From small whirls to the global ocean: how ocean eddies affect the AMOC

Caroline A. Katsman (Delft University of Technology, Hydraulic Engineering, Delft, Netherlands)

Séminaire du LMD à l’ENS-PSL.


Date de début 23/05/2024 10:00
Date de fin 23/05/2024
Organisateur LMD
Lieu ENS – salle Claude Froidevaux – E314 • 24, rue Lhomond 75005 PARIS


The AMOC has a pronounced signature in depth and density space, with lighter surface waters moving northward and denser deep waters returning. While it is appealing to assume that of dense water formation by convection is directly linked to sinking, this is not correct. In convection regions, diapycnal mixing peaks but the net vertical transport is negligible. Moreover, the convection itself does not contribute to the AMOC: it is the (southward) export of dense waters that matters.

We studied the characteristics of overturning in depth and density space and their linkages by analyzing the outcomes of eddy-resolving global ocean models and dedicated idealized models, with a focus on the Labrador Sea. These show that eddies play a crucial role: they control the convection cycle, the sinking, and the export of dense waters. The latter occurs along multiple pathways, which carry different water masses on timescales that deviate by several years.

In all, the studies reveal a complex three-dimensional view on sinking and overturning, involving the boundary currents, the ocean interior and the eddy field. From a modelling perspective, the studies emphasize the need to resolve eddies to properly represent the AMOC and its a future climate response. From an observational perspective, they reveal the challenge in interpreting observations, as they capture only the net result of all processes occurring upstream.

Informations supplémentaires

École normale supérieure – PSL
24 rue Lhomond – aile Erasme
salle Claude Froidevaux – E314