Estimation of First Year Sea Ice Thickness from Flexural-Gravity Wave Dispersion Observed by Seafloor Distributed Acoustic Sensing

Abstract Seismic methods for estimating sea ice thickness traditionally rely on surface-sited instrumentation and, consequentially, are limited in duration and spatial extent by the inherent logistical challenges of polar field deployments. We present a novel method for measuring sea ice thickness from the seafloor, utilizing distributed acoustic sensing (DAS) on a trenched seafloor telecommunications cable in the Beaufort Sea, Alaska. We apply a frequency–slowness transformation to DAS observations of flexural-gravity (FG) waves to extract phase velocity dispersion curves, which we then invert to estimate sea ice thickness using a simple grid search across ice thickness and rigidity space. We show that this method yields equivalent results for broadband FG waves generated by windstorms, hovercraft traffic, and thermal fracturing. DAS-derived estimates obtained throughout January to March 2023 are consistent with sea ice thicknesses measured at collocated ice boreholes, and with estimates from an air temperature cumulative freezing-day model. This novel method enables continuous, high resolution, multiyear seismic monitoring of sea ice thickness without the risk or burden of annual surface deployments.