The world’s largest iceberg floats freely in the Southern Ocean. 

Iceberg A23a is a 1,500 square mile ice mass larger than the state of Rhode Island. A23a weighs approximately 1 trillion tons and measures around 1,300 feet thick.

A23a began its journey in August 1986, when it calved, or broke off, from Antarctica’s Filchner Ice Shelf. The iceberg remained grounded on the seafloor in the Weddell Sea for the next three decades.

In 2020, A23a detached from the seabed and began drifting north. For the next four years, the iceberg followed the Antarctic Circumpolar Current on a path known as “Iceberg Alley.” 

Around April 2024, though, A23a became trapped in an ocean vortex—a Taylor column—near the South Orkney Islands. In Taylor columns, currents flowing around underwater mountains create rotating columns of water. A23a began spinning counterclockwise about 15 degrees every day, trapped in a swirling vortex for 8 months.

December 2024, A23a broke free from the Taylor Column and is drifting north in the Southern Ocean. The iceberg could collide with South Georgia, an island in the South Atlantic Ocean. Although the iceberg escaped one fate, A23a now floats toward its probable demise; if the iceberg doesn’t hit South Georgia, the British Antarctic Survey predicts A23a will likely split into smaller icebergs and meet a watery grave in the warmer currents of the north. 

Landsat images help scientists study icebergs and other surface phenomena, as well as indirectly reveal geological features beneath the ocean through observations such as those of sediment plumes and changes in ocean color.