Frontal‐Driven Water‐Mass Transformation in a Western Boundary Current: Evidence From the Yucatan Current

We report the recurrent formation of waters with thermohaline properties similar to Gulf Common Water (GCW) in the western Yucatan Channel, absent upstream in the Caribbean. Mooring observations and a partial submesoscale‐resolving model show that these Yucatan GCW forms locally when the Yucatan Current separates from the slope, intensifying a frontal zone with isopycnal uplift, cyclonic vorticity, and sharp lateral gradients, signatures of submesoscale activity. These conditions favor interleaving and mixing among Caribbean inflow waters within a vertically compressed isopycnal layer. Lagrangian backtracking confirms their local origin, while forward tracking reveals export within cyclonic frontal eddies along the Loop Current periphery. Our findings uncover a previously unrecognized pathway of water‐mass transformation in the Yucatan Channel and highlight its potential implications for Loop Current variability.