Is There the Equatorial Water Mass in the Atlantic Ocean?

Abstract

Using temperature and salinity profiles from the Argo data repository, a detailed volumetric temperature-salinity diagram is compiled for the upper 2,000 m layer of the Atlantic Ocean. It is generally accepted that, unlike the Pacific and Indian Oceans where the Equatorial Water is present, there is no Equatorial Water in the Atlantic Ocean and its place is occupied by the South Atlantic Central Water (SACW). However, the detailed volumetric T-S diagram shows that the main thermocline in the latitude range of 10°S–10°N is characterized by its own tight T-S relationship which is relatively close to but clearly distinguishable from the tight T–S relationship of SACW in the latitude range of 10°S–40°S. We argue that the Atlantic Equatorial Water can be considered as a separate water mass which is probably formed by isopycnal mixing of SACW and the North Atlantic Central Water (NACW) in proportion approx. 3.5:1.