Monitoring Dissolved Oxygen in New Jersey Coastal Waters Using Autonomous Gliders: Multi-year Trends and Event Response

While low Dissolved Oxygen (DO) concentrations are not uncommon in the coastal ocean, what is less understood is how the location and size of these low DO regions vary and what impact that variability has on ecosystem health. Therefore, alternative sampling strategies are needed to continuously map these low DO areas in a way that quantifies this variability. This project applies a series of Autonomous Underwater Vehicle (AUV) deployments from Sandy Hook to Cape May, NJ from 2010 to 2016 to address this need by mapping the subsurface DO concentration in near real-time within the near coastal ocean. The scales of variability of the DO concentration observed over these seven seasons were on the order of 60-80 km in space and 3-4 days in time. The strongest gradients were observed across the thermocline with surface waters usually much more oxygenated than the bottom waters. The occurrence of dangerously low DO was highly variable across the region with a tendency for the lowest values in the northern region last in the season. Based on these missions, we have begun to sample the dynamic coastal ocean environment at the scales of known variability. The results show that while there are persistent patterns in the dissolved oxygen fields off our coasts, rapid changes can occur with varied effects across the region.