Southwest subtropical pacific surface water radiocarbon in a high-resolution coral record

We have generated a high-resolution coral Delta C-14 record from the southw est subtropical Pacific spanning the last 50 yr. Prebomb (1950-1956) Delta C-14 values average -52 parts per thousand. Values begin to increase in 195 7, reaching a maximum in the early 1970s, about 10 yr after the atmospheric peak. There is a consistent 10-15 parts per thousand seasonal cycle whose relationship with vertical mixing evolves as a consequence of the penetrati on of the bomb transient into subsurface waters. Comparison of this record with that simulated in an ocean general circulation model highlights the di fficulty in modeling vertical exchange processes.