Changing snow and shrub conditions affect albedo with global implications
Article first published online: 7 SEP 2005
Copyright 2005 by the American Geophysical Union.
Journal of Geophysical Research: Biogeosciences (2005–2012)
Volume 110, Issue G1, September 2005
How to Cite
2005), Changing snow and shrub conditions affect albedo with global implications, J. Geophys. Res., 110, G01004, doi:10.1029/2005JG000013., , , and (
- Issue published online: 7 SEP 2005
- Article first published online: 7 SEP 2005
- Manuscript Accepted: 5 MAY 2005
- Manuscript Revised: 14 APR 2005
- Manuscript Received: 16 JAN 2005
 Observations suggest that shrub abundance in the Arctic is increasing owing to climate warming. We investigated the ramifications of a tundra-to-shrubland transition on winter energy exchange. At five sites in Alaska we suspended a 50-m-long cable above the vegetation and from this measured how the vegetation interacted with the snow and affected albedo. The sites defined a gradient from nearly shrub-free tundra to a woodland with a continuous shrub canopy. Where the shrubs were small, thin-stemmed, and supple, they were bent and buried by snow. Where they were tall, thick-stemmed, and stiff, the shrub canopy remained exposed all winter. Where shrubs were buried, mid-winter albedo values were high (0.85), but where they were exposed, the values were 30% lower (0.60). At these latter sites, melting began several weeks earlier but proceeded more slowly. Consequently, all sites were free of snow about the same time. Using the measurements and a solar model, we estimate that a land surface transition from shrub-free tundra to shrubland could produce a 69 to 75% increase in absorbed solar radiation during the snow-cover period, depending on latitude. This is two thirds the increase associated with a tundra-to-forest transition. When combined with measurements showing that a tundra-to-shrub transition would also produce a net increase in summer heating, our results suggest a positive feedback mechanism associated with a warming-induced increase in shrubs. To our knowledge, ours is the first study to document that shrubs could alter the winter energy balance of tundra in such a substantial way.