From the New York Times, March 15:

Ice Retreats in Arctic for 2nd Year; Some Fear Most of It Will Vanish
For the second year in a row, the cloak of sea ice on the Arctic Ocean failed to grow to its normal winter expanse, scientists said yesterday. The finding led some climate experts to predict a record expansion of open water this summer.

"We keep looking for the ice to recover, but it isn't," said Mark C. Serreze, a senior scientist at the National Snow and Ice Data Center in Boulder, Colo., which monitors the region using satellites. "Unless conditions turn unusually cold this spring and summer, we may be looking at sea ice losses in 2006 that will rival what we saw in 2005."

The ice retreat recorded last September was the biggest since satellites began routine monitoring in 1979 and was probably the biggest in 100 years, according to Dr. Serreze's research group and an independent University of Illinois team.

The new findings on winter ice were first reported yesterday in the British newspaper The Independent.

Next week, when the Arctic begins six months of daylight, the warming trend is likely to be amplified by the shift from ice to water, since water absorbs sunlight that ice would otherwise reflect.

Scientists studying the region are divided over how much of the Arctic shift is from the region's large natural variations and how much is being driven by the global buildup of carbon dioxide and other heat-trapping greenhouse gases emitted mainly by smokestacks and tailpipes.

Some experts on the region, including Jamie Morison of the University of Washington, say they remain convinced that the biggest force determining the extent of Arctic sea ice is wind patterns, which cause part of the ice cap to revolve like a giant turntable, propelling a steady river of floes out past Greenland into the North Atlantic.

When ice is purged that way, the resulting open water can absorb more heat from the air, then expel that heat through the winter, limiting the thickness and area of new ice.

"I have a feeling the temperature rise over the Arctic Ocean is more due to the loss of ice from wind-driven export, rather than the loss of ice being due to temperature rise," Dr. Morison said.

But Dr. Serreze and others disagree, saying it is hard to explain the changes in ice area without including the broader warming of the atmosphere and oceans that has been linked by almost all climate experts to the intensifying greenhouse effect.

Many experts agree that despite the short-term complexities, if emissions of greenhouse gases are not curbed the human influence will dominate and the region could well be nearly bereft of ice later in the century.

Yesterday, a NASA team reported that one of the greenhouse gases, ozone, which is also a component of smog, appeared to be having an outsize warming effect in the Arctic.

Carbon dioxide, the main greenhouse gas from human activities, can last a century and tends to diffuse uniformly around the world, exerting its warming influence evenly.

Ozone generated in polluted cities and by industrial sources in the Northern Hemisphere tends to accumulate in the lower layers of the atmosphere over the Arctic in winter, when a lack of sunlight prevents natural chemical reactions from breaking it down.

As a result, it appears to be contributing to winter warming there, said Drew Shindell, the leader of the NASA research, which was conducted at the agency's Goddard Institute for Space Studies in Manhattan.

Dr. Shindell said the findings showed there was a double benefit to curbing this particular pollutant.

"Reducing ozone pollution can not only improve air quality but also have the added benefit of easing climate warming, especially in the Arctic," he said.

See our last post on global climate destabilization.