Resuspension during Storms: Deployment of Gliders as Part of the ONR-OASIS Effort and a Retrospective Analysis

Characterizing in situ water turbidity is critical to numerous naval operations. In particular, water column turbidity impacts the efficacy of sensors that use optical measurements for a variety of purposes including laser detection of mines and prediction of the operational detection horizon for bioluminescence and diver visibility algorithms. Nepheloid layers, are optically significant and represent a nearly universal turbid feature in the coastal ocean. The maintenance of these nepheloid layers is regulated by the resuspension of material and the relative rates of aggregation and disaggregation. Aggregation and disaggregation rates depend on sediment concentration and turbulence in the water column, which in turn are functions of the wave and current shear stresses at the seabed, the distance from the bottom, and the stratification. Additionally, alternative mechanisms recently observed are associated with storm and tidally induced buoyancy instabilities. Finally, sea floor topography can play a major role in the formation and maintenance of the nepheloid layers. Given these processes, optical and physical data is required in both space and time over a range of sea states. Our long-term goal is to develop a coherent understanding of the dynamics and optics of nepheloid layers. To accomplish this, particle composition characteristics will be resolved with the relevant physical forcing mechanisms across a wide range of time and space scales.