A decade after scientists at British Antarctic Survey (BAS) first detected growth of vast cracks, a huge iceberg roughly the size of Los Angeles City (1182 square km) in Antarctica’s Brunt Ice Shelf has now broken off.
The first indication that a calving event was imminent came in November 2020 when a new chasm called North Rift headed towards another large chasm near the Stancomb-Wills Glacier Tongue 35km away, BAS said in a statement last week.
North Rift is the third major crack through the ice shelf to become active in the last decade.
During January, this rift pushed northeast at up to 1 km per day, cutting through the 150-metre-thick floating ice shelf.
The iceberg was formed when the crack widened several hundred metres in a few hours on Friday, releasing it from the rest of floating ice shelf.
“Our teams at BAS have been prepared for the calving of an iceberg from Brunt Ice Shelf for years,” said Professor Dame Jane Francis, Director of British Antarctic Survey.
“We monitor the ice shelf daily using an automated network of high-precision GPS instruments that surround the station, these measure how the ice shelf is deforming and moving. We also use satellite images from ESA (European Space Agency), NASA and the German satellite TerraSAR-X.”
The Brunt Ice Shelf is the location of British Antarctic Survey’s (BAS) Halley Research Station.
BAS glaciologists, who have been expecting a big calving event for at least a decade, say that the research station is unlikely to be affected by the current calving.
The glaciological structure of this vast floating ice shelf is complex, and the impact of “calving” events is unpredictable.
“Over coming weeks or months, the iceberg may move away; or it could run aground and remain close to Brunt Ice Shelf,” said British Antarctic Survey director Jane Francis
The mobile research base relocated inland for safety reasons in 2016-2017 as cracks in the ice threatened to cut it off. “That was a wise decision,” commented Simon Garrod, BAS director of operations.
The glaciologists said the latest event is unlikely to affect the station’s current location.
The base’s 12-person team left earlier this month, as they leave the base uninhabited in winter due to the unpredictable conditions.
While they are away, data from GPS instruments at the site goes to a centre in Cambridge, eastern England, for analysis.
Icebergs naturally break off from Antarctica into the ocean in a process accelerated by climate change. The BAS said in this case, there is “no evidence that climate change has played a significant role”.