The presence and degradation of residual permafrost plateaus on the western Kenai Peninsula Lowlands, southcentral Alaska

• Main Authors: Jones, Benjamin M., Baughman, Carson A., Romanovsky, Vladimir E., Parsekian, Andrew D., Jones, Miriam C., Grosse, Guido, Berg, Edward E.
• Format: Conference Object
• Language: unknown
• Published: 2016
• Subjects: Ice; permafrost; Alaska
• Online Access: https://epic.awi.de/id/eprint/42544/; https://epic.awi.de/id/eprint/42544/1/ICOP_2016_Book-of-Abstracts_894.pdf; https://hdl.handle.net/10013/epic.49201; https://hdl.handle.net/10013/epic.49201.d001

Permafrost influences roughly 80% of the Alaskan landscape (Jorgenson et al. 2008). Permafrost presence is determined by a complex interaction of climatic, topographic, and ecological conditions operating over long time scales such that it may persist in regions with a mean annual air temperature (MAAT) that is currently above 0 °C (Jorgenson et al. 2010). Ecosystem-protected permafrost may be found in these regions with present day climatic conditions that are no longer conducive to its formation (Shur and Jorgenson, 2007). The perennial frozen deposits typically occur as isolated patches that are highly susceptible to degradation. Press disturbances associated with climate change and pulse disturbances, such as fire or human activities, can lead to immediate and irrevocable permafrost thaw and ecosystem modification in these regions. In this study, we document the presence of residual permafrost plateaus on the western Kenai Peninsula lowlands of southcentral Alaska (Figure 1a), a region with a MAAT of 1.5±1 °C (1981 to 2010). In September 2012, field studies conducted at a number of black spruce plateaus located within herbaceous wetland complexes documented frozen ground extending from 1.4 to 6.1 m below the ground surface, with thaw depth measurements ranging from 0.49 to >1.00 m. Ground penetrating radar surveys conducted in the summer and the winter provided additional information on the geometry of the frozen ground below the forested plateaus. Continuous ground temperature measurements between September 2012 and September 2015, using thermistor strings calibrated at 0 °C in an ice bath before deployment, documented the presence of permafrost. The permafrost (1 m depth) on the Kenai Peninsula is extremely warm with mean annual ground temperatures that range from -0.05 to -0.11 °C. To better understand decadal-scale changes in the residual permafrost plateaus on the Kenai Peninsula, we analyzed historic aerial photography and highresolution satellite imagery from ca. 1950, ca. 1980, 1996, and ca. 2010. ...