The increase in atmospheric CO2 of approximately 50 ppm from the mid-nineteenth century to 1972 has led to a corresponding increase in the pCO2 of sea water. The record of this increase is present in the oceanic water masses, though the signal is obscured. By observing the alkalinity and total CO2 concentration within a water mass, and stripping off the perturbations of the CO2 system due to respiration, carbonate dissolution and nitrate addition, the original atmospheric equilibration signal may be recovered. The application of these calculations to GEOSECS (1972) data from the core of the Antarctic Intermediate water reveals propagation of the atmospheric CO2 signal northwards.