Approximation for the Inverse Speed of Sound in Seawater, Suitable for Assimilating Acoustic Tomography Data into Numerical Models

Abstract

An approximate formula for the reciprocal speed of sound in seawater is obtained in the form of a polynomial that is cubic in potential temperature, and quadratic in pressure and salinity. The expression provides a reformulation of Del Grosso's empirical formula for the speed of sound in seawater in terms of salinity, pressure, and potential temperature, which are the basic thermodynamic parameters describing oceanic state in numerical models. This makes the proposed approximation convenient for constraining the acoustic tomography data by dynamics.