A new crack has been noticed in the section of the floating ice shelf north of the McDonald Ice Rumples, which could cause the calving of several mountains. The extent of this new crack can be seen at the top of the picture. The temporary changes of the new crack come from the visual interpretation of Copernicus Sentinel-1 and Sentinel-2 images. The elongation of the other two main cracks in the ice shelf, only a few kilometers apart, was closely monitored by satellite images. Kloof 1, the large tear that runs northward, has been in place for more than 25 years, while the Halloween tear was first noticed on October 31, 2016. Credit: Contains amended Copernicus Sentinel data (2021), CC BY-SA 3.0 IGO
In early 2019, all eyes were on the Brunt Ice Shelf in Antarctica, where an iceberg, as large as Greater London, seemed to be breaking down. Nearly two years later, the mountain is desperately clinging, although current data indicate that calving is imminent. A new rift, observed in images captured by the Copernicus Sentinel missions, now indicates the potential for calving several mountains.
Glaciologists have been stopping a number of cracks in the Brunt ice shelf, which borders the Coats Land coast in the Weddell Sea sector of Antarctica for years. The extension of two main cracks in the ice shelf, which separated only a few kilometers from each other, was closely monitored by satellite images. Chasm 1, the large rift running north from the southernmost part of Brunt, has been in place for over 25 years, while the Halloween rift was first seen on October 31, 2016.
A more recent, unnamed tear was first noticed in observations of the Copernicus Sentinel-1 mission at the end of 2019, which recently stretched by more than 20 km. Satellite data were also used to track the motion and measure the resulting stress in the ice shelf. The map below shows the ice surface velocity at the Brunt and Stancomb-Wills Ice Shelf complex, derived by comparing two Sentinel 1 acquisitions captured on January 5 and January 17, 2021.
Satellite data were used to measure the surface motion of the ice shelf. The map shows the ice surface velocity on the Brunt ice shelf, derived by comparing two Copernicus Sentinel-1 acquisitions on January 5 and January 17, 2021. The surface velocity data indicate that the upper red area, northwest of the new crack, should be the most unstable, with an estimated movement of almost 5 m per day. The central part has an average velocity ranging from 2 to 2.5 m per day, while the lower area (blue visible) represents a more stable zone of the ice shelf in the vicinity of the ice on the coast. Credit: Contains amended Copernicus Sentinel data (2021), CC BY-SA 3.0 IGO
The data indicate that the area of the floating ice shelf, north of the new rift, is the most unstable, with an estimated movement of almost 5 m per day. The central part has an average velocity of 2 to 2.5 m per day, while the lower area (blue visible) represents a more stable zone of the ice shelf.
“Although it looks like it will calve in 2019, the southwesternmost region of the Brunt ice shelf has stubbornly resisted separation,” said Mark Drinkwater of ESA. “Since then, the Sentinel-1 data indicates that the nose of the ice shelf revolves clockwise around the McDonald Ice Rumples region, in which the rakys are based on shallow underwater topography.”
“Meanwhile, the strong slope in ice speed to the faster-moving Stancomb-Wills ice stream and ice shelf in the north triggered a new rift that now threatens the release of a second large iceberg.”
Location of the Brunt ice shelf. The Brunt ice shelf borders the Coats Land coast in the Weddell Sea sector of Antarctica. Credit: ESA (data sources: JAXA / University of Bremen / BAS)
Routine monitoring from satellites provides unprecedented views of events occurring in remote regions, showing how ice shelves respond to changes in ice dynamics, air and ocean temperatures. During the dark winter months in Antarctica, radar images are indispensable because radar, except in the remote region, still produces images regardless of the dark weather.
Mark Drinkwater continues: “With today’s Copernicus monitoring system, we are much better equipped to not only observe events in remote locations such as Antarctica in real time, but more importantly, to theoretically transform this scientific data into complex icebreaking processes.”
History shows that the last major event on the Brunt Ice Shelf took place in 1971, when a section of ice north of the area known as the McDonald Ice Rumples was calved into what is apparently being repeated by today’s Halloween Crack .
With the ice shelf considered unsafe due to the intrusive cracks in 2017, the British Antarctic survey closed their Halley VI research station and placed it south of Halloween Crack in a safer place again. Halley VI has been operating since 2012 and consists of eight interconnecting pods built on skis. This allows the pods to be moved easily in case of unstable ice and cracks on the ice shelf.