A 600-square-mile iceberg is bumping along South Georgia’s underwater shelf, nearly four years after it calved

Iceberg A-81, a slab of ice roughly 1,550 square kilometers (about 600 square miles) in area, has reached South Georgia and appears to be bumping along the edge of the island’s underwater shelf, nearly four years after it broke from Antarctica’s Brunt Ice Shelf. NASA’s Earth Observatory published the account on October 27, 2026, built on a Terra satellite image from October 20.

Help yourself and the planet: The Cool Down makes it easy to help yourself while helping the planet, with smart, simple changes to save more and waste less in your everyday life.

Get The Cool Down →

We may earn a commission if you sign up.

The berg’s progress slowed noticeably in the days before that image, according to Jan Lieser of Australia’s Bureau of Meteorology and Christopher Shuman, a retired University of Maryland glaciologist, whose observations NASA relays.

A journey of 2,300 kilometers from the Brunt Ice Shelf

NASA’s Earth Observatory account traces the berg from its birth to the Scotia Sea. After breaking away in January 2023, it spent more than three years carried along the coast of the Weddell Sea by the clockwise-flowing Weddell Gyre. By May 2026 it had reached the tip of the Antarctic Peninsula and turned north, and by late October it was approaching South Georgia, some 2,300 kilometers (1,400 miles) north-northwest of the Brunt Ice Shelf where it began. Counted from the January 22, 2023 calving to NASA’s October 20, 2026 image, the interval is three years and nine months, which is the “nearly four years” stated here. In distance, South Georgia lies 2,300 kilometers from the Brunt shelf, though the berg’s route along the Weddell coast and around the peninsula was far longer.

The calving itself was recorded at the time. NASA’s January 2023 report put the break late on January 22, 2023, according to the British Antarctic Survey, and said the U.S. National Ice Center named the new berg A-81. The crack that released it, known as Chasm 1, began growing in the 1970s, went quiet, resumed growing in 2012 and in the 2022 to 2023 summer broke past the McDonald Ice Rumples, a submerged bedrock knob that had helped pin that part of the shelf.

What bumping along the shelf edge means

The wording is careful. NASA says the berg “appeared to be bumping along the edge of the island’s underwater shelf,” and the account does not say that it has run aground or that it has stopped. Slowing is the signal. A berg this large sits deep in the water, and where the seabed rises toward an island its underside can touch bottom, which drags on a drift that had run steadily for years.

Nothing in the NASA record gives the berg’s draft or the water depth where it touched, so the contact is inferred from the change in speed rather than measured. The two scientists are cited for the slowing and the shelf contact, not for a confirmed grounding, and the wording here follows that.

A-23A, the precedent

South Georgia has seen this before. In its A-81 account NASA recalls that “in 2025, for instance, Iceberg A-23A ran aground on the shelf and later broke apart.” NASA’s March 2025 report described A-23A, then the largest iceberg on Earth at about 3,460 square kilometers, as having slowed sharply around February 25, 2025, after a drift north from the Filchner Ice Shelf, where it calved in 1986.

Josh Willis, an oceanographer at NASA’s Jet Propulsion Laboratory, said at the time that the question was whether the current “will trap it there as it melts and breaks up,” adding “Time will tell.” For A-23A, that is what happened. The same report noted that ice fragments were breaking off its edges and could affect plants and animals along the shoreline, in a region that supports seals, penguins and phytoplankton.

Shuman, who followed A-23A’s drift by satellite in 2025, is again among the observers tracking a berg at the same shelf. A-81 is about 45 percent the size of A-23A, so a grounding would play out on a smaller scale, but the shelf is the same one, and the wildlife concerns raised in 2025 would apply again if the berg sheds fragments near shore. NASA does not forecast whether A-81 will lodge, spin free or fragment.

The Brunt Ice Shelf keeps shedding

NASA’s account notes that scientists are watching the Brunt Ice Shelf closely because it has shed several large icebergs recently. A-74 calved from the North Rift in 2021 and has since broken up. A-83, which came away from the Halloween Crack in 2024, is intact and trailing A-81 north, along with other icebergs apparently leaving the Weddell Sea.

The British Antarctic Survey operates Halley Research Station on the floating Brunt shelf, a facility with meteorological and ozone records back to 1956, and the station was moved about 23 kilometers inland in 2017 to avoid a crack in the ice. The A-81 calving took place about 20 kilometers from the station, according to Wikipedia’s entry on the berg, and NASA’s 2023 report relays the British Antarctic Survey’s statement that the break did not affect the base.

What happens in the days after October 20 is the open question. NASA’s account stops at the image, with A-81 slowed at the shelf edge, and the satellite record that follows will show whether the berg stays pinned there or breaks up as A-23A did.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

Help yourself and the planet: Get The Cool Down →

We may earn a commission if you sign up.