The design of an instrument to measure vertically averaged oceanic currents using geomagnetic electric fields

Abstract

A bottom mounted electromagnetic current meter measures the vertically-averaged conductivity-weighted velocity. This measurement complements free-fall relative velocity profiles and is valuable for transport determination and dynamics studies. Such an instrument has been designed to measure the three components of the electric field, Ex, Ey, and Ez. Salt bridges used with switched electrodes permit the induced e1ectromotive forces to be measured with only a short baseline; eight foot arms are planned. The first part of this report covers the theory behind the bottom mounted electric field meter. The second part discusses the design of the instrument as well as a brief description of the prototype bottom mounted electric field meter.