Reconciling two alternative mechanisms behind bi-decadal variability in the North Atlantic ...

• Main Authors: Mignot, Juliette, Sévellec, Florian, Ortega, Pablo, Swingedouw, Didier, Guilyardi, Eric
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2015
• Subjects: 530 Physics; Laplace; Iceland; North Atlantic; Sea ice
• Online Access: https://dx.doi.org/10.7892/boris.73419; http://boris.unibe.ch/73419/

Understanding the preferential timescales of variability in the North Atlantic, usually associated with the Atlantic meridional overturning circulation (AMOC), is essential for the prospects for decadal prediction. However, the wide variety of mechanisms proposed from the analysis of climate simulations, potentially dependent on the models themselves, has stimulated the debate of which processes take place in reality. One mechanism receiving increasing attention, identified both in idealized models and observations, is a westward propagation of subsurface buoyancy anomalies that impact the AMOC through a basin-scale intensification of the zonal density gradient, enhancing the northward transport via thermal wind balance. In this study, we revisit a control simulation from the Institut Pierre-Simon Laplace Coupled Model 5A (IPSL-CM5A), characterized by a strong AMOC periodicity at 20 years, previously explained by an upper ocean–atmosphere–sea ice coupled mode driving convection activity south of Iceland. Our ...