Sea ice cover in the polar oceans has a key role in climate, ecology and society. It influences global ocean circulation, the radiation budget, global climate sensitivity and ice sheet mass loss; it offers habitats for plankton and wildlife; and it provides a vital lifeline for native communities. Sea ice extent (SIE, the total surface area with at least 15% sea ice concentration) is strongly seasonal. In the Arctic, it typically varies from a maximum of 15 million km² in March to a minimum of 6 million km² in September, whereas in the Antarctic, it spans from a minimum of 3 million km² in February to a maximum of 19 million km² in September. Superimposed on these seasonal cycles is longer-term variability driven by anthropogenic greenhouse emissions, ozone depletion and natural internal variability.

Image: Andrea Schettino/Pexels

Authors of a paper in Nature Briefing report that global sea ice continues to decline as a result of anthropogenic forcing and internal variability. Although the long-term global trend was once dominated by sea ice reductions in the Arctic, rapid changes in the Antarctic are now exerting a strong influence. Based on the satellite record, Antarctic SIE was at a record low for much of the year in 2023, including wintertime SIE 5 SD below average, shifting the previously positive trend to negative.

Key points from this overview paper is that Antarctic and Arctic sea ice in 2023 based on satellite observation of sea ice extent and concentration were;

• Global sea ice extent (Antarctic and Arctic combined) reached a satellite era record daily minimum of 15.86 million km² on 31st January 2023.
• Antarctic sea ice extent exhibited record lows in many months of the year, including the lowest monthly summer minimum (1.91 million km² in February) and the lowest monthly winter maximum (16.80 million km² in September).
• Arctic sea ice anomalies were largest in boreal summer, including a September sea ice extent of 4.37 million km², the 5th lowest on record.

Time series of annual mean sea ice extent (SIE) for the Arctic and Antarctic (from Roach & Meier, 2024)

To read the full paper in Nature Briefing  click here