Numerical simulations of mesoscale variability in the Straits of Florida |
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| Authors: | Christopher N K Mooers Jerome Fiechter |
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| Institution: | (1) Ocean Prediction Experimental Laboratory (OPEL), Division of Applied Marine Physics (AMP), Rosenstiel School of Marine and Atmospheric Science (RSMAS), University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149-1098, USA |
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| Abstract: | The circulation in the Straits of Florida is dominated by the throughflow of the Florida Current, as modified by tidal flows,
responses to atmospheric cold front and extratropical cyclone (easterly wave and tropical cyclone) passages in winter (summer),
and intrinsic mesoscale variability due to instabilities of the Florida Current front and jet system. Monthly meanders of
the Florida Current, persistent oceanic fronts associated with the Florida Current’s baroclinic jet, and frontal eddies shed
weekly by the Florida Current are the primary mesoscale features. A limited area model (Princeton Ocean Model: POM) is implemented
to cover the Straits of Florida with a curvilinear grid that resolves the mesoscale structure, especially where the baroclinic
flow is locked to steep topography in a 90 degree bend of the Straits. Florida Current cyclonic frontal eddies are spawned
spontaneously, grow as they translate downstream, interact with shelf waters, and exhibit the same space-time attributes that
characterize their observed counterparts, as evidenced by satellite imagery, shipboard synoptic mapping, coastal HF radar,
and moored time series. Here, a deeper understanding is attempted for the frontal eddy kinematics and dynamics by examining,
for example, their sensitivity to model parameter values, synoptic versus monthly atmospheric forcing, and other determinants
of the flow. The mean flow shears are concentrated along the shelfbreak, where these frontal eddies are trapped, favoring
the formation of the eddies by mean flow instabilities. In particular, it is found that the Florida Current frontal eddies
exist independent of the wind-forcing considered (i.e., no winds, monthly winds, and synoptic (but not mesoscale) winds);
however, they are modulated by the synoptic wind-forcing. Nevertheless, intriguingly, the frontal eddies have the same weekly
time scale as the weather cycle. |
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| Keywords: | Coastal ocean circulation Numerical simulation Model validation Sensitivity studies Mesoscale variability Florida Current |
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