by @Chris
Every winter the seas around the poles freeze, and every summer they thaw again. This map shows both ice caps at their extremes in every year of the satellite record, 1979–2026, as two polar discs side by side: the Arctic on the left, the Antarctic on the right. Each frame is one year: for each pole the winter maximum (blue) and, inside it, the summer minimum (white), each on its own date. The blue band between them is the ice that comes and goes with the seasons. The Arctic summer ice has shrunk the most: its September minimum averaged 7.0 million km² in 1979–1988 and 4.5 million km² in 2017–2026, with the record low of 3.39 million km² in 2012. The winter maximum fell less, from 16.2 to 14.7 million km². The Antarctic held steady for decades and reached its largest maximum, 20.16 million km², in 2014; since then it has dropped sharply, to a record low minimum of 1.85 million km² in 2023 and a record low maximum of 17.07 million km² in 2023. Pins mark each new record from 1985 on (the records that still stand as large pins); the bar at the top compares the two September extremes, the Arctic minimum and the Antarctic maximum. Both shades show sea ice extent: every 25 km grid cell where satellites measure at least 15% ice cover. Maxima and minima are dated on NSIDC's 5-day mean. Until August 1987 the satellites measured every other day, and NSIDC counts the small area around the North Pole that older satellites could not see as ice. The ice edge is smoothed and simplified to about 10 km, floes smaller than about 1,500 km² are left out, and the ice runs under the land, so the coast comes from the basemap. Each disc is a polar stereographic map, the projection NSIDC uses, reaching 40°N and 50°S. Values for 2026 are near-real-time and may still be revised slightly. Sources: NSIDC Sea Ice Index, Version 4 (G02135), daily extent maps and daily extent series, National Snow and Ice Data Center; Natural Earth (land, Antarctic ice shelves).
Arctic sea ice, winter maximum · Arctic sea ice, summer minimum · Antarctic sea ice, winter maximum · Antarctic sea ice, summer minimum