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The Antarctic ice sheet - Source: ONE News
An expansion of sea ice around Antarctica is linked to a hole in
the ozone layer high in the atmosphere, according to a study that
helps clear up a mystery about global warming.
The findings, by scientists at the British Antarctic Survey (BAS)
and the US space agency NASA, explain an apparent contradiction
between a thaw of ice in the Arctic to record lows and an increase
in ice around Antarctica over the past 30 years.
"This new research helps us solve some of the puzzle of why sea ice
is shrinking in some areas and growing in others," John Turner of
BAS, the lead author of the report, said.
The scientists said damage by manmade chemicals to the ozone layer,
which shields the planet from ultra-violet rays that can cause skin
cancer, cooled the stratosphere and disrupted wind patterns around
Antarctica.
The shift meant winds blew off the continent more often, cooling
the sea and creating more ice, they said.
Scientists found a hole in the ozone layer over Antarctica in
the 1980s and traced it to chemicals once used in refrigerants or
hairsprays.
"While there is increasing evidence that the loss of sea ice in the
Arctic has occurred due to human activity, in the Antarctic human
influence through the ozone hole has had the reverse effect and
resulted in more ice," Turner said.
Sea ice around Antarctica has expanded at a rate of around 100,000
sq kms a decade since the 1970s and covers an area of about 19
million sq kms at its winter maximum, doubling the size of the
continent.
Arctic
By contrast, summer sea ice around the North Pole shrank in 2007 to
the smallest since satellite records began in the 1970s.
The UN Climate Panel says warming is caused by greenhouse gases
from burning fossil fuels that will bring more floods, heat waves,
droughts and rising sea levels.
"Although the ozone hole is in many ways holding back the effects
of greenhouse gas increases on the Antarctic, this will not last,
as we expect ozone levels to recover by the end of the 21st
century," Turner said in a statement.
Tom Lachlan-Cope, a BAS meteorologist and one of the co-authors of
the study in the journal Geophysical Research Letters, said
Antarctica's sea ice had expanded most in the Ross Sea, south of
New Zealand.
"It's the classic way that sea ice is produced. You get an offshore
wind which blows the ice away from the shore and exposes open sea
water which then freezes over because of the cold air," he
said.
Understanding Antarctica is a priority for scientists since it
locks up enough ice to raise sea levels by 57 metres if it were
ever to melt.
Even a tiny thaw could threaten low-lying Pacific islands, or cities from New York to Beijing.
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