Abstract
A GIS-based census of Gulf Stream cyclonic eddies was compiled using synoptic oceanographic analysis charts of the Gulf Stream and its mesoscale eddies and filaments. The charts employ SST, altimetry, and field observations to map the path of the Gulf Stream, location and size of warm and cold eddies, and adjacent filaments. This census accounts for all cyclonic eddies from 2000-2022 in the Sargasso Sea between the Gulf Stream extension and 33°N. Findings suggest three different cyclonic eddy formation types: pinch-off rings, hook-type eddies, and Sargasso cyclonic eddies. Pinch-off rings form from a Gulf Stream meander trough amplifying, then encircling Slope Sea water and eventually detaching from the Gulf Stream as a cyclonic cold-core ring in the Sargasso Sea. Hook-type eddies form from a southward extending filament of the southern flank of the Gulf Stream establishing as a hook-like entity cyclonically encircling a body of Sargasso Sea water at its core. Sargasso cyclonic eddies are isolated from the Gulf Stream and occur in the Sargasso Sea. Using this new census as well as SST and Argo float data over the last two decades, the spatial distribution, vertical structure, annual and seasonal variations, size, and lifespan of cyclonic eddies in the Gulf Stream-Sargasso region were examined. From the census, 299 hook-type eddies, 133 pinch-off rings, and 143 Sargasso cyclonic eddies were identified. Hook-type eddies are formed off the southern flank of the Gulf Stream between 75˚W and 55˚W, pinch-off rings occur over and east of the New England Seamount Chain, and Sargasso cyclonic eddies form throughout the region of the Sargasso Sea. The vertical structure of different eddy types was characterized using available Argo float temperature and salinity profiles. The water masses associated with hook-type and Sargasso cyclonic eddies have shallow thermoclines (~100-200 m) while the thermocline in pinch-off rings are deeper (~400-500 m). The formation of cyclonic eddies peaks in the spring when hook-type eddies show the strongest seasonal peak signal. Pinch-off rings and Sargasso cyclonic eddies appear to have no seasonal cycle. On average, 25 cyclonic eddies are formed in a year. The size and lifespan of the three formation types have a great deal of variability which warrants future investigations.