Glacier trends and response to climate in Denali National Park and Preserve.

Glaciers cover approximately one-sixth of Denali National Park and Preserve in Alaska. They are not only enjoyed by visitors for their scenic and recreational values but are also an important driver of Denali's diverse ecosystems by defining the hydrologic regime, generating landscape-scale braided river systems, and shaping the landforms of the Alaska Range. Scientists from the National Park Service and University of Alaska-Fairbanks have been researching glacier dynamics and monitoring glacier trends for more than 20 years using glacier outlining from satellite imagery, index mass balance measurements, longitudinal elevation profiles, repeat photography, analysis of regional gravity changes, and other localized research. Mass balance measurements on the Traleika and Kahiltna glaciers showed a cumulative net gain of mass from 1991 to 2003. Since 2003 the mass balance data and satellite-based gravimetric analysis show a net loss of ice mass. Airborne laser and lidar elevation profiles corroborate the mass balance measurements and also show localized changes because of glacier dynamics. Analysis of glacier extent reveals an 8% loss in area since 1950; however, whereas most glaciers lost area, a few surge-type glaciers gained area. Repeated photographs from historical images help refine trends seen in other methods and include dramatic examples of smaller glaciers decreasing in size and a surge-type glacier that has not changed as noticeably. Relations to climate trends are complicated and clearly demonstrate the importance of local influences on glacier behavior and trends. Losses of ice from smaller glaciers and dramatic changes of other glaciers in Alaska suggest that global climatic change may be overwhelming the dominant influence of large-scale climate oscillations on glacier change in Denali. [ABSTRACT FROM AUTHOR]