Permafrost Monitoring in the Central Alaska Network of National Parks

Hill, Kenneth; Loso, Michael

The three national park units which comprise the National Park Service Inventory and Monitoring Program’s Central Alaska Network (CAKN: Wrangell-St. Elias, Denali, and Yukon-Charley Rivers) are underlain by permafrost—ground that remains at or below 0°C for at least two, but typically many, years. Much of that permafrost, however, is geographically discontinuous, thin, and close to the melting point of water. Under the warming conditions that characterize these parks, permafrost thaw is likely to have significant impacts on the landscapes of these parks. These impacts may include development of thermokarst, landslides and slumping, changes in hydrology and vegetation, growth and/or drainage of lakes, enhanced release of greenhouse gases, and decay of characteristic permafrost features like pingos and rock glaciers. The CAKN permafrost monitoring program is designed to monitor a subset of these changes over multiple decades, and focuses on tracking changes in the thermal and physical state of permafrost. Collected data will contribute directly to the Global Terrestrial Network for Permafrost, the primary international permafrost monitoring program. Thermal changes will be monitored with a broad network of shallow (<3 m) soil temperature measurements, and also with temperature measurements from a single deep (29-70 m) borehole adjacent to each park. These measurements will mostly be conducted in collaboration with existing monitoring programs to leverage existing resources. Physical changes will be monitored with a network of active layer thickness measurements that use late-summer mechanical probing to determine maximum thaw depth on fine-grained permafrost soils. The thaw depth measurements will be co-located with survey-grade differential global positioning system (dGPS) surveys of soil surface elevation to detect thaw-related subsidence. These physical changes will be conducted in grids or transects at sites selected to take advantage of previous studies, to maximize logistical/resource efficiency, and to represent areas expected to change most rapidly in coming decades. Many of the landscape-scale impacts of permafrost thaw are already monitored by the Arctic Network, but CAKN will monitor changes in one permafrost landform that is uniquely abundant in WRST: rock glaciers. The areal extent, surface elevations, and velocities of a well-studied rock glacier in the central Wrangells will be measured every 6th year. Opportunities for monitoring of other important permafrost changes, particularly including carbon cycling and thermokarst development, are not included in this protocol but will be considered for future studies. Sustainable inclusion of such work in the protocol itself would require a stable source of additional funds, but shorter-term opportunistic and collaborative research is an ongoing goal of the broader permafrost monitoring program.

Permafrost Monitoring in the Central Alaska Network of National Parks

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