Abstract
Abstract. Four high-resolution regional climate models (RCMs) have been set up for the area of Greenland, with the aim of providing future projections of Greenland ice sheet surface mass balance (SMB), and its contribution to sea level rise, with greater accuracy than is possible from coarser-resolution general circulation models (GCMs). This is the first time an intercomparison has been carried out of RCM results for Greenland climate and SMB. Output from RCM simulations for the recent past with the four RCMs is evaluated against available observations. The evaluation highlights the importance of using a detailed snow physics scheme, especially regarding the representations of albedo and meltwater refreezing. Simulations with three of the RCMs for the 21st century using SRES scenario A1B from two GCMs produce trends of between −5.5 and −1.1 Gt yr−2 in SMB (equivalent to +0.015 and +0.003 mm sea level equivalent yr−2), with trends of smaller magnitude for scenario E1, in which emissions are mitigated. Results from one of the RCMs whose present-day simulation is most realistic indicate that an annual mean near-surface air temperature increase over Greenland of ~ 2°C would be required for the mass loss to increase such that it exceeds accumulation, thereby causing the SMB to become negative, which has been suggested as a threshold beyond which the ice sheet would eventually be eliminated.
Highlights
During the 21st century, loss of mass from the Greenland ice sheet in response to anthropogenic climate change is expected to make a substantial addition to global mean sea level (Meehl et al, 2007)
Four regional climate models (RCMs) – HadRM3P, HIRHAM5, MAR and Regional Atmospheric Climate Model version 2.1 (RACMO2) – have been run for the area of Greenland to produce results for the recent past, forced by common sets of boundary conditions which were obtained from reanalysis data and output from two general circulation models (GCMs)
Three of the RCMs – HadRM3P, HIRHAM5 and MAR – were used to simulate the 21st century under two emissions scenarios, again with a common set of boundary conditions obtained from the GCMs
Summary
During the 21st century, loss of mass from the Greenland ice sheet in response to anthropogenic climate change is expected to make a substantial addition to global mean sea level (Meehl et al, 2007). Huybrechts et al, 2004; Hanna et al, 2005; Gregory and Huybrechts, 2006; Vizcaíno et al, 2008, 2010); and dynamical downscaling with regional climate models (RCMs) at high spatial resolution, forced at the boundaries by GCMs or reanalysis products (e.g. Box et al, 2004, 2006; Fettweis et al, 2005; Lefebre et al, 2005; Ettema et al, 2009, 2010; Mernild et al, 2010). High-resolution RCMs are an important tool for making reliable projections of sea-level rise Another aspect of systematic uncertainty in projections arises from the formulation of the ice sheet SMB model.
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