NOAA/WDS Paleoclimatology - Stewart - Treasure Creek - PCMA - ITRDB AK188

Alaska's infrastructure corridors are some of the more remote in North America; providing access to critical resources from a regional (e.g., Trans-Alaska Pipeline System) to a local scale (e.g., remote Alaska Native communities). 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). In collaboration with the Alaskan Department of Transportation and Public Facilities and the Alaska Division of Geological & Geophysical Surveys, we have leveraged reaction-wood analyses in black spruce (Picea mariana) to evaluate landscape stability 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 using COFECHA software with reaction-wood years recorded. At Northway Junction along the Alaska Highway in east-central Alaska, an area of discontinuous permafrost of low to moderate ice content, 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 in an area of sporadic permafrost, rapid onset of reaction wood began in 1978 and is likely associated with permafrost degradation due to increased heavy-equipment traffic from emplacement of the Trans- Alaska Pipeline. At the Treasure Creek site near Fairbanks, remote-sensing image analysis and geophysical data indicate land instability in an area of permafrost degradation, but the reaction wood signal is weak and monotonous from 1950 to the present (mean of 7 percent of recorded growth); this likely represents characteristic tree instability above frozen ground of variable ice content. Because each site is situated atop permafrost, unstable ground is expected under certain conditions (e.g., riverbank retreat, human influence) exacerbating the relatively quiescent process of permafrost thaw. As Alaska continues to modernize in concert with record population growth (10- fold increase in the past 70 years), 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.