Observations of a loop current frontal eddy intrusion onto the West Florida Shelf

Abstract

Hydrographic and satellite data from the west Florida shelf between April 1–7, 1982 showed the intrusion of a Loop Current frontal eddy onto the shelf. Data were examined to describe the structure of this feature and study effects of its intrusion on water masses in the outer shelf region. A frontal eddy, consisting of a warm filament separated from the main current by a region of cooler water, propagated southeastward at 30 cm/s intruding onto the shelf near 26°N between April 4 and 6. Temperature‐salinity (T‐S) properties revealed that water in the filament was Loop Current water that had been contiguous with 80 m deeper Loop Current water in the main body of the current; water in the cold region was Continental Edge water, a transitional water mass with cooler, fresher T‐S characteristics. Upwelling of deeper Loop Current water occurred under this region, and elevated nutrient concentrations were found in the upwelled dome under the cold region. Interleaving occurred along water mass boundaries enabling the exchange of heat and salt. This mixing and the supply of cool, nutrient‐rich water to the outer shelf was the major consequence of the intrusion. The length scale and speed of this Loop Current frontal eddy was similar to Gulf Stream frontal eddies through the upwelling was not as intense as in intrusions of Gulf Stream frontal eddies.