Abstract
Abstract. About 20 % of all snow accumulation in Antarctica occurs on the ice shelves. There, ice rises control the spatial surface mass balance (SMB) distribution by inducing snowfall variability and wind erosion due to their topography. Moreover these ice rises buttress the ice flow and represent ideal drilling locations for ice cores. In this study we assess the connection between snowfall variability and wind erosion to provide a better understanding of how ice rises impact SMB variability, how well this is captured in the regional atmospheric climate model RACMO2 and the implications of this SMB variability for ice rises as an ice core drilling site. By combining ground-penetrating radar (GPR) profiles from two ice rises in Dronning Maud Land with ice core dating, we reconstruct spatial and temporal SMB variations from 1983 to 2018 and compare the observed SMB with output from RACMO2 and SnowModel. Our results show snowfall-driven differences of up to 1.5 times higher SMB on the windward side of both ice rises than on the leeward side as well as a local erosion-driven minimum at the ice divide of the ice rises. RACMO2 captures the snowfall-driven differences but overestimates their magnitude, whereas the erosion on the peak can be reproduced by SnowModel with RACMO2 forcing. Observed temporal variability of the average SMBs, retrieved from the GPR data for four time intervals in the 1983–2018 range, are low at the peak of the easternmost ice rise (∼0.06 mw.e.yr-1), while they are higher (∼0.09 mw.e.yr-1) on the windward side of the ice rise. This implies that at the peak of the ice rise, higher snowfall, driven by orographic uplift, is balanced out by local erosion. As a consequence of this, the SMB recovered from the ice core matches the SMB from the GPR at the peak of the ice rise but not at the windward side of the ice rise, suggesting that the SMB signal is damped in the ice core.
Highlights
The surface mass balance (SMB) remains one of the largest sources of uncertainty when determining the overall mass balance of Antarctica and with that Antarctica’s contribution to sea level rise (Lenaerts et al, 2019; The IMBIE team, 2018; Rignot et al, 2019)
In this study we assess the connection between snowfall variability and wind erosion to provide a better understanding of how ice rises impact SMB variability, how well this is captured in the regional atmospheric climate model RACMO2 and the implications of this SMB variability for ice rises as an ice core drilling site
To investigate the regional SMB around the ice rises, we utilize the SMB reconstructed by the ground-penetrating radar (GPR) data (Fig. 3) as well as the SMB modeled by RACMO2 (Fig. 4)
Summary
The surface mass balance (SMB) remains one of the largest sources of uncertainty when determining the overall mass balance of Antarctica and with that Antarctica’s contribution to sea level rise (Lenaerts et al, 2019; The IMBIE team, 2018; Rignot et al, 2019). The SMB of an ice sheet is commonly defined as the annual sum of all surface processes that affect the mass balance of an ice sheet. This includes snowfall, runoff of surface melt water, sublimation, drifting snow sublimation, and snow erosion and deposition, of which snowfall is the dominant component in East Antarctica (Boening et al, 2012). Kausch et al.: Impact of coastal East Antarctic ice rises on surface mass balance and by substantial interannual as well as spatial variability (Lenaerts et al, 2013, 2014)
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