--> --> Geophysical Investigation of Active Layer Dynamics in Permafrost Soils from Interior Alaska

AAPG Foundation 2019 Grants-in-Aid Projects

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Geophysical Investigation of Active Layer Dynamics in Permafrost Soils from Interior Alaska

Abstract

Temperatures in Arctic regions are increasing at twice the rate of those in the mid latitudes; this merits concern because the infrastructure of arctic petroleum operations directly relies upon permafrost response to changing temperatures. Permafrost projection models vary greatly in their predictions of permafrost extent and rate of future thaw. This study considers the use of geophysical techniques to track the seasonal development of soil moisture distribution within the active layer thickness (ALT)—the superficial part of permafrost that seasonally freezes and thaws. Ultimately, soil moisture measurements from interior Alaska help to constrain predictions of permafrost dynamics and inform remote sensing models. To address the question of how soil moisture distribution evolves throughout a thaw season and influences thaw depths, I will conduct measurements using nuclear magnetic resonance and ground-penetrating radar techniques. Ground Penetrating Radar (GPR) yields information about electromagnetic wave propagation velocity which is used to calculate the dielectric constant of a medium (indicative of soil moisture). Borehole NMR (BNMR) measurements reveal information about water content and relative pore size distributions of bound- versus unbound-water surrounding a borehole. In this study soil moisture information from BNMR can be used to validate GPR-derived soil moisture measurements. Results from this investigation aim to evaluate uncertainty between geophysical measurements and constrain key parameters of soil-freezing-and remote-sensing-models of the ALT, which in turn inform the response of permafrost processes to environmental drivers.