Short-term volume changes of the Greenland ice sheet in response to doubled CO2 conditions

This paper focuses on the rôle of accumulation and cloudiness changes in the response of the Greenland ice sheet to global warming. Changes in accumulation or cloudiness were often neglected, or coupled to temperature changes. We used model output on temperature, precipitation and cloudiness from a GCM (ECHAM4 T106). The GCM output was used to drive the Greenland model that exists of a vertically averaged ice flow model, coupled to a 1D surface energy balance model that calculates the ablation. Variables are temperature, accumulation and cloudiness. Sensitivity experiments with this model show that changes in accumulation are very important for the ice sheet mass balance, whereas cloudiness is of secondary importance. If the Greenland model is forced by the GCM output, the Greenland model is found to contribute 70% less to sea level rise after 70 years than is indicated by the results presented in the IPCC report. This large discrepancy is mainly due to the fact that the enhanced ablation is strongly compensated by increased accumulation. Comparing the result obtained here with changes in mass balance derived directly from the same general circulation model, indicates a 20% larger contribution to sea level. This increase is due to changes in ice flow, and a different method for the ablation calculation.

[1]  Philippe Huybrechts,et al.  The Dynamic Response of the Greenland and Antarctic Ice Sheets to Multiple-Century Climatic Warming , 1999 .

[2]  Duncan J. Wingham,et al.  Changes in Sea Level , 2001 .

[3]  Martin Wild,et al.  A possible change in mass balance of Greenland and Antarctic ice sheets in the coming century , 1995 .

[4]  J. Oerlemans,et al.  Projections of global mean sea level rise calculated with a 2D energy-balance climate model and dynamic ice sheet models , 1997 .

[5]  A. Ohmura,et al.  Change in mass balance of polar ice sheets and sea level from high-resolution GCM simulations of greenhouse warming , 2000, Annals of Glaciology.

[6]  C. Ritz,et al.  Greenland under changing climates: sensitivity experiments with a new three-dimensional ice-sheet model , 1995 .

[7]  R. V. D. van de Wal,et al.  Mass-balance modelling of the Greenland ice sheet: a comparison of an energy-balance and a degree-day model , 1996 .

[8]  J. Oerlemans,et al.  Modelling the short-term response of the Greenland ice-sheet to global warming , 1997 .

[9]  R. Alley,et al.  Dominant influence of atmospheric circulation on snow accumulation in Greenland over the past 18,000 years , 1995, Nature.

[10]  N. Reeh.  Dynamic and climatic history of the Greenland ice sheet , 1989 .

[11]  Niels Reeh,et al.  Mass Balance of the Greenland Ice Sheet at Dye 3 , 1985, Journal of Glaciology.

[12]  R. S. W. van de Wal,et al.  An energy balance model for the Greenland ice sheet , 1994 .

[13]  W. Gates.  AMIP: The Atmospheric Model Intercomparison Project. , 1992 .

[14]  Ralf Greve.  Thermomechanisches Verhalten polythermer Eisschilde - Theorie, Analytik, Numerik , 1995 .

[15]  Niels Reeh,et al.  New precipitation and accumulation maps for Greenland , 1991 .