Tracers and modeling

The major tracer activity of the last four years was the completion in 1983 of a survey of the North and Tropical Atlantic begun in 1981 as part of the Transient Tracers in the Ocean (TTO) project (Brewer, et al., 1985). An early set of papers (Brewer et al., 1983, and Swift, 1984) discussed evidence from these observations for the freshening of the North Atlantic due to cessation of overflow across the Iceland‐Scotland ridge in the period between Geosecs and TTO. Broecker et al. (1985a) examined observations further south within the deep Northeastern Atlantic and showed that there was no change of nutrient contents in this region during the same time span, consistent with their conclusion that there is no ventilation of this region from the north. Kawase and Sarmiento (1985 and 1986) used the TTO data to produce a series of nutrient and salinity maps and property‐property plots on density surfaces in the thermocline and middepth waters. Of particular interest in these studies is the evidence from silica‐salinity observations of strong cross‐isopycnal mixing and advection in the equatorial region.