Fate of ocean oxygenation in a warming world

Oxygen is critical to the health of all higher life. In the oceans dissolved oxygen concentrations have declined by 2% since 1960, and are expected to continue to decline into the future in relation to man-made climate change. Future deoxygenation, along with overfishing, threatens the sustainability of economically important fisheries and marine ecosystems and will impact global biogeochemical cycles. It is therefore crucial that we obtain a well-informed view about what the future may hold. Current model simulations that predict the future carry considerable uncertainties; they do not all agree and grossly underestimate the document decrease of the last 50 years. This suggests the models are missing key interactions, calling for urgent action and a dedicated and inclusive scientific approach. FARGO provides such an approach by addressing why, and to what extent, seawater dissolved oxygen concentrations may change in a warming world. FARGO will study dissolved oxygen concentrations in the Pacific Ocean, the largest low-oxic water body in the current ocean, through an innovative and dedicated research programme incorporating a novel multi-proxy approach feeding IPCC-type climate model simulations across key warm time intervals: i- warmer climates across the closure of the American sea-way (4-15 million years); ii- warmer climates as future analogue (mid-Pliocene Warm Period, 3.3 to 3 million years ago); iii- Pleistocene warm intervals (interglacials of the last ca. 800,000 years). FARGO is structured into two phases: Phase I (years 1-4), and Phase II (years 5-7). The focus of the first four years is analytical, to advance method development and reconstruct time-series of oxygen concentrations and associated processes that drive changes (seawater warming, stratification, productivity, ventilation). The material FARGO will use to create these time-series involves the shells of microorganisms called foraminifera. Some species float near the ocean surface, called planktonic foraminifera, and can be used to assess the presence of subsurface oxygen minimum zones, seawater temperatures, etc. Species that live on or in sediments at the bottom of the ocean are termed benthic foraminifera and can be used to reconstruct bottom water oxygen concentrations and ventilation. FARGO will use sediments from the International Ocean Discovery Program to determine if there have been changes in the natural extent and intensity of the shallow Pacific Ocean OMZ oxygen minimum, or 'dead', zones (e.g. areas where oxygen levels are too low to support aerobic life), during the key warm intervals. The original time-series will feed the IPCC-type climate model simulations and provide robust tests to investigate if the simulations are realistic and correct for the specific time periods, and identify routes to improve the model simulations. Utilizing these improvements, FARGO will carry out simulations for future, including 1.5 and 2 degree warming scenarios. To raise awareness of ocean deoxygenation FARGO plans several bespoke impact and engagement activities aimed at scientific peers, policy makers, and the general public. To slow/reduce deoxygenation and protect our marine environment FARGO plans to work with government (Scottish and UK) to develop regional legislation to manage nutrient inputs from aquaculture and agriculture of UK waters.