The impacts of the atmospheric annular mode on the AMOC and its feedback in an idealized experiment

• Published in: Dynamics of atmospheres and oceans 2018-03, Vol.81, p.30-41
• Main Authors: Santis, Wlademir, Aimola, Luis, Campos, Edmo J.D., Castellanos, Paola
• Format: Article
• Language: English
• Subjects: AMOC; Annular mode; Idealized experiments
• ISSN: 0377-0265; 1872-6879
• DOI: 10.1016/j.dynatmoce.2017.11.004

•A resonance mechanism between ocean circulation and the annular mode is described.•Each ocean basin contributes to the resonance with its own characteristic timescale.•The annular mode also impacts on the The annular mode also impacts on the AMOC through buoyancy anomalies. The interdecadal variability of the atmospheric and oceanic meridional overturning circulation is studied, using a coupled model with two narrow meridional barriers representing the land and a flat bottomed Aquaplanet. Empirical orthogonal function (EOF) analysis are used in the atmospheric and oceanic meridional overturning cells, revealing the atmospheric interdecadal variability is dominated by an annular mode, in both hemispheres, which introduces in the ocean a set of patterns of variability. The most energetic EOFs in the ocean are the barotropic responses from the annular mode. The interaction between the heat anomalies, due to the barotropic response, and the thermohaline circulation of each basin leads to a resonance mechanism that feeds back to the atmospheric forcing, modulating the annular mode spectrum. Besides the barotropic response, the annular mode introduces anomalies of salinity and temperature in the subtropical Atlantic that affects its upper buoyancy. These anomalies are incorporated within the ocean circulation and advected until the areas of deep sinking in the northern Atlantic, impacting on its overturning circulation as well.