Antarctic ice shelf the size of France suddenly JUMPS twice a day - and scientists warn it could trigger a devastating icequake

Antarctica's biggest ice shelf is on the move and could trigger icequakes, a new study warns.

Researchers found that the Ross Ice Shelf – a platform of ice measuring nearly 200,000 square miles, just shy of the size of France – jumps suddenly twice a day. 

The sudden 'slip' is caused by two sections of ice moving against each other, a bit like the movement of plate tectonics that cause earthquakes. 

The phenomenon, identified for the first time in a new study, could create fractures in the ice shelf, which would make it more prone to falling apart. 

It could also trigger 'icequakes' – seismic events that can be dangerous for nearby animals or explorers. 

Ice shelves are permanent floating sheets of ice that connect to a landmass. Pictured is the Ross Ice Shelf, the largest ice shelf of Antarctica

Researchers studied data from 'seismometers' - little devices that record ground noises and movement - stationed around Antarctica. This image shows seismic records caused by ice in Antarctica in December 2014

The study was led by Professor Doug Wiens, a geophysicist at Washington University in St. Louis, Missouri and published in Geophysical Research Letters.

'We found that the whole shelf suddenly moves about 6 to 8 centimeters (or 3 inches) once or twice a day,' he said. 

'These sudden movements could potentially play a role in triggering icequakes and fractures in the ice shelf.' 

Ice shelves are large floating platforms of ice that connect to a landmass, such as Antarctica, although they're also found in other polar locations such as Greenland. 

These shelves act as a protective buffer for the mainland ice, keeping the whole Antarctic Ice Sheet from flowing into the ocean, which would dramatically raise global sea levels. 

So fractures or any kind of weakening in the ice shelves could potentially cause it to disintegrate in the next few decades, with serious implications for coastal cites.

There are about 300 ice shelves dotted around Antarctica and together they cover about three quarters of the Antarctic coastline. 

Professor Wiens and colleagues focused on the Ross Ice Shelf, which, at around the size of France, is the largest ice shelf of Antarctica. 

An image of Antarctica differentiating its landmass (dark grey), ice shelves (light grey) and sea ice (white). Ross Ice Shelf, the largest ice shelf of Antarctica, is in the south

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They studied data from 'seismometers' that they stationed around the continent in 2014 – little devices that record ground noises and movement. 

Scientists say there's a fast-moving river or 'conveyor belt' of ice called the Whillans Ice Stream that's pouring into the Ross Ice Shelf. 

The movement of the Ross Ice Shelf is triggered by a sudden movement of the Whillans Ice Stream known as a 'slip event', akin to the movement of plate tectonics that cause earthquakes. 

The researchers discovered there's a large section of Whillans Ice Stream measuring 60 miles by 60 miles that remains stationary, while the rest of the ice stream creeps forward – a junction described as a 'sticky spot'. 

Then, once or twice per day, the large section lurches forward against the Ross Ice Shelf.

It can move as much as 16 inches (40cm) in a few minutes, but if a human was there they would not be able to tell it was happening.

'One would not detect the movement just by feeling it,' Professor Wiens said. 

'The movement occurs over a time period of several minutes, so it is not perceptible without instrumentation.'

The Ross Ice Shelf (pictured) is a floating lip of ice that extends out over the ocean. Scientists are interested in interactions between ice shelves and ice streams in part because they are concerned about the stability of Antarctica’s ice shelves in a warming world

This image of the Ross Ice Shelf region highlights seismic stations shown as blue circles. The locations of Whillans Ice Stream slip spots are shown as red circles

However, the researchers do not think that this slip event and others like it are directly related to human-caused global warming.

One theory is that they are caused by loss of water in the bed of the Whillans Ice Stream, making it more 'sticky'. 

However, interactions between ice shelves and ice streams can still reveal more about the stability of Antarctica’s ice shelves in a warming world. 

'At this point, icequakes and fractures are just part of the normal life of the ice shelf,' Professor Wiens said. 

'There is a worry that the Ross Ice Shelf will someday disintegrate, since other smaller and thinner ice shelves have done so.'