The British Antarctic Survey (BAS) said the 1,550 square kilometre iceberg broke free of the shelf on Sunday when a crack known as Chasm-1 extended through it.
It happened close to the BAS’s Halley Research Station, which glaciologists said remains unaffected by the event, with 21 members of staff now maintaining the base and operating its scientific instruments.
The calving took place a decade after BAS scientists first detected the growth of vast cracks in the ice.
BAS director Dame Jane Francis said glaciologists had anticipated the event.
“Measurements of the ice shelf are carried out multiple times a day using an automated network of high-precision GPS instruments that surround the station,” she said.
“These measure how the ice shelf is deforming and moving and are compared to satellite images from ESA, Nasa and the German satellite TerraSAR-X.
“All data are sent back to Cambridge for analysis, so we know what is happening even in the Antarctic winter — when there are no staff on the station, it is dark for 24 hours and the temperature falls below minus 50°C.”
Research station relocated
In 2016, BAS relocated the Halley Research Station 23km inland of Chasm-1 after it began to widen.
Since 2017, staff have been deployed to the station only during the Antarctic summer, from November to March.
Staff at the station maintain power supplies and facilities that keep the scientific experiments operating remotely through the winter.
Their work will continue until they are collected by aircraft on about February 6.
The station sits on Antarctica’s up to 150m-thick Brunt Ice Shelf. The floating ice shelf flows at a rate of up to 2km per year west towards the sea and calves off icebergs regularly.
This is the second major calving in the area in the past two years.
In May 2021, the world’s largest iceberg — four times the size of Abu Dhabi — fell into the ocean in Antarctica after breaking off from the Ronne Ice Shelf.