Deglacial restructuring of the Eastern equatorial Pacific oxygen minimum zone

Rapid shoaling of the oxygen minimum zone in the Eastern Equatorial Pacific enabled transfer of carbon from the ocean to the atmosphere during the last deglaciation, suggests a foraminifera stable isotope record from the Panama Basin. 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.

Automated summary

A stable isotope record from foraminifera in the Panama Basin suggests that the oxygen minimum zone in the Eastern Equatorial Pacific became shallower during the last deglaciation, leading to the transfer of carbon from the ocean to the atmosphere. The study also finds evidence for an expansion of the oxygen minimum zone during the deglaciation and a restructuring of oxygen and carbon dynamics in the water column.