Antarctic ice shelves vulnerable to sudden meltwater-driven fracturing

Many of the ice shelves ringing Antarctica could be vulnerable to quick destruction if rising temperatures drive melt water into the numerous fractures that currently penetrate their surfaces. If they were to fail, global sea levels could surge rapidly, warns a new study.

Ice shelves are giant tongues of ice floating on the ocean around the edges of the continent. The vast land-bound glaciers behind them are constantly pushing seaward. But because many shelves are largely confined within expansive bays and gulfs, they are compressed from the sides and slow the glaciers’ march.

But ice shelves experience a competing stress: they stretch out as they approach the ocean, explains a statement. Satellite observations show that, as a result, they rip apart; most are raked with numerous long fractures perpendicular to the direction of stretching.

Currently, most of the shelves are frozen year round, and stable. But scientists project that widespread warming could occur later in the century. And, existing research has shown that even subtle temperature swings can spur widespread melting. This could send melt water surging into the surface fractures. Such surges would potentially cause hydrofracturing-a process in which liquid water, heavier than ice, would violently force the fractures to zip open, and cause the shelf to rapidly disintegrate.

The new study estimates that 50 to 70 percent of the areas of the ice shelves buttressing the glaciers are vulnerable to such processes.

“It’s not just about melting, but where it’s melting,” said lead author Ching-Yao Lai, a postdoctoral researcher at Columbia University’s Lamont-Doherty Earth Observatory, in the statement.

Hydrofracturing has already occurred in a few places. Parts of the Larsen Ice Shelf, which had been stable for at least 10,000 years, disintegrated within just days in 1995 and 2002. This was followed by the partial breakup of the Wilkins Ice Shelf in 2008 and 2009. The main agreed-upon causes: hydrofracturing.

The new study follows a 2017 paper led by Kingslake showing that seasonal ponds and streams on the ice surface are far more common across Antarctica than previously believed.

While the study flashes a warning, the researchers say they cannot predict the ice shelves’ behavior with any exactitude. Projections vary widely, depending on which models scientists use, how vigorously humanity cuts greenhouse gases and whether particular locations will undergo hydrofracturing.

Photo credit: Liam Quinn, flickr/Creative Commons

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