Eastern equatorial Pacific paleo-productivity and carbon cycling during the late Pleistocene

Abstract

A classical paradigm links enhanced marine biological production and resulting deep ocean carbon storage in the low latitude Pacific with reduced atmospheric CO₂ concentrations during Pleistocene ice ages. Subsequent studies of eastern equatorial Pacific paleo-productivity and associated processes do not unanimously characterize this system. Here, we present paleo-records of export production, sediment mass flux, dust flux, and bottom water oxygen derived from isotopes of U, Th, and Pa in marine sediments and synthesize existing paleo-records from a site in the eastern equatorial Pacific cold tongue over the last 160,000 years. Our results support the hypothesis that variations in marine export production were a consequence of changes in equatorial upwelling and in the nutrient concentrations of upwelled waters, not aeolian iron fertilization. We conclude that changes in marine export production in the eastern equatorial Pacific were not the principal driver of changes in local deep ocean carbon storage or atmospheric CO₂ across the late Pleistocene.