GrSMBMIP: intercomparison of the modelled 1980-2012 surface mass balance over the Greenland Ice Sheet
Fettweis, Xavier
University of Liege
Hofer, Stefan
University of Liege
Krebs-Kanzow, Uta
Helmholtz Association
Amory, Charles
University of Liege
Aoki, Teruo
Research Organization of Information & Systems (ROIS)
Berends, Constantijn J.
Utrecht University
Born, Andreas
University of Bergen
Box, Jason E.
Geological Survey Of Denmark & Greenland
Delhasse, Alison
University of Liege
Fujita, Koji
Nagoya University
Gierz, Paul
Helmholtz Association
Goelzer, Heiko
Utrecht University
Hanna, Edward
Sch Geog
Hashimoto, Akihiro
Japan Meteorological Agency
Huybrechts, Philippe
Vrije Universiteit Brussel
Kapsch, Marie-Luise
Max Planck Society
King, Michalea D.
University System of Ohio
Kittel, Christoph
University of Liege
Lang, Charlotte
University of Liege
Langen, Peter L.
Aarhus University
Lenaerts, Jan T. M.
University of Colorado System
Liston, Glen E.
Colorado State University System
Lohmann, Gerrit
Helmholtz Association
Mikolajewicz, Uwe
Max Planck Society
Modali, Kameswarrao
University of Hamburg
Mottram, Ruth H.
Danish Meteorological Institute DMI
Niwano, Masashi
Japan Meteorological Agency
Noel, Brice
Utrecht University
Ryan, Jonathan C.
Brown University
Smith, Amy
University of Sheffield
Streffing, Jan
Helmholtz Association
Tedesco, Marco
Columbia University
van de Berg, Willem Jan
Utrecht University
van den Broeke, Michiel
Utrecht University
van de Wal, Roderik S. W.
Utrecht University
van Kampenhout, Leo
Utrecht University
Wilton, David
University of Sheffield
Wouters, Bert
Utrecht University
Ziemen, Florian
Max Planck Society
Zolles, Tobias
University of Bergen
Journal
Cryosphere
ISSN
1994-0416
1994-0424
Open Access
gold
Volume
14
Start page
3935
End page
3958
Observations and models agree that the Greenland Ice Sheet (GrIS) surface mass balance (SMB) has decreased since the end of the 1990s due to an increase in meltwater runoff and that this trend will accelerate in the future. However, large uncertainties remain, partly due to different approaches for modelling the GrIS SMB, which have to weigh physical complexity or low computing time, different spatial and temporal resolutions, different forcing fields, and different ice sheet topographies and extents, which collectively make an inter-comparison difficult. Our GrIS SMB model intercomparison project (GrSMBMIP) aims to refine these uncertainties by intercomparing 13 models of four types which were forced with the same ERA-Interim reanalysis forcing fields, except for two global models. We interpolate all modelled SMB fields onto a common ice sheet mask at 1 km horizontal resolution for the period 1980-2012 and score the outputs against (1) SMB estimates from a combination of gravimetric remote sensing data from GRACE and measured ice discharge; (2) ice cores, snow pits and in situ SMB observations; and (3) remotely sensed bare ice extent from MODerate-resolution Imaging Spectroradiometer (MODIS). Spatially, the largest spread among models can be found around the margins of the ice sheet, highlighting model deficiencies in an accurate representation of the GrIS ablation zone extent and processes related to surface melt and runoff. Overall, polar regional climate models (RCMs) perform the best compared to observations, in particular for simulating precipitation patterns. However, other simpler and faster models have biases of the same order as RCMs compared with observations and therefore remain useful tools for long-term simulations or coupling with ice sheet models. Finally, it is interesting to note that the ensemble mean of the 13 models produces the best estimate of the present-day SMB relative to observations, suggesting that biases are not systematic among models and that this ensemble estimate can be used as a reference for current climate when carrying out future model developments. However, a higher density of in situ SMB observations is required, especially in the south-east accumulation zone, where the model spread can reach 2 m w.e. yr(-1) due to large discrepancies in modelled snowfall accumulation.
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