Variability of the global overturning circulation in high resolution climate models

The global overturning circulation is the largest component of the ocean circulation, associated with a global redistribution of key tracers such as heat and carbon.

This circulation generates much of the decadal to millennial climate variability, and may be associated with tipping points, i.e., abrupt irreversible climate changes.

Knowledge about the global overturning circulation heavily relies on general circulation models, owing to the difficulty to observe such a global, slow evolving system.

Several key drivers of the overturning variability have been identified, including wind pumping, convective activity, interior mixing, and eddy activity.

Until recently, only coarse resolution general circulation models could be used but higher resolution simulations are now becoming available.

These more realistic simulations are bringing a fundamentally different view about the hierarchy of drivers of the overturning variability.

In this project, we want to analyse the overturning variability in climate simulations available at different resolutions and identify how they differ when ocean eddies become resolved.

One key novelty will be to focus on budgets of potential energy to objectively compare the different drivers of the variability.

The proposed research will contribute to a better qualification of climate model predictions, helping to understand how the global ocean overturning might respond to climate changes and to infer how the ocean has influenced past climates.