Antarctic Sea Ice #4: Record lows between 2022 and 2025

o Antarctic sea ice forms a critical part of the regional and global climate system and is also a critical habitat. Following the first signs of decline in Antarctic sea ice in 2016/17 after decades of slight increase, there was a minor recovery in 2020-2021 before persistent and substantial low sea ice coverage was observed, especially in the winters of 2023 and 2024. The most recent extremes in sea ice coverage were driven by ocean changes, most notably ongoing warming at around 100-200 m depth, combined with regional atmospheric pressure anomalies. Strong evidence is emerging that the changes constitute a fundamental change, or ‘regime shift’, in the Antarctic sea ice system. However, lack of information on sea ice thickness and the sparseness of ocean observations limit our understanding. A relatively short satellite observational record of 45 years, combined with challenges associated with accurately simulating the ocean around Antarctica in climate models, make it difficult to interpret exactly how these extreme lows in sea ice coverage are impacted by climate change or how the future may evolve. The impacts of the extreme lows in sea ice coverage since 2022 are expected to be widespread and multifaceted. While many will take time to manifest, there is already evidence for impacts on the Antarctic coastline, increases in ocean heat loss and atmospheric storminess, and a negative impact on the breeding success of emperor penguins.