Variability of the global overturning circulation in high resolution climate models
Short description
The global overturning circulation (GOC) is responsible for the ventilation of deep and bottom water masses on decadal to millennial timescales. It induces a global redistribution of heat, carbon and nutrients, making it central to the earths' climate variability and to biogeochemical cycles.
In this project, we want to determine what drives the global overturning circulation in high resolution climate models, and whether it fundamentally differs from non-eddying models. One key novelty will be to focus on budgets of potential energy to objectively compare the different drivers of the variability.
The 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.
More about the research
In the current context of a fast-paced forced climate change, there are worries that the GOC could reach a tipping point, with long-term consequences on the Earth鈥檚 climate.
The recent availability of climate simulations with a high-resolution eddying ocean component offers a unique opportunity to investigate the overturning circulation with new eyes. In this project, we will focus on Earth system model simulations produced by the EC-Earth European consortium and used in the Coupled Model Inter-comparison Project (CMIP). The EC-Earth3P-HR has an eddy-permitting ocean component at a nominal 1/4 o resolution, so it will be compared to a lower resolution simulation EC-Earth3P at 1 o resolution.
To go deeper in the determination of drivers of the GOC, ocean-only simulations at 1/8 o resolution with a simplified geometry will also be analysed.
Three main goals
This project will be organized into three main aims:
- Aim 1: Review the literature on drivers of the GOC variability at different timescales.
- Aim 2: Compare the overturning in climate simulations available at two different resolutions.
- Aim 3: Identify the hierarchy of processes driving the GOC in eddying ocean-only simulations.
Project outcome
The outcome of this work will be a renewed understanding of how the GOC operates and how it responds to given changes in the climate forcing.
It will help identifying the impact of ocean resolution on the GOC variability, helping along the way to build trust in the projections of climate models at decadal to centennial time scales.