A Southern Greenland Ice Sheet Glacier Discharge Reconstruction: 1958-2007

The Greenland ice sheet has been observed to discharge more ice volume between 1996 and 2005 in apparent response to surface climate warming at glaciers south of 70° N latitude. We find that melt rates explain 60-90% of the ice discharge increase, with highest apparent sensitivity evident for the southwestern region. An empirical melt sensitivity model is then used to reconstruct total ice discharge variations due to apparent melt sensitivity from the southern Greenland ice sheet over 50 years (1958-2007). Recent increases in reconstructed southern glacier discharge exceed one standard deviation of the 1958-2007 mean in two years: 2003 and 2007. The 2007 estimated ice discharge value nearly exceeds the reconstruction uncertainty determined using Monte Carlo methods. In combination with climatological surface mass balance estimates, the reconstructed ice discharge suggests that Greenland's sea level contribution during 1961 to 2003 resolves over half of the unexplained IPCC [2007] global sea level rise.