A tie with recent years
Arctic sea ice reached its smallest extent of the year on September 12, NASA and the National Snow and Ice Data Center (NSIDC) reported. The ice covered about 4.6 million square kilometres, or 1.78 million square miles, tying with 2008, 2010 and 2025 for the tenth-lowest minimum since satellite records began in 1978.
Sea ice grows through the winter and shrinks through the summer, reaching its annual low in September. This year's minimum fits a clear pattern: the past 20 years, from 2007 to 2026, have produced the 20 lowest minimums in the record.
What a low minimum changes
Less ice in September means less bright surface to reflect sunlight, so more solar energy is absorbed by the ocean. That heat is released back into the atmosphere in autumn, which can influence weather patterns across the northern hemisphere.
Thinner, younger ice also changes life in the region. Marine mammals that depend on stable ice for hunting and resting have less reliable habitat, and coastal communities face more erosion from autumn storms.
Antarctica on the other side
At the opposite pole, Antarctic sea ice probably reached its yearly maximum on September 14 at 17.59 million square kilometres. If the ice does not grow further this season, it will be the third-lowest Antarctic maximum on record.
Scientists note that the two poles behave differently, because Antarctic ice is shaped by winds and ocean currents as much as by air temperature. Researchers will keep tracking both through the southern spring, when the Antarctic maximum is normally confirmed.