Use of Airborne Electromagnetic Geophysical Survey to Map Discontinuous Permafrost in Goldstream Valley, Interior Alaska
Abstract
An airborne electromagnetic (AEM) survey was conducted in Goldstream Valley, Alaska, to map the electrical resistivity of the ground by sending a magnetic field down from a transmitter flying 30m above the ground into the subsurface. The recorded electromagnetic data are a function of the resistivity structure in the ground. The RESOLVE system used in the survey records data for six frequencies, resulting in a depth of investigation from 1-3 meters and up to 150 meters, depending on resistivity of the ground. Recording six frequencies enables the use of inversion methods to find a solution for a discretized resistivity model providing resistivity as a function of depth below ground surface. Using the airborne RESOLVE system in a populated study area involved challenges related to signal noise, access, and public opinion. Noise issues were mainly the consequence of power lines, which produce varying levels and frequencies of noise. We were not permitted to fly directly over homes, cars, animals, or people because of safety concerns, which resulted in gaps in our dataset. Public outreach well in advance of the survey informed residents about the methods used, their benefits to understanding the environment, and their potential impacts on the environment. Inversion of the data provided resistivity models that were interpreted for frozen and thawed ground conditions; these interpretation were constrained by alternate data sources such as well logs, borehole data, ground-based geophysics, and temperature measurements. The resulting permafrost map will be used to interpret groundwater movement into the valley and methane release from thermokarst lakes.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMNS21A1886D
- Keywords:
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- 0702 Permafrost;
- CRYOSPHEREDE: 0706 Active layer;
- CRYOSPHEREDE: 1823 Frozen ground;
- HYDROLOGYDE: 1829 Groundwater hydrology;
- HYDROLOGY