School for Marine Science & Technology at UMass Dartmouth

SMAST East 101-103 and Via Zoom Abstract: A GIS-based census of Gulf Stream (GS) cyclonic eddies was compiled using synoptic oceanographic analysis charts of the GS and its mesoscale eddies and filaments. The charts employ SST, altimetry, and field observations to map the path of the GS, 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 GS extension and 33N. Dates of birth and demise for cyclonic eddies from 2000-2019 reported by Silver et al. 2021 was the reference to begin this census, which now details digitized location and size of cyclonic eddies and other key parameters such as annulus and inner core areas. Findings suggest different cyclonic eddy formation types: pinch-off ring, hook-type eddy, and Sargasso cyclonic eddies. Pinch-off rings form from a GS meander through amplifying, then encircling Slope Sea water and eventually detaching from the GS as a cyclonic cold-core ring in the Sargasso Sea. Hook-type eddies form from a southward extending filament of the GS's southern flank 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. Analyses of the census showed that the formation of cyclonic eddies peaks in Spring. Hook-types are observed most often, followed closely by pinch-off rings and Sargasso eddies. Hook-types form preferentially west of the New England Seamount Chain, while pinch-off rings often occur over and east of the Chain. Using this new census as well as SST and Argo float data over the last two decades, the spatial distribution, vertical structure, seasonality, interannual variability, size, and lifespan of cyclonic eddies in the Gulf Stream-Sargasso region is examined.

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