Pathways of the water masses exiting the Labrador Sea: The importance of boundary–interior exchanges

Georgiou, Sotiria; Ypma, Stefanie; Brüggemann, Nils; Sayol, Juan Manuel; Pietrzak, Julie D.; Katsman, Caroline A.

doi:10.1016/j.ocemod.2020.101623

Cited by 10 publications

(45 citation statements)

References 55 publications

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“…They are associated with the LSW density range in MOM (i.e., σ=27.75-27.83 kg m −3 ). This confirms the findings from the idealized study of Georgiou et al (2020), that the densest water masses formed in the interior of the Labrador Sea stay in the basin longer.…”

Section: Timescales Associated With the Pathwayssupporting

confidence: 90%

“…All rights reserved. manuscript submitted to JGR: Oceans boundary current are exported faster than the denser water masses formed in the central-LS ( Figure 6), in line with the more qualitative results obtained from the idealized studies of Brüggemann and Katsman (2019) and Georgiou et al (2020): 90% of the volume transport carried by the withinBC and interiorShortparticles reaches 53 o N within 1.5 and 3 years, respectively (Figure 6c). In particular, we show that the denser water masses formed in the central-LS first follow an eddy-driven path towards the West Greenland coast (WG-path, Figure 4a) and re-enter in the boundary current there before reaching 53 o N. Therefore, these water masses travel longer distances than the ones that formed within the boundary current itself (withinBC particles) or the lighter water masses that formed in the central-LS and are rapidly exported at the Labrador side (LC-path).…”

Section: Accepted Articlesupporting

confidence: 82%

“…The T-S diagrams in Figure 3c Georgiou et al (2020) who showed by using passive tracers that the densest water masses formed in the interior of the basin are steered towards the topographic narrowing aided by the velocity shear induced by the presence of the eddy field.…”

Section: Pathways and Final Properties Of Convected Water Massesmentioning

confidence: 94%

“…In this study, we analyze the upstream pathways of all water masses exiting the Labrador Sea at 53 o N revealed by Lagrangian particle tracking, using the model output from a state-of-the-art global ocean-sea ice model. Our approach and analyses strongly build on the highly idealized model study of Georgiou et al (2020) in which qualitative insights gained. The use of output from a realistic simulation introduces among others more realistic atmospheric forcing, more realistic bathymetry, the effects of salinity, potential connections between the sub-basins of the SPNA and the presence of overflow waters and allows us to characterize the transports and water mass transformation along pathways quantitatively.…”

Section: Accepted Articlementioning

confidence: 99%

“…13 of 19 findings from the idealized study of Georgiou et al (2020), that the densest water masses formed in the interior of the Labrador Sea stay in the basin longer.…”

Section: 1029/2020jc016654mentioning

confidence: 99%

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Direct and Indirect Pathways of Convected Water Masses and Their impacts on the Overturning Dynamics of the Labrador Sea

et al. 2021

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The dense waters formed by wintertime convection in the Labrador Sea play a key role in setting the properties of the deep Atlantic Ocean. To understand how variability in their production might affect the Atlantic Meridional Overturning Circulation (AMOC) variability, it is essential to determine pathways and associated timescales of their export. In this study, we analyze the trajectories of Argo floats and of Lagrangian particles launched at 53°N in the boundary current and traced backward in time in a high-resolution model, to identify and quantify the importance of upstream pathways. We find that 85% of the transport carried by the particles at 53°N originates from Cape Farewell, and it is split between a direct route that follows the boundary current and an indirect route involving boundary-interior exchanges. Although both routes contribute roughly equally to the maximum overturning, the indirect route governs its signal in denser layers. This indirect route has two branches: part of the convected water is exported rapidly on the Labrador side of the basin and part follows a longer route toward Greenland and is then carried with the boundary current. Export timescales of these two branches typically differ by 2.5 years. This study thus shows that boundary-interior exchanges are important for the pathways and the properties of water masses arriving at 53°N. It reveals a complex three-dimensional view of the convected water export, with implications for the arrival time of signals of variability therein at 53°N and thus for our understanding of the AMOC.

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Section: Timescales Associated With the Pathwayssupporting

confidence: 90%

Section: Accepted Articlesupporting

confidence: 82%

Section: Pathways and Final Properties Of Convected Water Massesmentioning

confidence: 94%

Section: Accepted Articlementioning

confidence: 99%

“…13 of 19 findings from the idealized study of Georgiou et al (2020), that the densest water masses formed in the interior of the Labrador Sea stay in the basin longer.…”

Section: 1029/2020jc016654mentioning

confidence: 99%

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Direct and Indirect Pathways of Convected Water Masses and Their impacts on the Overturning Dynamics of the Labrador Sea

et al. 2021

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Fast mechanisms linking the Labrador Sea with subtropical Atlantic overturning

et al. 2022

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We use an ocean general circulation model and its adjoint to analyze the causal chain linking sea surface buoyancy anomalies in the Labrador Sea to variability in the deep branch of the Atlantic meridional overturning circulation (AMOC) on inter-annual timescales. Our study highlights the importance of the North Atlantic Current (NAC) for the north-to-south connectivity in the AMOC and for the meridional transport of Lower North Atlantic Deep Water (LNADW). We identify two mechanisms that allow the Labrador Sea to impact velocities in the LNADW layer. The first mechanism involves a passive advection of surface buoyancy anomalies from the Labrador Sea towards the eastern subpolar gyre by the background NAC. The second mechanism plays a dominant role and involves a dynamical response of the NAC to surface density anomalies originating in the Labrador Sea; the NAC adjustment modifies the northward transport of salt and heat and exerts a strong positive feedback, amplifying the upper ocean buoyancy anomalies. The two mechanisms spin up/down the subpolar gyre on a timescale of years, while boundary trapped waves rapidly communicate this signal to the subtropics and trigger an adjustment of LNADW transport on a timescale of months. The NAC and the eastern subpolar gyre play an essential role in both mechanisms linking the Labrador Sea with LNADW transport variability and the subtropical AMOC. We thus reconcile two apparently contradictory paradigms about AMOC connectivity: (1) Labrador Sea buoyancy anomalies drive AMOC variability; (2) water mass transformation is largest in the eastern subpolar gyre.

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Coastal circulation and water transport properties of the Red Sea Project lagoon

et al. 2021

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Pathways of the water masses exiting the Labrador Sea: The importance of boundary–interior exchanges

Cited by 10 publications

References 55 publications

Direct and Indirect Pathways of Convected Water Masses and Their impacts on the Overturning Dynamics of the Labrador Sea

Direct and Indirect Pathways of Convected Water Masses and Their impacts on the Overturning Dynamics of the Labrador Sea

Fast mechanisms linking the Labrador Sea with subtropical Atlantic overturning

Coastal circulation and water transport properties of the Red Sea Project lagoon

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