Drivers of summer Antarctic sea-ice extent at interannual time scale in CMIP6 large ensembles based on information flow

The trend in Antarctic sea-ice extent has been slightly positive between 1979 and 2015. However, a series of record lows in Antarctic sea ice have occurred since 2016, especially during summer, which could indicate a regime shift. In this context, it is of crucial importance to better understand the drivers of changes in summer Antarctic sea-ice extent. In our study, we make use of five different large model ensembles and compute cause-effect relationships between variables based on the Liang-Kleeman information flow method at the interannual time scale over the period 1970–2100. We find that proximate factors, such as the previous spring sea-ice extent, sea-surface temperature and surface air temperature, are generally the most important drivers of changes in summer Antarctic sea-ice extent at the pan-Antarctic scale, as well as in most Antarctic sectors. The Southern Annular Mode (SAM), Amundsen Sea Low (ASL), and teleconnection patterns associated with El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) also have direct and indirect influences on summer sea-ice extent, but with a generally weaker impact compared to proximate factors. An exception is the Western Pacific Ocean, where ENSO and IOD play the largest role. The Indian and Western Pacific Oceans generally present fewer causal connections compared to the Bellingshausen-Amundsen, Weddell and Ross Seas, partly leading to smaller values of direct causal influences on summer sea-ice extent, which indicates a more unpredictable behavior of sea ice in these two sectors.