After years of drifting, the world's largest iceberg, A-23A, has run aground near South Georgia, mirroring icebergs that have melted and broken up in these waters in the past. It spent decades in the southern Weddell Sea before breaking away from the ice sheet and moving slowly but steadily northward - eventually possibly sinking in shallow waters. Scientists are watching closely to see if it either breaks up like icebergs in the past or manages to escape the island's grip.
Antarctic iceberg A-23A, the largest iceberg on Earth, appears to have run aground near South Georgia. As of early March 2025, satellite images showed little movement from the massive 3,460 square kilometers (1,240 square miles) iceberg, which had been drifting across the Scotia Sea before reaching the island's waters.
South Georgia is the largest of the nine islands in the British Overseas Territory of South Georgia and the South Sandwich Islands. Although there is no permanent human settlement here, scientists conduct research there and tourists visit its historic sites. The area is home to a rich ecosystem including seals, penguins and tiny phytoplankton. It's also on "Iceberg Alley," a common route for Antarctic icebergs to drift northward.
According to Christopher Shuman, a retired glaciologist at the University of Maryland, Baltimore, the A-23A's movement slowed significantly around February 25, 2025. Schumann, who used satellite imagery to track the iceberg's path, noted that the iceberg broke free from the seafloor in the early 2020s after being trapped in the southern Weddell Sea for decades. It now lies more than 2,000 kilometers (1,200 miles) north of the Filchner Ice Shelf in Antarctica, where it originally calved in 1986.
The image above shows the iceberg's position relative to the remote island and its underwater ice shelf on March 4, 2025. Its location is based on images acquired by MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Aqua satellite (below).
Josh Willis, an oceanographer at NASA's Jet Propulsion Laboratory, agrees that ocean currents appear to have brought the A-23A to the shallow continental shelf areas where some of the famous icebergs have encountered before. The last large iceberg to approach South Georgia was A-68A, a one-trillion-ton behemoth that encountered the island's shallow continental shelf in December 2020. The iceberg soon split into two main blocks, continued to fracture, and eventually broke apart in the northern Scotia Sea around South Georgia.
Scientists later discovered that during the three months the A-68A stayed near the island, the melting ice at the bottom added 152 billion metric tons of fresh water to the ocean. Iceberg meltwater may affect the local marine environment. It also adds nutrients to the water and promotes biological production.
Currently, many pieces of ice have broken off the edges of the A-23A. Although these fragments appear small in the image above and are not large enough to be named by the National Ice Center, they could still affect the flora and fauna along the island's coastline.
It remains to be seen what will become of the rest of the iceberg's main body. When icebergs reach this far north, they eventually succumb to warmer waters, winds and currents, making this stretch of sea a challenge for all mariners.
"I think the big question now is whether strong ocean currents will trap it there as it melts and breaks apart, or whether it will spin around the southern part of the island like previous icebergs did," Willis said. "Time will tell."
The NASA Earth Observatory image was taken by Liang Wanmei, using MODIS data from NASA's EOSDISLANCE and GIBS/Worldview, the General Bathymetric Chart of the Oceans (GEBCO) from the British Ocean Data Center, and ocean bathymetry data and digital elevation data from the British Antarctic Survey.
Compiled from /scitechdaily