TY - JOUR
T1 - Direct measurements of meltwater runoff on the Greenland ice sheet surface
AU - Smith, Laurence C.
AU - Yang, Kang
AU - Pitcher, Lincoln H.
AU - Overstreet, Brandon T.
AU - Chu, Vena W.
AU - Rennermalm, Åsa K.
AU - Ryan, Jonathan C.
AU - Cooper, Matthew G.
AU - Gleason, Colin J.
AU - Tedesco, Marco
AU - Jeyaratnam, Jeyavinoth
AU - van As, Dirk
AU - van den Broeke, Michiel R.
AU - van de Berg, Willem Jan
AU - Noël, Brice
AU - Langen, Peter L.
AU - Cullather, Richard I.
AU - Zhao, Bin
AU - Willis, Michael J.
AU - Hubbard, Alun
AU - Box, Jason E
AU - Jenner, Brittany A.
AU - Behar, Alberto E.
N1 - Funding Information:
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.
Funding Information:
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.
PY - 2017/12/12
Y1 - 2017/12/12
N2 - 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-km
2 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.
AB - 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-km
2 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.
KW - Climate models
KW - Fluvial catchment
KW - Ice sheet meltwater runoff
KW - Surface mass balance
KW - Surface water hydrology
UR - http://www.scopus.com/inward/record.url?scp=85038562660&partnerID=8YFLogxK
U2 - 10.1073/pnas.1707743114
DO - 10.1073/pnas.1707743114
M3 - Article
SN - 0027-8424
VL - 114
SP - E10622-E10631
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 50
ER -