Net accumulation of the Greenland ice sheet: High resolution modeling of climate changes

[1] High-resolution (50 km) climate change simulations for an area covering the entire Arctic have been conducted with the regional climate model (RCM) HIRHAM. The experiments were forced at the lateral boundary by large-scale atmospheric conditions from transient climate change scenario simulations performed with the Max Planck Institute for Meteorology coupled ocean atmosphere general circulation model (OAGCM) ECHAM4/OPYC3 with a resolution of similar to 300 km. The emission scenarios used were the IPCC SRES [Nakicenovic, 2000] marker scenarios A2 and B2. Three 30-year time slice experiments were conducted with HIRHAM for periods representing present-day ( 1961 - 1990) and the future ( 2071 - 2100) in the two scenarios. We find that due to a much better representation of the surface topography in the RCM, the geographical distribution of present-day accumulation rates simulated by the RCM represents a substantial improvement compared to the driving OAGCM. Estimates of the regional net balance are also better represented by the RCM. In the future climate the net balance for the Greenland Ice Sheet is reduced in all the simulation, but discrepancies between the amounts when based on ECHAM4/OPYC3 and HIRHAM are found. In both scenarios, the estimated melt rates are larger in HIRHAM than in the driving model.