Monitoring Shelf Sea Dynamics with Ocean-Bottom Distributed Acoustic Sensing

Abstract

The mixing of ocean waters on continental shelves, which is mainly driven by waves, tides, and currents, plays a key role in the physics, biogeochemistry, and ecology of coastal regions. This study focuses on four months of continuous data recorded along a telecommunication cable offshore Oregon, USA, with Distributed Acoustic Sensing (DAS). We apply a cross-correlation approach to the continuous DAS data to infer the propagation of ocean surface gravity waves in the 3 to 100 s period range and estimate near-surface ocean flows. We observe strong spatio-temporal variations of ocean flows along the cable over four months, with strong impacts from a series of storms in late October 2021. We find that our measurements capture oceanic surface motions as those measured by nearby traditional oceanographic instruments. This study demonstrates that ocean-bottom DAS can be used to infer the dynamic properties of near-shore oceans with an unprecedented spatio-temporal resolution.

Detection of Earthquake Infragravity and Tsunami Waves With Underwater Distributed Acoustic Sensing

“…The seabed then drops from 150 to 400 m between 40 and 60 km from the interrogator, indicating the beginning of the continental slope. From the coastline, the mean azimuth of the cable is ∼254° from the north, representing a direction almost perpendicular to the mean shoreline orientation (Viens et al., 2023).…”

“…DAS utilizes the optical phase changes in Rayleigh backscattered light within an optical fiber to function as thousands of vibration sensors. This innovative approach enables the fiber to act as a dense array capable of continuously detecting and analyzing seismo-acoustic signals along tens of kilometers (Farghal et al, 2022;Lindsey et al, 2019;Lior et al, 2021;Romanowicz et al, 2023;Sladen et al, 2019;Spica et al, 2020Spica et al, , 2022Spica et al, , 2023Viens et al, 2023;Williams et al, 2019;Xiao et al, 2022;Yang et al, 2022;Zhan, 2019). Unlike traditional sensors, DAS provides high-resolution data over large distances, allowing for real-time monitoring of seismic and ocean waves with unprecedented coverage.…”