Arctic ice melt off hits 'tipping point'
Pastor Dale Morgan
Arctic ice melt off hits 'tipping point'*
By Roger Highfield, Science Editor
Last Updated: 2:13am GMT 16/03/2007
Dwindling Arctic sea ice may have reached a 'tipping point' that could
make British winters even wetter, according to researchers.
Polar bear: Arctic ice levels hit tipping point
Temperatures in the Arctic have risen from
2F (-17C) to 7F (-14C) in recent decades
Arctic sea ice levels naturally ebb and flow throughout the year and are
always lowest in September. But September 2005 marked their lowest level
in 50 years and satellite data show average September sea ice extent
down by 8.6 per cent per decade and accelerating.
Some computer models even predict an ice-free Arctic Ocean in September
by 2050.
The loss of Arctic sea ice is most often tied to harmful effects to
wildlife and increasing erosion of coastlines. But today, scientists at
the University of Colorado warn in the journal Science of a link between
Arctic sea ice loss and changes in atmospheric patterns. These patterns
could result in reduced rainfall in the American West and increased
precipitation over western and southern Europe.
Dr Mark Serreze, of the university's National Snow and Ice Data Centre,
who led the study, said the Arctic sea-ice extent trend has been
negative in every month since 1979 and is linked to both rising
concentrations of greenhouse gases and strong natural variability in
Arctic sea ice.
"When the ice thins to a vulnerable state, the bottom will drop out and
we may quickly move into a new, seasonally ice-free state of the
Arctic," Dr Serreze said.
"I think there is some evidence that we may have reached that tipping
point, and the impacts will not be confined to the Arctic region." The
wider impact on temperate regions such as Europe is discussed by Dr
Serreze and Julienne Stroeve of the centre and Marika Holland of the
National Centre for Atmospheric Research.
The decline in Arctic sea ice could affect western American states by
lessening the severity of Arctic cold fronts and reducing snowfall,
affecting the ski industry and agriculture, he said. "Just how things
will pan out is unclear, but the bottom line is that Arctic sea ice
matters globally."
The changes could also cause increased rainfall in western and southern
Europe in winter. He told The Daily Telegraph: "The basic issue is that
the Arctic acts as the Northern Hemisphere 'refrigerator' of the climate
system. Change the nature of the refrigerator, and the rest of the
climate system will respond."
Because Arctic temperatures have risen from 2F (-17C) to 7F (-14C) in
recent decades, there is no end in sight to the decline in sea ice
extent, said Dr Serreze.
"While the Arctic is losing a great deal of ice in the summer months, it
now seems that it also is regenerating less ice in the winter," he said.
"With this increasing vulnerability, a kick to the system just from
natural climate fluctuations could send it into a tailspin."
The potential for such rapid ice loss was highlighted in a December 2006
study co-written by Dr Holland in Geophysical Research Letters. In one
climate model simulation, the Arctic Ocean became nearly ice-free in
September between 2040 and 2050.
"Given the growing agreement between models and observations, a
transition to a seasonally ice-free Arctic Ocean as the system warms
seems increasingly certain," the researchers write today in Science.
Another study in Science, by Kathy Law at IPSL-CNRS in Paris, France,
and Andreas Stohl at Université Pierre et Marie Curie in Paris, warns
that if large portions of sea ice melt, more pollution and stronger
climate effects are predicted because of the resulting increase in
shipping and Arctic oil drilling.
In a study of the other pole, University of Edinburgh scientists
identified four Antarctic glaciers that pose a threat to future sea
levels. Working with University College London, they determined the
effect melting ice in Antarctica and Greenland has on global sea level
and concluded they were responsible for a rise of 0.35 millimetres a
year over the past decade - about 12 per cent of the global trend.