Radiocarbon as a thermocline proxy for the eastern equatorial Pacific

• Published in: Geophysical Research Letters
• Main Authors: Rodgers, Keith B., Aumont, Olivier, Madec, Gurvan, Menkes, Christophe, Blanke, Bruno, Monfray, Patrick, Orr, James C., Schrag, Daniel P.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2004
• Subjects: Antarctic; Galapagos; Pacific; Antarc*
• Online Access: http://nora.nerc.ac.uk/id/eprint/164807/; http://www.agu.org/pubs/crossref/2004/2004GL019764.shtml; https://doi.org/10.1029/2004GL019764

An ocean model is used to test the idea that sea surface Δ14C behaves as a thermocline proxy in the eastern equatorial Pacific. The ORCA2 model, which includes Δ14C as a passive tracer, has been forced with reanalysis fluxes over 1948–1999, and the output is compared with a previously reported Galapagos Δ14C record. The model reproduces the abrupt increase in the seasonally minimum Δ14C in 1976/77 found in the data. This increase is associated with neither a shift of thermocline depth over the NINO3 region, nor a change in the relative proportion of Northern/Southern source waters. Rather, it is due to a decrease in the Sub-Antarctic Mode Water (SAMW) component of the upwelling water, thereby representing a decrease in entrainment of water from below the base of the directly ventilated thermocline.