Thursday, October 26, 2006
Mapping temperature-sensitive snowpacks and the frequency of warm winters in the coterminous United States
One of the most visible and widely felt impacts of climate warming is the change (mostly loss) of low elevation snow cover in the mid-latitudes. Snow cover that accumulates at temperatures close to the ice-water phase transition is at greater risk to climate warming than cold climate snowpacks because it affects both precipitation phase and ablation rates. This study maps areas in the coterminous United States that are potentially at-risk of converting from a snow-dominated to a rain-dominated winter precipitation regime, under a climate warming scenario. We use a data-driven, climatological approach of snow cover classification to reveal these “at-risk” snow zones and also to examine the relative frequency of warm winters for the region. Using 4-km resolution temperature and precipitation data, Nolin and Daly (2006) have shown that the Pacific Northwest snowpacks are particularly vulnerable to climate warming with approximately 9200 km 2 of the normally snow-covered area converting to a rain-dominated regime by mid-century. Furthermore, the frequency of warm winters is projected to increase although the changes are non-uniformly distributed with largest projected impacts at lower elevations in the mountain regions. This extended work maps those portions of the California Sierra Nevada that have “at-risk” snowpacks as well as some smaller regions in the eastern United States. A number of lower elevation ski areas could experience negative impacts because of the shift from winter snows to winter rains. The results of this study point to the potential for using existing data sets to better understand the potential impacts of climate warming.
Anne Nolin is an Assistant Professor in the Department of Geosciences at Oregon State University.