Climate: Arctic greening to amplify regional warming

New study suggests large-scale northward shift of forests

Tundra treeline in Siberia.

By Summit Voice

SUMMIT COUNTY — A massive greening of the Arctic that’s already under way will intensify in the next few decades and speed up the planet’s warming process, according to a new study published this week in Nature Climate Change.

Forested areas in the Arctic could increase by 50 percent, reducing the albedo of the region and speeding up the warming of the Arctic, according to Richard Pearson, lead author on the paper and a research scientist at the American Museum of Natural History’s Center for Biodiversity and Conservation.

“Such widespread redistribution of Arctic vegetation would have impacts that reverberate through the global ecosystem,”  said Pearson, part of a research team including scientists with AT&T Labs-Research, Woods Hole Research Center, Colgate University, Cornell University, and the University of York.

Using climate models, the study projected changes expected by mid-century and developed models that statistically predict the types of plants that could grow under certain temperatures and precipitation. Although it comes with some uncertainty, this type of modeling is a robust way to study the Arctic because the harsh climate limits the range of plants that can grow (as opposed to a rainforest environment where many more types of plants could exist in the same temperature range).

The models reveal the potential for massive redistribution of vegetation across the Arctic under future climate, with about half of all vegetation switching to a different class and a massive increase in tree and shrub cover — in Siberia, trees could grow hundreds of miles north of the present tree line.

“We are already getting a glimpse of this as taller shrubs are now rapidly taking over some of the warmer tundra areas,” said co-author Pieter Beck, a research associate at the Woods Hole Research Center. “Future impacts would extend far beyond the arctic region,” Pearson said. “For example, some species of birds seasonally migrate from lower latitudes and rely on finding particular polar habitats, such as open space for ground-nesting.”

The scientists also tried to model different climate feedback effects related to the changes in vegetation, finding that the reduced reflectivity of the Arctic region would have the greatest impact on the Arctic’s climate. Darker colored trees and shrubs absorb more of the sun’s heat energy

“Increased plant growth will not offset this warming effect because plants in the Arctic absorb atmospheric carbon relatively slowly,” said co-author Michael Loranty, an assistant professor at Colgate University.

“By incorporating observed relationships between plants and albedo, we show that vegetation distribution shifts will result in an overall positive feedback to climate that is likely to cause greater warming than has previously been predicted,” said co-author and, Woods Hole Research Center Senior Scientist, Scott Goetz.

This work was funded by the National Science Foundation, grants IPY 0732948, IPY 0732954, and Expeditions 0832782. Other authors involved in this study include Steven Phillips (AT&T Labs-Research), Theodoros Damoulas (Cornell University), and Sarah Knight (American Museum of Natural History and University of York).


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