January 2023 Calving Of London-Sized Iceberg Powered Acceleration Of Brunt Ice Sheet

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It took four years for a rift that spanned the width of the Brunt Ice Shelf finally broke on January 24, 2023. The iceberg named A81 was 600 square miles or the size of metropolitan London.

Once considered stable, The Brunt Ice Shelf is accelerating rapidly into the Weddell Sea, according to the British Antarctic Survey (BAS), which monitors Brunt at its Halley Research station. Halley Station recorded the retreat after two massive icebergs calved.

The surge of glacial ice occurred shortly after Iceberg A81 when it snapped off the 500-foot thick ice shelf. The floating shelf has moved from half a mile in January to almost one mile today. The abstract notes, "Initially, the rate of acceleration increased by a factor of ten, with a second, smaller calving at the end of June 2023 leading to further tripling of acceleration. The acceleration is caused by reduced buttressing at the McDonald Ice Rumples due to losing contact with the sea floor. It has led to high strain rates to the south, with potential consequences for the stability of the remaining ice shelf." The shelf has given researchers no reason to believe that the remaining shelf will disintegrate anytime soon. They believe the glacier will be grounded again at some point. Where that would be was not identified; it could be another ridge at the McDonald Ice Rumples. The BAS monitors the glacier daily.

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The data comes from precise GPS measurements around Halley and radar observations by the European Union's Sentinel-1a satellite. The acceleration follows the calving of two major icebergs from the leading edge of the Brunt - a 1,300-sq-km (500-sq-mile) behemoth called A74, in February 2021, and an equally mammoth slab called A81, in January this year.

A74's impact was minimal but A81 appears to have released the shelf from a shallow section of seafloor that normally pins it in place and slows the seaward momentum. What is more, these calvings - and there was another smaller one in June - have prompted new areas of stress in the ice shelf.

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https://www.dailykos.com/stories/2023/9/13/2193040/-Brunt-glacier-rapidly-accelerates-into-the-Weddell-Sea-after-pinning-point-lost-to-iceberg-A81

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1. Brief Communication: Rapid acceleration of the Brunt Ice Shelf after calving of iceberg A-81

Brief Communication: Rapid acceleration of the Brunt Ice Shelf after calving of iceberg A-81