Abstract
Abstract. Regional climate models compute ice sheet surface mass balance (SMB) over a mask that defines the area covered by glacier ice, but ice masks have not been harmonised between models. Intercomparison studies of modelled SMB therefore use a common ice mask. The SMB in areas outside the common ice mask, which are typically coastal and high-precipitation regions, is discarded. Ice mask differences change integrated SMB by between 40.5 and 140.6 Gt yr−1 (1.8 % to 6.0 % of ensemble mean SMB), equivalent to the entire Antarctic mass imbalance. We conclude there is a pressing need for a common ice mask protocol.
Highlights
Detailed estimates of the surface mass balance (SMB) of the Antarctic ice sheet (AIS) are important for interpreting observed ice and sea-level-rise budgets
This results in integrated SMB values that are between 40.5 and 140.6 Gt yr−1 smaller when using the common mask compared to the native mask, which is up to 6.04 % of the ensemble mean SMB (Mottram et al, 2021) (Table 1)
We have quantified the importance of the choice of ice mask for the Antarctic domain by comparing six different ice masks from the regional climate models (RCMs) – COSMO-CLM2, HIRHAM5, MARv3.10, MetUM and RACMO2.3p2 – with the common mask defined by Mottram et al (2021)
Summary
Detailed estimates of the surface mass balance (SMB) of the Antarctic ice sheet (AIS) are important for interpreting observed ice and sea-level-rise budgets. The intercomparison in Mottram et al (2021) gives an ensemble mean of 2329 ± 94 Gt yr−1 for the common period of 1987 to 2015 with a range of 1961 ± 70 to 2519 ± 118 Gt yr−1 for individual models. Their results show that while all models vary on an interannual basis directed by the driving ERA-Interim reanalysis, the spread in mean annual SMB estimates originates predominantly from differences in the dynamical core, physical parameterisations, model set-up and the digital elevation model (DEM).
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