Characterizing the interannual variability of North Atlantic subpolar overturning

Fu, Yao ORCID: https://orcid.org/0000-0003-2227-3694; Lozier, M. Susan; Bower, Amy ORCID: https://orcid.org/0000-0003-0902-4984; Burmeister, Kristin ORCID: https://orcid.org/0000-0003-3881-0298; Carrilho Biló, Tiago ORCID: https://orcid.org/0000-0002-4007-5862; Cyr, Frédéric ORCID: https://orcid.org/0000-0002-1581-7502; Cunningham, Stuart A. ORCID: https://orcid.org/0000-0001-9439-5442; deYoung, Brad; Dilmahamod, Ahmad Fehmi ORCID: https://orcid.org/0000-0003-1110-940X; de Jong, M. Femke ORCID: https://orcid.org/0000-0001-5683-0570; Fried, Nora ORCID: https://orcid.org/0000-0001-5457-1026; Holliday, N. Penny ORCID: https://orcid.org/0000-0002-9733-8002; Fraser, Neil J. ORCID: https://orcid.org/0000-0002-2171-9060; Johns, William E.; Li, Feili ORCID: https://orcid.org/0000-0002-3073-9813; Karstensen, Johannes ORCID: https://orcid.org/0000-0001-5044-7079; Pickart, Robert S. ORCID: https://orcid.org/0000-0002-7826-911X; Straneo, Fiammetta; Yashayaev, Igor ORCID: https://orcid.org/0000-0002-6976-7803. 2025 Characterizing the interannual variability of North Atlantic subpolar overturning. Geophysical Research Letters, 52 (19). 10.1029/2025GL114672

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Text © 2025 The Author(s).This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes, Geophysical Research Letters - 2025 - Fu - Characterizing the Interannual Variability of North Atlantic Subpolar.pdf - Published Version Available under License Creative Commons Attribution Non-commercial 4.0. Download (820kB) | Preview

Abstract/Summary

Variability of the Atlantic Meridional Overturning Circulation (MOC) has drawn extensive attention due to its impact on the global redistribution of heat and freshwater. Here we present the latest time series (2014–2022) of the Overturning in the Subpolar North Atlantic Program and characterize MOC interannual variability. We find that any single boundary current captures ∼30% of subpolar MOC interannual variability. However, to fully resolve MOC variability, a wide swath across the eastern subpolar basin is needed; in the Labrador Sea both boundaries are needed. Through a volume budget analysis for the subpolar basins' lower limbs, we estimate the magnitude of unresolved processes (e.g., diapycnal mixing) required to close the mean budget (∼2 Sv). We find that in the eastern subpolar basin surface-forced transformation variability is linked to lower limb volume variability, which translates to MOC changes within the same year. In contrast, this linkage is weak in the Labrador Sea.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1029/2025GL114672
ISSN:	0094-8276
Additional Keywords:	AMOC, OSNAP, MOC interannual variability, water mass transformation, boundary currents
NORA Subject Terms:	Marine Sciences
Date made live:	19 Nov 2025 10:42 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/540601

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