A BASELINE STUDY OF PERMAFROST IN THE TOKLAT BASIN, DENALI NATIONAL PARK AND PRESERVE, ALASKA

The Toklat Basin, a remote, intact ecosystem in northeastern Denali National Park & Preserve, has repeatedly come under threat from a proposal to develop a northern access route into Kantishna along the Stampede Trail, which bisects the Basin. Most of the natural and physical resources in the Basin, an area of approximately 64,749 ha, had never been inventoried; even reconnaissance-level data were sparse. To assist park managers in protecting park resources, the National Park Service (NPS) began baseline studies in the Toklat Basin in 2003. One of our goals was to evaluate permafrost, the Basin's dominant geomorphic process, and any related features. The Natural Resources Conservation Service (NRCS) recently completed a joint NPS-NRCS soils survey of the 6-million acre park which mapped permafrost extent across Denali for the first time. The Toklat Basin is a large alluvial plain predominantly underlain by continuous and discontinuous permafrost. To determine site selection, we analyzed aerial photography and satellite imagery. Aerial reconnaissance also provided for observation of previously unknown permafrost features. Site investigation included soil pit analysis, geomorphology description, and depth-to-frozen-ground (DTFG) measurements. Fieldwork occurred in the summers of 2003 and 2004. The Toklat Basin is a permafrost-rich environment with many characteristic features, including ice-wedge polygons, thermokarst depressions and ponds, cryoturbation steps, gelifluction lobes, beaded streams, palsas, drunken forests, nonsorted stripes and nonsorted circles. Standing water due to impenetrable ground is very common, particularly in the northern half of the Basin. DTFG measurements at 135 sites yielded an average depth of 50 cm. Numerous thermokarsts and thawing ice-wedge polygons demonstrate that the Toklat Basin is a fragile permafrost environment vulnerable to the warming effects of climate change and to human activities that destroy overlying ground cover. Knowledge of the role of permafrost in the Toklat Basin will allow for a more complete understanding of the ecosystem, and more informed, science-based management. Ongoing work in the area, conducted through university partnerships, includes borehole temperature measurements, thermokarst monitoring, and carbon cycling research.