Antarctic ozone depleted naturally, researchers say
- From: d.086@xxxxxxxxxxx
- Date: Fri, 27 Jul 2007 17:13:05 -0700
Antarctic ozone depleted naturally, researchers say
Last Updated: Thursday, July 26, 2007 | 4:52 PM ET
CBC News
British researchers have found large quantities of natural ozone-
depleting chemicals in Antarctica.
Chemists from the University of Leeds, the University of East Anglia
and the British Antarctic Survey reported finding high concentrations
of halogens, such as bromine and iodine oxides.
"The springtime peak of iodine oxide [20 parts per trillion] is the
highest concentration recorded anywhere in the atmosphere," said an
abstract of their study, published in the journal Science on Thursday.
The bromine came from sea salt and the iodine from "almost certainly
bright orange algae that coat the underside of the sea ice around the
continent," they said in a release.
Halogens deplete the ozone above the ice surface, which reduce the
capacity of the atmosphere to remove certain chemical compounds.
"We still have to work out what the ramifications of this discovery
are," said John Plane, professor of atmospheric chemistry at the
University of Leeds.
The chemists did an 18-month study of the lowest part of the
atmosphere on the Brunt Ice Shelf, about 20 kilometres from the
Weddell Sea.
The scientists projected a beam of light across the shelf, and
analyzed the levels of chemicals in the reflected light. Moreover,
satellite observations by team member Alfonso Saiz-Lopez "have
confirmed that iodine oxides are widespread throughout coastal
Antarctica."
The scientists are planning additional studies to assess the impact on
the local environment.
The finding may raise questions about the belief that chemicals made
by humans are behind the disappearance of ozone over the continent.
The ozone layer is the part of the atmosphere 25 kilometres up that
acts as a shield protecting life on Earth from damaging UV rays, which
can cause sunburns, skin cancer and cataracts. The rays can also harm
marine life.
The layer has decreased globally by about 0.3 per cent per year. The
loss is seen as a hole over the South Pole because of atmospheric and
wind conditions during the southern winter.
The hole grows during the winter, peaking in the southern spring, and
is seen until the summer in November or December.
It is a common belief that chlorofluorocarbons (CFCs) produced by
humans are breaking down the ozone layer. For example, the UN
Environment Programme Ozone Secretariat said in 2006 the depletion of
the ozone over Antarctica "cannot be explained by natural cycles but
is caused by the impact of synthetic chemicals in the stratosphere."
CFCs were banned under the Montreal Protocol in 1987. In August 2006,
the UN group said the ozone layer could return to pre-1980 levels by
2049 over much of the world, but it would take until 2065 to restore
the shield over Antarctica.
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