Propagation and Transformation of Upper North Atlantic Deep Water From the Subpolar Gyre to 26.5°N

Petit, Tillys; Lozier, M. Susan; Rühs, Siren; Handmann, Patricia; Biastoch, Arne

doi:10.1029/2023jc019726

Cited by 4 publications

(3 citation statements)

References 59 publications

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“…The advective pathways of LSW discussed herein have been previously documented and supported in a multitude of studies using advective tracers, Lagrangian float trajectories, and circulation models (Spall, 1996;Molinari et al, 1998;Bower and Hunt, 2000a;Bower and Hunt, 2000b;Fischer & Schott, 2002;Straneo et al, 2003;Bower et al, 2009;Kieke et al, 2009;Bower et al, 2011;Gary et al, 2011;van Sebille et al, 2011;Gary et al, 2012;Zou and Lozier, 2016;Le Bras et al, 2017;Andres et al, 2018;Bilóand Johns, 2019;Bower et al, 2019;Zhai et al, 2021;Chomiak et al, 2022;Fox et al, 2022;Lozier et al, 2022;Petit et al, 2023). In this study, we present the first, to our knowledge, description of the time-varying spread of two discrete LSW masses.…”

Section: Discussionsupporting

confidence: 56%

“…Furthermore, by expanding the analysis over the entire North Atlantic rather than just along the boundary, other LSW propagation and advective pathways supported in past and current literature (ex. Spall, 1996;Bower and Hunt, 2000a;Bower and Hunt, 2000b;Bower et al, 2009;Bower et al, 2011;Bilóand Johns, 2019;Bower et al, 2019;Chomiak et al, 2022;Lozier et al, 2022;Petit et al, 2023) are reinforced with these CEOF analyses. The CEOF 1 explains approximately 30% of the salinity variance in both isopycnals, which is a relatively large number considering that it relates to the entire North Atlantic domain; the other modes explain significantly less variance and are not used in the analysis.…”

Section: Investigating Signal Propagation Using Complex Eofsmentioning

confidence: 56%

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The interior spreading story of Labrador Sea Water

Chomiak,

Volkov,

Schmid

2023

Front. Mar. Sci.

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The unique convective anomalies of Labrador Sea Water (LSW) can be used as advective tracers when assessing equatorward spreading pathways and timescales of LSW. In this study, we explore advective pathways of two LSW classes formed in the 1990s and early 2000s, respectively, along constant neutral density planes. Hydrographic observations showcase the prevalence of both LSW classes within the Atlantic interior, supporting a recirculation feature that branches from the Deep Western Boundary Current (DWBC) at 36°N among other pathways. Spreading characteristics of both LSW classes from the Labrador Sea to the subtropics are reinforced through a spatial pattern analysis of salinity anomalies and geostrophic velocities along the characteristic neutral density planes of each respective LSW class. We observe both classes to advect out of the Labrador Sea to (i) the eastern subpolar region and down the eastern boundary towards the Atlantic interior, (ii) directly into the Atlantic interior likely from an injection by recirculations from the subpolar gyre and DWBC leakage, and (iii) equatorward along the western boundary via the DWBC. Findings highlight the abundance of LSW within the Atlantic interior, not just along the western boundary, suggesting that interior pathways play an influential role on the export of these subpolar climate signals.

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Section: Discussionsupporting

confidence: 56%

Section: Investigating Signal Propagation Using Complex Eofsmentioning

confidence: 56%

The interior spreading story of Labrador Sea Water

Chomiak,

Volkov,

Schmid

2023

Front. Mar. Sci.

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“…Most UNADW formed in the Irminger and Icelandic basin, as well as DSOW, enters the Labrador Sea, and these waters can be seen in both the boundary currents and interior (see [97][98][99][100][101] for UNADW pathways and [9,102] for DSOW pathways). For example, [103] shows that the majority of UNADW passes through the Labrador Sea prior to being exported to the subtropics. In the Labrador Sea, UNADW is densified, cooled and freshened.…”

Section: (D) Spreading Of Nadw and Export To The Subtropicsmentioning

confidence: 99%

Buoyancy forcing and the subpolar Atlantic meridional overturning circulation

Buckley,

Lozier,

Desbruyères

et al. 2023

Phil. Trans. R. Soc. A.

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The North Atlantic meridional overturning circulation and its variability are examined in terms of the overturning in density space and diapycnal water mass transformation. The magnitude of the mean overturning is similar to the surface water mass transformation, but the density and properties of these waters are modified by diapycnal mixing. Surface waters are progressively densified while circulating cyclonically around the subpolar gyre, with the densest waters and deepest convection occurring in the Labrador Sea and Nordic Seas. The eddy-driven interaction between the convective interior and boundary currents is a key to the export of dense waters from marginal seas. Due to the multitude of pathways of dense waters within the subpolar gyre, as well as mixing with older waters, waters exiting the subpolar gyre have a wide range of ages, with a mean age on the order of a decade. As a result, interannual changes in water mass transformation are mostly balanced locally and do not result in changes in export to the subtropics. Only persistent changes in water mass transformation result in changes in export to the subtropics. The dilution of signals from upstream water mass transformation suggests that variability in export of dense waters to the subtropics may be controlled by other processes, including interaction of dense waters with the energetic upper ocean. This article is part of a discussion meeting issue ‘Atlantic overturning: new observations and challenges’.

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Competition Between Advected and Local Variability Determines Coherent Propagation of Labrador Sea Water Along the DWBC

Fortin,

Lozier

2024

JGR Oceans

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The Deep Western Boundary Current (DWBC) is a major conduit for the equatorward export of dense waters formed in the subpolar North Atlantic and Nordic Seas that constitute the lower limb of the Atlantic Meridional Overturning Circulation. Here, we investigate the extent to which there is coherent propagation of property anomalies along the DWBC from the Labrador Sea exit to 26.5°N. Past studies have focused on relationships between DWBC anomalies at selected sites. Here we use a hydrographic data set (EN4) that covers the time period of 1970–2020 to examine coherence continuously along the boundary current. Our findings reveal sharp differences between the upper and deep Labrador Sea Water (uLSW, dLSW). Specifically, dLSW property anomalies are highly correlated at all points downstream to the Labrador Sea exit. Furthermore, the lags that yield maximum correlations uniformly increase with distance along the boundary. uLSW, however, shows a sharp decline in coherence along the boundary such that the anomalies downstream are poorly correlated with those at the Labrador Sea exit and the lag times are not monotonic. Most of the decline in uLSW coherence occurs from the Labrador Sea exit to Flemish Cap, where local variability at uLSW densities is large. Our study sheds light on the competition between advected property variability and local property variability that impacts the identification of anomalies downstream. The uLSW and dLSW differences expressed along the DWBC are also evident offshore, consistent with past Lagrangian studies.

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Propagation and Transformation of Upper North Atlantic Deep Water From the Subpolar Gyre to 26.5°N

Cited by 4 publications

References 59 publications

The interior spreading story of Labrador Sea Water

The interior spreading story of Labrador Sea Water

Buoyancy forcing and the subpolar Atlantic meridional overturning circulation

Competition Between Advected and Local Variability Determines Coherent Propagation of Labrador Sea Water Along the DWBC

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