Modelling the oceanic meridional overturning circulation: challenges and insights

– Julie Deshayes, Scientist, LOCEAN, Paris –

Résumé :

The purpose of this seminar is to present to LEGOS my history of the meridional overturning circulation (MOC) as described in my HDR, which examines in parallel recent advances in understanding the MOC and ocean modeling. Although the MOC is a complex ocean structure, simple models provide useful insight into the processes that influence it. This is the method I followed to clarify the role of eddies in dense water formation zones. More complex models, representing the whole ocean dynamics on a global scale, allow to examine the interactions between processes and the large-scale mechanisms of variability they induce. I have shown that the link between MOC and dense water formation depends on the spatial resolution of the ocean model, a critical parameter for the representation of western boundary currents. Unfortunately, the production of such models is costly and prevents the quantification of uncertainties related to numerical choices. For this, it is preferable to use climate models, less expensive because of their lower spatial resolution. I have therefore focused on the coupled IPSL-CM6 model since 2015 and conducted a collaborative project exploring various parameterizations and spatial resolutions, in the atmosphere and ocean, to quantify the uncertainties of the simulations produced for the CMIP6 exercise. The most important result is that the uncertainty related to model calibration is as large as that related to spatial resolution, for the range of resolutions explored (1/4 to 1 degree in the ocean). This leads to the development of new methods to calibrate the parameters of ocean and climate models, as well as to improve the parameterizations of fine scale processes in low resolution models, two objectives that are central in my future projects.

Lien Zoom :

https://zoom.us/j/92300194860?pwd=aDErT203L2tYdkROUTdhRm1EMWVpZz09