Spatial variability and landscape controls of near‐surface permafrost within the Alaskan Yukon River Basin

Abstract

The distribution of permafrost is important to understand because of permafrost's influence on high-latitude ecosystem structure and functions. Moreover, near-surface (defined here as within 1 m of the Earth's surface) permafrost is particularly susceptible to a warming climate and is generally poorly mapped at regional scales. Subsequently, our objectives were to (1) develop the first-known binary and probabilistic maps of near-surface permafrost distributions at a 30 m resolution in the Alaskan Yukon River Basin by employing decision tree models, field measurements, and remotely sensed and mapped biophysical data; (2) evaluate the relative contribution of 39 biophysical variables used in the models; and (3) assess the landscape-scale factors controlling spatial variations in permafrost extent. Areas estimated to be present and absent of near-surface permafrost occupy approximately 46% and 45% of the Alaskan Yukon River Basin, respectively; masked areas (e.g., water and developed) account for the remaining 9% of the landscape. Strong predictors of near-surface permafrost include climatic indices, land cover, topography, and Landsat 7 Enhanced Thematic Mapper Plus spectral information. Our quantitative modeling approach enabled us to generate regional near-surface permafrost maps and provide essential information for resource managers and modelers to better understand near-surface permafrost distribution and how it relates to environmental factors and conditions.

Effect of permafrost thaw on the dynamics of lakes recharged by ice-jam floods: case study of Yukon Flats, Alaska

“…The permafrost extends to depths of approximately 100 m, except below rivers and large lakes where it is typically absent (Minsley et al , ). Active layer thicknesses in Yukon Flats range from 0.2 to 1.3 m (Pastick et al , ). We observed annual ground surface temperatures within a few degrees of 0°C at two sites in the Twelvemile Lake watershed (Figure c) (Jepsen et al , ), indicating a great potential for permafrost thaw in response to atmospheric warming and/or land cover disturbance (Prowse et al , ).…”

Interactive effects of wildfire and climate on permafrost degradation in Alaskan lowland forests

“…After fire, reaccumulation of the surface organic layer may initiate permafrost recovery [ Jafarov et al , ; Jorgenson et al , ; Shur and Jorgenson , ; Viereck et al , ]; or changes in climatic conditions, hydrology, or plant successional trajectories may cause further degradation [ Genet et al , ; Jafarov et al , ; Johnstone et al , ; Jorgenson et al , ; Shur and Jorgenson , ; Viereck et al , ]. In addition to the temporal controls over permafrost dynamics, the spatial variations in microclimate, snow depth, vegetation, topography, soil texture, and soil moisture contribute to the heterogeneity of the permafrost response to fire [ Genet et al , ; Harden et al , ; Johnson et al , ; Jorgenson et al , ; Nossov et al , ; Pastick et al , ].…”

Dendrogeomorphic evidence of frequent mass movement using reaction wood in black spruce: Alaska Highway milepost 1267, Northway Junction, Alaska

“…Growth-ring disturbances due to tilting are usually in the form of reaction wood (Shroder, 1978;Owczarek, 2005), where individual rings become considerably wider and slightly darker in appearance compared to the upslope side as the tree puts on structural mass to correct its posture (Warensjö and Rune, 2004;Carrara and O'Neill, 2010) (figs. 6 and 7).…”