Cryospheric and Polar Processes Seminar
Using Interferometric Synthetic Aperture Radar to Study Permafrost Dynamics by Kevin Schaefer, Permafrost Scientist, NSIDC
We measure ground subsidence using Interferometric Synthetic Aperture Radar (InSAR) to study permafrost dynamics. Permafrost is perennially frozen ground and the active layer is the surface layer of soil that thaws in summer and refreezes in winter. Permafrost is difficult to monitor using visible remote sensing because it occurs underground. However, we use InSAR to measure seasonal subsidence resulting from the expansion of soil water into ice as the active layer freezes and thaws each year. We use the seasonal subsidence to directly measure the Active Layer Thickness (ALT), a key parameter of permafrost stability. We use Ground Penetrating radar to gather in situ measurements of ALT for validation. We use the subsidence trends to identify thermokarst features, and important processes, such as the impacts of fire on permafrost. We use the loss of coherence to measure fire severity. We combine InSAR with backscatter measurements of soil moisture as part of NASA’s Arctic-Boreal Vulnerability Experiment (ABoVE) field campaign in Alaska and northwest. Our InSAR techniques can lift the veil to peer under the surface to study permafrost dynamics.