Study of tidal frequencies using a transatlantic telecommunications cable.

We report the results of determinations of tidal periods from analysis of the voltage induced across an unpowered length of TAT-7 telecommunications cable in the North Atlantic Ocean over an approximately 19 day interval. Particularly prominent tidal components are observed at several frequencies, including those identified as corresponding to the K(1),S(2)M(m), and M(2) components. In addition, a large amplitude component of high statistical significance was observed at a frequency of 3.0051 cpd, approximately one-third the sidereal day. This component possibly corresponds to the K(3) frequency, although the amplitude is very much larger than that expected. The common lunar tides appear to be a minor component of the data. Such cable data can be used for studies and refinement on a global scale of large-scale tidal (ocean and ionosphere) models.