The Long Final Drift of A23a, the World's Former Largest Iceberg

After nearly four decades drifting through the Southern Ocean, A23a—an iceberg once spanning 2,000 square miles—has effectively vanished. The massive block, which broke from Antarctica's Filchner Ice Shelf in 1986, disintegrated into fragments after a final, turbulent journey through warmer waters near South Georgia.

Editorial·August 31, 2026·reads: 2,929

The Long Final Drift of A23a, the World's Former Largest Iceberg

The iceberg’s existence was defined by its size and its stubborn refusal to drift. For decades, it remained pinned to the ocean floor in the Weddell Sea before finally breaking loose in 2020. By November 2023, it reached the open Southern Ocean, only to become ensnared in a Taylor column—a rotating ocean current caused by an underwater mountain—which forced it to spin in place for eight months.

As it progressed toward South Georgia in 2025, the iceberg became a spectacle of nature, described by documentarian Jerome Bouvier as an "infinite wall" teeming with whales, penguins, and seals. During this period, the iceberg shed pieces of its history, including debris from the Soviet research station Druzhnaya 1, which had been swept away alongside the ice in 1986. By June 2025, the structure had shrunk below 1,200 square miles, relinquishing its title as the world's largest. The US National Ice Center officially ceased tracking the formation in March 2026, as satellite imagery confirmed it had fractured into small, melting remnants scattered across the sea.