THICKNESS AND EXTENT OF PERMAFROST DETERMINED BY RESISTIVITY PROFILES COMPARED TO VEGETATION TYPE IN TANANA FLATS, ALASKA

Resistivity data was collected in Tanana Flats, Alaska, using an Advanced Geosciences Incorporated Super Sting R8 IP Earth resistivity meter to determine local thickness and extent of permafrost. This project is part of a wide scale effort to improve spatial resolution of current permafrost extent estimates which will be used as input for future permafrost change modeling. Seven profiles were collected at five different locations using either dipole-dipole or wenner setups. Data was inverted using RES2DINV with RTK GPS for surface topography correction using either a distorted finite-element grid with damped distortion or uniform distortion. In general, higher resistivity is interpreted as permafrost with thicknesses ranging between 0-15 m in most places and beginning within 1-3 m of the surface. In some regions, permafrost extends outside the maximum depth range of the resistivity surveys. High resolution (1 m) World View imagery was obtained over portions of the study site and unsupervised k-means classification was performed with 25 classes. The classification was based on a pre-existing 30-m resolution vegetation classification of Alaska. Only two transects, labeled TF50 and TF70 were in the range of the imagery. However, there appears to be good qualitative correspondence of vegetation cover type to permafrost depth and extent. Namely, thicker permafrost is generally covered by thicker vegetation cover and depth to the top of permafrost is generally minimal (1-2 m) in the same regions. Efforts to expand this comparison are ongoing and include borehole logging and field vegetation mapping, for ground truth.