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Fri Apr 21, 2017, 09:48 AM

Water Is Streaming Across Antarctica--New Survey Finds Liquid Flow More Widespread Than Thought

http://blogs.ei.columbia.edu/2017/04/19/water-is-streaming-across-antarctica/
[font face=Serif][font size=5] Water Is Streaming Across Antarctica[/font]
[font size=4]New Survey Finds Liquid Flow More Widespread Than Thought[/font]

by Kevin Krajick|April 19, 2017


Scientists have discovered that seasonally flowing streams fringe much of Antarctica’s ice. Each red ‘X’ represents a separate drainage. Up to now, such features were thought to exist mainly on the far northerly Antarctic Peninsula (upper left). Their widespread presence signals that the ice may be more vulnerable to melting than previously thought. Image adapted from Kingslake et al., Nature 2017.

[font size=3]In the first such continent-wide survey, scientists have found extensive drainages of meltwater flowing over parts of Antarctica’s ice during the brief summer. Researchers already knew such features existed, but assumed they were confined mainly to Antarctica’s fastest-warming, most northerly reaches. Many of the newly mapped drainages are not new, but the fact they exist at all is significant; they appear to proliferate with small upswings in temperature, so warming projected for this century could quickly magnify their influence on sea level. An accompanying study looks at how such systems might influence the great ice shelves ringing the continent, which some researchers fear could collapse, bringing catastrophic sea-level rises. Both studies appear this week in the leading scientific journal Nature.

Explorers and scientists have documented a few Antarctic melt streams starting in the early 20th century, but no one knew how extensive they were. The authors found out by systematically cataloging images of surface water in photos taken from military aircraft from 1947 onward, and satellite imagery from 1973 on. They found nearly 700 seasonal systems of interconnected ponds, channels and braided streams fringing the continent on all sides. Some run as far as 75 miles, with ponds up to several miles wide. They start as close as 375 miles from the South Pole, and at 4,300 feet above sea level, where liquid water was generally thought to be rare to impossible.

“This is not in the future—this is widespread now, and has been for decades,” said lead author Jonathan Kingslake, a glaciologist at Columbia University’s Lamont-Doherty Earth Observatory. “I think most polar scientists have considered water moving across the surface of Antarctica to be extremely rare. But we found a lot of it, over very large areas.” The data are too sparse in many locations for the researchers to tell whether the extent or number of drainages have increased over the seven decades covered by the study. “We have no reason to think they have,” said Kingslake. “But without further work, we can’t tell. Now, looking forward, it will be really important to work out how these systems will change in response to warming, and how this will affect the ice sheets.”

Many of the newly mapped drainages start near mountains poking through glaciers, or in areas where powerful winds have scoured snow off underlying bluish ice. These features are darker than the mostly snow-covered ice sheet, and so absorb more solar energy. This causes melting, and on a slope, liquid water then melts a path downhill through overlying snow. If the continent warms this century as projected, this process will occur on a much larger scale, say the authors. “This study tells us there’s already a lot more melting going on than we thought,” said coauthor Robin Bell, a Lamont-Doherty polar scientist. “When you turn up the temperature, it’s only going to increase.”



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Seen from an aircraft, a 400-foot-wide waterfall drains off the Nansen Ice Shelf into the ocean. Video: Wong Sang Lee/Korea Polar Research Institute

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Could this be a problem? [FONT COLOR=RED][BLINK]IRONY[/BLINK][/FONT]

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