| Abstrakt: |
Surface melt in East Antarctica is strongly correlated with the Southern Annular Mode (SAM) index, but the spatiotemporal variability of the relationship, and the physical processes responsible for it, have not been examined. Here, using melt flux estimates and climate variables from the RACMO2.3p3 regional climate model, we show that a decreasing SAM index is associated with increased melt in Dronning Maud Land primarily owing to reduced precipitation and greater absorption of solar radiation. Conversely, in Wilkes Land, a decreasing SAM index corresponds to increased melt because of greater incoming longwave radiation from a warmer atmosphere. We also demonstrate that SAM‐melt correlations are strongest in December as the melt season develops, and that the SAM's influence on peak melt intensities in January occurs indirectly through the snowmelt‐albedo feedback. Future work must account for such variability in the physical processes underlying the SAM‐melt relationship to reduce uncertainty in surface melt projections. Plain Language Summary: The Southern Annular Mode (SAM) index describes the strength and location of the westerly winds in the Southern Hemisphere. It has previously been linked to interannual variability in the number of satellite‐observed melt days on the surface of East Antarctica's floating ice shelves. Here, we use melt estimates from a regional climate model adapted for the polar regions to show that the SAM‐melt relationship is also observed for meltwater fluxes, and to identify the influence of the SAM on the different energy sources driving surface melt. We find that a more negative SAM index (weaker westerlies) is associated with higher air temperatures across most of East Antarctica, and leads to increased incoming longwave radiation and sensible heat fluxes in Wilkes Land. In contrast, in Dronning Maud Land (DML), incoming longwave radiation is unaffected by the SAM, leading to net longwave energy losses, and sensible heat fluxes are reduced because of weaker surface winds. Instead, greater melt in DML is driven through increased absorption of solar radiation, owing to reduced precipitation and a darker surface. We also find differences in the strength of the SAM‐melt relationship on both sub‐seasonal and decadal timescales. Key Points: Modeled surface meltwater fluxes on East Antarctic ice shelves are negatively correlated with the Southern Annular Mode (SAM) indexMelt fluxes increase for a decreasing SAM index owing to reduced precipitation in Dronning Maud Land, and a warmer atmosphere in Wilkes LandThe SAM‐melt relationship is stronger in December than January, highlighting the importance of the snowmelt‐albedo feedback [ABSTRACT FROM AUTHOR] |
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