Antarctica’s sea ice has undergone a stunning reversal

Antarctic sea ice reached its annual winter peak in September 2026, but the ice covered less ocean than in nearly any other year since satellite measurements began. Its maximum extent was the third lowest on record, adding to growing evidence of a dramatic shift in Antarctica's frozen waters.

Antarctica is surrounded by a vast ocean, giving its sea ice plenty of room to spread outward during the Southern Hemisphere's winter. This differs from the Arctic, where an ocean basin is enclosed by surrounding land. Although Antarctica's geography allows winter sea ice to expand over enormous distances, it also pushes the ice into warmer latitudes, where melting becomes more likely during summer. As a result, Antarctic sea ice generally reaches its largest extent in September before shrinking to its annual minimum in February.