Salinity changes along the upper limb of the Atlantic thermohaline circulation

Lagrangian analyses of a global ocean circulation model quantify the salinity changes experienced by the warm limb of the thermohaline circulation during the northward flow to the Atlantic deep convection regions. 6 Sv out of the estimated 10-Sv transfer from 45 degrees S to 47 degrees N flow through regions of prevailing surface evaporation: the southern and northern formation regions of Salinity Maximum Water and the Gulf of Cadiz/Mediterranean Sea domain. The remaining transport gains salinity through mixing with adjacent waters. As much as 6 Sv flow through the low-salinity surface mixed layer at the latitudes of the ITCZ whose effect annihilates that of the southern region of Salinity Maximum Water. Most of the salinity increase corresponds to the transformation of South to North Atlantic Central Water, with strong diapycnal transfers for the water that intersects the high and low salinity regions, and nearly isopycnal modifications for the water that avoids these regions.