Canek: Measuring Transport in the Yucatan Channel

Abstract

The Yucatan Channel is one of the key restrictions of the North Atlantic surface circulation, and also a privileged location to understand the circulation within the Gulf of Mexico and the Caribbean Sea. From September 1999 to June 2000 a set of eight instrumented moorings measured currents and temperatures across the Yucatan Channel. The main result of such measurements, published elsewhere, is that the mean transport amounts to only 23 Sv instead of the 28–30 Sv believed until recently to be a robust value. This result implies the need of an overall review of the other Gulf Stream’s sources. Here we show that the second period of measurements with essentially the same array, from July 2000 to May 2001 is in good agreement with the first period’s mean transport. The correlation functions of both velocity components, in the subinertial band, show 500 m in the vertical and 70 km in the horizontal as the characteristic scales. An array of only fourteen currentmeters, slightly optimized in position, scattered through the section allows an adequate estimation of transport and fluctuations, with a standard error of 0.3 Sv. But an array of even more time series from only three moorings, each consisting of a near-surface, upward-looking ADCP plus two single point currentmeters distributed below, degrades the skill down to 2.5 Sv; this is because each ADCP measures highly correlated series, and the other meters are too far apart, thus producing a poor coverage.

In memory of Pedro Ripa 1946–2001