Flow structure and transport in the Yucatan Channel

The direct ocean current observations across the Yucatan Channel collected during the Canek program allow the best description to date of the exchange between the Caribbean Sea and the Gulf of Mexico. A net transport of 23.8 ± 1 Sv (1 Sv = 106m3s−1; 95% confidence interval) flowed through the Yucatan Channel from the Caribbean Sea into the Gulf of Mexico, during the period between September 1999 and June 2000. This is about 20 percent less than the 30 Sv accepted as the nominal transport of the Florida Current, and less also than the 28 Sv assumed for Yucatan in closing the transport budgets for Caribbean passages. The discrepancy may be an imbalance due to fluctuations in the transports through other passages of the system, especially the Old Bahama and Northwest Providence Channels, which remain poorly known. Our data corroborate the principal features of the flow through the Yucatan Channel: The northerly surface Yucatan Current and its southerly Under‐current off Mexico, and the southerly surface Cuban Counter‐current near Cuba; but previously unobserved mean currents are found to exist at depth, especially on the eastern side of the channel. Fluctuations seen in the deep flows are related to volume anomalies over the Gulf of Mexico. A transport through the Yucatan Channel smaller than previously thought has significant implications for the dynamics of the Gulf of Mexico and its modeling, since this transport is the principal forcing of its circulation. The circulation budgets in the Western Subtropical Atlantic should be revised considering these new results.