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Antarctic Meltwater Isn't the Crisis We Thought It Was

21 April 2017

"I think most polar scientists have considered water moving across the surface of Antarctica to be extremely rare". Scientists have always known that the Antarctic Western Peninsula is melting at an alarmingly high rate but they didn't expect the whole continent to be awash with meltwater during the ephemeral summer. "This process might have been responsible for the large-scale break-up of Antarctica's Larsen B Ice Shelf in 2002, when more than 2000 lakes drained in just a few days".

The systems, described in two new studies published Wednesday in the journal Nature, vary from a collection of ponds to a roaring seasonal river that dumps meltwater into the ocean via a 400-foot-wide waterfall.

The floating ice shelves that buttress Antarctica are less icy than we thought, it turns out.

Much of Antarctica's ice is littered with seasonally flowing meltwater streams. Each
Antarctic Meltwater Isn't the Crisis We Thought It Was

Scientists are also studying Greenland for clues as to how these streams might develop and affect sea level rises - between 2011 and 2014, about 70 percent of the 269 billion tons of ice and snow lost by Greenland to the oceans was due to meltwater.

Images and photographs of the surface water were taken from military aircraft from the year 1947 and satellite imagery from 1973. Meltwater from more stable parts of the ice sheet could flow toward the melting ice shelves on the continent's edges and encourage them to break off.

The continent's vast ice sheets contain enough ice to raise global sea levels by almost 200 feet were it all to melt, though even partial melt could cause vulnerable coastal areas that are home to millions to be gradually claimed by the sea.

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It is unknown whether rivers and waterfalls form on other ice shelves, she says.

The survey also showed that numerous meltwater streams and channels begin near mountains poking through glaciers or in areas with little or no snow, exposing the underlying bluish ice.

This isn't great news for the stability of the ice shelf. As the ice melts, liquid water will create a path downhill through overlying snow.

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He said: "Despite extensive studies in Greenland and observations of individual meltwater drainage systems in Antarctica, we previously had little understanding of how water moves across the surface of Antarctica's ice sheets".

"We have these two different scenarios and we don't know which one is more likely", Kingslake said, though that will likely vary from ice shelf to ice shelf.

Newly recorded drainages usually start near mountains finding their way down through glaciers. The pace of the damage will increase as temperatures continue to rise as a result of man-made global warming. Decades of satellite imagery and aerial photography have revealed an extensive network of lakes and rivers transporting liquid meltwater across the continent's ice shelves - almost 700 systems of connected pools and streams in total.

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The movement "changes the way we think about the impact of meltwater", Dr. Bell says.

Antarctic Meltwater Isn't the Crisis We Thought It Was