Dipolar distribution of cyclones and its influence on sea ice extremes in the Amundsen-Bellingshausen Seas

The Amundsen-Bellingshausen Seas (ABS) have experienced a notable decline in sea ice extent (SIE) since 1979, alongside strengthening cyclone activity. This study examines the role of cyclones in driving extreme SIE events using satellite observations and atmospheric reanalysis data. A comparison of two contrasting extreme years (1980 and 2010) reveals that SIE fluctuations during the retreat season are significantly correlated with cyclone intensity, with the sea ice response peaking at a one-day lag. Compared to high-SIE years, low-SIE years are characterized by more frequent, stronger, and slower-moving cyclones over the Amundsen Sea, and weaker, faster-moving systems over the Bellingshausen Sea. A composite analysis of the top five extreme high and low SIE years alongside a 44-year EOF analysis of cyclone intensity indeed shows a robust zonal dipole pattern in cyclone intensity in ABS. A Dipole Cyclone Index (DCI) is thus derived from the second leading EOF pattern of cyclone intensity, representing the key dipole structure linked to extreme SIE events, which has a significant correlation with minimum SIE. Our results indicate that the intensity and speed of cyclones may act as one of the precursors to extreme sea ice conditions in ABS, improving knowledge of short-term sea ice variability and mechanisms of air–ice–ocean coupling in this rapidly changing region.