R. A. Green, P.A. Rafter, C. Sun, W. R. Gray, J. W. B. Rae, M. Pelly, C. Xu, K. Thirumalai, J R Southon, F. Pavia, M. P. Hain
Abstract There is currently no explanation or carbon cycle model scenario for severe radiocarbon ( 14 C) depletion reconstructed in the intermediate depth eastern tropical North Pacific Ocean (ETNP) at the end of the last ice age. Here, we develop new constraints on hypothesized geologic carbon release based on the boron isotope pH proxy and regional refinement of a global carbon cycle model. We find that pH‐neutral release of ∼800 Pg C over 5,000 years can produce the radiocarbon anomalies in the ETNP while inducing neither a large pH anomaly nor CaCO 3 dissolution (as observed) and causing minimal atmospheric CO 2 rise. Mass‐balance considerations dictate that the anomalous carbon was concentrated near the geologic source in the ETNP without significantly affecting radiocarbon‐based reconstructions of global ocean circulation change.