ALL ABSTRACTS BY AUTHOR             ABSTRACTS FOR THIS SESSION

Arctic Science 2000 - Crossing Borders: Science and Community
Whitehorse, Yukon, Canada, Sept 21-24 2000
American Association for the Advancement of Science & Yukon Science Institute

Are Northern Wetlands Drying Up? A Case Study in the Old Crow Flats, Yukon.

The Canadian Wildlife Service and several other partners examined changes in shallow thermokarst lakes on the Old Crow Flats over the past 26 years. Many local residents have noticed a general decline in water levels, including some lakes literally drying up. The study attempted to determine if there has been a change in the total surface area of water on the Flats during this time. This was done using a series of satellite images obtained from the various Landsat satellites between 1973 and 1999. The ground resolution of these images varies from about 60 meters for the early images (Landsat Multispectral Scanner data, 1973 to 1983), to 25 meters for images obtained since 1986 (Landsat Thematic Mapper data). For each of the satellite images, we used a computer to separate the image into "land" and "water" classes, and compared these images over the 26-year period. The results suggest that since 1973 there has been a decline of about 5% in the surface area of water on the Flats. This includes only areas that have completely dried up, not those areas where the water levels have decreased without exposing the lake bottom. Most of the change has come from two large lakes and about 10 smaller ones that partially or completely drained during this period. These lakes have been changing for thousands of years and they will continue to do so, but at the moment it appears that there is an overall drying trend resulting from an imbalance between the rate at which basins drain/dry versus the rate at which they refill.

We will continue to look at satellite images of this area as they become available and report on the changes they show. We will also be working with other partners interested in this area to understand what is happening. All this information will be shared with everyone, especially the community of Old Crow.

TOP