Antarctic Winter Sea Ice Extent Second lowest in Satellite History

October 11, 2024
Japan Aerospace Exploration Agency
National Institute of Polar Research

As part of the Arctic Challenge for Sustainability II (ArCS II*1), the Japan Aerospace Exploration Agency (JAXA) and the National Institute of Polar Research (NIPR) have visualized temporal and spatial changes in sea-ice extent in the Northern and Southern Hemispheres based on observation data from the Advanced Microwave Scanning Radiometer 2 (AMSR2) onboard the Global Change Observation Mission – Water “SHIZUKU” (GCOM-W), and have made the data available on the Arctic Data archive System (ADS*2) website.

Figure 1 shows the seasonal changes in Antarctic sea-ice extent (*3). As the seasons are reversed between the Northern and Southern Hemispheres, September marks the beginning of winter in the Antarctic Ocean, when sea-ice extent reaches its annual maximum. Analysis of sea-ice data for 2024 revealed that the Antarctic sea-ice extent recorded its annual maximum (approximately 17.1729 million square kilometers) on September 9. This is the second-lowest winter sea-ice extent in the satellite observation era and is approximately 82,800 square kilometers larger than that in 2023 (Figure 2). In addition, in terms of sea-ice extent in summer (February), the second low was observed in 2024, following the record low in 2023 (related article). In the Antarctic Ocean, the sea-ice extent has been extremely low in both winter and summer for two consecutive years. Comparing the distribution of sea ice in winter (September) in those years, in 2024, sea ice advanced to lower latitudes in the Ross Sea, while significant sea-ice retreat was observed in the northern part of the Riiser-Larsen Sea (Figure 3). This suggests that the extent of sea ice varies across different regions, likely due to year-to-year differences in atmospheric conditions. In addition, winter sea-ice extents in 2017, 2018, 2022, 2023, and 2024 rank among the top 10 lowest in the 46-year record from 1979 to 2024, indicating a rapid decline in the Antarctic sea-ice extent in recent years following 2016 (Table 1).  Such changes likely reflect the effects of climate change, including global warming, and elucidating its causes will be an important issue in future research.

*1: Arctic Challenge for Sustainability II (ArCS II)
National Arctic research projects led by the National Institute of Polar Research. Researchers in the natural sciences, engineering, humanities, and social sciences participate in this project, which aims to contribute to the realization of a sustainable society through collaboration with different research fields and society and international cooperation based on an accurate understanding of the actual situation and mechanisms of global warming and future projections. The implementation period is from June 2020 to March 2025. https://www.nipr.ac.jp/arcs2/e/

*2: The Arctic Data archive System (ADS)
A data archive system for preserving and managing observation data and model simulation products obtained in the Antarctic and Arctic regions through the GRENE Arctic Climate Change Research Project (2011-2016), Arctic Challenge for Sustainability (ArCS, 2015- 2020), and ArCS II. https://ads.nipr.ac.jp/

*3: The sea-ice extent is defined as a temporal average of several days to eliminate calculation errors due to a lack of data. In this article, we adopt an average of five days. The ADS (https://ads.nipr.ac.jp/vishop/#/extent) provides preliminary figures for the 2-day average.