The Yin-Yang of Polar Sea Ice
 
Dec. 4, 2014: The world is getting warmer.
 
It comes as no surprise, therefore, when researchers announce as they did this
past September that Arctic sea ice extent is still below normal, continuing a
years-long downward trend, covering less and less of the north polar seas with
a frozen crust. On the heels of that announcement, came another, a little more
puzzling.  While Arctic sea ice was melting, Antarctic sea ice was at an
all-time high.  In 2014, sea ice surrounding Antarctica covered more of the
southern oceans than it has since satellite record began in the late 1970s.
 
Is this also a sign of global warming?
 
"There is no doubt that climate change is real," says Walt Meier of NASA's
Goddard Space Flight Center.  "The two poles are just responding in their own
unique way to the same global phenomenon."
 
https://www.youtube.com/watch?v=hauoepPqns4&feature=youtu.be  
A new ScienceCast video explores the curious differences between north- and
south-polar sea ice. Play it
 
He points out that Earth, taken as a whole, is losing sea ice. According to
satellite measurements from NASA and the National Snow and Ice Data Center,
the Arctic has lost an average of 20,800 square miles of sea ice a year since
the late 70s.  Meanwhile, the Antarctic has gained an average of 7,300 square
miles per year-not enough to balance loses at the other end of the planet.
But why do the Arctic and Antarctic behave in different ways?
 
"The increase we've seen in Antarctic sea ice is a little bit of a mystery,"
allows Meier.  "We're still trying to figure out how a warmer global climate
leads to these regional increases in ice cover."
 
The culprit could be weather.  Climate change is altering weather patterns
around the planet, and one of those changes is an increase in windiness around
the continent of Antarctica.  Cold air blows from the ice-covered continent
out over the sea, freezing the waters and pushing sea ice outward to cover
record-setting areas.
 
"That's one theory," says Meier.  "I think that winds are definitely playing a
substantial role.  But other factors could be at work, too." For instance, he
points out that glaciers melting around the edges of the continent could,
ironically, produce more ice in the surrounding ocean.  "Fresh meltwater from
glaciers is easier to freeze than briny seawater," he explains.
 
Snowfall could be important, too.  Snow landing on thin sea ice can weigh the
ice down and push it just below the water. Cold ocean water seeps up through
the ice and floods the snow - leading to a slushy mixture that freezes and
thickens the sea ice.
 
Some scientists feel that these processes could simply be due the natural
variations in the Antarctic region's climate. While it is clear that global
warming is playing a significant role in the loss of Arctic sea ice, the trend
in the Antarctic is small enough that it could be explained simply due to
natural variations in the region's climate. "Ultimately," says Meier, "we
expect that continued warming will take its toll, and even Antarctic sea ice
will begin to decline."
 
What we are seeing, he suggests, is the quirky regional way Earth responds to
a global stimulus.  Earth's climate system is complex, and climate change will
continue to have fascinatingly unpredictable consequences in the years ahead.
 
Credits:
Author: Dr. Tony Phillips | Production editor: Dr. Tony Phillips | Credit:
Science@NASA
 
More information:
Antarctic Sea Ice Reaches New Record Maximum -- Science@NASA
The Cloudy Future of Arctic Sea Ice -- Science@NASA
2014 Arctic Sea Ice Minimum 6th Lowest on Record -- Science@NASA
 
 
Regards,
 
Roger

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