The huge iceberg A81 is about the size of Greater London and measures 1550 km2. It calved from the Brunt Ice Shelf on January 22, 2023, and has traveled south along the coastline for about 150 km.

As the summer team left the nearby British Antarctic Survey (BAS) Halley Research Station, they witnessed the beginning of the iceberg’s journey to the Weddell Sea from the air. The team recently released a video showing the sheer scale of the hefty mountain, which looks like its own ice sheet and gives rise to small icebergs along the shoreline.

The first images of the massive A81 iceberg show the dynamic nature of the iceberg surrounded by smaller icebergs that have also broken off.

A81 was released when Chasm-1, a massive ice crack, ran across the entire ice shelf. It is currently drifting 150 kilometers from its starting point. The BAS Halley Research Station is located on the Brunt Ice Shelf, one of the most accurately observed ice shelves in the world. The area around the research station is currently largely undisturbed by the calving period, according to monitoring by BAS glaciologists. The calving of A81, the region’s second major iceberg in the past two years, is a natural occurrence along the Antarctic coast.

After the iceberg breaks off the ice shelf, it has spun and heads south. The A81 is expected to travel west in a similar fashion to previous icebergs swept by the powerful Antarctic coastal current. As the A81 continues to move through the Weddell Sea and further north towards the South Atlantic basin, BAS scientists and the general public will continue to track and monitor it.

Glaciologist Dr. Oliver Marsh studies the Brunt Ice Shelf and has just returned from Halley Research Station. He says:

“This was a calf we knew was coming. BAS has been tracking the Brunt Ice Shelf and the abysses that have formed over it for more than a decade. Since glaciologists first observed the broadening of Chasm-1 in 2012, BAS science and operations teams have been anticipating the calving. High-precision GPS instruments and satellite data have been used to track the widening of the canyon, and in 2016 BAS took the precaution of moving the Halley Research Station inland to protect it.

Professor Geraint Tarling, head of the Ecosystems team at BAS, was on board. He says:

“An iceberg of this size will have a major impact on the ocean ecosystems that support the rich diversity of marine life in this Antarctic region. These effects can be both positive and negative. On the positive side, if the iceberg melts, it will release many nutrients that could benefit the growth of microscopic plants, such as phytoplankton at the base of the oceanic food webs. The downside is that the same melting, on such a large scale, dumps a lot of fresh water into the ocean, decreasing salinity and making the water unsuitable for much of the phytoplankton and the zooplankton that feed on it. These effects can then flood the food web to fish, birds, seals and whales.”