A measurement and interpretation of the temporal coherence of acoustic continuous wave propagation in the Barents Sea

Abstract

As part of the Barents Sea Polar Experiment in the summer of 1992, a continuous wave transmission at 224 Hz was made for 1 h from a near-bottom-moored source to a navigated, vertical array separated by approximately 35 km. The waveguide was approximately 200 m in depth, and its oceanography was dominated by the Barents Sea Polar Front separating the cold, fresh polar water from the warm, saline Atlantic water and a strong thermocline due to surface insolation. Following the methods described by Dahl etal. [J. Acoust. Soc. Am. 83, 2175–2179 (1988)], the variance of the phase rate (ν2) is found for single hydrophones, for beam-formed (plane wave) data, and for mode-formed data. The parameter ν governs the frequency spread and is a measurement of the dynamic effects of the ocean on acoustic propagation. The estimates of ν are related to measured ocean temperature fluctuations and sea surface conditions from the experiment and compared with estimates from the MIZEX data of Dahl etal. The implications of the measurements for sonar system performance including matched field and matched mode techniques are presented. [Research supported by ONR Code 322, High Latitude Dynamics.]