A tipping point in West Antarctica in 2023's circumpolar 5-sigma event? a glimpse from the emperor penguin's perspective

Emperor penguins are one of the seabird species most vulnerable to climate change in Antarctica, as they depend on stable sea ice for breeding and molting. Recent extremes of warming have taken to the lowest records of sea ice in West Antarctica in 2022 and 2023, raising concerns to the extent that emperor penguins have been affected. We evaluated historical satellite data (1985-2022) of sea ice around the 10 emperor penguin breeding colonies, identified so far along the coast of the Amundsen and Bellingshausen Seas, and compared them to recent sea ice cover (2022-2023) to identify where and when critical thresholds of sea ice cover have been crossed. We found that the sea ice retreated below the critical thresholds in 2022-2023 during the chick-rearing and in some cases failed to return at the start of the following breeding season, hence likely affecting 9 of the 10 emperor penguin colonies in the region. This is an unprecedented climatic phenomena affecting breeding habitat of emperor penguin colonies over a large area, potentially affecting numerically important colonies in West Antarctica.