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Big Iceberg Break up From the Antarctic Ice Shelf

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A-74 Iceberg Annotated

March 1, 2021

A big iceberg lastly break up from the Antarctic ice shelf, however one other piece stubbornly hangs on.

Antarctica’s Brunt Ice Shelf lastly calved a big iceberg in February 2021, two years after rifts opened rapidly throughout the ice and raised issues in regards to the shelf’s stability.

The break was first detected by GPS tools on February 26, 2021, after which confirmed the subsequent day with radar images from the European Area Company’s Sentinel-1A satellite tv for pc. On March 1, clouds had been sparse sufficient for the Operational Land Imager (OLI) on Landsat 8 to amass this natural-color picture of the brand new iceberg.

Named A-74, the berg spans about 1270 sq. kilometers (490 sq. miles), or about twice the dimensions of Chicago. That’s a big piece of ice for the Brunt Ice Shelf, however Antarctica is thought for churning out some monumental bergs. For comparability, Iceberg A-68A was nearly 5 occasions that dimension when it calved from the Larsen C Ice Shelf in 2017.

A-74 broke from the ice shelf northeast of the McDonald Ice Rumples—an space the place the movement of ice is impeded by an underwater formation that causes stress waves, crevasses, and rifts to type on the floor. The rift that spawned the brand new berg appeared close to the rumples in satellite tv for pc pictures in September 2019, and it advanced across the ice shelf with outstanding pace throughout the austral summer season of 2020-2021.

“I’d not have thought that this rift might go zipping throughout the northeast facet of the Brunt Ice Shelf and trigger a major calving—all in a tiny fraction of the time it has taken Chasm 1 to increase towards the ice rumples from the south,” mentioned Christopher Shuman, a College of Maryland, Baltimore County, glaciologist based mostly at NASA’s Goddard Area Flight Middle.

Chasm 1 is a separate rift positioned south of the ice rumples and the Halloween Crack. After decades of growth after which a speedy acceleration in 2019, that rift appeared poised to spawn its personal iceberg, prompting security issues for researchers “upstream” on the British Antarctic Survey’s Halley VI Analysis Station. This part of the shelf continues to be holding on, however when it will definitely breaks the berg will doubtless measure about 1700 sq. kilometers (660 sq. miles).

Scientists are ready to see how the advanced construction responds to the latest calving. “The Halloween Crack could or will not be the primary to reply,” Shuman mentioned. “We’ll be carefully watching that pinning level for modifications to the bigger Brunt Ice Shelf remnant.”

It additionally stays to be seen what’s going to change into of the brand new iceberg. More than likely, it can ultimately get caught up within the Weddell Gyre—much like the destiny of A-68. However first it must be pushed offshore, and so far it doesn’t seem to have moved very far.

NASA Earth Observatory picture by Joshua Stevens, utilizing Landsat information from the U.S. Geological Survey and information © OpenStreetMap contributors by way of CC BY-SA 2.0. Story by Kathryn Hansen with data from Christopher Shuman (NASA GSFC/UMBC JCET).





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