Abstract :
The post-nuclear time-series curves of Δ14C from corals at different locations in the surface of the Pacific Ocean show a variation in the shape, amplitude and timing of the peak, with the subtropical records peaking first, followed by the western, and then eastern tropical records with lower maxima. This work takes an in-depth look at the processes that shape the time histories of Δ14C in surface waters at different locations in the Pacific. A one-dimensional (1-D) model is used to examine whether convection and diffusion can delay the peaking of the Δ14C time series. Using the three-dimensional (3-D) MIT general circulation model (GCM), the distribution and evolution of Δ14C is simulated “offline” from 1955 onwards at 1° resolution globally. The GCM is used to tease apart the contribution of various processes, viz. advection, air–sea flux, convection and diffusion, to altering the Δ14C content of surface waters at different locations in the Pacific. A time history of 14C column inventories from the model is constructed to examine the role of horizontal advection in supplying tropical locations with 14C much after the peak atmospheric flux. This model analysis supports the idea of 14C-rich waters from the subtropics being transported to the western tropics via the subsurface, and then being advected eastward in the equatorial undercurrent and upwelled in the east.
