*Arctic sea ice melts to new low*

By Mark Kinver
Science and nature reporter, BBC News

The extent of sea ice has been declining over the past 30 years

Arctic sea ice is expected to retreat to a record low by the end of this
summer, scientists have predicted.

Measurements made by the US National Snow and Ice Data Center (NSIDC)
showed the extent of sea ice on 8 August was almost 30% below the
long-term average.

Because the region's melting season runs until the middle of September,
scientists believe this summer will end with the lowest ice cover on record.

Researchers have forecast ice-free summers in the Arctic by 2040.

NSIDC data showed sea ice extent for 8 August as 5.8m sq km (2.2m sq
miles), compared to the 1979-2000 August average of 7.7m sq km (3.0m sq
miles).

The current record low was recorded in 2005, when Arctic sea ice covered
just 5.32m sq km (2.09m sq miles).

Graph showing extent of Arctic sea ice (Image: BBC)

"If you look at data for the first week in August, we are way below what
we saw in 2005," explained Mark Serreze, a senior research scientist at
the NSIDC.

"So unless something really changes, for example the Arctic suddenly
becomes a lot colder, it is going to be hard not to beat the previous
record."

Dr Serreze added that it was very likely that sea ice cover in the polar
region was starting to respond to human induced climate change,
resulting from a greater concentration of greenhouse gases in the
atmosphere.

"We know that natural climate variability can strongly influence the sea
ice, but I think we are starting to see a positive feedback now.

"In other words, we cannot explain everything that we have seen just
through natural processes.

"Overall, the pattern will be that you melt a little bit more during the
summer and you grow back a little less during the winter," he told BBC News.

Retreating ice

In December 2006, a study by US researchers forecast that the Arctic
would be ice-free by 2040.

A team of scientists from the National Center for Atmospheric Research
(NCAR), the University of Washington, and McGill University, found that
"positive feedbacks" were likely to accelerate the decline of the
region's ice system.

Sea ice has a bright surface that reflects 80% of the sunlight that
strikes it back into space. However, as the ice melts during the summer,
more of the dark ocean surface becomes exposed.

Rather than reflecting sunlight, the ocean absorbs 90% of it, causing
the waters to warm and increase the rate of melting.

Scientists fear that this feedback mechanism will have major
consequences for wildlife in the region, not least polar bears, which
traverse ice-floes in search of food.

On a global scale, the Earth would lose a major reflective surface and
so absorb more solar energy, potentially accelerating climatic change
across the world.