City-sized iceberg finally breaks off in Antarctica after decade of cracking

An iceberg the size of the Hobart or London metropolitan area has broken away from the Brunt Ice Shelf on the edge of British Antarctic Territory.

The 1,550 square kilometre hunk of ice separated from the 150-metre-thick ice shelf on Sunday. Cracking had first been observed by British scientists in 2012 after showing no activity for at least 35 years.

A gap, ominously named Chasm-1, has progressively widened with the British Antarctic Survey (BAS) forced to relocate its Halley Research Station 23 kilometres away from the crack in 2016.

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BAS glaciologists have spent much of the last decade taking daily measurements of the ice shelf to understand the characteristics of the cracking. Halley is staffed during the summer.

Few ice shelves are monitored as closely as Brunt. 16 GPS instruments measure the shelf each hour, while four satellites capture imagery of its deformation, and radar and drones provide warning of sudden shifts in the ice.

Although iceberg calving is increasing with climate change, scientists say this event is not related to increasing temperatures from global warming.

“This calving event has been expected,” says BAS glaciologist Professor Dominic Hodgson. “[It] is part of the natural behaviour of the Brunt Ice Shelf. It isn’t linked to climate change.”

A similar event took place in 2021 when the A74 iceberg calved from part of the ice shelf to the north of the Halley research station. The new iceberg – likely to be known as A81 – lies to the west of the station.

Imagery released by the BAS shows A81 separating from the ice shelf, and it is expected to follow the path of A74 into the Weddell Sea in coming months.

Professor Hodgson says while the BAS will continue monitoring the Brunt, the calving event should not impact the work of the Halley station monitoring space weather and ozone levels in the atmosphere.