• Both the southern hemisphere summer (2022/23) and winter (2023) sea ice extent were at a record low.
  • The winter sea ice maximum extent was over 1 million square kilometres less than the previous record.
  • The very low Antarctic sea ice extent throughout 2023 is unmatched in historical observations.

Antarctic sea ice extent has a large seasonal cycle: it grows steadily from March to September and rapidly declines from October to February. Satellite records for sea ice extent began in 1979 with Antarctic sea ice extent relatively stable and with a small significant increasing trend from 2006 onward. Between 2007-2015 Antarctic sea ice extent was mostly above average throughout the year. From 2016, Antarctic sea ice extent shifted to below average, setting summer minimum extent record lows while the winter maximum extent remained close or within past records.

Figure 1: Annual Antarctic sea ice extent since the start of the satellite records in 1979. The anomalous record of 2023 is highlighted in red. Source: https://zacklabe.com/antarctic-sea-ice-extentconcentration/ Dr Zachary Labe.

The shift to below average sea ice extent after 2016 is consistent with climate change projections and aligns with warmer ocean temperatures. The year 2023 stands out as significantly below average sea ice extent for almost the entire year, setting new summer and winter minimum extent records. Sea ice still grew in the cooler months but much slower than in previous years.

Most sectors of Antarctica had below average sea ice in 2023, with record low monthly anomalies in June totalling an area comparable to the size of Western Australia.

The largest loss of sea ice was observed in the Ross Sea region and large parts of the Indian Ocean. Only the Amundsen Sea region had above average sea ice extent.

Sea ice extent anomalies prior to 2016 responded mostly to changes in atmospheric circulation patterns. However, the relationship broke down in recent years resulting in a regime shift where the ocean now plays a larger role, with atmospheric circulation influencing the regional structure of the anomalies but not the magnitude.

The recent decline of Antarctic sea ice extent has implications within the global climate system that have negative consequences for Earth’s heat budget, global circulation and sea level rise. Impacts in Antarctica include habitat loss for penguins, seals and smaller creatures, decreasing primary production in the ocean, exposing ice shelves and hindering Antarctic operations.

The Australian and international scientific community closely follows the development of Antarctic sea ice and collaborates to better understand the drivers for these changes and their implications.

Research contacts:

Dr Wilma Huneke, wilma.huneke@anu.edu.au Dr Danielle Udy, danielle.udy@utas.edu.au Dr Amelie Meyer, amelie.meyer@utas.edu.au