Madeira Fiber-Optic Groundtruthing (M-FOG)

Distributed acoustic sensing (DAS) uses Rayleigh scattering along an optical fiber along the seafloor to measure acoustic and seismic energy along the fiber’s length.  Noise interferometry can potentially use this information, when a loud source goes overhead, to invert for the lateral and depth structure of ocean temperature.  Sometimes this is called acoustic tomography.  Since currents change the arrival time of sound to the left and right of the source, ocean currents can in principle be determined as well.  Since it’s hard to measure ocean currents and temperature at great ocean depth, these techniques could change the way we sense the ocean; however, the limits of the technique are not known.  In this project we will instrument the 56-km-long seafloor cable extending down the continental slope from Madeira, and simultaneously emplace our high-resolution physical oceanography moorings as well as ocean bottom seismometers on the seafloor nearby.