Arctic sea ice minimum
The Arctic's September sea-ice minimum has shrunk to about 4.75 million km² (2025) — down from around 7.05 million km² in 1979.
Source: NSIDC Sea Ice Index, via Our World in Data. Data through 2025. Download the data (JSON).
About this indicator
Each September the floating ice cap on the Arctic Ocean reaches its yearly minimum, after melting through the summer. Satellites have measured this minimum extent since 1979.
The trend is a steep, long-term decline: the Arctic is warming several times faster than the global average, and its late-summer ice has lost roughly a third of its area over the record.
Why it matters: Losing bright sea ice exposes dark ocean that absorbs more heat, accelerating Arctic warming and disrupting weather far to the south.
How to read this chart
The vertical axis is millions of square kilometres of sea-ice extent, which counts every ocean grid cell that is at least 15% covered by ice. Each point is one September minimum — the lowest extent of that year, reached at the end of the melt season — so the series is one value per year rather than a continuous line.
Extent measures the area covered, not how thick or how old the ice is, and Arctic ice has thinned as well as shrunk. Individual years swing with summer weather, so one higher year is not a recovery. The signal worth reading is the multi-decade slope since satellite measurement began in 1979, and the JSON download lists every yearly minimum in the record.