ice Sheet

Sarah M. Lewis ^1,* and Laurence C. Smith ^1,2

(Received 8 September 2008; accepted 24 March 2009.)

^Abstract

A 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).

1Department of Geography, University of California, Los Angeles, CA, U.S.A. 2Department of Earth & Space Sciences, University of California, Los Angeles, CA, U.S.A. *Correspondence: Department of Environmental Science, Policy, and Management, University of California, Berkeley, 137 Mulford Hall #3114, Berkeley, CA 94720-3114, U.S.A. e-mail: sarahlewis@berkeley.edu

Funded by: NASA Cryosphere Sciences Program; Grant Number: NNG05GN89G

Link to abstract: http://www3.interscience.wiley.com/journal/122393853/abstract

Sarah Lewis & Laurence Smith, Hydrologic outlets of the Greenland Ice Sheet

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Hydrologic Outlets of the Greenland Ice Sheet

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The Hydrologic Outlets of the Greenland Ice Sheet data set contains GIS point shapefiles that include 891 observed and potential hydrologic outlets of the Greenland Ice Sheet as identified by Lewis and Smith (2009) using satellite imagery. There are 460 observed hydrologic outlets that include proglacial streams and rivers emerging from the ice sheet (length scale >1 km), proglacial lakes touching the ice edge or clearly connected to it via streams or rivers (length scale >3 km), and sediment-rich plumes exiting tidewater glaciers into fjörds. Also, there are 431 potential hydrologic outlets that include point locations with release of meltwater from fjords without obvious sediment discharge, as well as locations where the ice sheet directly connects to the ocean that cannot be proven to release meltwater.

Meltwater features along the entire edge of the ice sheet were mapped via photointerpretation of GoogleEarth and Landsat ETM+ 15 m panchromatic data. The exact acquisition dates of the imagery are not availabe; however, owing to the light and relatively snow-free conditions seen in the GoogleEarth and Landsat images, it is presumed that they were taken during the summer season. Neither Landsat or GoogleEarth images were available for a section of ice sheet within the northern Tunu region; therefore, that region was excluded from the study. This excluded area represents approximately 0.9% of the ice sheet perimeter. Data are available via FTP, and can be read in any GIS software. The following journal article provides documentation for this data set: Lewis, Sarah, & Smith, Laurence. 2009. Hydrologic drainage of the Greenland Ice Sheet. Hydrological Processes, doi: 10.1002/hyp.7343. This journal article can be accessed from the Access External Documentation link at the top of this Web page.

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Data Citation

The following example shows how to cite the use of this data set in a publication. List the principal investigators, year of data set release, data set title and version number, publisher: NSIDC, and digital media.

Lewis, Sarah, & Smith, Laurence. 2009. Hydrologic Outlets of the Greenland Ice Sheet. Boulder, CO, U.S.A.: National Snow and Ice Data Center. Digital media.

Link to this NASA page: http://nsidc.org/data/nsidc-0372.html