# Presentation: 164733

## Sampling SubMesoscale Vortices shoreward of the Florida Current

- Mesoscale (50-100 km) and sub-mesoscale (5-20km) eddies are characteristic features of the narrow coastal regime between the Florida Current and the Keys.  The former have been well known for some time and significantly affect local recruitment and transport processes.  The latter structures became apparent to us only in May 1994 when the Ocean Surface Current Radar (OSCR) was developed concomitantly with a pilot physical-biological sampling survey.  One analysis suggests they are inertial instabilities.  Not only can such frontal eddies redistribute plankton but they can also cause differential growth and/or survivorship depending on eddy dynamics, location, persistence and timing relative to biological processes.   This hypothesis is consistent with the elevated fluorescence and naupliar concentrations we observed.  Both types of eddies affect local recruitment processes by affecting cross-shelf transport and the exchange of coastal and ocean waters.  This hypothesis is consistent with higher larval fish abundances seen in the convergence zones.  Whether purely physical redistribution or biological processes are at work is and open question but in either case these eddies are important in structuring the plankton communities of this subtropical littoral environmental. There is no question that prediction of the particulate field in this system requires a quantitative understanding of the eddies and their effect upon the plankton community.

- P.B. Ortner, S. Smith (RSMAS), G. Hitchcock (RSMAS), T. Lee (RSMAS) and H. Graber (RSMAS)

- Mesoscale eddies in this region typically move downstream at  relatively slow speeds (5-20km/day) and can persist for up to 4 weeks in the middle Keys.  The submesoscale eddies move along the edge of the Florida Current relatively rapidly (20-30km/day).  Given this speed their smaller size and subtlety of the surface temperature, salinity or fluorescence signatures we saw in 1994 they can best be sampled by a fixed mooring array optimally within a region continually scanned by an OSCR system.

- Acoustic and optical data obtained with our prototype high speed integrated plankton sampler show that the convergences and divergences in the velocity fields of the spin-off eddies structure the particulate field

- A pilot experiment of this type was conducted in May 1999. Prior to it, preliminary data had already been obtained using prototype instrumentation at a test mooring near the experimental site. Those data show the passage of a different water mass with a very different particulate load preceded by movements across the position for the front separating that water mass from more typical coastal waters. The source of the anomalous water mass was likely to have been Florida Bay.

- Diver servicing mooring instrumentation during month long May 1999 pilot study. Sensors included an optical particle counter, fluorometer, CTD and Tracor Acoustic Profiler (multiple high frequency) as well as an upward looking ADCP attached at the anchor point. These sensors are duplicated on the AOML Aquashuttle so that Eulerian data can be extended into three dimensional space.

**Photo by Dave Forcucci**

**In-Situ OPC Details**