The influence of vertical and lateral turbulence on the characteristics of the waters at mid‐depths

In a previous paper (Iselin 1936) the writer considered that the temperature and salinity of the main thermocline layer (400–1200 meters) in the Sargasso Sea were mainly determined by vertical turbulence. At that time special significance was attached to the very consistent temperature‐salinity correlation at mid‐latitude stations from the western North Atlantic. Thus, when plotted on a temperature‐salinity diagram, the great majority of the modern observations fell along a narrow and slightly curving path connecting the characteristics of the superficial layer with those of deep water. The fact that in the main thermocline the temperature‐salinity correlation was somewhat fresher than a pure mixture of deep water and surface‐water was thought to result from the inflow of relatively large volumes of subantarctic intermediate water which appeared to enter the Sargasso Sea in two ways. First, this low‐salinity layer seemed to penetrate northward across the Northern Equatorial Current at mid‐depths and second, a considerable volume of it was observed leaving the Florida Straits to be, discharged into the Sargasso Sea along the southern edge of the Gulf Stream. In short, lt was considered that the negative salinity‐anomalies brought to the Sargasso Sea by the subantarctic intermediate layer more than counteracted the positive anomalies arriving at similar depths from the westward flow of water carrying Mediterranean characteristics.