Deep circulation variability through the eastern subpolar North Atlantic

Li, Feili ORCID: https://orcid.org/0000-0002-3073-9813; Fu, Yao; Lozier, M. Susan; Le Bras, Isabela A.; de Jong, M. Femke; Wang, Yuan; Sanchez-Franks, Alejandra ORCID: https://orcid.org/0000-0002-4831-5461. 2024 Deep circulation variability through the eastern subpolar North Atlantic. Journal of Climate, 37 (23). 6221-6234. 10.1175/JCLI-D-23-0487.1

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Text © Copyright [2024] American Meteorological Society (AMS). For permission to reuse any portion of this Work, please contact permissions@ametsoc.org. Any use of material in this Work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC § 108) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. All AMS journals and monograph publications are registered with the Copyright Clearance Center (https://www.copyright.com). Additional details are provided in the AMS Copyright Policy statement, available on the AMS website (https://www.ametsoc.org/PUBSCopyrightPolicy). clim-JCLI-D-23-0487.1.pdf - Published Version Download (10MB) | Preview

Abstract/Summary

The export of the North Atlantic Deep Water (NADW) from the subpolar North Atlantic is known to affect the variability in the lower limb of the Atlantic meridional overturning circulation (AMOC). However, the respective impact from the transport in the upper NADW (UNADW) and lower NADW (LNADW) layers, and from the various transport branches through the boundary and interior flows, on the subpolar overturning variability remains elusive. To address this, the spatiotemporal characteristics of the circulation of NADW throughout the eastern subpolar basins are examined, mainly based on the 2014–20 observations from the transatlantic Overturning in the Subpolar North Atlantic Program (OSNAP) array. It reveals that the time-mean transport within the overturning’s lower limb across the eastern subpolar gyre [−13.0 ± 0.5 Sv (1 Sv ≡ 10 6 m 3 s −1 )] mostly occurs in the LNADW layer (−9.4 Sv or 72% of the mean), while the lower limb variability is mainly concentrated in the UNADW layer (57% of the total variance). This analysis further demonstrates a dominant role in the lower limb variability by coherent intraseasonal changes across the region that result from a basinwide barotropic response to changing wind fields. By comparison, there is just a weak seasonal cycle in the flows along the western boundary of the basins, in response to the surface buoyancy-induced water mass transformation.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1175/JCLI-D-23-0487.1
ISSN:	0894-8755
Additional Keywords:	Meridional overturning circulation, Ocean dynamics, Wind; In situ oceanic observations
Date made live:	18 Dec 2024 15:42 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/538572

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