Amplified Interannual Variation of the Summer Sea Ice in the Weddell Sea, Antarctic After the Late 1990s

The sea-ice extent (SIE) in the Weddell Sea plays a crucial role in the Antarctic climate system. Many studies have examined its long-term trend, however whether its year-to-year variation has changed remains unclear. We found an amplified year-to-year variance of the Weddell Sea SIE in austral summer since 1998/1999 in observational datasets. Analyses of sea-ice concentration budget and surface fluxes indicate that it is the thermodynamic process that drives the amplification of SIE variations, rather than the sea-ice-drift- related dynamic process. Compared to 1979–1998, the Southern Annular Mode in the preceding spring shows a closer linkage with the Weddell Sea SIE in 1999–2021 through a stronger and more prolonged impact on sea surface temperature, which thermodynamically modulates local sea ice via changing surface heat and radiation fluxes. Our study helps advance the understanding of extreme low Antarctic-SIE records occurring in recent decades and improve future projections of the Antarctic sea-ice variability.