Major Antarctic Ice Shelf May Disappear by 2020

With climate change heating things up, and the Earth's poles rapidly melting, it should come as no surprise that a major Antarctic ice shelf may completely disappear by 2020, according to a new NASA study.

The last remaining section of the Larsen B Ice Shelf, which partially collapsed in 2002, is quickly weakening, flowing faster, and becoming more and more fragmented as well as developing large cracks. This, plus the fact that two of its tributary glaciers are also flowing faster and thinning rapidly, does not bode well for the ice shelf.

"These are warning signs that the remnant is disintegrating," Ala Khazendar of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., who led the study, said in a news release. "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."

This news directly follows research published just last week that a neighboring ice shelf, called the Larsen C Ice Shelf, is simultaneously thinning from above and below.

Ice shelves such as these are extremely important because they prevent Antarctic glaciers from flowing out to sea and dumping massive amounts of freshwater into the ocean. Without ice shelves like the Larsen B Ice Shelf, the rate of global sea level rise will quickly accelerate.

To better understand the consequences of climate change in the future, this latest NASA study took the first comprehensive look at the health of the Larsen B remnant and the glaciers that flow into it. The results were published in the journal Earth and Planetary Science Letters.

Khazendar's team used data collected by aircraft measuring ice surface elevations and bedrock depths as part of an annual NASA survey campaign. Data on flow speeds came from spaceborne synthetic aperture radars operating since 1997.

The scientists predicted that the Larsen B Ice Shelf will completely disappear by 2020 - that is, assuming that the huge, widening rift that has formed near its grounding line will crack all the way across, a likely future scenario. The free-floating remnant will shatter into hundreds of icebergs that will drift away, and the glaciers will have nothing to stop them from moving out to sea.  (Scroll to read on...)

Currently, the Larsen B remnant, located on the coast of the Antarctic Peninsula, is about 625 square miles (1,600 square kilometers) in area and about 1,640 feet (500 meters) thick at its thickest point. However, these dimensions are expected to shrink further and further as the climate continues to warm.

"What is really surprising about Larsen B is how quickly the changes are taking place," Khazendar said. "Change has been relentless."

The scientists fear that the cracking of the shelf could see its three glaciers - named Leppard, Flask and Starbuck - accelerate rapidly towards the ocean. In the first couple of years following the 2002 collapse, the glaciers' thicknesses and flow speeds changed only slightly, leading experts to believe that they were stable. However, the new study reveals that that's not the case.

The Leppard and Flask glaciers have thinned by a staggering 65-72 feet (20-22 meters) and accelerated considerably in the intervening years. The fastest-moving part of Flask Glacier had accelerated 36 percent by 2012 to a flow speed of 2,300 feet (700 meters) a year - comparable to a car accelerating from 55 to 75 mph.

Flask's acceleration, while the Larsen B remnant has been weakening, may be just a preview of what will happen when the remnant breaks up completely. After the 2002 Larsen B collapse, the glaciers behind the collapsed part of the shelf accelerated as much as eight-fold.

Much of Antarctica is melting faster than ever, and Arctic sea ice is also projected to disappear completely in our lifetime, and these phenomena paint a bleak future in terms of global sea level rise as a result of climate change.

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