Water mass and tracer analysis of the deep flow in the Atlantic Ocean

Abstract

The THC is essentially a meridional, vertically overturning circulation system with its sources of deep and bottom water at high latitudes, both in the northern and the southern hemisphere. A useful way to study the THC, following the example set by the German oceanographer Georg Wüst (1935), is the analysis of meridional vertical sections of the tracers potential temperature, θ, and salinity, S. Both parameters are conservative, which means that outside the direct influence of air-sea interaction in the upper ocean the salinity and potential temperature of a water particle only change due to mixing. The conservation of potential enthalpy is fundamentally a better approximation of the first law of thermodynamics (Fofonoff 1962; McDougall 2003), but for most oceanographic applications the conservation of potential temperature and of salinity function quite well. The “spreading path” of the cold deepwater, formed in high latitude source regions, often is derived from sections of potential temperature and salinity by a combination of intuition and physical reasoning. In this section we start, as an example, with the distribution of potential temperature and salinity in the Atlantic Ocean, since the main sources of deepwater, both arctic and antarctic, are found in that ocean.