Temperature Sensing With DAS for Fiber-Optic Oceanography
Description:
Although typically used to measure dynamic strain from seismic and acoustic waves, Rayleigh-based distributed acoustic sensing (DAS) is also sensitive to temperature, offering longer range and higher sensitivity to small fluctuations than conventional Raman-based distributed temperature sensing. In this presentation, we demonstrate that ocean-bottom DAS on pre-existing fiber-optic cables is sensitive to, for example, both large-amplitude internal waves propagating on the near-surface thermocline as well as the intensified internal tide at sloping bottom boundaries, which are regions of enhanced ocean mixing but scarce observations. In particular, we interpret temperature transients up to 4 K (equivalent to 40 microstrain) along a power cable in the Strait of Gibraltar, associated with passing groups of internal solitary waves in water depth <200 m. We then show how temperature variability of about 2 K at 1-km depth decreasing to 0.2 K at 2.5-km depth on the slope of Gran Canaria, an island off the coast of west Africa, reveals the bore-like propagation of the nonlinear internal tide at locations where the slope is near critical. While the temperature sensitivity of DAS opens new frontiers in fiber-optic oceanography, it also presents a significant challenge for long-period seismology and seafloor geodesy with fiber-optic strainmeters, as temperature fluctuations associated with internal waves and boundary-layer flows may overprint elastic strain from fault creep or slow earthquakes.
Session: Understanding Earth Systems with Fiber-optic Cables
Type: Oral
Date: 4/19/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Ethan F. Williams
Student Presenter: No
Invited Presentation: Yes
Authors
Ethan Williams Presenting Author Corresponding Author efwillia@caltech.edu California Institute of Technology |
Arantza Ugalde a.ugalde@icm.csic.es Institute of Marine Sciences, ICM-CSIC |
Hugo Martins hugo.martins@csic.es Instituto de Optica, CSIC |
Carlos Becerril carlos.becerril@uah.es University of Alcala |
Jörn Callies jcallies@caltech.edu California Institute of Technology |
Mariona Claret mclaret@icm.csic.es Institute of Marine Science, ICM-CSIC |
Maria del Rosario Fernandez-Ruiz rosario.fernandezr@uah.es University of Alcala |
Miguel Gonzalez-Herraez miguel.gonzalezh@uah.es University of Alcala |
Sonia Martin-Lopez sonia.martinlo@uah.es University of Alcala |
Josep L Pelegri pelegri@icm.csic.es Institute of Marine Science, ICM-CSIC, Barcelona, , Spain |
Kraig B Winters kbwinters@ucsd.edu University of California, San Diego, La Jolla, California, United States |
Zhongwen Zhan zwzhan@caltech.edu California Institute of Technology, Pasadena, California, United States |
Temperature Sensing With DAS for Fiber-Optic Oceanography
Category
Understanding Earth Systems with Fiber-optic Cables