Present-Day Regional Antarctic Sea Ice Response to Extratropical Cyclones

Both atmospheric warming and poleward moisture transport increase the likelihood of sea ice surface melt. In the Southern Hemisphere, short-lived extratropical cyclones (ETCs) are responsible for a bulk of total heat and moisture transport toward high latitudes. Although these storms form ubiquitously in the midlatitudes, moisture availability and temperature characteristics vary by source region. In this study, we assess atmospheric, oceanic, and sea ice concentration (SIC) anomalies associated with austral winter ETCs over different Antarctic regions using ERA5 reanalysis data. Between 1990 and 2019, we find a total of 514 ETCs, with greater storm frequency in the eastern hemisphere groups. Compared to the climatology, sea ice melts (grows) behind the warm (cold) front of each system and is negatively correlated with atmospheric poleward moisture transport, temperature, meridional winds, and sea surface temperature for all ETCs. We find that Bellingshausen storms move moisture and warm air furthest poleward over their lifespan. However, East Weddell and East Antarctic ETCs are responsible for greater absolute poleward moisture transport than Bellingshausen and Ross systems. More intense ETCs correspond to greater SIC through Day 1, suggesting that SIC impacts ETC strength, regardless of ETC region. From cyclogenesis to cyclolysis, sea ice extent declines underneath composite ETCs, trends are generally not significant. Overall, while sea ice response produced by ETC-induced atmospheric and oceanic changes varies regionally, the long-term impacts of ETCs on regional sea ice are negligible over the study period. Antarctic air has become warmer and moister recently. Most of this warming and moistening is caused by short-lived, large-scale storms (i.e., extratropical cyclones (ETCs)). However, the ETC formation location impacts its ability to move warm, moist air toward Antarctica. Here, we investigate how 514 detected wintertime ETCs from different regions impact Antarctic atmosphere, ocean, and sea ice conditions using ERA5 reanalysis between 1990 and 2019. For all storm locations, the storm's east side moves warmer, moister air toward the Antarctic coast, while the west side moves colder, drier air toward the equator. We also find that Bellingshausen Sea ETCs produce greater atmospheric warming and moistening closer to the Antarctic shoreline (relative to average conditions). However, East Weddell and East Antarctic ETCs move more total moisture toward Antarctica. Even though ETCs warm and moisten the local air, stronger ETCs correspond to enhanced sea ice when they form. Despite this relationship, we find that the sea ice edge moves closer to the Antarctic shoreline between ETC formation and dissipation. Overall, ETC impacts on sea ice through air and oceanic changes vary around the Antarctic coastline. However, it does not seem like historical ETCs had long-term impacts on Antarctic sea ice. Bellingshausen extratropical cyclones (ETCs) induce greater atmospheric moisture transport and warming at high latitudes than other cyclone groupsSea ice concentration (SIC) change is best related to 2-m temperature anomalies for all cyclone locationsETC intensity corresponds to greater SIC between cyclogenesis and day 1