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A hemispheric mechanism for the Atlantic Multidecadal Oscillation

Domenii publicaţii > Ştiinţele pământului şi planetare + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Dima, M., and G. Lohmann

Editorial: Journal of Climate, 20(11), 2007.


The physical processes associated to the ~70 year period climate mode, known as the Atlantic Multidecadal Oscillation (AMO), are examined. Based on analyses of observational data, a deterministic mechanism relying on atmosphere-ocean-sea-ice interactions, is proposed for the AMO. Variations in the thermohaline circulation are reflected as uniform sea surface temperature anomalies in the North Atlantic. These anomalies are associated with a hemispheric wave-number-one SLP structure in the atmosphere which is amplified through atmosphere-ocean interactions in the North Pacific. The SLP pattern and its associated wind field affect the sea-ice export through the Fram Strait, the freshwater balance in the northern North Atlantic, and consequently the strength of the large-scale ocean circulation. It generates sea surface temperature anomalies with opposite signs in the North Atlantic and complete a negative feedback. We find that the timescale of the cycle is associated to the thermohaline circulation adjustment to freshwater forcing, the SST response to it, the oceanic adjustment in the North Pacific, and the sea-ice response to the wind forcing. Finally, we argue that the Great Salinity Anomaly in the late 1960s and 1970s is part of AMO.

Cuvinte cheie: Atlantic Multidecadal Oscillation, thermohaline circulation, hemispheric mechanism, atmosphere-ocean-sea-ice interactions