Circulation and water mass distribution in the Gulf of Mexico.

Abstract

Oceanographic data collected by the "Alaska" and the "Jakulla" in the Gulf of Mexico from 1951 to 1955 are analyzed. The circulation of the upper layer is greatly influenced by the wind drift, as seen in the location of the low salinity water. According to seasonal change of the temperature and salinity, the water mass in the upper layer is classified into five types: three coastal and two off-shore. The statistical T-S oxygen-density and phosphate-density Oceanographic data collected hy the "Alaska" and the "Jakulla" in the Gulf of Mexico from 1951 to 1955 are analyzed. The circulation of the upper layer is greatly influenced by the wind drift, as seen in the location of the low salinity water. According to seasonal change of the temperature and salinity, the water mass in the upper layer is classified into five types: three coastal and two off-shore. The statistical T-S oxygen-density and phosphate-density correlations show little difference between the western and eastern parts in the layer deeper than 1,000 m. In the intermediate layer, however, the difference between two parts becomes more distinct due to the water flowing in the eastern part through Yucatan Channel. Semi-permanent anticyclonic gyres are found in the eastern part on dynamic topography, sigma-t surfaces and isotherm pattern at 200 m depth, These vortices seem to be in contact with the flow through Yucatan Channel occasionally. Comparison with the Japan Sea suggests that vertical convection is more intense in that sea, where the water mass of uniform nature spreads widely in the intermediate and deep layer. Three dynamic problems are discussed in the appendices. Firstly, the wind drift in a circular basin with a shelf is derived and applied to the Gulf of Mexico. The results indicate a good agreement with observed seasonal change of the circulation in the upper layer of the Gulf of Mexico manifested by patterns of isohalines. Secondly, the vertical profiles of the temperature and salinity in the upper layer are explained by solutions of the equation of eddy diffusion and advection of heat and water mass. Thirdly, meandering of the Yucatan Current, and horizontal stability of gyres are discussed.