Abstract
Abstract. In this study, simulations at 25 km resolution are performed over the Greenland ice sheet (GrIS) throughout the 20th and 21st centuries, using the regional climate model MAR forced by four RCP scenarios from three CMIP5 global circulation models (GCMs), in order to investigate the projected changes of the surface energy balance (SEB) components driving the surface melt. Analysis of 2000–2100 melt anomalies compared to melt results over 1980–1999 reveals an exponential relationship of the GrIS surface melt rate simulated by MAR to the near-surface air temperature (TAS) anomalies, mainly due to the surface albedo positive feedback associated with the extension of bare ice areas in summer. On the GrIS margins, the future melt anomalies are preferentially driven by stronger sensible heat fluxes, induced by enhanced warm air advection over the ice sheet. Over the central dry snow zone, the surface albedo positive feedback induced by the increase in summer melt exceeds the negative feedback of heavier snowfall for TAS anomalies higher than 4 °C. In addition to the incoming longwave flux increase associated with the atmosphere warming, GCM-forced MAR simulations project an increase of the cloud cover decreasing the ratio of the incoming shortwave versus longwave radiation and dampening the albedo feedback. However, it should be noted that this trend in the cloud cover is contrary to that simulated by ERA-Interim–forced MAR for recent climate conditions, where the observed melt increase since the 1990s seems mainly to be a consequence of more anticyclonic atmospheric conditions. Finally, no significant change is projected in the length of the melt season, which highlights the importance of solar radiation absorbed by the ice sheet surface in the melt SEB.
Highlights
These results suggest that Latent heat flux (LHF) is expected to become less of an energy sink in a future warmer climate and to turn eventually into an average energy source over masks of daily melt events (MSKmelt), mainly because of the projected warmer air and the significant addition of moisture brought to the low-elevation ice sheet
MAR simulations forced by Coupled Model Intercomparison Project phase 5 (CMIP5) global circulation models (GCMs) (CanESM2, NorESM1-M and MIROC5) with respect to different RCP scenarios have been performed to assess the surface energy balance (SEB) changes of the Greenland ice sheet (GrIS) related to Greenland warming
As MAR is only based on physical parameterizations, investigations of the GrIS and its SEB in a warmer climate based on model simulations are easier, as opposed to when statistics are compiled for the current climate
Summary
The significant increase of the surface melting (Mote, 2007; Hall et al, 2008; Tedesco et al, 2008; Fettweis et al, 2011a) and corresponding meltwater runoff of the Greenland ice sheet (GrIS) (Hanna et al, 2005; Box et al, 2006; Fettweis, 2007; Ettema et al, 2009), which accounts for more than half of its recent mass loss (van den Broeke et al, 2009), is generally attributed to Arctic warming (Box and Cohen, 2006; Hanna et al, 2008) as a consequence of an increased concentration of atmospheric greenhouse gases (GHG) (Fettweis, 2007; Stroeve et al, 2007; Hanna et al, 2008, 2009). The incoming shortwave irradiance (i.e. solar radiation) absorbed by the ice sheet surface is highlighted as the largest energy source for enabling the surface
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