labs_title

Caldeira Lab Research:Ocean acidification and ocean carbon cycle

A three-dimensional model calculation of ocean uptake of bomb 14C and implications for the global budget of bomb 14C

Philip B. Duffy & Ken Caldeira

In two papers published previous to this one, it was suggested that there is an imbalance in the global bomb radiocarbon budget - i.e. that there is more radiocarbon inventory than there are radiocarbon sources. However, inventory levels were calculated using a fairly simple one-dimensional model. It is shown here that when calculated using a more complex three-dimensional model, ocean inventory of radiocarbon is much smaller and the imbalance is not statistically significant.


Duffy, P.B., and K. Caldeira, A three-dimensional model calculation of ocean uptake of bomb 14C and implications for the global budget of bomb 14C, Global Biogeochemical Cycles 9, 373–375, 1995.

Ocean inventory of radiocarbon: Radiocarbon inventory in the ocean previously predicted by one dimensional models (top and middle curves) and the three dimensional model used in this study (bottom curve). The three dimensional model shows much lower radiocarbon inventory, suggesting no imbalance.

Abstract

Two recent papers have suggested that there is an apparent imbalance in the global bomb 14C budget. These results are based in part on calculations made using simple one dimensional ocean models. We recalculate the ocean inventory of bomb 14C using a three-dimensional ocean general circulation model, and find a significantly smaller inventory after about 1980 than in previous one-dimensional model estimates. Our new estimate of the ocean inventory implies that the apparent imbalance in the global budget of bomb 14C is smaller than previously thought and is not significantly different from zero. In addition, we use our three-dimensional model to obtain whole ocean inventories of bomb 14C during the Geochemical Ocean Sections Study (GEOSECS) period; these inventories can be used as benchmarks in calibrating one-dimensional ocean models.