An iceberg with a surface area as large as the entire province of Milan has detached from the Antarctic ice shelf. The British Antarctic Service said the meltdown was not due to climate change, although global warming is accelerating the disappearance of polar ice.
The detachment
The calving of the iceberg from the Antarctic ice shelf occurred from the 150-metre-high wall of the Brunt ice shelf. Scientists had noticed the first fractures about ten years ago, which then led to complete division. The event was therefore expected and follows other detachments that have taken place in recent yearsas for example from the Larsen-C platform in July 2017, which generated the iceberg A-68, the size of Liguria.
When the iceberg broke off
The rift was first reported by the British Antarctic Survey (BAS) and occurred on January 22 between 19:00 and 20:00 UTC during a spring tide. The BAS’s Halley VI research station, where glaciologists monitored the behavior of the ice shelf, was unaffected by the calving event.
Expert observations
Glaciologists have monitored the giant iceberg for years, so much so that the European Space Agency even speaks of “birth” and explains that the timing of the detachment, although unexpected, had long been anticipated. Glaciologists have for years monitored the many cracks and chasms that have formed in the thick Brunt Ice Shelf, which borders the coast of Coats Land in Antarctica’s Weddell Sea sector. It was only a matter of time before Chasm 1, which had been dormant for decades, met Halloween Crack, first spotted on Halloween 2016.
Natural detachment
European Space Agency researcher and ice expert Mark Drinkwater has welcomed the news of the calving of the giant iceberg, 5 times the size of Malta. According to British Antarctic Survey glaciologist Dominic Hodgson, the event is not related to climate change. Drinkwater pointed out in a post on esa.int that after several years of tracking the iceberg, the long-awaited separation of the Brunt A81 iceberg has finally happened.
How the new iceberg will be identified
The European Space Agency (ESA) points out that it is expected that the new iceberg will be called A-81, with the smaller northern piece probably identified as A-81A or A-82. Icebergs are traditionally identified using a capital letter indicating the Antarctic quadrant where they were originally sighted, followed by a sequential number. If the iceberg breaks into smaller pieces, sequential lowercase letters are used to identify each piece.
Securing Halley Base
Thanks to the monitoring of Copernicus and the measurements made by the British Antarctic Survey, the safety of the Halley base has been guaranteed. In addition, the use of summer images of Sentinel-2 and Sentinel-1 radar has allowed to examine in detail the processes that led to the calving of the iceberg.
Hodgson added that BAS science and operations teams continue to monitor the ice shelf in real time to make sure it is safe and to keep all Halley Base activities operational.
Monitoring from space
Routine satellite surveillance provides unprecedented insight into events occurring in remote regions and shows how ice shelves are actively responding to changes in ice dynamics, air and ocean temperatures. In February 2021, another gigantic iceberg, about 1270 km², broke away from the northern section of Brunt. It was spotted on Sentinel-1 images and has already moved away from the Brunt Ice Shelf towards the Weddell Sea.
What will happen now
The calving of ice floes from an ice shelf has been observed to be followed by a regulation of ice flow in the ice shelf. If Brunt is now boosted, it could affect the behavior of other rifts in the area.
Drinkwater explained: “The calving of iceberg A74 and its latest separation brings attention back to the Halloween crack, the extension of which could help further destabilize the Brunt Ice Shelf“.
Drinkwater added that “A typical accompaniment to such log-release events and the unconstraining of the ice shelf front by underlying features such as McDonald Bank, which forms the McDonald Ice Rumples, may be an acceleration of the speed of ice flowing into the ice shelf. We will use the capabilities of the Copernicus Sentinels to closely monitor the behavior and stability of the remaining Brunt ice shelf.”
