Transient tracer measurements have been a major factor in identifying the DWBC core and confirming the fast responses along the western boundaries of the oceans to formation processes at high latitudes. The early transient tracer measurements in recently formed NADW and in the DWBC have had a significant impact in terms of demonstrating that these data could be used to estimate the rate of the thermohaline circulation. Data in these publications [e.g. Roether and Munich, 1972; Östlund et al., 1974; Roether and Munich, 1974; Jenkins and Clarke, 1976] were used to show the NADW spreading equatorward as a transient tracer maximum.