Upper-layer circulation in the approaches to Yucatan Channel

The Yucatan Current originates where the Cayman Current turns northwards off the Mayan coast. The latitude at which the current meets the coast fluctuates every few months from the Mexico-Belize border to the island of Cozumel, modulating the currents near the coast. A two-year measurement program recorded the Yucatan Current transporting close to 23 Sv, smaller than the classical value for the Florida Current off Miami, so parts of the Florida Current must flow through Windward Passage or bypass the Caribbean entirely. The velocity fluctuations of the Yucatan Current are larger than the mean everywhere except in its core, and have been attributed mostly to the passage of eddies. About one fourth of the Yucatan Current flows through Cozumel Channel, where significant ageostrophic episodes have been recorded, related to the curvature of the currents entering the channel, and caused possibly by the passage of large mesoscale features. The current also appears to shift laterally, including reversals of the southerly Cuban Countercurrent on the eastern side of the channel. The proper observation of eddies passing offshore might shed better light on the nature of current fluctuations and on the triggering of Loop Current eddies, but they remain elusive even in their bulk integral characteristics, as both the instrumentation deployed and remote sensors appear insufficient to resolve them. A construction of pseudo-streamlines from moored observations is used to signal large eddies passing through the channel.