The Gulf Loop Current is that portion of the Gulf Stream System which connects the Yucatan Current and the Florida Current in the eastern Gulf of Mexico. An experiment to test the annual cycle proposed by Leipper (1970) was conducted from August, 1972, through September, 1973. Twelve pathlines of the 22°C isotherm at 100 meters depth were made from Yucatan to the Florida Keys at 36-day intervals in conjunction with a satellite oceanography project....