Glacial to postglacial drop in productivity in the western equatorial Pacific: Mixing rate vs. nutrient concentrations

Primary productivity in the western equatorial Pacific was distinctly higher during the last glacial period than today, judging from the abundance patterns of benthic foraminifers in box cores from the Ontong Java Plateau. The export of organic matter dropped by a factor of ∼1.7 during the last glacial to interglacial transition, on the basis of global calibration of estimated export against accumulation rates of benthic foraminifers. Using detailed information on δ¹³C stratigraphy of planktic and benthic foraminifers for the past 20 ka together with a simple two-box ocean model, we calculate that upward mixing and diffusion of subsurface waters decreased by a factor of 1.4, while nutrient content decreased by a factor of 1.2, over this time span.