The role of atmospheric and oceanic factors on the record low Antarctic sea ice extent of 2023

Abstract

In February 2023, the Antarctic Sea ice extent (SIE) reached a historic low of 1.7 million km², which was 43 % lower than the monthly average extent recorded since 1979. This marked the second consecutive year of record lows, surpassing the minimum SIE from the previous year. Our study aims to understand the atmospheric and oceanic factors from September 2022 to August 2023 that contributed to these new lows. Throughout the study period, the monthly SIE consistently indicated lower extents compared to the long-term average. The Weddell Sea and Amundsen-Bellingshausen Sea (ABS) experienced the most decline in austral spring and summer, respectively, while the Ross Sea showed the minimum sea ice loss. The lower stratospheric cooling patterns observed during summer resulted in a reinforcement of the Southern Annular Mode (SAM), which caused intensification of the surface temperature inversion. This disturbance led to the Antarctic Polar Vortex shifting towards the Equator. The transition from the distinct triple La Niña event to the onset of a warm phase in 2023 resulted in the Amundsen Sea Low (ASL) deepening, which advected warm air into the region and push sea ice back towards the coast, reducing its extent particularly in the west of the Antarctic Peninsula region. Additionally, anomalies in the upper ocean (0–300 m) indicate subsurface ocean warming in most sectors.