Antarctic Sea Ice through a low extent period

Record breaking minimums

After consecutively setting record-low sea-ice extent minima in February 2022 and February 2023, Antarctic sea ice coverage has remained remarkably low for the past 15 months. From May to October 2023, it continuously broke records, reaching an unprecedented lowest maximum extent that was 4.8% lower than the previous record-low maximum in 1986 (18.443 million km²) and approximately 7.6% below the median maximum (~19 million km²). Although the minimum for 2024, recorded on the 20th of February was above the record-low, it still ranks among the four lowest minima. It is higher than the levels observed in 2022 and 2023 but closely comparable to 2017 (cf. table below).

left : in black the curve for 2024 up to the 04th of march, plus the reference curves of the two years with the highest (2014) and lowest (2023) ice extents ever recorded with satellite monitoring in the Antarctic.
Right : every year in record is displayed. 2023 is shown in black. The record-low period from May to October is clearly visible.

Despite the fact that this record-low sequence is impressive, it keeps being too short in time to allow scientists to get a clear overview over the Antarctic regional climatic trends. It is however now clear that this sea ice extent low period will not remain without consequences, as for example on temporary shelves melting (Naughten et al. 2023), iceberg release, but as well on biodiversity (Fretwell et al. 2023). The abrupt transition between the positive trend has led some scientists to explore the possibility that Antarctic sea ice has undergone a regime shift (Hobbs et al. 2024, Ionita 2024, Purich & Doddridge 2023, Schroeter et al. 2023)

Aside from the unprecedented global record-low, the extent of sea ice varied across regions. The Bellingshausen and Amundsen Seas exhibited even greater sea ice coverage than usual. However, a substantial September record-low was documented in numerous Antarctic seas, notably in the King Haakon VII Sea (located between the Weddell Sea and the Indian Ocean) and the offshore areas of the Ross Sea.

Just like the uneven distribution observed in the 2023 record-low maximum extent, the 2024 minimum extent was not uniformly distributed. The Weddell Sea and the western portion of the Ross Sea displayed a strong sea ice preservation. In contrast, the eastern part of the Ross Sea and the Bellingshausen Sea experienced a severe deficiency in sea ice, with melting extending right up to the coast in the Bellingshausen Sea.

Release of large icebergs

2023 austral spring was also marked by the release of a notably large iceberg named A23a. This tabular iceberg had originally calved during the previous record-low maximum year 1986 from the Filchner-Ronne Ice Shelf. After remaining grounded on sea bed until 2020, it melted enough to lose sufficient weight, releasing its grip and start moving during last austral spring. It has then been drifting northward, passing the northern tip of the Antarctic peninsula in November 2023. While not the largest iceberg ever recorded, it is still an exceptionally large one, spanning some 3900 km² (40 times the size of Paris city and twice that of Greater London) and as tall as the eiffel tower. The iceberg's considerable size allows for satellite observation. It consequently appeared on our Ice products as for example on the Ice Edge image for the 20th of february 2024 below (A23a have been circled in orange).

The Iceberg currently poses no immediate threat apart from navigational concerns and potential impact on wildlife if it were to ground on an island. However, its calving is linked to the melting of Antarctic ice shelves, which are extensions of glaciers onto the sea. As the melting of continental ice is a primary factor contributing to rising sea levels, iceberg formation has gained the attention of the scientific community. A23a is then an iconic illustration of what happens to the Ice Shelves.

The ESA has released an animation of satelite image that allow to visualise the iceberg drift between november 2023 and january 2024 (see below)

The size of the iceberg attracted the attention of the community on X (see below two tweets by Copernicus, and Leon Simons), but as well of the media, such as the BBC.
 

Conclusion

Antarctic sea-ice extent kept setting new records low over the past few years. While it may be premature to reach conclusions, scientists are increasingly concerned about potential shifts in wind patterns, ocean currents, and ice regimes. Drawing conclusions from individual events remains highly challenging, as the situation may vary significantly when examining specific regional areas. Nevertheless, there appears to be a trend leaning towards a reduction in the extent of sea ice and ice shelves.

In this context, the OSI SAF high latitude processing center enables monitoring the status of sea ice in the Southern Hemisphere. The Sea Ice Index, currently in version 2.2, provides real-time data on sea ice for both hemispheres, offering a convenient and quick overview without the need for in-depth data analysis. We use our websites to offer information on this global issue, catering to both scientists and the wider public.

You can find continuous OSI SAF information about sea ice status at both poles on the following websites :

• OSI SAF High Latitude processing center
• Cryo MET Norway