Baroclinic flows, transports, and kinematic properties in a cyclonic‐anticyclonic‐cyclonic ring triad in the Gulf of Mexico
Authors: Vidal Víctor M. V. , Vidal Francisco V. , Hernández Abel F. , Meza Eustorgio , Pérez‐Molero José M. 
Published: February 2004

During October‐November 1986 the baroclinic circulation of the central and western Gulf of Mexico was dominated by an anticyclonic ring that was being bisected by two north and south flanking cyclonic rings. The baroclinic circulation revealed a well‐defined cyclonic‐anticyclonic‐cyclonic triad system. The anticyclone's collision against the western gulf continental slope at 22.5°N, 97°W originated the north and south flanking cyclonic rings. The weakening of the anticyclone's relative vorticity, during the collision, was compensated by along‐shelf north (26 cm s−1) and south (58 cm s−1) jet currents and by the anticyclone's flanking water mass's gain of cyclonic vorticity from lateral shear contributed by east (56 cm s−1) and west (42 cm s−1) current jets with individual mass transports of ∼18 Sv. Within the 0–1000 and 0–500 dbar layers and across 96°W the magnitudes of the colliding westward transports were 17.80 and 8.59 Sv, respectively. These corresponding transports were 85 and 94% balanced by along‐shelf jet currents north and south of the anticyclone's collision zone. This indicates that only minor amounts (<15%) of the anticyclone's colliding westward transports might have flowed into the western gulf's continental shelf water mass or else they sank into deeper water along the continental slope during the anticyclone's collision event. The resultant effect of the coupled interaction between the anticyclone and the cyclonic pair was the surging of the water mass in the cyclones and its sinking in the anticyclone. This mechanism controlled the magnitude, direction, location of vertical advection, and transfer of kinetic energy from the upper to the deeper water layers. Our vertical transport estimates through the 1000‐m‐depth surface revealed a net vertical descending transport of 0.4 Sv for the ring triad system. This mass flux occurred primordially within the south central gulf region and most likely constituted a principal mechanism that propelled the gulf's deep horizontal circulation. The volume renewal time is ∼5 years for the ring triad system within 0–1000 dbar. The volume renewal time for the gulf's deep water layer (2000–3000 dbar), estimated as a function of its horizontal outflowing mass flux (1.96 Sv), is of the same order of magnitude and reveals that the deeper layer of the Gulf of Mexico is as well ventilated as its upper layer (0–1000 dbar). The ring triad's surface kinematic properties were derived from the sea surface baroclinic circulation field referenced to 500 dbar. Within this layer, individual ring geometries were conserved. Maximum tangential ring velocities were 60 and 58 cm s−1, for the north and south cyclones respectively, and 30 cm s−1 for the anticyclone. The corresponding periods of revolution were 16, 19, and 26 days, and vertical velocities calculated at the rings' peripheries, where maximum horizontal divergence was encountered, were 1.5, 1.0, and −1.0 m d−1.