Summer Snowfall Impact on Greenland Ice Sheet SMB

Abstract:

Recently, the regional climate model RACMO2 has been updated to the version 2.3. The main physics update consists of an enhanced rainfall to snowfall conversion rate, favouring solid over liquid precipitation at higher temperatures, especially in summer. In the updated RACMO2.3 simulation, SMB anomalies are generated through a feedback mechanism involving increased summer snowfall, surface albedo rise as well as cloud cover reduction, resulting in a subsequent decrease of snowmelt and runoff. When compared against K-transect measurements in western Greenland, these updates improve the modelled surface energy balance and surface mass balance relative to the previous RACMO2 version. In addition, the heavier summer snowfall improves the simulated surface albedo in comparison with stations measurements.

In recent years, the surface albedo close to the equilibrium line declined notably in summer due to a prolonged bare ice exposure and a decreasing ice albedo. RACMO2.3 results reveal that this rapid reduction in bare ice albedo is not exclusively driven by surface processes related to melt. A major summer snowfall reduction also plays a role in extending the period of bare ice exposure, in turn lowering surface albedo.