The 1950-2020 variability of the Greenland Ice Sheet surface mass balance

We use the diurnal Energy Balance Model (dEBM) in combination with ERA5 reanalysis forcings to simulate the surface mass balance (SMB) of the Greenland Ice Sheet (GrIS). The dEBM (Krebs-Kanzow et al., 2021) is based on the energy balance of glaciated surfaces. In contrast to most empirical schemes, it is physics based and accounts for variations in the radiative forcing due to changes in the Earth's orbit and atmospheric composition. The dEBM scheme only requires monthly atmospheric forcing (precipitation, temperature, shortwave and longwave radiation and cloud cover) and is computationally inexpensive, which makes it particularly suitable to investigate the response of ice sheets to long-term climate change. After calibration and validation, we investigate the contribution of individual climate forcings (temperature, precipitation, clouds and radiation) to the interannual SMB variability.                     

Furthermore, we compare 1979-2016 ERA5 and ERA-Interim with respect to the main atmospheric drivers of the melt season over the GrIS. In summer, ERA5 differs remarkably from ERA-Interim: averaged over the lower parts of the GrIS, the mean near-surface temperature is 1 K lower while mean downward shortwave radiation at the surface is on average 15W/m^2 higher than in ERA-Interim. In consequence those methods which hitherto have estimated the GrIS surface mass balance from the ERA-Interim surface energy balance need to be carefully recalibrated before they can be progressed to ERA5 forcing.

Krebs-Kanzow, U., Gierz, P., Rodehacke, C. B., Xu, S., Yang, H., and Lohmann, G., 2021: The diurnal Energy Balance Model (dEBM): a convenient surface mass balance solution for ice sheets in Earth system modeling, The Cryosphere, 15, 2295–2313, https://doi.org/10.5194/tc-15-2295-2021.