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A possible 10-15 year variability of the AMOC and its climatic impacts

Authors

Nnamchi,  Hyacinth
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Farneti,  Riccardo
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Keenlyside,  Noel
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Kucharski,  Fred
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Mojib,  Latif
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Reintges,  Annika
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Martin,  Thomas
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

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Citation

Nnamchi, H., Farneti, R., Keenlyside, N., Kucharski, F., Mojib, L., Reintges, A., Martin, T. (2023): A possible 10-15 year variability of the AMOC and its climatic impacts, XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) (Berlin 2023).
https://doi.org/10.57757/IUGG23-2093


Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5018732
Abstract
An important feature of ocean circulation in the Atlantic is the cross-equatorial and northward transport of water masses at the surface and southward transport at the bottom of the ocean by the Atlantic Meridional Overturning Circulation (AMOC). However, the link between the AMOC and tropical Atlantic variability remain poorly understood. This is partly due lack of long-term observations of the AMOC, with the longest direct measurements available since 2004. Here we construct a dynamic sea-level proxy of the AMOC variability during the twentieth century, which is strongly correlated with the AMOC index during the observational period from 2005-2019 (r=0.50; p=1.48×10-9). This sea-level proxy exhibits a 10-15 year periodicity similar to the pan-Atlantic Decadal Oscillation (ADO) – the north-south bands of alternate anomalies in surface-ocean temperatures with the maximum variance over the tropical Atlantic, and winds from colder bands to the warmer. The sea level-derived proxy leads the ADO pattern by several years, through the interactions of overturning and gyre circulations with Kelvin wave anomalies that propagate from the North Atlantic to the low latitudes and by the thermocline feedback in the Atlantic cold tongue region. The peak of the sea surface temperature variability in the tropical Atlantic in turn drives inter-hemispheric atmospheric teleconnections represented by negative North Atlantic Oscillation phase over the North Atlantic. These findings imply that, rather than a passive role postulated by the prevailing thermodynamic paradigm, AMOC-related ocean circulation plays an active role in ADO variability.