NOAA/WDS Paleoclimatology - Line Islands Northern Equatorial Pacific Authigenic Metal Data 0-144 ka

The expansion of oxygen-deficient zones (ODZs) within the ocean interior is anticipated to be a major consequence of anthropogenic climate change, but past changes in ODZs are poorly defined. Recent mapping efforts have revealed plumes of the redox active metal cobalt within ODZs, driving a basin-scale correlation between high cobalt and low O2. Here, we investigate the cobalt flux to Equatorial Pacific sediments as a novel paleoceanographic record of basin-scale fluctuations in ODZ extent. After accounting for remobilization by diagenesis, we document a ~40% increase in cobalt accumulation over the last glacial period, with a more pronounced peak during the Last Glacial Maximum, indicative of larger ODZs compared to the Holocene. Our results link ODZ expansion with colder climates and lend support to model-based assertions that ongoing deoxygenation may reflect a transient response to warming.