Glider-Based Active Acoustic Monitoring of Currents and Turbidity in the Coastal Zone

Abstract

The recent integration of Acoustic Doppler Current Profilers (ADCPs) onto underwater gliders changes the way current and sediment dynamics in the coastal zone can be monitored. Their endurance and ability to measure in all weather conditions increases the probability of capturing sporadic meteorological events, such as storms and floods, which are key elements of sediment dynamics. We used a Slocum glider equipped with a CTD (Conductivity, Temperature, Depth), an optical payload, and an RDI 600 kHz phased array ADCP. Two deployments were carried out during two contrasting periods of the year in the Rhone River region of freshwater influence (ROFI). Coastal absolute currents were reconstructed using the shear method and bottom tracking measurements, and generally appear to be in geostrophic balance. The responses of the acoustic backscatter index and optical turbidity signals appear to be linked to changes of the particle size distribution in the water column. Significantly, this study shows the interest of using a glider-ADCP for coastal zone monitoring. However, the comparison between suspended particulate matter dynamics from satellites and gliders also suggests that a synoptic view of the processes involved requires a multiplatform approach, especially in systems with high spatial and temporal variability, such as the Rhone ROFI area.

Accuracy of high resolution coastal flow speed simulations during and outside of wind, wave and stratification events (Gulf of Lion, NW Mediterranean)

“…Acoustic Doppler Current Profiler, ADCP), but single point measurements are still common (Schroeder et al, 2013;Durrieu De Madron et al, 2019). ADCPs which were previously only deployed at fixed moorings (Guizien et al, 1999) are now being mounted on the hulls of ships (Système Acquisition Validation Exploitation de Données des Navires de l'INSU -Projet SAVED https://sextant.ifremer.fr/record/6f6e95e9-8e97-48d6-b536-b40f2ad87402/, accessed 04/06/2021) or on autonomous underwater vehicles (Dohan et al, 2010;Bourrin et al, 2015;Gentil et al, 2020).…”