New Chicago-sized iceberg breaks off Antarctica

The new iceberg A-84 has spent part of the southern hemisphere's 2024-2025 austral summer bouncing off parts of the Antarctic coast. It measures 30 kilometers long by 17 kilometers wide , the size of the city of Chicago.

Over the past month, the potato-shaped iceberg has drifted about 250 kilometers from its point of origin near the southern end of the George VI Ice Shelf along the base of the Antarctic Peninsula.

The iceberg's journey is visible in an animation released by NASA Earth Observatory, composed of satellite images acquired between January 15 and February 15, 2025. The images are from the MODIS (Moderate Resolution Imaging Spectroradiometer) instruments on NASA's Terra and Aqua satellites, as well as the VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite.

In late 2024, a crack was observed in the remnant of the George VI Ice Shelf, but the future iceberg was still surrounded by sea ice at the Ronne Inlet, the bay that abuts the southern end of the ice shelf. The George VI Ice Shelf is unusual in that it has an ice front to both the north and south. By January 2025, most of the seasonal sea ice had melted and ocean currents carried the new iceberg away.

"I'm impressed by how quickly it's moved in the longshore current," Christopher Shuman, a retired glaciologist at the University of Maryland, said in a statement. "It makes me wonder what's happening in the water beneath the ice shelf."

Iceberg calving is a normal occurrence on ice shelves. However, factors such as warming air and water, along with the decline of protective sea ice, can accelerate calving and lead to collapse, as has happened with several ice shelves along the Antarctic Peninsula.

Observations made by explorers in the early 1940s, and later by remote sensing, show that George VI has been losing shelf ice. So far, the retreat has been gradual, helped by the stability provided by its unique location between the Antarctic Peninsula and Alexander Island.