Mobile Bay Estuary Acoustic Field Experiment

Prepared for: The Office of Naval Research, Code 32, and the Office of Naval Research GlobalThe Mobile Bay Estuary Acoustic Field Experiment 2021 (MBE2021) was funded by the Office of Naval Research (ONR) as part of the multi-university Undersea Remote Sensing (USRS) program directed by Dr. Reginald Beach (ONR 322). During the experiment, environmental and acoustic data were collected during June 9-15 in the vicinity of the mouth of Mobile Bay, focused on assessing the impact on acoustic propagation by the tidal intrusion front during flood and the ebb plume front during ebb. This report documents details of the equipment used by the Naval Postgraduate School during the study and presents initial findings. Initial findings indicate (a) that rather than being limited to a surface layer, bubbles are present through the entire water column in the "Dixey V", the persistent feature near Mobile Point formed by the convergence of seawater in the bay mouth during flood; (b) bottom currents in the bay mouth exceed 1 m/s; and (c) the bubble clouds in the Dixey V contribute to effective sound speeds well below the intrinsic sound speed of bubble-free seawater. Results of ongoing analysis will be published in peer-reviewed scientific journals.The Office of Naval Research, Code 32Office of Naval Research GlobalN0001420WX00287Approved for public release; distribution is unlimite