Iceberg A-81 reaches South Georgia after a three-year drift from Antarctica

An iceberg of roughly 1,550 square kilometers (600 square miles) that broke away from Antarctica’s Brunt Ice Shelf in January 2023 has arrived off South Georgia, a remote island in the South Atlantic, NASA’s Earth Observatory reported on Oct. 27. Satellite imagery shows the berg, designated A-81, slowing as it meets the edge of the island’s shallow underwater shelf.

The image, captured on Oct. 20 by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, shows A-81 just southwest of the island. Its progress slowed noticeably in the days before. According to Jan Lieser of Australia’s Bureau of Meteorology and Christopher Shuman of the University of Maryland (retired), the iceberg “appeared to be bumping along the edge of the island’s underwater shelf.”

A three-year journey

A-81 spent more than three years in the Weddell Sea after it calved, carried along the Antarctic coast by the clockwise-flowing Weddell Gyre, according to NASA. It reached the tip of the Antarctic Peninsula by May 2026 and then moved north into the Scotia Sea. South Georgia lies about 2,300 kilometers (1,400 miles) north-northwest of the Brunt Ice Shelf.

The berg’s birth was years in the making. NASA’s January 2023 report on the calving described how a rift known as Chasm 1 began growing in the 1970s, went dormant, and resumed growth in 2012. It lengthened for almost a decade, at rates of as much as 4 kilometers (2.5 miles) per year in early 2019, when a break seemed imminent. The British Antarctic Survey (BAS) said the iceberg finally broke free late on Jan. 22, 2023, after the rift cut past the McDonald Ice Rumples, a submerged bedrock knob that had acted as a pinning point. The U.S. National Ice Center named it A-81.

The Brunt Ice Shelf is home to Halley Research Station, which BAS operates and which had been relocated farther inland as the chasm widened. BAS reported that the station was unaffected by the break. At the time, Shuman, then described as a University of Maryland, Baltimore County glaciologist based at NASA’s Goddard Space Flight Center, said: “We have no solid idea what ‘normal’ really is for this unusual ice shelf.”

Not the only traveler

The Brunt Ice Shelf has recently shed several large icebergs, NASA noted. A-74 calved from the shelf’s North Rift in 2021 and has since broken up. A-83, which calved from a feature called the Halloween Crack in 2024, remains intact and is trailing A-81 northward, along with other icebergs that appear to be leaving the Weddell Sea.

South Georgia’s shallow shelf has stopped giant icebergs before. In 2025, Iceberg A-23A, which calved from the Filchner Ice Shelf in 1986, ran aground there and later broke apart. By September 2025, NASA reported in a follow-up, A-23A’s largest remaining fragment covered just over 1,500 square kilometers (580 square miles) after the berg had lost about two-thirds of its area during its drift north.

An earlier giant, A-68A, encountered the island’s shallow shelf in December 2020, according to a March 2025 Earth Observatory article. It split into two main pieces that fractured further and eventually disintegrated in the northern Scotia Sea. Researchers later estimated that melting from its base added 152 billion metric tons of fresh water to the ocean during its roughly three-month stay near the island.

Why it matters

South Georgia is a wildlife-rich island. “The region supports abundant life, from seals and penguins to tiny phytoplankton,” NASA wrote in 2025, adding that iceberg meltwater can potentially affect the local ocean environment and can also add nutrients that foster biological production. Whether A-81 lodges on the shelf, breaks up or drifts on is not yet known, and the Oct. 27 article does not assess any ecological effects of A-81 itself.

The arrival also shows how closely large icebergs can now be followed from orbit. “We can see and monitor these large icebergs—including A-23A and its named offspring—quite well with spaceborne sensors,” Lieser told NASA in 2025. NASA’s latest article also notes: “Calving is a normal part of the life cycle of ice shelves.”

The caveats

The 1,550-square-kilometer figure is the size given for A-81 at calving and repeated in the October article as approximate. NASA’s report does not give the berg’s exact distance from the island or confirm that it has grounded, only that its drift slowed near the shelf edge.

Corrections and tips: email the editor using the address on the Contact page.