LANDSCAPE INSTABILITY, PERMAFROST AND REMOTE INFRASTRUCTURE CORRIDORS: DENDROGEOMORPHOLOGY USING BLACK SPRUCE, ALASKA

Alaska’s infrastructure corridors are some of the more remote in North America; providing access to critical resources. Many corridors were developed quickly and with limited planning and understanding of cold-regions engineering in geologically complex terrains with widespread permafrost. This results in unique climate-driven maintenance requirements with a projected need of an additional $6.1 billion for normal wear-and-tear costs until 2030 (Larsen et al., 2008). Supporting the Alaskan Department of Transportation and Public Facilities, we evaluated the dendrogeomorphic response of black spruce (Picea mariana) to reveal landscape change along important infrastructure corridors in three sites across Alaska—Northway Junction, Tonsina Hill, and Treasure Creek. At each site, 60 samples from 30 visibly tilted trees were collected, digitized, and quality checked with disturbance years recorded. At Northway Junction along the Alaska Highway in east-central Alaska, there was a site-wide, rapid onset of reaction wood in 1989. Widespread tilting of trees on a retrogressive mass movement, likely a response to thawing permafrost conditions, necessitated an expensive road realignment. At the Tonsina Hill site along the Richardson Highway south of Glennallen, rapid onset of reaction wood began in 1978 and is likely associated with permafrost degradation due to road refurbishment and increased heavy-equipment traffic from the emplacement of the Trans-Alaska Pipeline. At the Treasure Creek site near Fairbanks, remote-sensing and geophysical data indicate land instability in the area, but the reaction wood signal is weak and monotonous from 1950 to the present; this likely represents characteristic tree instability above permafrost. Because each site is situated atop permafrost, unstable ground is expected under certain conditions, which may exacerbate the relatively quiescent process of permafrost thaw. As Alaska continues to modernize in concert with record population growth, efforts to recognize, mitigate, and/or prevent permafrost-thaw-induced landscape changes have become a focus for infrastructure projects. Improved evaluation of infrastructure siting and smarter technologies could help minimize the effects of permafrost thaw on human concerns.