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Crack in the Pine Island Glacier (symbolic image)

Photo: ESA

It is a natural process that cracks form in ice sheets in Antarctica and huge icebergs break off from time to time.

Last year, for example, the continent released an iceberg measuring around 1,550 square kilometers into the ocean.

But climate change is accelerating the process.

Experts have now investigated exactly how warmer oceans contribute to ice shelves pushed out to sea by glaciers breaking off.

The University of Washington research team analyzed a 2012 crack in the ice shelf of the giant Pine Island Glacier.

The glacier pushes ice into the Amundsen Sea in western Antarctica, where at one point it begins to float on the sea.

The team of experts combined information from a radar satellite with data from seismic instruments that other researchers had placed on the glacier's ice shelf in 2012.

It turned out that the crack was over 10.5 kilometers long in just about five and a half minutes.

This corresponds to a crack speed of 35 meters per second or 126 kilometers per hour.

"To our knowledge, this is the fastest crack opening ever observed," says lead author Stephanie Olinger, who analyzed the crack as part of her doctoral thesis at Washington and Harvard University.

According to the researchers, in other parts of Antarctica it often takes months or years for such large cracks to form.

The study was published in the specialist magazine “AGU Advances”.

more on the subject

  • Chasm-1: Giant iceberg breaks away from land in Antarctica

  • Iceberg break-off on the Pine Island Glacier: Antarctica is becoming a lot smaller

  • Satellite image of the week: Glacier in distress

Cracks in the ice shelf form before the glacier calves, i.e. before whole chunks of ice break off from the ice shelf and float away.

In the case observed, the iceberg that broke off has long since separated from the continent.

Pine Island Glacier fractured similar to glass

But how exactly do the cracks that ultimately separate the ice from the mainland come about?

Does the ice break in a similar way to glass or rather like tearing apart plasticine?

“Our calculations for this case show that it is more likely a case of glass breakage,” says Olinger in a statement.

The seawater probably ensured that the ice did not tear apart even faster - as would have been possible with brittle material.

It penetrates into cracks from below and apparently slowed the spread of the crack somewhat.

Whether the unusually rapid break in the Pine Island Glacier represents a new class of such cracks or whether such cracks have simply not been observed before remains an open question, the researchers write.

There is so much frozen water in the glaciers of Greenland and Antarctica that if it were to melt, the world's oceans would rise by several meters.

About ten percent of the mass of the West Antarctic Ice Sheet is found in the Pine Island Glacier System.

In addition, it blocks the ice masses behind it in the region from draining into the sea.

The condition of the glacier is therefore crucial to the question of how much sea level rises globally (you can read more about this here).

Ice from glaciers raises sea levels as it flows into the ocean.

However, if large pieces of ice shelf break off particularly quickly, this can increase the flow speed of a glacier - and thus also accelerate sea level rise.