Current variability and its relation to sea‐surface topography in the Caribbean Sea and Gulf of Mexico

Abstract

The circulation in the Caribbean Sea and Gulf of Mexico exhibits considerable variability, which manifests itself in the form of changes in the intensity and location of the major currents. These changes in current intensity and location are coupled with changes in the distribution of the sea‐surface topography. Little is known of the temporal and spatial distribution of currents in the eastern Caribbean Sea. Recent direct measurements suggest a complicated current structure with large meanders and eddies; such a structure implies a complicated sea‐surface topography. An anticyclonic gyre, characterized by a rise in the sea‐surface topography, is frequently found in the western Caribbean Sea. The gyre is bounded on the south and west by intense currents. Sea‐surface slopes of 0.4m/200km have been observed across the southern limb of the gyre, the Cayman Current, and 0.5m/100km across the western limb, the Yucatan Current. There appears to be a seasonal cycle in the intensity of this gyre, which implies seasonal variability in the slope of the sea surface. The sea surface can slope 0.5m/ 100km across the northern edge of the Loop Current. Similar slopes are observed across the western and eastern edges of this flow, which “loops” into the Gulf of Mexico. The position of the northern edge anl associated sea‐surface slopes can vary from 24°N to 28°N during a cycle of the Loop Current intrusion. When an eddy detaches from the Loop, the topography becomes more complicated. For example, a sea‐surface topography section through an eddy and Loop Current would, within 500 km, rise 0.5m/100km, fall 0.5m/100km, and then rise again the same amount. Although the Loop intrusion cycle appears to occur every year, the phase of events in the cycle varies considerably. Data are presented which show that the phase of a particular event in the Loop Current cycle, such as maximum penetration, can occur during any season.