Antarctic sea ice growth does not negate climate change, scientists say

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    Antarctic sea ice growth does not negate climate change, scientists say

    Date
    September 3, 2014 - 7:52AM
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    Julia Rosen


    Sea ice growth in the Antarctic is a symptom of climate change, scientists say. Photo: Nerilie Abram
    In the blue half-light of the Antarctic autumn, a thin film spreads across the continent's coastal waters. It's an embryonic form of sea ice: a mush of microscopic crystals that floats on the dense, salty water of the Southern Ocean.
    As winter takes root, this proto-sea ice grows thicker and stronger until it encircles Antarctica in a vast frozen ring. The ice spans nearly 7 million square miles at its peak, an area roughly twice the size of the United States.
    This year, Antarctic sea ice has expanded its frigid reach with unprecedented speed, setting records in June and July. By the time spring punctures the long Antarctic night, 2014 stands a decent chance of topping 2012 and 2013, which each broke records of maximum total ice extent.
    In fact, since scientists started making satellite observations in the late 1970s, they have watched winter sea ice around Antarctica swell slowly but indisputably, despite predictions that it should shrink.
    This poses a puzzle that climate scientists struggle to explain: How can sea ice grow in a warming world?
    Climate change sceptics have pounced on this apparent discrepancy, citing it as proof that climate change isn't real, or at least that scientists don't completely understand it. But those who study Antarctic sea ice say their curious observations shouldn't shake anyone's confidence.
    Dramatic changes in temperature, sea level and extreme weather around the world are proof enough the planet is warming, they say; the only question is how these changes affect the Antarctic as they ripple through the climate system.
    "Climate is a complicated thing," said Ted Maksym, an oceanographer at the Woods Hole Oceanographic Institute in Massachusetts. "Understanding how these kinds of changes play out in different regions is tricky business."
    The westerly winds blow fierce and constant around Antarctica, isolating the continent in a kind of permanent polar vortex. Scientists think they exert the most direct control over the state of Antarctic sea ice.
    Ice requires cold temperatures to form, and winds help it grow by blowing it around the polar ocean. When the ice moves, new water is exposed to the chilly air, creating an opportunity to make more ice.
    In the landlocked Arctic, winter sea ice gets hemmed in by Russia, Greenland, Canada and Alaska, said Thorsten Markus, head of cryospheric sciences at NASA's Goddard Space Flight Center. But in the Antarctic, unflagging winds push ice ever farther into the empty Southern Ocean.


    Read more: http://www.smh.com.au/environment/c...ntists-say-20140903-10bon6.html#ixzz3CCd0B8CI
 
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