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

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.