Remote and local controls on dissolved oxygen in the Western Tropical Pacific thermocline during the last 700 kyr

Abstract

The dissolved oxygen level of the low-latitude Pacific thermocline is a sensitive tracer of global ocean circulation, especially at high latitudes. However, its variability covering glacial–interglacial cycles has not been well documented. Based on the thermocline-dwelling foraminiferal population extracted from Calypso Core MD06–3047, we derived a record of the Western Tropical Pacific (WTP) thermocline oxygenation over the last 700 kyr. We found that the glacial thermocline oxygenation gradually enhanced to dome-like peaks during glacial periods, with significant relative abundance of thermocline-dwelling species minimum events. We suggest that the remote physical process of lateral O2 supply (dominated by Southern Ocean (SO) ventilation and Antarctic Intermediate Water advection, with a minor contribution of North Pacific Intermediate Water (NPIW)) and the local biological process of O2 consumption (by organic biological productivity, determined by iron supply and NPIW-driven nutrient supply) may together control the WTP thermocline oxygenation on glacial–interglacial cycles. The surprisingly synchronous co-variation indicates that SO ventilation and Antarctic Intermediate Water advection have the potential to be the primary controlling factors. Furthermore, the consistent and simultaneous dramatic increments in Marine Isotope Stages 13–11 transition and each deglacial period provide robust support for a close coupling between the global (mid-Brunhes) climatic shift scenario of SO ventilation and the WTP thermocline oxygenation.