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Arctic sea ice ties for 10th-lowest minimum as a low September plateau holds
Arctic sea ice shrank to 4.6 million square kilometers on Sept. 12, tying for the 10th-lowest minimum on record, NASA and NSIDC said. Matching a 2008 value puts 2026 in the middle of a low band the ice has held since 2007.
The Scientist · Science desk
What happened
- Arctic sea ice reached its 2026 minimum on Sept. 12 at an estimated 4.6 million square kilometers, according to NASA and the National Snow and Ice Data Center.
- That extent ties 2008, 2010 and 2025 for the 10th-lowest minimum in the satellite record.
- The 20 lowest Arctic minima since continuous satellite measurement began in late 1978 all occurred from 2007 through 2026.
- NASA sea ice scientist Linette Boisvert says increased cloud cover over the past decade has kept solar radiation from further accelerating the melt.
- Antarctic sea ice shrank by roughly 300,000 square kilometers over six days in August before resuming its seasonal growth toward the annual maximum.
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Why it matters
- constraint Baselines built from pre-2007 Septembers describe an Arctic ice cover that has not recurred in any of the last 20 summers of satellite observation.
- exposure If Boisvert is right that clouds have held back extra solar heating, the recent stability rests partly on weather, and a run of clearer summers would remove the shading she credits.
- constraint Antarctic ice swings so widely from year to year that one six-day drop cannot yet be read as evidence for or against a long-term decline there.
The satellite record began in October 1978, after that year's September low had passed, so it holds 48 annual minima, 1979 through 2026 [1]. It is stitched from successive instruments: Nimbus-7 first, Defense Meteorological Satellite Program sensors from 1987, NASA's Aqua from 2002 to 2011, and since 2012 the AMSR2 radiometer on JAXA's GCOM-W satellite [4]. Set against the post-2007 run, that leaves 28 earlier minima, and every one of them sits above every minimum measured since [2].
Within that low band, 2026 lands in the middle. Nine years came in lower [3]. The figure matches 2010, last year, and 2008, a minimum set 18 years ago [2][4]. A value that recurs after 18 years fits a step down followed by a long flat stretch. "We've plateaued, but we're still low relative to the earlier part of the record," said Walt Meier, a senior research scientist at NSIDC [9].
Boisvert's cloud account has a clear physical pathway: clouds block solar radiation that would otherwise speed the melt, and NASA says that has contributed to the relatively stable September extent [7][8]. The thing this doesn't tell you is the size of the effect. The release attributes part of the plateau to clouds without putting a number on it or naming the study behind it [7][8]. Weather already moves melt substantially from one summer to the next [6]. On the evidence released, cloudier summers arriving alongside flat minima is a correlation with a plausible physical link.
Antarctica's August drop works out to roughly 50,000 square kilometers a day over the six days [5]. Meier said it appeared to be associated with weather conditions that pushed and compacted the thin, mobile ice near the outer edge [11]. "Those types of things happen all the time," Meier said. "But the magnitude of it certainly is unusual." [12]
Antarctic ice swings more from year to year than Arctic ice because it is not surrounded by land and can respond more freely to wind and weather [13]. Its annual maximum has generally been lower in recent years, but Boisvert and Meier remain cautious about calling that a long-term trend [14].
What to watch
- The 2026 Antarctic maximum, which NASA and NSIDC will announce once they confirm seasonal growth has ended, typically in late September or early October.
- A published attribution analysis putting a number on how much of the stable September extent cloud cover accounts for.
- A less cloudy Arctic summer, and whether its minimum drops below the nine years now ranked lower than 2026.