Hydrography of the Central and Western Gulf of Mexico

This study describes in detail the water masses of the Gulf of Mexico (GoM) west of 88°W based on their thermohaline properties and dissolved oxygen concentration. The existent historical information is complemented with new data from 14 cruises, Argo floats, and over one year of continuous glider monitoring. The results describe the general hydrography of the central and western GoM with focus on the difference between the water properties inside and outside Loop Current Eddies (LCEs). Caribbean Surface Water, Subtropical Underwater, and 18 °C Sargasso Sea Water (18SSW) are exclusive of the LCEs, and they are found along the LCEs preferred path between 23°N and 27°N. Outside the LCEs, the prominent characteristics of these water masses erode, and the Gulf Common Water is ubiquitous in the subsurface. It is shown that the water masses in the GoM need to be described in the frame of the dominant mesoscale features that take place there and that the dissolved oxygen is a key variable to identify some water masses of Caribbean origin as the Tropical Atlantic Central Water and the 18SSW. The previous potential temperature and salinity limits of the water masses within the GoM were revised and redefined in terms of absolute salinity and conservative temperature in the frame of the Thermodynamic Equation of Seawater, 2010 (TEOS‐10). While temperature values after conversion have little variation compared to the previous ones, the absolute salinity is in average 0.2 units greater than the former practical salinity. Key Points A new and detailed definition of the water masses found in the Gulf of Mexico west of 88°W is proposed using TEOS‐10 The Loop Current Eddies are the main source of variability of the water masses below 100 m depth Dissolved oxygen is a key variable to identify and describe some water masses of the Gulf of Mexico like the 18 °C Sargasso Sea Water