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Surface mass balance of the Greenland Ice Sheet from climate analysis data and accumulation/ablation models

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Citation:
Hanna, E. , Huybrechts, P. and Mote, T. (2001): Surface mass balance of the Greenland Ice Sheet from climate analysis data and accumulation/ablation models , International symposium on Ice Cores and Climate, Kangerlussuaq (Greenland)August 2001. .
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Abstract:

We used surface temperature and precipitation from high-resolution (~0.56x0.56o) European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses (1992-8), together with a comprehensive and up-to-date runoff/meltwater retention model (Janssens and Huybrechts 2000), to produce novel maps of Greenland Ice Sheet (GIS) runoff and surface mass balance (SMB). The Ekholm digital elevation model was used to correct the ECMWF surface climate fields for errors in the ECMWF orography schemes, using an assumed lapse rate derived from comparison of model temperatures with those from in situ stations. GIS runoff was ~0.4 of precipitation averaged across the Ice Sheet (mean of 1992-8). We compared our ablation maps with similarly scaled maps from Special Sensor Microwave/Imager (SSM/I) passive-microwave satellite snowmelt data. Patterns of melt and their interannual variations with the reanalysis compared well with those from the SSM/I, e.g. ablation/runoff from both methods was overall low in 1992 but high in 1995. However, the SSM/I data showed about twice as much melt averaged across Waleed Abdalatis (Goddard Space Flight Center) GIS mask area. This may be due to problems with the boundary layer (too cold) in the earlier ECMWF analyses. We plan to use Program in Arctic Regional Climate Assessment (PARCA) ice cores and Geological Survey of Denmark and Greenland field data, to further validate our model output. The results of our study show great promise for meaningfully estimating GIS SMB based on forthcoming second generation ECMWF reanalysis (ERA-40) data. It is intended to compare these estimates with recently published laser/satellite altimetry results (of GIS surface elevation) to see whether the observed patterns of change are just a short mass-balance-only effect or reflect longer-term processes.

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