A three-dimensional global tracer transport model (derived from a general circulation model) simulates geographic variations in atmospheric &Dgr;14C in response to oceanic boundary conditions. Regional atmosphere-ocean 14CO2 fluxes are controlled by regional wind-dependent gas exchange coefficients (E), air-sea pCO2 differences (&Dgr;pCO2) and oceanic 14C/12C deficiencies. We find that various preindustrial oceanic scenarios reconstructed from reasonable sets of such air-sea variables all produce model latitudinal gradients in atmospheric &Dgr;14CO2 (the ''NS &Dgr;14C'') significantly greater than the measured preindustrial NS &Dgr;14C of +4.4¿0.5% (45 ¿N to 45 ¿S), as estimated from pre-twentieth century tree rings. The NS &Dgr;14C is insensitive to regional &Dgr;pCO2 but is strongly contingent on the chosen values for surface ocean &Dgr;14C and E of southern high latitudes (>50 ¿S). The simultaneous seasonality in sea ice extent and high-latitude wind speeds may in part explain the discrepancy between modeled and measured preindustrial NS &Dgr;14C. Terrestrial 14C sinks with longer turnover times (such as peatlands) also potentially may help to reduce the NS &Dgr;14C. With our best estimates for preindustrial surface ocean &Dgr;14C, &Dgr;pCO2, and E values for other regions, we find a ''best fit'' ocean scenario in which the preindustrial southern surface ocean &Dgr;14C is -95¿10%, its &Dgr;pCO2 is 0¿20 ppmv, and its E is 0.088¿0.010 M m-2 yr-1 &mgr;atm-1 (about 20% reduced from the widely accepted value of 0.110). An independent estimate of +6.5¿0.5 kg yr-1 for the net preindustrial oceanic 14C uptake is an important constraint on global mean and Antarctic E. ¿ American Geophysical Union 1995