A vast iceberg the size of Greater London has broken off Antarctica near a British research station.
The 'calving' came after cracks that have been developing naturally over the last few years extended across the entire Brunt Ice Shelf, causing the new iceberg to break free.
The Brunt Ice Shelf is the location of BAS Halley Research Station, which has measured the ozone since 1956 and which led to the discovery of the ozone hole in 1985.
Known as Chasm-1, the crack fully extended through the ice shelf.
The break-off is the second major calving from this area in the last two years and has taken place a decade after scientists at British Antarctic Survey (BAS) first detected growth of vast cracks in the ice.
BAS glaciologists, who have been monitoring the behaviour of the ice shelf, said that the area of the ice shelf where the research station is located currently remains unaffected by the recent calving events.
Professor Dame Jane Francis, director of BAS, said: "Our glaciologists and operations teams have been anticipating this 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.
"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 50C."
The glaciological structure of the Brunt Ice Shelf is complex, and the impact of calving events is unpredictable.
In 2016, BAS took the precaution of relocating Halley Research Station 23km inland of Chasm-1 after it began to widen.
Currently, 21 staff are on the station working to maintain the power supplies and facilities that keep the scientific experiments operating remotely through winter.
They will be collected by aircraft around 6 February.
Professor Dominic Hodgson, BAS glaciologist, added: "This calving event has been expected and is part of the natural behaviour of the Brunt Ice Shelf. It is not linked to climate change.
"Our science and operational teams continue to monitor the ice shelf in real-time to ensure it is safe, and to maintain the delivery of the science we undertake at Halley."
The changes in the Brunt Ice Shelf are a natural process.
There is no connection to the rapid calving events seen on the Larsen C Ice Shelf, which had extensive surface meltwater at the time of its collapse in July 2017, and no evidence that climate change has played a significant role.
Watch: London-sized iceberg breaks off Antarctica