A new methodology to monitor soil moisture over a complex arctic environment, Kobuk River valley, Alaska

Abstract

Frozen ground is a sensitive indicator of environmental change. In this study, we examine the relevance of L-band synthetic aperture radar (SAR) data for extracting information on frozen ground, above discontinuous permafrost, in the Kobuk River valley, Alaska. A new methodology based on multi-temporal image acquisition is presented. This approach uses Oh's model with image acquisition during the period of frozen ground, and incorporates a vegetation model during the thawing period. The methodology is optimized to retrieve not only the soil moisture content but also the albedo and the extinction coefficient of the vegetation layer. Estimated soil moisture maps produced for one year reveal high values in late spring in response to snowmelt, rainfall, and spring vegetation growth. Low values in late summer/early fall are in response to seasonal rainfall variation, increased evapotranspiration, and the end of the growing season. These results provide insights for monitoring change in complex arctic environments.

Acknowledgements

Special thanks to R. Guritz and S. Arko from the Alaska SAR Facility, University of Alaska, Fairbanks, for help in producing the Kobuk River valley DSM. We also thank S. Stothoff and G. Walter for their technical and programmatic reviews, and C. Dinwiddie and two anonymous reviewers for insightful reviews and suggestions. ALOS PALSAR data sets were provided by the Alaska Satellite Facility (ASF) and Japan Aerospace Exploration Agency (JAXA). Vegetation and soil maps were provided by the US National Park Service.