High frequency broadband acoustic systems as a tool for high latitude glacial fjord research

Abstract. High frequency broadband echosounders enable the monitoring of complex dynamics, through rapid collection of high resolution, near-synoptic observations of the water column and quantitative geophysical measurements. Here, we demonstrate the applicability and utility of broadband active acoustics systems to improve observational capabilities in high latitude glaciate fjords. These isolated and challenging field locations are a critical environment, linking the terminal end of terrestrial ice sheets to the broader ocean, undergoing complex changes due to accelerated high-latitude warming trends. Using broadband (160–240 kHz) acoustic data, collected in tandem with ground truth measurement from a CTD and microstructure probe, in Hornsund fjord in southwest Svalbard we address three crucial topics: 1) variability of the thermohaline structure and mixing across different temporal and spatial scales, 2) identification and characterization of processes in play at dangerous glacier terminus, and 3) remote estimation of dissipation rates associated with mixing. Through these analyses, we illustrate the potential of broadband echosounders as a relatively low-cost, low-effort addition to experimental field kits, well suited for field deployment in high-latitude fjords where observations are limited by length of season and generally challenging conditions.