UCLA

Antarctic sea ice extent has changed substantially over the satellite observation period since 1979. Total sea ice extent experienced a small but significant linear increase until 2016 when it plummeted from record highs in winter to record lows in summer. Up until recently, models have failed to capture the fluctuations of the highly variable sea ice extent. Fogt et al. (2022) and Maierhofer et al. (2024) created observation-based reconstruction ensembles since 1905 for seasonal and monthly data, respectively allowing the opportunity to put the contemporary variability of Antarctic sea ice into a historical context. This study compared the two datasets with a series of metrics. Each metric revealed the similarities and differences between the datasets and provided additional insight into pre-satellite sea ice behaviors, including extremes and temporal variability. In general, the datasets align better in sectors and seasons during sea ice maximums, with correlations up to 0.94. Additionally, the Maierhofer et al. (2024) dataset revealed interannual and decadal variability similar to that recorded in observations. Overall, both datasets suggest a general decrease in Antarctic sea ice in most sectors during the 20th century, except the Amundsen-Bellingshausen sector. However, there are distinctive differences between the two datasets which could be due to the different methods used to create the reconstructions, the initial resolution of the reconstructions, and the methods used to calculate the anomalies for the Fogt et al. (2022) data.