FARGO - 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. To fully prepare for what the future holds for our oceans, we must better understand the history of global biogeochemical cycles.

Current model simulations that predict the future carry considerable uncertainties; they do not all agree and grossly underestimate the documented 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, a 6-year project supported by UK Research and Innovation, provides such an approach by addressing why, and to what extent, seawater dissolved oxygen concentrations may change in a warming world.

FARGO, led by Lyell Centre Professor, Babette Hoogakker, is studying past 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, the team are analysing climate model simulations to help understand how environmental changes, like temperature or ocean circulation, impacted seawater oxygen across key warm geological time intervals.

These are:

- Warmer climates across the closure of the American sea-way (4-15 million years);

- Warmer climates as future analogue (mid-Pliocene Warm Period; 3.3 to 3 million years ago, early Pliocene interglacials; 4.0-4.8 million years ago);

- Pleistocene warm intervals (interglacials of the last ca. 800,000 years)

During its first three years, FARGO made important advances to improve bottom water and subsurface water oxygen reconstructions using foraminifera, microorganisms that live on or in sediments in the ocean, which can be used to reconstruct bottom water oxygen concentrations and ventilation.

The remainder of the project will continue to generate proxy reconstructions, using two models to test the robustness of results, and utilise the findings to carry out simulations for the future, including analysing the effects of the globe warming by 1.5 and 2 degrees, as predicted by existing climate models.