New permittivity measurements of seawater

We have measured the permittivity of representative samples of natural seawater, synthetic seawater, and aqueous NaCl solutions over the frequency range 3-20 GHz, in 0.1-GHz steps and over the temperature range -2 degrees-30 degrees C in 1 degrees steps. Additional measurements have been made at spot frequencies (23.8, 36.5, and 89 GHz) and at selected temperatures between -2 degrees and 30 degrees C. The data from these measurements have allowed us to deduce an interpolation function for epsilon(nu, t, S) in the ranges 2 less than or equal to nu less than or equal to 20 GHz, -2 degrees less than or equal to t less than or equal to 30 degrees C, and 20 parts per thousand less than or equal to S less than or equal to 40 parts per thousand with a precision of 1%. If the frequency range is extended up to 40 GHz, the precision of the interpolation function is about 3%. The data have also allowed us to compare the permittivities of natural seawater, synthetic seawater, and aqueous NaCl solution with the same salinities. Natural and synthetic seawater have the same permittivities within a 1% experimental error estimate. An aqueous NaCl solution has a significantly different permittivity (up to about 6% difference, depending upon the frequency and temperature).