Re: Climate change gathers steam, say scientists

When the reflective ice surface retreats, the Sun's radiation -- heat -- is absorbed by open water rather than bounced back into the atmosphere, creating a vicious circle of heating.

"We had always known that the Arctic was going to respond first," said Mark Serreze of the National Snow and Ice Data Center in Boulder, Colorado. "What has us puzzled is that the changes are even faster than we would have thought possible," he said by phone.

The part of the puzzle they may be missing is that the difference in albedo between the ocean and sea-ice may not be as large as often described. That's because the process of melting the sea-ice produces ponds of water on the surface, which has nowhere to go and which has a much lower albedo than sea-ice, especially sea-ice covered with fresh snow. There is evidence that the melting is being accentuated by warmer waters below, water which flows into the Arctic from the Pacific and Atlantic. These flows may not be well represented in the models used to date. Also, there seems to be an increase in the deposition of "black carbon" (or soot) particles on to the sea-ice, which tends to reduce the albedo early in the melt season. The burning of coal without emissions control in China hay have added to this soot deposition.

E. Swanson