Observing Plumes and Overturning Cells with a New Coastal Bottom Drifter

A new platform, the Coastal Bottom Drifter, was designed and built to observe near-bottom environments in coastal regions. It is capable of observing properties by drifting near the bottom with a prescribed clearance or at a constant depth of up to 300 m. The platform can observe physical and biochemical parameters, such as temperature, salinity, oxygen, and velocities, and has the capacity to carry additional sensors to measure, for example, pH, turbidity, and nutrients. In addition, it can profile to the surface at chosen intervals and can be deployed for days or up to several months. The integrated Iridium communication allows the user to receive positions and data while the platform is surfaced, as well as send new missions to the instrument. The use of an acoustic bottom-tracking device allows the construction of a drifter trajectory while providing information about ocean circulation. Additionally, the ADCP provides information about suspended particles and possible sediment transport. These measurements are valuable in understanding coastal environments as well as the dominant physical processes that cause mixing and set the conditions for local biological activity. An example deployment in Apalachicola Bay shown in this study demonstrates the ability of the drifter to observe small-scale features, such as overturning cells and plumes of dense water, that are caused by local topography.