Attenuated Interannual Variability of Austral Winter Antarctic Sea Ice Over Recent Decades

Changes in Antarctic sea ice modify surface circulation, deep-water formation, and overturning circulation, affecting the ecosystem and the atmosphere-ocean-ice interaction. Recent studies focused on long-term trends of Antarctic sea ice, but whether its variability has changed is less clear. By examining reanalysis data sets, we show an interdecadal attenuation in variability of austral winter Antarctic sea ice since the late 1990s. This mainly arises from declined surface pressure variations in response to a combined effect of El Nino-Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). Compared to the pre-1999 period, ENSO and the SAM have reduced variability in the post-1999 period, and the linkage between them and Antarctic climate has weakened. The decreased level of variability over the 1999-2017 period may facilitate a more sensitive response of Antarctic sea ice to an external forcing, by enhancing the signal-to-noise ratio.