Final countdown for Larsen B Ice Shelf

Eric Hopton for redOrbit.com – Your Universe Online

Data from NASA’s Operation IceBridge survey has provided a stark warning of the effects of global warming. Latest results from the survey revealed the last remaining section of Antarctica’s 10,000 year old Larsen B Ice Shelf is about to disappear forever. A huge, ever-widening rift near the ice shelf’s grounding line will eventually crack all the way across, and the free-floating remnant will shatter into hundreds of icebergs that will just drift away before melting.

This NASA video shows the stunning beauty of the glacier and the enormity of what we are about to lose.

The new NASA study, led by Ala Khazendar of NASA’s Jet Propulsion Laboratory found that Larsen B, which partially collapsed in 2002, is weakening rapidly. The ice shelf is flowing faster, fragmenting, and developing large cracks. By the end of this decade it will be gone. Two tributary glaciers are also flowing faster and thinning rapidly.

Operation IceBridge is an airborne survey of Antarctica’s glaciers, ice shelves, and ice sheets. Spaceborne synthetic aperture radars have measured flow speeds since 1997 while instrumented aircraft gathered the data on ice surface elevations and bedrock depths.

A front row seat to a disaster movie no-one wants to see

“These are warning signs that the remnant is disintegrating,” said Khazendar. “Although it’s fascinating scientifically to have a front-row seat to watch the ice shelf becoming unstable and breaking up, it’s bad news for our planet. This ice shelf has existed for at least 10,000 years, and soon it will be gone.”

Ice shelves act as “gatekeepers” for Antarctic glaciers, slowing down their flow into the ocean. Without them, glacial ice moves unhindered into the sea, and this can only accelerate the rise in global sea levels.

Leppard, Flask, and Starbuck are part of the problem

The Larsen B remnant covers around 625 square miles and is more than 1,600 feet deep. Its three major tributary glaciers, named Leppard, Flask, and Starbuck (the latter two after characters in Moby Dick) are fed by their own inland tributaries.

Khazendar was taken aback by the speed of the break-up. He and his team believed that ice depths and flow rates had been stable since the 2002 collapse. “What is really surprising about Larsen B is how quickly the changes are taking place,” he said, “Change has been relentless.”

We now know that the Leppard and Flask glaciers have thinned by 65-72 feet and accelerated since 2002. The fastest-moving part of the Flask glacier had accelerated 36 percent by 2012. It is now moving at 2,300 feet each year.

Of the three glaciers, the smallest, Starbuck, has changed the least. Starbuck has a narrow channel and is strongly anchored to the bedrock, making it more stable.

“This study of the Antarctic Peninsula glaciers provides insights about how ice shelves farther south, which hold much more land ice, will react to a warming climate,” said JPL glaciologist, Eric Rignot.

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Source: http://www.redorbit.com/news/science/1113391754/final-countdown-for-larsen-b-ice-shelf-051515/