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A caution on the use of surface digital elevation models to simulate supraglacial hydrology of the Greenland ice sheet

TitleA caution on the use of surface digital elevation models to simulate supraglacial hydrology of the Greenland ice sheet
Publication TypeJournal Article
Year of Publication2015
AuthorsYang K, Smith LC, Chu VW, Gleason CJ, Li M
JournalIEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
Volume8
Issue11
Start Page5212
Pagination5212-5224
Date Published10/15
ISSN1939-1404
KeywordsDigital elevation model (DEM), Greenland ice sheet (GrIS), hydrology, supraglacial lake, supraglacial river
Abstract

Digital elevation models (DEMs) of ice surface topography are often used for hydrologic analysis of the Greenland ice sheet (GrIS), but their suitability for this purpose has received little quantitative assessment. We compare remotely sensed maps of supraglacial lakes, rivers, and moulins with their DEM-modeled counterparts, using two moderate-resolution DEMs (SPIRIT DEM and ASTER GDEM) for a ~24 000 km2 area of the southwestern GrIS. We find that modeled hydrological features are critically sensitive to selection of a depression area threshold (a user-specified parameter used to fill noise and/or true topographic depressions in the ice surface DEM), with small depression area thresholds over-predicting observed supraglacial lake abundance and large thresholds under-predicting lake abundance. Few remotely sensed moulins are identified in either DEM, even if a small depression area threshold is used. A standard practice of filling all DEM depressions yields modeled surface flow paths that broadly match remotely sensed supraglacial river networks, but are far less fragmented than reality (owing to moulin capture), raising into question the realism of this standard practice. In sum, moderate-resolution DEMs do hold value for simulating broad-scale hydrography of the GrIS surface, but are critically sensitive to choice of the filling threshold, and insensitive to moulins which also influence supraglacial drainage pattern. Our preliminary analysis suggests using a depression area threshold of 0.1-0.2 km2 for lakes, advises against using DEMs to predict moulin locations, and urges caution when using 100% DEM filling to model flow paths of supraglacial rivers.

DOI10.1109/JSTARS.2015.2483483