The largest ice shelf in Antarctica is moving and could cause earthquakes, warns a new study.
Researchers discovered that the Ross Ice Shelf, an ice shelf measuring nearly 200,000 square miles, just shy of the size of France, suddenly jumps twice a day.
The sudden “slide” is caused by two sections of ice moving against each other, a bit like the movement of tectonic plates that cause earthquakes.
The phenomenon, identified for the first time in a new study, could create fractures in the ice shelf, making it more likely to crumble.
It could also trigger “ice earthquakes,” seismic phenomena that can be dangerous to nearby animals or explorers.
Ice shelves are permanent floating sheets of ice that are connected to a land mass. Pictured is the Ross Ice Shelf, the largest ice shelf in Antarctica.
The researchers studied data from ‘seismometers’ (small devices that record noises and ground movements) stationed around Antarctica. This image shows ice-triggered seismic records 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 entire shelf suddenly moves about 6 to 8 centimeters (or 3 inches) once or twice a day,” he said.
“These sudden movements could contribute to earthquakes and fractures in the ice shelf.”
Ice shelves are large floating shelves of ice that are connected to a land mass, such as Antarctica, although they are also found in other polar locations such as Greenland.
These shelves act as a protective buffer for continental ice, preventing the entire Antarctic ice sheet from flowing into the ocean, which would dramatically raise global sea levels.
Therefore, fractures or any type of weakening of the ice shelves could cause them to disintegrate in the coming decades, with serious implications for coastal cities.
There are around 300 ice shelves spread across Antarctica and together they cover approximately three-quarters of the Antarctic coast.
Professor Wiens and his colleagues focused on the Ross Ice Shelf, which, at about the size of France, is the largest ice shelf in Antarctica.
An image of Antarctica differentiating its land mass (dark gray), ice shelves (light gray), and sea ice (white). The Ross Ice Shelf, the largest ice shelf in Antarctica, is located in the south.
They studied data from ‘seismometers’ they placed across the continent in 2014: small devices that record noises and ground movements.
Scientists say there is a fast-moving river or “conveyor belt” of ice called the Whillans Ice Stream that is emptying into the Ross Ice Shelf.
The movement of the Ross Ice Shelf is caused by a sudden movement of the Whillans Ice Stream known as a “slip event,” similar to the movement of tectonic plates that cause earthquakes.
Researchers discovered that there is a large section of the Whillans Ice Stream measuring 60 miles by 60 miles that remains stationary, while the rest of the ice stream slowly moves forward, a junction described as a “sticky spot.”
Then, once or twice a day, the large section lurches toward the Ross Ice Shelf.
It can move up to 16 inches (40 cm) in a few minutes, but if a human were there they wouldn’t be able to realize what was happening.
“You wouldn’t detect movement just by feeling it,” Professor Wiens said.
“The movement occurs over a period of several minutes, so it is not noticeable without instrumentation.”
The Ross Ice Shelf (pictured) is a lip of floating ice that extends out over the ocean. Scientists are interested in the 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. Whillans Ice Stream slide point locations are shown as red circles.
However, researchers do not believe that this slide event and others like it are directly related to human-caused global warming.
One theory is that they are caused by water loss in the bed of the Whillans Ice Stream, making it more “sticky.”
However, interactions between ice shelves and ice streams may still reveal more about the stability of Antarctic ice shelves in a warming world.
“At the moment, earthquakes and fractures are just part of normal life on the ice shelf,” said Professor Wiens.
“There is concern that one day the Ross Ice Shelf will disintegrate, as other smaller, thinner ice shelves have done so.”