Thursday 31 October 2013


Pine Island Glacier: Plugging Up the West Antarctic Slide
Nicholas St. Fleur

30 October, 2013

Have you ever spent a relaxing afternoon at a local park watching as kid after kid joyfully files down a playground slide? And every now and then there's that one wise aleck who refuses to get off the end of the slide and causes a congestion of children to pile up behind him. Well, imagine that scene but replace the kids on the slide with gigantic ice sheets on top of a warm river current and you get an idea of what's happening at the farthest reaches of Antarctica, in a region called the West Antarctic Ice Sheet.

This titanic ice shelf is slowly melting into the Amundsen Sea, which is an arm of the Southern Ocean and connected to the global ocean system, similar to the chain of children going down the slide. Right now the West Antarctic Ice Sheet contributes only a few centimeters per year to global sea levels. But the shelf has enough freshwater to raise global sea levels by several feet. That additional fresh water, though minute, would spread across the world in a matter of days.

The problem with increasing sea level rise is that most of humanity is crusted around the coastlines, particularly in low-lying areas. Even a small fraction of the added water coming from the West Antarctic Ice Sheet can threaten people along the coasts because it could make storm surges more severe.

But barricading the West Antarctic Ice Sheet from sliding into the ocean is a large glacier called Pine Island Glacier. The 31-mile-long stretch of ice is akin to the child sitting at the base of the slide in our playground analogy. But unlike the kid who won't budge, the Pine Island Glacier is succumbing to the warming waters beneath it and the heavy pressure of the West Antarctic Ice Sheet behind it. It's melting, but scientists just don't know how fast.

Now, after a two-month trip to the remote region, some 810 miles away from the nearest research station in Antarctica, an international team of scientists has found just how fast the glacier is liquefying and slipping into the Amundsen Sea.

Their research, which was published Sept. 12 in the journal Science, revealed that Pine Island Glacier is melting at a ferocious rate of 2.4 inches per day.

The findings surprised Tim Stanton, the expedition's team leader and a researcher from the Naval Postgraduate School. He said that not only was the rate much faster than he thought it would be, but that it was also hundreds of times faster than the ice melting in the Artic.

His team drilled through 1,640 feet of ice -- about five and a half football fields' worth -- into the glacier to uncover the melting rate. At those depths the team used its instruments to decode features of the current flowing beneath the ice, such as its temperature, salinity, and how quickly it was eating away the ice.

The scientists analyzed the physics behind how the underground river as it whisked away parts of Pine Island Glacier into the Amundsen Sea, adding to sea level rise.

Now that they've uncovered how fast Pine Glacier Island is melting, the team plans to make predictive models to simulate what would happen if it continues to melt at this rate, or if it were to melt at increased rates. Stanton said that his measurements are a small part of the puzzle of understanding the physics behind how glaciers melt globally.

"We have one planet and we can't run the experiment as a physical experiment," he said. "It would be more satisfying to use our big brains and our big computers to give us predictability." He said that in the long run the goal is to have models skillful enough to predict changes in the ocean depending on current glacier melt rates.

The intensive melting under the Pine Island ice shelf could cause the glacier to break off from the rest of the ice shelf, according to a statement by David Holland, mathematics professor at the Center for Atmosphere Ocean Science at New York University who contributed to analyzing the data from the trip in order to create predictive models.

"That's important, as this ice shelf is currently holding back inland ice, and without that restraining force, the Pine Island catchment basin could further contribute to global sea-level rise," he said in the statement.

If that were to happen, it would be like the kid unplugging himself from the slide and releasing an avalanche of children into the ground below. But instead of ending up with bruises and scrapped knees, we get increased sea levels.

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