Understanding Seasonal Variations of In-situ Thermal and Seismic Characteristics of Degrading Permafrost in the Arctic based on Distributed Fiber Optic Sensing

Abstract

Under climate change, the Arctic is experiencing an accelerated increase in both air and permafrost temperatures compared with the global trend, a phenomenon known as Arctic amplification. This temperature increase has induced widespread permafrost degradation across the Arctic and sub-Arctic regions. As permafrost degrades, it not only degrades the geomechanical properties of soils but also disrupts natural environments, damages infrastructure systems, and escalates maintenance costs, resulting in enduring societal impacts. It is therefore important to understand the geotechnical implications of permafrost affected by the changing climate. This dissertation endeavors to construct a comprehensive research framework employing distributed fiber optic sensing technologies to understand permafrost degradation in the Arctic. The primary objective is to understand the seasonal variations of thermal and seismic characteristics of degrading permafrost in the Arctic and assess the influences of climate change, civil infrastructure, and freeze-thaw cycles. The research comprises three pivotal tasks: (1) Development and deployment of 2-kilometer-long fiber-optic cables for Distributed Temperature Sensing (DTS) and Distributed Acoustic Sensing (DAS) in Utqiaġvik, Alaska for long-term, in-situ permafrost monitoring. The study area encompasses undisturbed tundra permafrost and disturbed permafrost affected by civil infrastructure. (2) Conversion of DAS data to S-wave velocity profiles and DTS data to temperature profiles of permafrost; this enables the examination of changing permafrost at spatial and temporal scales. (3) Multi-technique analysis of permafrost dynamics by integrating the results based on DAS, DTS, Multichannel Analysis of Surface Waves (MASW), soil sampling, laboratory testing, thermometer measurements, Electrical Resistivity Tomography (ERT), and published meteorology data.