ABSTRACT
The Gulf of Mexico is a small ocean substantially enclosed by land. It is microtidal, with most shelf areas having tides of <0.5 m although values of 1 m are attained along part of the Florida coast. As it lies between latitudes 18 and 30° N the climate is tropical to subtropical. Salinities are 35-36‰ except along those parts of the northern shelf under the influence of the Mississippi input of fresh water. Surface-water temperatures range from −17 to 29 °C and a surface mixed layer extends down to −100 m. Beneath this, from 100 to 300 m, is Subtropical Underwater with salinities of 36.2-36.6‰, temperature of 10-25 °C and oxygen of 3.8-3.4 ml l-1 (Nowlin 1971).
