Resource Assessment

Regional Oceanic Modeling

Led by Mingshun Jiang, Ph.D.
Affiliated Home Campus: Harbor Branch
Affiliated Department: Harbor Branch Oceanographic Institute
REU Scholar: Rhys Tallentire
REU Scholar Home Institution: University of California-San Diego

The waters in the Florida Straits are an ideal candidate for ocean current turbines due to the Florida Current’s fast flow speed, and consistent direction. However, due to the strong instability of the currents produced by the shear of the Florida Current and its interactions with the topography, mesoscale- and submesoscale-eddies with sizes > 10 km often spawn and/or propagate through the areas. These eddies change the strength and/or direction of the current, sometimes even reversing the flow, resulting in significant changes of available power. Thus far, characterization of the kinetic power able to be harnessed by ocean current turbines has been performed by relatively low resolution (> 1.5 km) models. On the other hand, data gathered from instruments, while accurate, is not practical due to typically long deployment times, high costs needed and limited spatial coverage (e.g. a few mooring stations). To remedy the limitation of grid resolution in current models, a nesting modeling technique is implemented to an existing hydrodynamic model based on the Regional Oceanic Modeling System (ROMS) that has a 1.5 km grid resolution. With this technique, a 500-m resolution child model for a focused area (northern Florida Straits) was developed and nested inside the coarse resolution (1.5 km) parent ROMS model, which covers a much larger domain including the south Florida shelf and entire Florida Straits. Two nesting techniques were tested, first, one-way nesting in which the parent model provides boundary conditions to the child model only, second, two-way nesting where the child model also provides feedback to the parent model. The nested models ran from September until December of 2011 with the objectives of understanding and quantifying the impacts of higher resolution simulation on the eddy frequency, magnitude, and power density. Average predicted power density was similar across all models irrespective of the nesting types. Despite this, at a given instance in time each nesting often predicted differing power density and eddy occurrence especially towards the later period (Nov. - Dec.) of the simulations. Model performance was gauged using in-situ data collected from two different moorings deployed at 250 m and 312 m water depth, offshore off Miami in 2011-2012, covering the same model period. These models could potentially be used to optimize design and identify optimal locations for ocean current turbines in Florida.

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