Drifting snow climate of the Greenland ice sheet: a study with a regional climate model

Abstract. This paper presents the drifting snow climate of the Greenland ice sheet, using output from a high-resolution (∼11 km) regional climate model. Because reliable direct observations of drifting snow do not exist, we evaluate the modeled near-surface climate instead, using automatic weather station (AWS) observations from the K-transect and find that RACMO2 realistically simulates near-surface wind speed and relative humidity, two variables that are important for drifting snow. Integrated over the ice sheet, drifting snow sublimation (SU_ds) equals 24 ± 3 Gt yr⁻¹, and is significantly larger than surface sublimation (SU_s, 16 ± 2 Gt yr⁻¹). SU_ds strongly varies between seasons, and is only important in winter, when surface sublimation and runoff are small. A rapid transition exists between the winter season, when snowfall and SU_ds are important, and the summer season, when snowmelt is significant, which increases surface snow density and thereby limits drifting snow processes. Drifting snow erosion (ER_ds) is only important on a regional scale. In recent decades, following decreasing wind speed and rising near-surface temperatures, SU_ds exhibits a negative trend (0.1 ± 0.1 Gt yr⁻¹), which is compensated by an increase in SU_s of similar magnitude.