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Antarctic ice sheets losing their grip

Rifts along the northern shear margin of Pine Island Glacier (upper right of image). Credit: Michael Studinger, NASA's Operation IceBridge.
Rifts along the northern shear margin of Pine Island Glacier (upper right of image). Credit: Michael Studinger, NASA's Operation IceBridge.

AUSTIN, Texas, March 27 (UPI) -- Floating ice shelves in Antarctica are losing their grip on adjacent bay walls, potentially worsening an accelerating loss of ice to the sea, researchers say.

Scientist at the University of Texas reported the finding based on analysis of 40 years of satellite imagery of West Antarctica ice sheets.

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The ice sheet margins, where they hold onto rocky bay walls or slower ice masses, are fracturing and retreating inland where these already-thinning ice shelves will be even less able to hold back grounded ice upstream, the researchers said.

"Typically, the leading edge of an ice shelf moves forward steadily over time, retreating episodically when an iceberg calves off, but that is not what happened along the shear margins," researcher Joseph MacGregor said.

Calving is when an iceberg breaks off the ice shelf created when a glacier moves off land.

"As a glacier goes afloat, becoming an ice shelf, its flow is resisted partly by the margins, which are the bay walls or the seams where two glaciers merge," study co-author Ginny Catania said.

"An accelerating glacier can tear away from its margins, creating rifts that negate the margins' resistance to ice flow and causing additional acceleration."

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