January 26, 2011

Expedition To Study How Arctic Sea Ice Melts Begins

Scientists and explorers will shortly set off on an expedition aiming to discover how Arctic sea ice melts.

This year's Catlin Arctic Survey is focused on the thin layer of water immediately under the floating ice.

Arctic ice is melting faster in the summer than many computer models have predicted.

Survey data could improve forecasts of the region's future, and show how likely it is that the flow of warm water in the North Atlantic will switch off.

This would bring colder weather to the U.K. and other parts of western Europe.

"The Arctic is one of best barometers of climate change, where we see big changes taking place today," Simon Boxall from the National Oceanography Centre (NOC) at the UK's University of Southampton told BBC News.

"This is not just about polar bears - it's about our lives in the UK and in North America."

Four explorers will set out on foot from the geographic North Pole in early March, trekking across the ice and ending up 10 weeks later in Greenland.

They will make regular stops to drill holes through the floating ice and lower a package of instruments into the water on the end of a rope.

This data will allow scientists to calculate the rate at which the water is sinking.

"We're measuring the critical 200m layer of water between the ice and the deep ocean beneath," Boxall, who conceived the project, told BBC.

"The hypothesis has been that the layer stays there, trapped, acting to insulate the cold ice from the warm salty water below.

"On the other hand, the water might be taken away more quickly - and that might accelerate the rate of Arctic melting."

He said the old-fashioned approach is really the only one available for this kind of work.

The findings could prove to be crucial in terms of projecting the future for Arctic sea ice.

Both the area and volume of summer sea ice are steadily shrinking, and the last four summers have seen ice extent fall to sizes that a few years ago were being projected for the latter half of this century.

Boxall said that if mixing in the crucial top ocean layer is happening more, that could help explain the trend and refine models.

The project could also improve forecasts on the climate of western Europe.

The North Atlantic Drift brings in warm water from the tropics into northern latitudes, where it gives up some of its heat to the air.

In colder regions north and west of the U.K., winds whip water molecules from the sea, cooling it and making it more saline.

A layer of ice forms in cold seasons, which again adds to the water's salinity.

The cold salty water sinks, and eventually returns southward deep in the ocean, which forms part of the global thermohaline circulation (THC).

It draws the warm surface waters northwards as it sinks.

Warmer and fresher water does not sink so readily, which could turn off the "ocean convertor."

"Overall, if these changes... contribute to a lowering of the salt content of the North Atlantic, it could have a major impact on the entire planet - from significant temperature drops in Europe to intensified monsoons in Asia," Richard Zimmerman, a bio-optics specialist at Old Dominion University in Norfolk, Virginia, U.S., told BBC.

"It may also impact weather patterns throughout North America, including a dramatic increase in the frequency and intensity of severe storms, including hurricanes and tornadoes across the eastern US."

Recent work at NOC suggests that if it happens then it would be a quick change.

It would be likely to cool the U.K.'s climate, with the sort of winter seen in the last three years becoming the norm.

Scientists encamped on Ellef Ringnes Island off the north coast of Greenland will sample seawater and ice from colored dissolved organic materials (CDOM), which affect the ocean's absorption of sunlight.

"We'll be taking ice core sections and melting them, filtering and measuring particulates and the CDOM fraction within melted ice, and measuring algae," said Victoria Hill, also from Old Dominion University.

Results from the season's work will be published in science journals the first half of next year.


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