1. Nature

   Antarctic winter sea ice went from a record high to a record low in 9 years

   In September 2014, ice around Antarctica covered 19.76 million km², the most since 1979. In September 2023: 16.89 million km², the least on record.

   Source: NOAA/NSIDC Sea Ice Index v4Open on the chart →

   More

   The same month of the satellite record contains both a record high and a much later low. A selected early segment cannot summarize the southern record.

   The line shows September each year. The scale is in million km²; the maximum and minimum are marked.

   • September high → low million km²

     19.756 (2014) → 16.891 (2023)

     Sea ice in both hemispheres: area and extent

   Maximum and minimum September monthly mean extent selected from 1979–2025. This is an explicitly labeled comparison of extremes, not an estimate of the expected rate of change.

   Fetterer et al. (2025), Sea Ice Index v4, DOI 10.7265/a98x-0f50. Northern/Southern Hemisphere are not countries. Extent counts whole grid cells with ice concentration ≥15%; area weights by concentration. Monthly satellite estimates in million km², not volume or land glaciers. Recent points may be preliminary. The published annual mean is calendar-day weighted and retained only with all 12 months present. Hemispheres are not summed into a universal climate index.

   A question for this picture

   Which measure would change this story?

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