Huge iceberg adrift off Antarctica
A large iceberg about 20 times the size of Manhattan broke off the Brunt Ice Shelf in the Weddell Sea section of Antarctica during the past day, following the buildup of a large crack in the floating ice during the past decade.
The iceberg is about 1270 square kilometres and 150 metres thick, according to the British Antarctic Survey (BAS).
The iceberg is large, but not as huge as one that in 2017 calved from the Larsen C Ice Shelf and recently threatened to run aground on South Georgia Island.
The BAS maintains a research station, the Halley Research Station, on the Brunt Ice Shelf. In 2016, the BAS moved the station, which is built on skis, to protect it from spreading cracks that could have left it marooned, floating out to sea aboard an iceberg.
Over the past decade three major cracks have developed through the floating ice shelf, according to the BAS.
‘‘This is a dynamic situation. Four years ago, we moved Halley Research Station inland to ensure that it would not be carried away when an iceberg eventually formed. That was a wise decision,’’ said Simon Garrod, director of operations at the BAS.
‘‘Our job now is to keep a close eye on the situation and assess any potential impact of the present calving on the remaining ice shelf.’’
Ice shelves are floating areas of ice that help to hold back ice anchored on land. Because they are already displacing water, the calving will not raise sea levels, but icebergs are carefully monitored in case they move into shipping lanes.
Adrian Luckman, a researcher at Swansea University in Wales, has closely tracked satellite images of Brunt as the cracks have progressed.
‘‘Although the breaking off of large parts of Antarctic ice shelves is an entirely normal part of how they work, large calving events such as the one detected at the Brunt Ice Shelf . . . remain quite rare and exciting,’’ Luckman told the BBC.
‘‘Time will tell whether this calving will trigger more pieces to break off in the coming days and weeks.
‘‘At Swansea University, we study the development of ice shelf rifts because, while some lead to large calving events, others do not, and the reasons for this may explain why large ice shelves exist at all,’’ he said.
It is also not clear whether the calving event was driven in part by climate change, since this is a natural part of ice shelf behaviour.
Calving events can act to speed up the movement of inland ice into the sea, though it is not clear whether this is the case with the Brunt Ice Shelf in particular.
Such movement would add to sea level rise, and there are growing concerns about the potentially unstoppable melting of the West Antarctic Ice Sheet from warming waters that are weakening ice shelves and penetrating the bases of inland glaciers.
According to the European Space Agency, the most recent calving event on the Brunt Ice Shelf before this one occurred in 1971.