Arctic Going Green from Warming, Study Finds

Tia Ghose LiveScience Yahoo News 4 Apr 13;

Large swaths of the Arctic tundra will be warm enough to support lush vegetation and trees by 2050, suggests a new study.

Higher temperatures will lessen snow cover, according to the study, which is detailed in the March 31 issue of the journal Nature Climate Change. That, in turn, will decrease the sunlight reflected back into the atmosphere and increase warming. About half the areas will see vegetation change, and areas currently populated by shrubs may find woody trees taking their place.

"Substitute the snowy surface with the darker surface of a coniferous tree, and the darker surface stores more heat," said study co-author Pieter Beck, a vegetative ecologist at the Woods Hole Research Center in Massachusetts. "It's going to exacerbate warming."

Warming Arctic

The Arctic climate affects the world: Changes in sea ice affect ocean circulation, which, in turn, affects atmospheric circulation that then impacts the globe, said Bruce Forbes, a geographer at the Arctic Center at the University of Lapland in Finland, who was not involved in the study. [Images of Melt: Earth's Vanishing Ice]

Past research suggested that warming has already brought later winters and earlier springs to the Arctic. And fossil forests reveal the Arctic was once green as well.

To find out exactly how much greening Arctic warming would bring, the team used a model that projected how temperature changes would affect snow cover, vegetation, and the increased evaporation and transpiration from plants in the Arctic.

Transformed tundra

The team found that at least half of the tundra would see changes in the plant types it supported by 2050. In addition, they found more than a 50 percent increase in how much woody greenery — such as coniferous trees — would populate the Arctic. The tree line would also shift north, with coniferous forests sprouting where shrubs once grew.

Most of the greening was driven by the loss of reflectivity, or albedo, from snow cover. With less snow to reflect heat back into the atmosphere and more dark trees, the Earth gets warmer, "just like a dark car gets hotter in a warm parking lot than a light car does," Beck told LiveScience.

That warmth supports more tree and shrub growth, creating a positive feedback cycle to the warming, Beck said.

Real effect

The findings match forecasts for Arctic greening predicted by various other methods, and they foreshadow effects that will strike closer to home later, Forbes said.

"What's happening now in the Arctic is a faster version of what will be happening at lower latitudes," Forbes told LiveScience.

That could worsen extreme weather events like Hurricane Sandy in the future.

"The snowstorms in Washington, D.C., and New York, and the flooding and the freezing on the River Thames — the extreme weather will continue to be extreme but it won't be so uncommon," Forbes said.