Mapping velocity fields in coastal waters using an autonomous underwater vehicle

High resolution spatial and temporal observations are essential in determining mechanisms driving dynamic ocean processes. Mobile oceanographic sensors are often used to observe these processes at spatial resolutions unattainable by cast-based techniques. By undulating the sensor path (seesaw pattern), ocean parameters (e.g., velocity, salinity, colored dissolved organic matter (CDOM)) are profiled synoptically and utilized to characterize the process of interest. We present the methods employed to estimate velocity fields observed by a Doppler Velocity Log (DVL) deployed on an Autonomous Underwater Vehicle (AUV) during two field campaigns at New River, North Carolina, and Huntington Beach, California. In addition, we discuss the utilization of synoptic observations to characterize (1) the mixing region of the New River Inlet discharge during maximum ebb tide and (2) the nearshore discharge region of a wastewater outfall. The AUVs sampling resolution, adaptive sampling capabilities, and suite of instruments were key in determining the mechanisms of these processes.