Sensing whales, storms, ships and earthquakes using an Arctic fibre optic cable

Abstract

Our oceans are critical to the health of our planet and its inhabitants. Increasing pressures on our marine environment are triggering an urgent need for continuous and comprehensive monitoring of the oceans and stressors, including anthropogenic activity. Current ocean observational systems are expensive and have limited temporal and spatial coverage. However, there exists a dense network of fibre-optic (FO) telecommunication cables, covering both deep ocean and coastal areas around the globe. FO cables have an untapped potential for advanced acoustic sensing that, with recent technological break-throughs, can now fill many gaps in quantitative ocean monitoring. Here we show for the first time that an advanced distributed acoustic sensing (DAS) interrogator can be used to capture a broad range of acoustic phenomena with unprecedented signal-to-noise ratios and distances. We have detected, tracked, and identified whales, storms, ships, and earthquakes. We live-streamed 250 TB of DAS data from Svalbard to mid-Norway via Uninett’s research network over 44 days; a first step towards real-time processing and distribution. Our findings demonstrate the potential for a global Earth-Ocean-Atmosphere-Space DAS monitoring network with multiple applications, e.g. marine mammal forecasting combined with ship tracking, to avoid ship strikes. By including automated processing and fusion with other remote-sensing data (automated identification systems, satellites, etc.), a low-cost ubiquitous real-time monitoring network with vastly improved coverage and resolution is within reach. We anticipate that this is a game-changer in establishing a global observatory for Ocean-Earth sciences that will mitigate current spatial sampling gaps. Our pilot test confirms the viability of this ‘cloud-observatory’ concept.

Distributed acoustic sensing of ocean-bottom seismo-acoustics and distant storms: A case study from Svalbard, Norway

“…Ocean-bottom DAS can be used for monitoring low-frequency ocean-bottom vibrations corresponding to OSGWs and, hence, ocean swells. In this section, we elaborate our detailed analysis of the same DAS data for storm monitoring as presented in Landrø et al (2022). Figure 9 shows spectrograms from three individual DAS recording channels at different water depths and distances from the shore.…”

“…DAS in submarine fiber-optic cables can measure pressure fluctuations at the ocean bottom, originating from a variety of sources (Landrø et al, 2022). DAS in ocean-bottom telecommunication fiber-optic cables can detect ocean surface gravity waves, microseisms and earthquakes (Lindsey et al, 2019;Sladen et al, 2019).…”

“…use DAS data resulting from marine impulsive seismic sources at a few hundred hertz for subsurface seismic imaging. In addition,Bouffaut et al (2022) use DAS to record frequency-swept acoustic waves at a few ten hertz produced by whales and generate their corresponding seismic profiles for subsurface exploration. Our data characterization affirms that DAS can record highquality, low-frequency seismo-acoustic data ranging from 0.01 to 10 Hz, as also shown 35…”

Polarization sensing using submarine optical cables

“…In addition to seismic monitoring, fiber sensing technologies have been applied to understand ocean dynamics and detect underwater phenomena. Lindsey et al 5 demonstrated the use of dark fiber distributed acoustic sensing for mapping seafloor faults and monitoring ocean dynamics, while Landrø et al 6 utilized arctic fiber optic cables for sensing whales, storms, ships, and earthquakes, proving the versatility of fiber sensing in harsh environments. Skarvang et al 7 presented observations of local small magnitude earthquakes using state-ofpolarization monitoring in a passive arctic submarine communication cable, highlighting the potential of polarization-based sensing techniques in seismic monitoring.…”

Submarine optical fiber communication provides an unrealized deep-sea observation network

“…Applying distributed sensing to the telecommunication fiber network can leverage the communication cable for ocean monitoring. In addition to the intrinsic function of optical fibers for data transmission across oceans, optical fiber sensing technology can monitor the ambient environment near the fiber across oceans 17 , 18 . For instance, optical fiber distributed acoustic sensing (DAS) can achieve seismological data collection 15 , 19 , geophysical monitoring 20 , earthquake wavefields sensing 21 , and other ocean monitoring data collection applications 16 .…”