. Can Seafloor Voltage Cables be Used to Study Large Scale Transport? An Investigation in the Pacific Ocean.

Abstract
Marine electromagnetic (EM) signals largely depend on three factors: oceanic transport (i.e., depth-integrated flow), the local main magnetic field, and the local seawater conductivity (which depends on the local temperature and salinity). Thus, there is interest in using seafloor telecommunication cables to isolate marine EM signals and study ocean processes because these cables measure voltage differences between their two ends. Data from such cables can provide information on the depth-integrated transport occurring in the water column above the cable. However, these time-varying data are a superposition of all EM fields present at the observatory, no matter what source or process created the field. The main challenge in using such submarine voltage cables to study ocean circulation is properly isolating its signal. Here, we analyze voltage data from Pacific Ocean submarine voltage cables and compare the observed inter-annual voltage variations with those from a time-domain 3-D EM induction solver, elmgTD. The 0.5 degree resolution model is driven by the latest version of the Estimating the Circulation & Climate of the Ocean (ECCO) model and the NOAA World Ocean Atlas monthly seawater conductivity climatologies. We only use seafloor data from geomagnetically quiet days (Ap index < 20) to effectively remove EM noise caused by solar disturbances in near-Earth space. We then evaluate and discuss the implications of using voltage data across ocean basins to study and monitor ocean flow.