Antarctic iceberg A-23A, currently the largest iceberg on Earth, appears to have run aground off the coast of South Georgia island. As of early March 2025, satellite images showed little movement of the 3,460-square-kilometer (1,240-square-mile) berg after its long and winding journey across the Scotia Sea and final approach toward the island.
South Georgia is the largest of nine islands that make up the South Georgia and South Sandwich Islands, a British overseas territory. While the remote island lacks a permanent human population, scientists visit its research station, and tourists visit its historical sites. The region supports abundant life, from seals and penguins to tiny phytoplankton. It also happens to lie along the northern extent of an ocean route traveled by many Antarctic bergs known as “iceberg alley.”
A-23A’s northward drift suddenly slowed around February 25, 2025, according to Christopher Shuman, a retired glaciologist with the University of Maryland, Baltimore County. Shuman has used satellite images to track A-23A’s drift since it wiggled free from the seafloor in the early 2020s after decades grounded in the Southern Weddell Sea. The berg is now parked more than 2,000 kilometers (1,200 miles) north of its birthplace at Antarctica’s Filchner Ice Shelf, where it calved in 1986.
The map above shows the iceberg’s location on March 4, 2025, with respect to the remote island and its underwater shelf. Its position is based on an image (below) acquired by the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Aqua satellite.
Josh Willis, an oceanographer at NASA’s Jet Propulsion Laboratory, agrees that currents appear to have carried A-23A into the same shallow shelf region previously encountered by some notable icebergs. The last large iceberg to approach South Georgia was A-68A, a trillion-ton behemoth that encountered the island’s shallow shelf in December 2020. That berg quickly broke into two main pieces that continued to fracture and eventually disintegrate in the northern Scotia Sea around South Georgia.
Researchers later found that melting from the bottom of A-68A added 152 billion metric tons of fresh water to the ocean during its three-month stay near the island. Iceberg meltwater can potentially affect the local ocean environment. It can also add nutrients to the water that foster biological production.
Already, many ice fragments have broken from A-23A’s margins. Though these pieces appear small in the image above and are not large enough to be named by the U.S. National Ice Center, they could still affect the flora and fauna along the island’s shoreline.
It remains to be seen what becomes of the remainder of the berg’s main mass. When icebergs make it this far north, they eventually succumb to the warmer waters, winds, and currents that make this ocean area a challenge for all seafarers.
“I think the big question now is whether the strong current will trap it there as it melts and breaks up or whether it will spin around to the south of the island like previous bergs,” Willis said. “Time will tell.”
NASA Earth Observatory images by Wanmei Liang, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview, ocean bathymetry data and digital elevation data from the British Oceanographic Data Center’s General Bathymetric Chart of the Oceans (GEBCO) and the British Antarctic Survey. Story by Kathryn Hansen.
