Impact of short-term atmospheric warming events on the Ice sheet surface and subsurface temperatures of coastal Dronning Maud Land, East Antarctica

Abstract. Short-term, episodic atmospheric warming events over Antarctica have received considerable attention for their direct role in establishing record-high temperatures, surface melting, and their indirect impacts via associated high wind speed and precipitation. However, there is limited knowledge of the effect of these warming events on the ice sheet surface and subsurface temperatures, despite their critical role in firn microphysical properties. Using reanalysis dataset ERA5 and ice sheet surface and subsurface temperature records from an ice core-borehole (71.5 °S, 10.25 °E) from coastal Dronning Maud Land (cDML), we examined the air (T2m) warming, subsurface warming, regional and large scale drivers of 70 short term ice sheet surface warming (ISSW) events covering a period 2014–2018. Out of 70 ISSW events, 60 occurred during periods of strong easterly winds with high snow accumulation and the rest during strong southeasterly winds (katabatic) without any precipitation. The former events resulted from increased downward longwave radiation and warmer air above associated with warm air advection from cyclonic intrusions. With an average frequency of 12 events/year, they established the highest ISSW over the region including the maximum warming of ~11 °C raising the ISST from -34 °C to -25 °C (in 9 days) recorded over the period and penetrating deeper in the snowpack (40–125 cm). Here, the T2m showed a minimum warming of 4.4 °C and a maximum of 24.6 °C, leading the ISSW by two days. The latter events were associated with turbulent mixing from strong, dry and anomalously warm winds from the interior. Although the T2m warmed significantly (4.4–15 °C) without any lead/lag, these events showed modest ISSW (2–5 °C) and shallow heat penetration to snowpack (40–60 cm) but resulted in significant sublimation over the region. Our study suggests that the impact of atmospheric warming events on ice sheet surface and subsurface temperatures varies with meteorological conditions. The frequent occurrence of these events might alter the firn's water-retaining capacity, which becomes crucial when surface melting reaches beyond the grounding line in a continued warming scenario. In the future, it is anticipated that their effects will increase as greenhouse gas concentrations rise.