Big break looms as crack in Antarctic ice shelf spreads
Scientists say an iceberg more than 5000sq km in size is about to be spawned.
In recent years, Greenland’s enormous Petermann glacier has lost huge pieces of ice, one four times the size of Manhattan, one two times its size.
What scientists fear is about to happen in Antarctica would make that look tiny.
A growing rift on the floating Larsen C ice shelf on the Antarctic Peninsula – a rift that grew dramatically by another 18 kilometres last month, according to a team of scientists watching it closely – is setting the shelf up for an imminent loss of nearly 5200sq km of ice, these scientists say.
‘‘It is not visible on optical data yet, but the radar data analysis showed a growth of the rift of about 18km,’’ said Daniela Jansen, a researcher with the Alfred Wegener Institute in Germany who collaborates with the British Project MIDAS team, which announced the rift’s growth.
The growth comes on top of a 20km growth that occurred earlier this year, during the polar night in Antarctica.
The researchers with the MIDAS Project, a British governmentfunded collaboration based at Swansea and Aberysthwyth universities in Wales, report that only 19km of remaining ice now connect the shelf to the emerging mega-iceberg, perhaps more properly called an ice ‘‘island’’.
The rift has now grown by some 80km since 2011 and has widened to well over 300m.
The consequences could be dramatic.
‘‘When it calves, the Larsen C Ice Shelf will lose more than 10 per cent of its area to leave the ice front at its most retreated position ever recorded; this event will fundamentally change the landscape of the Antarctic Peninsula,’’ the researchers say.
‘‘We have previously shown that the new configuration will be less stable than it was prior to the rift, and that Larsen C may eventually follow the example of its neighbour Larsen B, which disintegrated in 2002 following a similar riftinduced calving event.’’ of the break This event will fundamentally change the landscape of the Antarctic Peninsula.
The British Antarctic Survey also said a huge iceberg was set to calve from Larsen C.
‘‘Because of the uncertainty surrounding the stability of the Larsen C ice shelf, we chose not to camp on the ice this season,’’ said David Vaughn, the survey’s director of science.
The floating ice shelf is fed by glaciers that sit above sea level on the Antarctic Peninsula. As the shelf loses mass, these glaciers could flow more quickly – which would contribute to rising sea levels.
The Larsen C ice than 300m thick. It shelf is more is the fourthlargest ice shelf in Antarctica, although nothing compared with the two largest, the Ross and Ronne-Filchner shelves.
During a flight in November, space agency Nasa captured several spectacular photos of the rift. But that was before further extension of the rift last month.
Swansea University’s Adrian Luckman, who heads up Project Midas, said: ‘‘If it doesn’t go in the next few months, I’ll be amazed.’’
Jansen largely agrees. ‘‘I think the iceberg will calve soon,’’ she said. ‘‘The jumps of the rift tip occurred in shorter time intervals the longer the rift got. This is probably due to the longer ‘lever’ for the forces acting to advance the rift, such as the up and down of the tides or strong winds towards the sea. Whether it will be months or maybe next year, I don’t know.’’
So stand by. Things in Antarctica have been getting increasingly interesting for some time, and that shows no sign of stopping.