Mapping Snow Persistence for the Range of the Western Arctic Caribou Herd, Northwest Alaska,Using the Landsat Archive (1985-2011)
Dates
Year
2012
Citation
Macander, M. J., and Swingley, C. S., 2012, Mapping Snow Persistence for the Range of the Western Arctic Caribou Herd, Northwest Alaska,Using the Landsat Archive (1985-2011): National Park Service: Fort Collins, CO, v. 643.
Summary
A critical part of the National Park Service’s Arctic Network Inventory and Monitoring Programis monitoring the Western Arctic Caribou Herd (WACH). The status, distribution, movementsand trends in the condition of caribou in all five park units are monitored. Accurate and detailedmodels of snow cover within the range of the Western Arctic Caribou Herd will provideimportant context to help understand movement patterns and timing of caribou migrations. Snowdepth influences caribou winter distribution and habitat availability by impacting the costs oflocomotion and cratering for forage plants and lichens. Snow depth patterns on the landscapealso influence plant communities, affecting the distribution of preferred forage species. Physical [...]
Summary
A critical part of the National Park Service’s Arctic Network Inventory and Monitoring Programis monitoring the Western Arctic Caribou Herd (WACH). The status, distribution, movementsand trends in the condition of caribou in all five park units are monitored. Accurate and detailedmodels of snow cover within the range of the Western Arctic Caribou Herd will provideimportant context to help understand movement patterns and timing of caribou migrations. Snowdepth influences caribou winter distribution and habitat availability by impacting the costs oflocomotion and cratering for forage plants and lichens. Snow depth patterns on the landscapealso influence plant communities, affecting the distribution of preferred forage species. Physical modeling techniques (e.g. Liston and Hiemstra 2011) and remote sensing methods (e.g.Hall et al. 2001, Brodzik et al. 2007) have been used to provide information on snow cover andsnow depth data at daily to weekly timescales, and at spatial resolutions of 500–25,000 m.However, much of the variability in snow cover happens at much finer spatial scales, particularlyfor mountain and tundra snowpacks (Sturm 1995). To help characterize winter and spring habitat conditions related to snow depth for the WesternArctic Caribou Herd, we used a combination of image interpretation and statistical modeling todescribe patterns of snow persistence on the landscape at fine spatial resolution (30-m pixels). Toaccomplish this we compiled and analyzed an extensive time series of over 10,000 Landsatimages (1985–2011) that covered the caribou range. We used the results of this analysis to mapthe typical date of snowmelt across the range, which can provide information on the spatialdistribution of snow cover patterns relevant to caribou winter habitat quality. Areas windscoured during winter generally lack suitable lichen forage, and can be identified because theyare often snow-free during winter and early spring. Sites with shallow snow provide easier traveland foraging and they will tend to melt earlier. Deeper snow, which melts later, can makeforaging more difficult for caribou. Snow persistence and snow depth patterns affect other wildlife species, plant communities,hydrologic and aquatic systems, and soil temperatures. For example, polar bears and wolverineslocate dens in snow drifts. Snowbed plant communities often include unique species assemblagesand have delayed phenology. Late melting snow drifts can help support stream flow during drysummers. Deep snow insulates plants and the soil and can facilitate shrub expansion (Sturm2001). Many wildlife species use the snow-free lands that are exposed earlier in the season forgrazing and nesting.
