climate models; fluvial catchment; ice sheet meltwater runoff; surface mass balance; surface water hydrology; Multidisciplinary
Abstract :
[en] Meltwater runoff from the Greenland ice sheet surface influences surface mass balance (SMB), ice dynamics, and global sea level rise, but is estimated with climate models and thus difficult to validate. We present a way to measure ice surface runoff directly, from hourly in situ supraglacial river discharge measurements and simultaneous high-resolution satellite/drone remote sensing of upstream fluvial catchment area. A first 72-h trial for a 63.1-km2 moulin-terminating internally drained catchment (IDC) on Greenland's midelevation (1,207-1,381 m above sea level) ablation zone is compared with melt and runoff simulations from HIRHAM5, MAR3.6, RACMO2.3, MERRA-2, and SEB climate/SMB models. Current models cannot reproduce peak discharges or timing of runoff entering moulins but are improved using synthetic unit hydrograph (SUH) theory. Retroactive SUH applications to two older field studies reproduce their findings, signifying that remotely sensed IDC area, shape, and supraglacial river length are useful for predicting delays in peak runoff delivery to moulins. Applying SUH to HIRHAM5, MAR3.6, and RACMO2.3 gridded melt products for 799 surrounding IDCs suggests their terminal moulins receive lower peak discharges, less diurnal variability, and asynchronous runoff timing relative to climate/SMB model output alone. Conversely, large IDCs produce high moulin discharges, even at high elevations where melt rates are low. During this particular field experiment, models overestimated runoff by +21 to +58%, linked to overestimated surface ablation and possible meltwater retention in bare, porous, low-density ice. Direct measurements of ice surface runoff will improve climate/SMB models, and incorporating remotely sensed IDCs will aid coupling of SMB with ice dynamics and subglacial systems.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Smith, Laurence C; Department of Geography, University of California, Los Angeles, CA 90095, lsmith@geog.ucla.edu
Yang, Kang; School of Geographical and Oceanographic Sciences, Nanjing University, 210093 Nanjing, China
Pitcher, Lincoln H; Department of Geography, University of California, Los Angeles, CA 90095
Overstreet, Brandon T; Department of Geography, University of Wyoming, Laramie, WY 82071
Chu, Vena W; Department of Geography, University of California, Santa Barbara, CA 93106
Rennermalm, Åsa K; Department of Geography, Rutgers, The State University of New Jersey, Piscataway, NJ 08854
Ryan, Jonathan C; Department of Geography, University of California, Los Angeles, CA 90095 ; Institute at Brown for Environment and Society, Brown University, Providence, RI 02912
Cooper, Matthew G; Department of Geography, University of California, Los Angeles, CA 90095
Gleason, Colin J; Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, MA 01003
Tedesco, Marco; Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964
Jeyaratnam, Jeyavinoth; The City College of New York, New York, NY 10031
van As, Dirk; Geological Survey of Denmark and Greenland (GEUS), 1350 Copenhagen, Denmark
van den Broeke, Michiel R; Institute for Marine and Atmospheric Research, Utrecht University, Utrecht 3508, The Netherlands
van de Berg, Willem Jan; Institute for Marine and Atmospheric Research, Utrecht University, Utrecht 3508, The Netherlands
Noël, Brice ; Université de Liège - ULiège > Département de géographie > Climatologie et Topoclimatologie ; Institute for Marine and Atmospheric Research, Utrecht University, Utrecht 3508, The Netherlands
Langen, Peter L; Climate and Arctic Research, Danish Meteorological Institute, DK-2100 Copenhagen O, Denmark
Cullather, Richard I; Earth System Science Interdisciplinary Center, University of Maryland at College Park, College Park, MD 20740 ; NASA Goddard Space Flight Center, Greenbelt, MD 20771
Zhao, Bin; NASA Goddard Space Flight Center, Greenbelt, MD 20771
Willis, Michael J ; Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO 80309
Hubbard, Alun; Centre for Arctic Gas Hydrate, Environment, and Climate, University of Tromsø, N-9037 Tromsø, Norway ; Centre for Glaciology, Institute of Geography and Earth Sciences, Aberystwyth University, Aberystwyth SY23 3DB, United Kingdom
Box, Jason E; Geological Survey of Denmark and Greenland (GEUS), 1350 Copenhagen, Denmark
Jenner, Brittany A; SonTek, San Diego, CA 92107
Behar, Alberto E; NASA Jet Propulsion Laboratory, Pasadena, CA 91109
NASA - National Aeronautics and Space Administration ERC - European Research Council NSF - National Science Foundation
Funding text :
This project was funded by the NASA Cryosphere Program Grant NNX14AH93G managed by Dr. Thomas P. Wagner. DigitalGlobe WorldView imagery and geospatial support were provided by the Polar Geospatial Center (PGC) at the University of Minnesota with support from the National Science Foundation Awards 1043681 and 1559691 (all WorldView imagery Copyright DigitalGlobe, Inc.). Additional funding to K.Y. was provided by National Natural Science Foundation of China (41501452) and the Fundamental Research Funds for the Central Universities. Funding to M.T. was provided by NASA Grants NNX14AD98G and NNX16AH38G, and NSF Grant PLR-1643187. Funding to P.L.L. was provided by the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant Agreement 610055 as part of the ice2ice project. The KAN_M weather station is funded by the Greenland Analogue Project (GAP) and is part of the weather station network of the Programme for Monitoring of the Greenland Ice Sheet (www.PROMICE.dk). M.J.W. acknowledges the University of North Carolina at Chapel Hill Research Computing group for computational resources and National Science Foundation Grant ARC-1111882. Polar Field Services, Inc. and Kangerlussuaq International Science Support (KISS) provided logistical support, with special thanks to Kathy Young, Susan Zager, and Kyli Cosper. Constructive requests from anonymous reviewers and the editor greatly strengthened the paper.ACKNOWLEDGMENTS. This project was funded by the NASA Cryosphere Program Grant NNX14AH93G managed by Dr. Thomas P. Wagner. DigitalGlobe WorldView imagery and geospatial support were provided by the Polar Geospatial Center (PGC) at the University of Minnesota with support from the National Science Foundation Awards 1043681 and 1559691 (all WorldView imagery Copyright DigitalGlobe, Inc.). Additional funding to K.Y. was provided by National Natural Science Foundation of China (41501452) and the Fundamental Research Funds for the Central Universities. Funding to M.T. was provided by NASA Grants NNX14AD98G and NNX16AH38G, and NSF Grant PLR-1643187. Funding to P.L.L. was provided by the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant Agreement 610055 as part of the ice2ice project. The KAN_M weather station is funded by the Greenland Analogue Project (GAP) and is part of the weather station network of the Programme for Monitoring of the Greenland Ice Sheet (www.PROMICE.dk). M.J.W. acknowledges the University of North Carolina at Chapel Hill Research Computing group for computational resources and National Science Foundation Grant ARC-1111882. Polar Field Services, Inc. and Kangerlussuaq International Science Support (KISS) provided logistical support, with special thanks to Kathy Young, Susan Zager, and Kyli Cosper. Constructive requests from anonymous reviewers and the editor greatly strengthened the paper.
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