Analysis of high-frequency multitone transmissions propagated in the marginal ice zone

Abstract

This work presents estimates of frequency and time coherence functions of acoustic transmissions centered at 50 kHz over a 1-km horizontal underice path in the marginal ice zone (MIZ). The data were collected during the MIZEX ’84 experiment as part of a feasibility study for an underwater acoustic telemetry link. It is shown that the acoustic fluctuations are dominated by a 10-Hz process conjectured due to the turbulent under-ice boundary layer. Significant fluctuation energy in the 0.1-Hz band was also observed. The two processes differ in frequency coherence characteristics. An underwater telemetry system designed for this channel will be dominated by the high-frequency fluctuations, but the slower process is capable of causing disastrous data losses unless its effects are anticipated.