Why Climate Change May Be Increasing Sea Ice Around Antarctica

[HuffingtonPost]

* Melted ice re-freezes faster than sea water in  winter-study                

* Antarctica's expanding ice at odds with melting Arctic                

By Environment Correspondent Alister Doyle                

OSLO, March 31 (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 tonnes of ice a year - equivalent to 0.07  millimetre(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  tonnes 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: (http://www.nature.com/doifinder/10.1038/ngeo1767)     (Reporting By Alister Doyle; Editing by Stephen Powell)

Via: HuffingtonPost