Druffel,-E.R.M. Decade time scale variability of ventilation in the North Atlantic: High-precision measurements of ` bomb radiocarbon in banded corals. J.-GEOPHYS.-RES.-C- OCEANS. 1989. vol. 94, no. C3, pp. 3271-3285. High-precision radiocarbon data for the upper ocean are presented for banded corals from 2 North Atlantic sites. Dissimilarities between post-1950 records at Bermuda (Sargasso Sea) and the Florida Straits (Gulf Stream) show the different mixing processes. Convective overturn associated with 18 degree water formation during late winter in the northern Sargasso facilitates storage of considerable quantities of bomb radiocarbon at depth, which accounts for the damping of the Delta super(14)C signal at Bermuda during the 1960's. A multibox isopycnal mixing model estimates the ventilation rate of the upper 700 m of the water column in the Sargasso from 1950-83. An inverse model is used; i.e. water mass renewal rate was calculated for the post-bomb period to satisfy the bomb radiocarbon time history in the corals. Sea water radiocarbon data from GEOSECS (1972- 1973) and Transient Tracers in the Ocean (1980-1981) surveys are used to constrain the subsurface radiocarbon values calculated by the model. Water mass renewal in the Sargasso was high during 1963-64, fell in the late 1960s, remaining low during the 1970s. The super(14)C-derived record of water mass renewal precedes by about 4 yr that derived from isopycnal salinity in the Sargasso, illustrating that coral super(14)C record is controlled to a large extent by ocean circulation rather than atmospheric exchange of CO sub(2).