RAFOS Float

RAFOS FLOATS IN THE MEDITERRANEAN - The trajectories of four different floats are shown in the formation of Mediterranean eddies, also known as "meddies" off the southwestern corner of the Iberian Peninsula. The floats were released in 1993 to 1994 south of the Iberian Peninsula into the Mediterranean undercurrent. This is a subsurface current that carries salty water from the Mediterranean (which has left through the Strait of Gibraltar) along the continental slope of the Iberian Peninsula.

Near Cape St. Vincent, the floats started looping rapidly in the clockwise direction, with periods of rotation between two and seven days. This looping motion indicates that the floats were caught in the formation of new meddies near Cape St. Vincent. Some floats were trapped near the center of a meddy, and thus rotated more rapidly and with smaller loops, while others were entrained near the periphery of a meddy and thus rotated more slowly and with larger loops.

The floats are tracked underwater acoustically (as described elsewhere on this site). Sometimes acoustic transmissions are not heard by the float, resulting in a gap in the float's trajectory, when tracking was not possible. Although meddies had been discovered in the open Atlantic earlier, and recognized as important in the spreading of Mediterranean water in the Atlantic, these float trajectories represent the first observations of the formation of meddies. Knowing where meddies form is the first step to understanding why they form and how often. Based on these observations, it is now thought that the sharp corner in the coast at Cape St. Vincent is important in meddy formation. (Illustration by Jayne Doucette, WHOI)