Abstract
Abstract. Results from a regional climate simulation (1970–2006) over the Greenland ice sheet (GrIS) reveals that more than 97% of the interannual variability of the modelled Surface Mass Balance (SMB) can be explained by the GrIS summer temperature anomaly and the GrIS annual precipitation anomaly. This multiple regression is then used to empirically estimate the GrIS SMB since 1900 from climatological time series. The projected SMB changes in the 21st century are investigated with the set of simulations performed with atmosphere-ocean general circulation models (AOGCMs) of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4). These estimates show that the high surface mass loss rates of recent years are not unprecedented in the GrIS history of the last hundred years. The minimum SMB rate seems to have occurred earlier in the 1930s and corresponds to a zero SMB rate. The AOGCMs project that the SMB rate of the 1930s would be common at the end of 2100. The temperature would be higher than in the 1930s but the increase of accumulation in the 21st century would partly offset the acceleration of surface melt due to the temperature increase. However, these assumptions are based on an empirical multiple regression only validated for recent/current climatic conditions, and the accuracy and time homogeneity of the data sets and AOGCM results used in these estimations constitute a large uncertainty.
Highlights
Mass balance variations of the Greenland ice sheet (GrIS) play an important role in global sea level fluctuations and oceanic THC changes.On the one hand, GrIS mass balance changes appear to have contributed several metres to some of the sea-level fluctuations since the last interglacial period known as the Eemian, 125 K yr BP (Cuffey and Marshall, 2000) and are expected to contribute to sea-level rise under the projected future global warming throughout this century (Meehl et al, 2007)
It should be noted that the MAR model simulates for 2003 and 2006 negative Surface Mass Balance (SMB) anomalies equivalent to those projected by the atmosphere-ocean general circulation models (AOGCMs) on average for the end of the 21st century. These recent SMB rates are the result of low precipitation and very high temperatures, suggesting that some AOGCMs could underestimate changes resulting from the global warming over the GrIS
We have derived a multiple-regression relation that has been used with climatological time series to empirically estimate the GrIS SMB since 1900
Summary
Mass balance variations of the GrIS play an important role in global sea level fluctuations and oceanic THC changes. A 37-yr (1970– 2006) simulation of the GrIS performed by the regional climate model MAR (Modele Atmospherique Regional) shows that 97% of the interannual variability of the modelled SMB is explained by these anomalies (Fettweis, 2007). Such a strong correlation is confirmed by the model of Hanna et al (2008) driven by the ECMWF (re)analysis.
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