Transport measurements from in-service undersea telephone cables

The motion of the ocean through the Earth´s magnetic field creates a cross-stream voltage proportional to the transport of the stream. These motion-induced voltages have been observed for more than ten years by the use of an abandoned cable spanning the Florida Current. In-service undersea telephone cables, including fiber optic cables with branch lines, can also be used to determine the motion-induced voltages between the cable sea-Earth grounds because the repeaters in these cables are powered by a nearly constant electric current, the return path for this current is through the ocean via the sea-Earth grounds, and the power voltage and current are readily measured at the cable station or stations. Ocean voltages between West Palm Beach, FL, and Eight Mile Rock, Grand Bahama Island, observed since 1985 by use of an in-service cable yield monthly estimates of the Florida Current transport with an r.m.s. accuracy of 1.1 Sv when compared with the monthly voltage-derived transports between Jupiter, FL, and Settlement Point, Grand Bahama Island, observed by the use of an abandoned cable. This corresponds to an accuracy of 3% of the mean transport of 32.3 Sv