The large-scale temperature-salinity relationship is the result of numerous processes acting at many spatial and temporal scales. Here, we analyze the role of mesoscale isoneutral stirring and small-scale turbulence dianeutral stirring setting this relationship in the southwest Atlantic Ocean. We use hydrographic and microstructure data collected during the GEOTRACES 40S cruise, between the mid-Atlantic Ridge and the American coast along 40ºS in the framework of a triple decomposition (Garret, 2001; Ferrari and Polzin, 2005). The underlying premise is that large scale variance of potential temperature generated by these two mixing processes is dissipated by molecular processes. Dianeutral velocities are higher near the surface and the bottom layers, especially in those stations near the Mid-Atlantic Ridge or the Brazil Current Overshoot (BC-O) where values approach 10-4 m2 s-1; stations between those two features show the lowest values, of about 0.3 × 10-5 m2 s-1 for all layers. The range of isoneutral diffusivities span at least three orders of magnitude: 102 to 105 m2 s-1 being usually higher in the eastern than in the western BC-O flanks. In almost no layer or station the dianeutral production of temperature variance balances its dissipation, the latter usually being two or more orders of magnitude larger. Our results suggest that isoneutral production by mesoscale stirring is the main factor contributing to the variance production in this region

This research has been supported by the Ministerio de Economía y Competitividad of the Spanish Government through project VA-DE-RETRO (CTM2014-56987-P). Dorleta Orúe-Echevarría has been funded through a FPU contract of the Ministerio de Educación y Ciencia

V Encuentro de la Oceanografía Física (EOF 2018) - V Physical Oceanography Meeting, VI Simposio Internacional de Ciencias del Mar - VI International Symposium of Marine Sciences (ISMS 2018), 20- 22 June 2018, Vigo.-- 1 page

Peer Reviewed