Giant Iceberg Split From the Antarctic Ice Shelf

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A-74 Iceberg Annotated

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March 1, 2021

A big iceberg lastly divided from the Antarctic ice rack, however another piece stubbornly holds on.

Antarctica’s Brunt Ice Shelf lastly calved a big iceberg in February 2021, 2 years after rifts opened quickly throughout the ice and raised issues about the rack’s stability.

The break was very first identified by GPS devices on February 26, 2021, and after that validated the next day with radar images from the European Space Agency’s Sentinel-1A satellite. On March 1, clouds were sporadic enough for the Operational Land Imager (OLI) on Landsat 8 to get this natural-color picture of the brand-new iceberg.

Named A-74, the berg covers about 1270 square kilometers (490 square miles), or about two times the size of Chicago. That’s a big piece of ice for the Brunt Ice Shelf, however Antarctica is understood for producing some massive bergs. For contrast, Iceberg A-68A was practically 5 times that size when it calved from the Larsen C Ice Shelf in 2017.

A-74 broke from the ice rack northeast of the McDonald Ice Rumples—a location where the circulation of ice is hampered by an undersea development that triggers pressure waves, crevasses, and rifts to form at the surface area. The rift that generated the brand-new berg appeared near the rumples in satellite images in September 2019, and it advanced throughout the ice rack with impressive speed throughout the austral summertime of 2020-2021.

“I would not have thought that this rift could go zipping across the northeast side of the Brunt Ice Shelf and cause a significant calving—all in a tiny fraction of the time it has taken Chasm 1 to extend toward the ice rumples from the south,” stated Christopher Shuman, a University of Maryland, Baltimore County, glaciologist based at NASA’s Goddard Space Flight Center.

Chasm 1 is a different rift situated south of the ice rumples and the Halloween Crack. After decades of growth and after that a fast velocity in 2019, that rift appeared poised to generate its own iceberg, triggering security issues for scientists “upstream” at the British Antarctic Survey’s Halley VI Research Station. This area of the rack is still hanging on, however when it ultimately breaks the berg will likely determine about 1700 square kilometers (660 square miles).

Scientists are waiting to see how the complex structure reacts to the current calving. “The Halloween Crack may or may not be the first to respond,” Shuman stated. “We’ll be closely watching that pinning point for changes to the larger Brunt Ice Shelf remnant.”

It likewise stays to be seen what will end up being of the brand-new iceberg. Most likely, it will ultimately get captured up in the Weddell Gyre—comparable to the fate of A-68. But initially it requires to be pressed offshore, and to date it does not appear to have actually moved really far.

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