PO2 Scientific goals

1) Determine the climate impact during the last glacial period (and deglaciation) on global ocean oxygenation, oxygen distribution:

This period is well understood (spatially and temporally) with regards to climate and oceanographic proxies, but knowledge about oxygen cycling is poor. Previous data syntheses (Jaccard and Galbraith 2012; Galbraith and Jaccard 2015) show non-uniform qualitative changes to the glacial oxygen distribution. New proxies (several quantitative), proxy records and model simulations, will allow a reassessment of seawater oxygenation (and associated nutrient cycling) over this period at much higher resolution.

2) Investigate what lessons notable hypoxic events from the geologic past hold for the future:

Hypoxia or anoxia occurred under high greenhouse gas concentrations in the past and provide a longer timescale perspective for assessing drivers and feedback mechanisms in global biogeochemical cycles, and ecosystem responses (extinctions, adaptations, migrations, recoveries)(Jenkyns, 2010, Reershemius and Planavsky, 2021). We will synthesis data from Cretaceous OAEs, sapropels, and other well documented events and DeepMIP simulations to draw links between how, why, and under which climate states these events occur. Proximal and climate drivers, and ecosystem responses will be contrasted between events and with future projections following carbon-intensive pathways.

3) Assess if the drivers of coastal hypoxia in the common era have changed as a result of human activities:

Coastal and estuarine hypoxia have a profound influence on marine ecosystems, global biogeochemical cycles and coastal economies (fisheries, aquaculture, and tourism). Combined with global climate, the direct alteration of nutrient cycles by humans (agriculture, land use, fishing, sewage, atmospheric emissions and subsequent deposition) leads to hypoxia via eutrophication. To what extent is not always clear. Here we will assess regional pre-anthropogenic baselines of hypoxia and determine if (and where) human activities are exacerbating coastal hypoxia, through synthesis of high resolution coastal and estuarine data and modeling efforts.