Deglacial restructuring of the Eastern equatorial Pacific oxygen minimum zone

Abstract

Oxygenation in the Eastern Equatorial Pacific is responsive to ongoing climate change in the modern ocean, although whether the region saw a deglacial change in extent or position of the Oxygen Minimum Zone remains poorly constrained. Here, stable isotopes from the shells of an Oxygen Minimum Zone-dwelling planktic foraminifer are used to reassess the position of the mid-water Oxygen Minimum Zone relative to both the thermocline and benthos. Oxygen isotopes record a rapid shoaling of the Oxygen Minimum Zone towards the thermocline associated with Heinrich Stadial 1 and persisting through the deglaciation. Meanwhile, carbon isotope similarities between Oxygen Minimum Zone-dwelling Globorotaloides hexagonus and benthic Cibicidoides wuellerstorfi suggest a shared source water through the deglaciation. Results support a direct role for the Eastern Equatorial Pacific in venting carbon to the atmosphere through the deglaciation, a deglacial expansion of the Oxygen Minimum Zone, and a restructuring of mid-water oxygen and carbon dynamics from the glacial to Holocene intervals.