Can deep ocean carbonate preservation history inferred from atmospheric pCO2 account for 14C and %CaCO3 profiles on the Ontong¯Java Plateau?

Bulk 14C and 210Pbexcess measurements were made on box cores from water depths of ~ 2300 and ~4200 m from the equator on the Ontong¯Java Plateau. A sediment mixed layer thickness of approximately 6 cm and a mixing rate of 20¯45 cm2/kyr are inferred from these radionuclide measurements and model simulations of their depth profiles. Using these sediment mixing characteristics, the model is then forced with a deep sea carbonate preservation history derived from an ice core atmospheric pCO2 record, in order to examine whether the derived history can account for depth profiles of 14C age and CaCO3 content from the deep western equatorial Pacific. Results show that 14C and %CaCO3 data from the deep site can be simulated simultaneously with some success using the assumed carbonate preservation history and a time-varying non-carbonate flux function. However, the model is unable to use the same forcing functions to simulate the 14C and %CaCO3 data from the shallower core. These results suggest that local carbonate accumulation is not driven simply by generalized deep water carbonate chemistry inferred from atmospheric pCO2. Potentially important local processes and aspects of the model that may have contributed to the results are also discussed.