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- Title
Estimation of the Antarctic surface mass balance using the regional climate model MAR (1979-2015) and identification of dominant processes.
- Authors
Agosta, Cécile; Amory, Charles; Kittel, Christoph; Fettweis, Xavier
- Abstract
We evaluate new simulations of the polar-oriented regional climat model (RCM) MAR forcedby three reanalyses, ERA-Interim, JRA-55 and MERRA2, for the period 1979-2015, over theAntarctic ice sheet. We compare MAR results to the last outputs of the RCM RACMO2forced by ERA-Interim. We show that MAR and RACMO2 perform similarly well insimulating coast to plateau SMB gradients, and we find no significant differences in theirsimulated SMB when integrated over the ice sheet or its major basins. More importantly, weoutline and quantify missing or underestimated processes in both RCMs. Alongstake transects, we show that both models accumulate too much snow on crests,and not enough snow in valleys, as a result of drifting snow transport fluxes notincluded in MAR and probably underestimated in RACMO2 by a factor of three.Our results tend to confirm that drifting snow transport and sublimation fluxes aremuch larger than previous model-based estimates and need to be better resolved andconstrained in climate models. Sublimation of precipitating particles in low-levelatmospheric layers is responsible for the significantly lower snowfall rates in MAR than inRACMO2 in katabatic channels at the ice sheet margins. Atmospheric sublimationin MAR represents 363 Gt yr−1 over the grounded ice sheet for the year 2015,which is 16 % of the simulated snowfall loaded at the ground. This estimate isconsistent with a recent study based on precipitation radar observations, and is morethan twice as much as simulated in RACMO2, because of different time residenceof precipitating particles in the atmosphere. The remaining spatial differences insnowfall between MAR and RACMO2 are attributed to differences in advectionof precipitation, snowfall particles being likely advected too far inland in MAR.
- Subjects
ATMOSPHERIC models; ICE sheets; SNOW; MASS budget (Geophysics); METEOROLOGICAL precipitation; ATMOSPHERE; IDENTIFICATION
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article