An iceberg the size of London breaks off from Antarctic ice shelf

Satellite imagery showed that an iceberg almost the size of Greater London has once again broken off the Antarctic ice shelf.

The British Antarctic Survey (BAS) said on Monday that the 1,550 square km block had broken off from the 150-metre-thick Brunt Ice Shelf.

Cracks that have been developing naturally over the last few years extended across the entire ice shelf on Sunday, causing the new iceberg to break free in a process called ‘calving’. 

‘The iceberg calved when the crack known as Chasm-1 fully extended through the ice shelf,’ said the BAS.

‘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,’

According to the BAS, the changes to the Brunt Ice Shelf are a natural process, with no evidence of climate change playing a significant role. 

In 2021, an iceberg (now known as A74) broke off and has since drifted away from the Brunt Ice Shelf into the Weddell Sea. 

This new iceberg formed along the line of Chasm-1 is slightly larger than A74.

It is expected to follow the path of A74 in the Antarctic Coastal Current while BAS glaciologists will track its movement. 

The yet unnamed iceberg will eventually be given a name by the US National Ice Center. 

‘Our glaciologists and operations teams have been anticipating this event,’ said Professor Dame Jane Francis, Director of BAS.

In preparation for future calving events, scientists measure the ice self and compare it 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 degrees C (or -58F),’ said Professor Dame Jane Francis, Director of BAS.

The Brunt Ice Shelf also hosts a BAS research station, the Halley Research Station. While the current location of the research station remains unaffected by recent calving events, the 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 23 km inland of Chasm-1 after it began to widen.  

Since 2017, staff have been deployed to the station only during the Antarctic summer (between November to March).

Currently 21 staff are on station working to maintain the power supplies and facilities that keep the scientific experiments operating remotely through the winter. Their work will continue until they are collected by aircraft around 6 February.  

The Brunt Ice Shelf is probably the most closely monitored ice shelf on Earth.  A network of 16 GPS instruments measure the deformation of the ice and report this back on a hourly basis. 

European Space Agency satellite imagery, TerraSAR-X, Nasa Worldview satellite images, US Landsat 8 images, ground penetrating radar, and on-site drone footage have been critical in providing the basis for early warning of changes to the Brunt Ice Shelf. 

These data have provided science teams with a number of ways to measure the cracks with very high precision. In addition, scientists have used computer models to predict how close the ice shelf was to calving. 

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