Compiled from National Institute of Polar Research, National Snow and Ice Data Center, The Guardian. Sources checked . Claims are attributed; limits of the evidence and analysis are identified in the report.
Event / release date: . Read the source list.
Japan’s monitoring record shows a low winter peak
Japan’s National Institute of Polar Research reported on September 28 that Antarctic sea-ice extent reached 17.71 million square kilometres on September 11. It ranked that winter maximum third-lowest in its satellite record, which begins in 1979.
The U.S. National Snow and Ice Data Center’s September 23 assessment reported a likely maximum of 17.59 million square kilometres on September 14. NSIDC said that would be the third-lowest maximum in its record if the date held.
The Guardian separately reported the unusually low Antarctic winter peak on September 30.
Why agencies report different measurements
The two monitoring reports agree on a low seasonal peak but do not give identical dates or extents. This article retains each institution’s own values rather than combining them into an artificial single measurement.
NIPR’s regional account also shows that conditions were uneven: some sectors had more ice than their 2010s average while others had less. An Antarctic-wide figure does not describe every coastline.
Peak identification and attribution remain provisional
NSIDC cautioned that large fluctuations near the seasonal maximum can delay a confident identification of the peak. Its number should therefore retain its provisional status. The measurements alone do not establish how much of this particular season’s outcome is attributable to any one cause.
The seasonal record beyond the ranking — analysis
A winter maximum measures how far sea ice expanded during the growth season. Following both the seasonal record and the regional pattern provides a more useful picture than a ranking alone. Subsequent agency analysis may refine the peak without erasing the broader finding of unusually limited winter extent.
Sources
National Institute of Polar Research — 2026 Arctic minimum and Antarctic maximum sea-ice extents
Primary satellite monitoring analysis · 2026-09-28
National Snow and Ice Data Center — 2026 sea-ice seasonal extremes and provisional Antarctic maximum
Primary monitoring analysis; Antarctic peak provisional · 2026-09-23
The Guardian — Reporting on the low Antarctic winter sea-ice maximum
Independent reporting · 2026-09-30