By 2040, Greenhouse Gases Could Lead to an Open Arctic Sea in Summers
By Andrew C. Revkin
New studies project that the Arctic Ocean could be mostly open water in summer by 2040- Several decades earlier that previously expected - partly as a result of global warming caused by emissions of greenhouse gases.
The projections come from computer simulations of climate and ice and from direct measurements showing that the amount of ice coverage has been declining for 30 years.
The latest modeling study, being published today in the journal geophysical Research letters, was led by Marika Holland of the National center for Atmospheric Research in Boulder, Colo.
The study involved seven fresh simulations on supercomputers at the atmospheric center, as well as an analysis of simulations developed by independent groups. In simulations where emissions where emissions continue to rise, sea ice persists for long period by then abruptly gives way to open water, Dr. Holland said
In the simulations, the shift seems to occur when a pulse of warm Atlantic Ocean water combines with the thinning and retreats of ice under the influence of teh global warming trend, Scientist ascribe most of that planet-scale warming, includes a warming of the shallow layers of the oceans, to the buildup of carbon dioxide and other heat-trapping smokestack and tailpipe gasses in the atmosphere.
After 2040 or so, ice persists in summer mainly around Canada's northern maze of islands and the northern coast of Greenland, a region that always tends to accumulate a clot of thick ice.
Separately, scientists at the National Snow and Ice data Center in Boulder found that the normal expansion of sea ices the Arctic chilled in fall had been extraordinarily sluggish this year, following a pattern seen in recent years. The November average ice coverage was by far that lowest since satellite measurements began in 1979, said Walt Meier, a scientist at the ice center.
"It's becoming increasingly unlikely that things will be able to run around," he said. "It would take several very cold winters and cool summers, which seems unlikely under global warming conditions."
Several experts not involved with the studies said they were significant for human affairs, as well as biology.
Polar bears will struggle, these scientists said, and so will Arctic people who still go out on sea ice to hunt seals. By contrasts countries and businesses pursuing new shipping lanes, energy supplies and finishing grounds could profit.
The melting is likely to shift weather patters, too. More sea ice means colder winters, because frigid winds blowing over ice picks up little heat from the warmer waters below.
The change will have ramifications beyond summertime, experts said. Having open water Research year would mean that almost all ice forming in winter would be freshly frozen and just a year or so thick.
This would greatly ease the task of maintaining shipping Lanes with icebreaking vessels, said Lawson W. Brigham, deputy director of the Artic Research Commission, which advises that White House on Arctic matters. Mr. Brigham and other experts said the new research raised the urgency of establishing common standards for protecting the Artic environment and patrolling shipping lanes. The commission plans to deliver letters to the Bush administration and Congress this week urging them to commit at least $1 million to start work on replacing the country's two aging, ailing polar-class icebreakers.
