Global warming means seas freeze more off Antarctica: study

OSLO Sun Mar 31, 2013 1:03pm EDT

A 20 metre-high ice cliff forming the edge of the Wilkins Ice shelf on the Antarctic Peninsula is seen from a plane January 18, 2009. REUTERS/Alister Doyle

A 20 metre-high ice cliff forming the edge of the Wilkins Ice shelf on the Antarctic Peninsula is seen from a plane January 18, 2009.

Credit: Reuters/Alister Doyle

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OSLO (Reuters) - Global warming is expanding the extent of sea ice around Antarctica in winter in a paradoxical shift caused by cold plumes of summer melt water that re-freeze fast when temperatures drop, a study showed on Sunday.

An increasing summer thaw of ice on the edges of Antarctica, twinned with less than expected snowfall on the frozen continent, is also adding slightly to sea level rise in a threat to low-lying areas around the world, it said.

Climate scientists have been struggling to explain why sea ice around Antarctica has been growing, reaching a record extent in the winter of 2010, when ice on the Arctic Ocean at the other end of the planet shrank to a record low in 2012.

"Sea ice around Antarctica is increasing despite the warming global climate," said Richard Bintanja, lead author of the study at the Royal Netherlands Meteorological Institute.

"This is caused by melting of the ice sheets from below," he told Reuters of the findings in the journal Nature Geoscience.

Ice is made of fresh water and, when ice shelves on the fringes of Antarctica thaw in summer because of upwellings of warming sea water, the meltwater forms a cool layer that floats on the denser, warmer salty sea water below, the study said.

In winter, the melt water readily turns to ice because it freezes at zero degrees Celsius, above sea water at -2C (28.4F).

At a winter maximum in September, ice on the sea around Antarctica covers about 19 million sq kms (7.3 million sq miles), bigger than Antarctica's land area. It then melts away into the ocean as summer approaches.

WINDS

Among other scientists, Paul Holland of the British Antarctic Survey stuck to his findings last year that a shift in winds linked to climate change was blowing a layer of melt water further out to sea and adding to winter ice.

"The possibility remains that the real increase is the sum of wind-driven and melt water-driven effects, of course. That would be my best guess, with the melt water effect being the smaller of the two," he said.

Bintanja's study also said the cool melt water layer may limit the amount of water sucked from the oceans that falls as snow on Antarctica. Cold air can hold less moisture than warm.

"Cool sea surface temperatures around Antarctica could offset projected snowfall increases in Antarctica, with implications for estimates of future sea-level rise," it said.

The U.N. panel of climate scientists has estimated that sea levels will rise by between 18 and 59 cm (7-24 inches) this century, more if thaws of Antarctica and Greenland accelerate.

The panel's main scenarios assume that Antarctica alone will make sea levels fall by between 2 and 14 cms this century because more snowfall will extract water from the sea.

But Sunday's study said that Antarctica was losing about 250 billion metric tons of ice a year - equivalent to 0.07 millimeter(0.003 inch) of sea level rise a year, Bintanja said. "Antarctic mass loss seems to be accelerating," it said.

Another study in Nature Geoscience said Antarctica's snowfall had been over-estimated by between 11 and 36.5 billion metric tons a year because of fierce winds blasting many regions.

Strong winds created conditions to "sublimate" snow, or make it pass from a frozen state to a gas without first becoming liquid, a U.S.-led team wrote.

Link to Antarctica melt water study: (here)

(Reporting By Alister Doyle; Editing by Stephen Powell)

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Comments (3)
Echo2000 wrote:
The idiocy of this headline and hypothesis is almost beyond belief. Since Earth is primarily covered in water, the process would by necessity be termed “Global Cooling”. But from hot, to static, to cold. Much as ancient tribes attributed phenomena to Air Gods.

Mar 31, 2013 2:44pm EDT  --  Report as abuse
Jose3 wrote:
This is good news, the earth needs more fresh water.

Mar 31, 2013 9:22pm EDT  --  Report as abuse
Antarctic sea ice has a larger geographical footprint, but it is thinner because it melts every year. Therefore, the actual mass of ice of Antarctica is decreasing, not increasing. Although not represented in this article, the speed of ice flows has also increased. Therefore the ejection of ice into the sea is happening faster than before.
Antarctica is an ice engine; it is now producing more sea ice than before. Southern hemisphere sea temps will decrease. Because sea temp is changing, global deep sea currents will change. The food supply of sea animals could be disrupted, quickly killing most of the aquatic life. Also, ice fields around the horn will interfere with sea lanes.

Apr 01, 2013 3:18am EDT  --  Report as abuse
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