In February 2019, a fault covering most of Antarctica’s Brant Ice Shelf appeared poised to give birth to an iceberg roughly twice the size of New York City. It was not the question among scientists or the growing fault will complete the shelf transition and break and When? ? Now, almost four years later, he has done just that.

The break occurred late in the evening of January 22, 2023, revealing a new iceberg measuring 1,550 square kilometers (about 600 square miles), according to the British Antarctic Survey (BAS). The US National Ice Center named it Iceberg A-81. Berg can be seen in this image taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite on January 24, 2023.

Glacier ice on the shelf flows away from the interior of Antarctica and floats along the eastern part of the Weddell Sea. (For reference, the Antarctic Peninsula and ice shelf are on the opposite side of Weddell.) The shelf has long been home to the British Antarctic Survey’s Halley Research Station, where scientists study terrestrial, atmospheric and space weather processes. BAS said the station, which was moved further inland in 2016 as the rift widens, was unaffected by the recent break.

The fault occurred along a fissure known as Abyss 1. This gap began to widen in the 1970s, followed by a period of dormancy before continuing to grow in 2012. It continued to stretch for nearly a decade, extending up to 4 kilometers (2.5 miles) per year from early 2019. But even this growth spurt has slowed down. That is, by the Antarctic summer of 2022-2023, the cliff accelerated and eventually passed the Macdonald Ice Fold, the submerged bedrock mound that served as the anchor point for this portion of the shelf. Several factors may have contributed to the completion of the dispersal by 2023, including the absence of sea ice to help counter or “push back” the loads on the ice shelf.

A second image obtained by the Operational Terrain Imager (OLI) on Landsat 8 shows the size of Abyss 1 on January 12, 2021, nearly two years before it ruptured. Note a few other cracks in the northeast portion of the shelf. The “new crack” in this image finally broke apart in February 2021, forming Iceberg A-74.

“The rapid formation of subsequent rifts before ancient Rifts 1 and 2 and recent rifts to the northeast suggest that these shelf zones are dynamic with tensions that are not fully understood,” said Christopher Shuman, a glacier expert at the University of Maryland, Baltimore County. Flight Center Goddard NASA.

The rupture of icebergs from the ice shelf is part of the natural, cyclical process of growth and decay at the edge of Earth’s ice sheets. As glacial ice flows over land and spreads out into the sea, the shelf areas furthest from the coast thinner. These areas are pressed by storms and tides and thin as they melt from above or below, ultimately making them more prone to cracking and shrinking.

As for the “new” Brant, it’s still unclear how complex floating glacier ice will respond to the latest calving event. According to Shuman, “We don’t have a clear idea of ​​what is ‘normal’ for this unusual ice shelf.”