Going from local to global: Deciphering unknowns in oceanic oxygenation

Widespread oceanic deoxygenation observed since the mid-20^th century has led to intensification and expansion of oxygen minimum zones (OMZ), many of which intersect with regions that support important fisheries. Current deoxygenation is largely associated with anthropogenic activities (e.g., CO₂-forced climate warming and nutrient-rich river discharge) that could exacerbate oxygen deficiency under current climate change. Predicting how oxygenation respond to climate change is thus critical for evaluating future deoxygenation impacts on marine ecosystems. Nevertheless, the short duration (~60 years) of available oxygenation instrumental records limits our ability to reveal longer term oxygenation responses and the underlying mechanisms. In this talk, I will outline the overarching questions in my research, which aims to go beyond the localized oxygenation reconstructions and to unravel drivers of oxygenation through an integrative understanding of the Earth system feedbacks. I will use a case study in the North Pacific OMZ, where a model and data comparison reveals natural oxygenation responses to atmospheric forcing on multidecadal to millennial timescales. Beyond local reconstructions, I will also present new development of the thallium isotope redox proxy that has a global perspective, with new possibilities of high-resolution (millennial) reconstructions in more variable environments that can be used to compare with localized oxygen reconstructions. Ultimately, this interdisciplinary and multi-proxy approach will help unravel the unknowns in oceanic oxygenation in the past and in the future.