Iceberg the size of Greater London breaks away from Antarctica ice shelf

This one isn't due to climate change.
Ameya Paleja
Scientists have known about the Chasm for many years now
Scientists have known about the Chasm for many years now

British Antarctic Survey 

A giant iceberg the size of Greater London has calved from the Brunt Ice Shelf in Antarctica, the British Antarctic Survey (BAS) reported. The event took place during a spring tide on Sunday, January 22, between 19.00 and 20.00 UTC. This event wasn't like Iceberg D28, which caught scientists by surprise.

The Brunt Ice Shelf is one of the most closely monitored ice shelves on the planet. As many as 16 instruments keep an eye on the deformation of ice on this shelf and report back on an hourly basis. Among the satellites keeping a tab on the shelf is the Sentinel 2 from the European Space Agency, Worldview satellite from NASA, Landsat 8 from the US, and TerraSAR-X from Germany.

The 492 feet (150 m) Brunt Ice Shelf that floats westward at the rate of one and a quarter mile (two km) every year is also where the BAS' Halley Research Station has been based since the year 1956 and has been studied closely by glaciologists.

Chasm-1 and icebergs

Over a decade ago, satellite monitoring data revealed the first signs of the potential calving on the western side of the Brunt Ice Shelf, which was referred to as Chasm-1. Using ice-penetrating radar, BAS glaciologists began looking for the most likely path and the rate of formation of the chasm in 2015-16.

Between 2015 and 2022, the chasm continued to grow and extended across the entire Ice Shelf that marked the beginning of the calving event, BAS said on its website. In October 2016, a new crack was detected and dubbed Halloween Crack, which was followed by another crack in late 2020, which led to the formation of iceberg A74 that calved in February of 2021.

The new iceberg that calved on Sunday does not have a name yet, but it formed along the line of Chasm-1 and is larger than A74. It has now drifted into the Weddell Sea and is likely to follow A74's path in the Antarctic Coastal Current.

The cause of the calving

Unlike the collapse of the Conger Ice Shelf on the eastern side of Antarctica in March last year, the recent calving is not the result of climate change, the BAS said. Instead, the changes in the Brunt Ice Shelf are a result of a natural process, and the calving was an event that was much anticipated and not at all sudden.

Iceberg the size of Greater London breaks away from Antarctica ice shelf
The Halley VI Research station moved inland, away from the Chasm

As a matter of fact, the BAS glaciologists were so well aware of the event coming to a pass and its extent that they shifted the Halley VI Research Station as early as 2016-17. The eight modules at the station were uncoupled and transported by a tractor over 14 miles (23 km) inland of the chasm.

As of now, 21 members of staff are at the station working on maintaining power supplies and facilities so that the experiments can continue at the station. The personnel is scheduled to return on February 6, prior to the end of Antarctic summer in March.

During Antarctic winters, when temperatures dip to -58° Fahrenheit (-50° Celsius), and it is dark for 24 hours of the day, the task of supplying power is handled by the Halley Automation project, which was installed in 2018-19, the webpage added.

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