West Antarctica Splitting at the Seams

A new study which represents the most extensive study of the evolution of floating ice shelves in the eastern Amundsen Sea Embayment in West Antarctica has revealed that the ice is steadily losing their grip on adjacent bay walls, a problem which scientists believe may hasten the loss of ice to the sea.

Rifts in Pine Island Glacier 2011
Rifts in Pine Island Glacier 2011

“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,” says Joseph MacGregor, research scientist associate and lead author of the study.

Another process by which ice can be fed into the oceans is not welcome news in a day and age where we are monitoring how quickly the same ice is melting as a result of global warming.

The scientists studied nearly 40 years of satellite imagery of the region and found that where the ice shelves grip to the rocky bay walls or slower-moving masses of ice are moving further and further inland, fracturing as they go. As that grip continues to loosen, these already-thinning ice shelves will be even less able to hold back grounded ice upstream, according to glaciologists at The University of Texas at Austin’s Institute for Geophysics (UTIG).

Published in the Journal of Glaciology the UTIG scientists found that the extent – how far out to sea the shelves make it before they start to calve – has been diminishing rapidly over the period of time that the Landsat satellite has operated, between 1972 and 2011, a process which has increased in speed over the later portion of that time.

Location of Amundsen Sea Embayment
Location of Amundsen Sea Embayment

“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,” explains Ginny Catania, assistant professor at UTIG and co-author of the study. “An accelerating glacier can tear away from its margins, creating rifts that negate the margins’ resistance to ice flow and causing additional acceleration.”

According to the UTIG, “the observed style of slow-but-steady disintegration along ice-shelf margins has been neglected in most computer models of this critical region of West Antarctica, partly because it involves fracture, but also because no comprehensive record of this pattern existed.”

Source: The University of Texas at Austin’s Institute for Geophysics

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