Preprints
https://doi.org/10.5194/egusphere-2024-388
https://doi.org/10.5194/egusphere-2024-388
12 Feb 2024
 | 12 Feb 2024
Status: this preprint is open for discussion.

New insights into the eastern Subpolar North Atlantic meridional overturning circulation from OVIDE

Herlé Mercier, Damien Desbruyères, Pascale Lherminier, Antón Velo, Lidia Carracedo, Marcos Fontela, and Fiz F. Pérez

Abstract. The Atlantic Meridional Overturning Circulation (AMOC) is a key component of the Earth's climate. However, there are few long series of observations of the AMOC and the study of the mechanisms driving its variability depends mainly on numerical simulations. Here, we use four ocean circulation estimates produced by different data-driven approaches of increasing complexity to analyze the seasonal to decadal variability of the subpolar AMOC across the Greenland–Portugal OVIDE line since 1993. We show that the variance of the time series is dominated by seasonal variability, which is due to both seasonal variability in the volume of the AMOC limbs (linked to the seasonal cycle of density in the East Greenland Current) and to seasonal variability in the transport of the Eastern Boundary Current. The decadal variability of the subpolar AMOC is mainly caused by changes in velocity, which after the mid-2000s are partly offset by changes in the volume of the AMOC limbs. This compensation means that the decadal variability of the AMOC is weaker and therefore more difficult to detect than the decadal variability of its velocity-driven and volume-driven components, which is highlighted by the formalism that we propose.

Herlé Mercier, Damien Desbruyères, Pascale Lherminier, Antón Velo, Lidia Carracedo, Marcos Fontela, and Fiz F. Pérez

Status: open (until 08 Apr 2024)

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Herlé Mercier, Damien Desbruyères, Pascale Lherminier, Antón Velo, Lidia Carracedo, Marcos Fontela, and Fiz F. Pérez
Herlé Mercier, Damien Desbruyères, Pascale Lherminier, Antón Velo, Lidia Carracedo, Marcos Fontela, and Fiz F. Pérez

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Short summary
Here, we study the Atlantic Meridional Overturning Circulation (AMOC) measured between Greenland and Portugal between 1993–2021. We identify changes in AMOC limb volume and velocity as two major drivers of AMOC variability at subpolar latitudes. Volume variations dominate on the seasonal time scale, while velocity variations are more important on the decadal time scale. This decomposition proves useful for understanding the origin of the differences between AMOC time series.