Interior Pathways of Labrador Sea Water in the North Atlantic From the Argo Perspective

Biló, Tiago Carrilho; Johns, William E.

doi:10.1029/2018gl081439

Cited by 26 publications

(42 citation statements)

References 44 publications

(77 reference statements)

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“…Similar cyclonic recirculations around FC were reported in circulation estimates based on profiling floats (Lavender et al 2005), and in numerical simulations by Xu et al (2015), which noted that the recirculations are consistent with the distribution of Tritium [see also Fig. 2a in Biló and Johns (2018) and Fig. 1a in Getzlaff et al (2006)].…”

Section: B Eulerian Characterization Of Leakinesssupporting

confidence: 79%

“…These findings of DWBC leakiness and interior pathways represent a significant revision of the classical picture of deep southward AMOC transport being confined to the DWBC. Furthermore, Argo observations (Biló and Johns 2018) and numerical simulations (Gary et al 2011(Gary et al , 2012Lozier et al 2013) suggest that interior pathways continue south farther than the 2-yr ExPath observations demonstrate. Gary et al (2012) show that 75% of simulated floats initialized within the DWBC and traveling from 448 to 308N did so in the interior rather than within the DWBC.…”

Section: Introductionmentioning

confidence: 90%

“…Based on Eulerian transport measurements at southeast FC and at southeast GB, Mertens et al (2014, hereafter M14) estimated that out of '30 Sv (1 Sv [ 10 6 m 3 s 21 ) of southward flowing NADW at southeast FC, 15 Sv are lost offshore before the southern tip of the GB. Biló and Johns (2018) analyzed interior pathways of LSW based on Argo data, and found that of the water leaked from the DWBC within the Nfl Basin, 9.3 6 3.5 Sv recirculates within the subpolar basin, while 3.2 6 0.4 Sv continues eastward. These studies therefore show that DWBC leakiness has a significant (on the order of multiple Sverdrups) uncompensated component, i.e., that there is a net loss of mass from the DWBC, rather than simply an exchange of mass with the ambient ocean.…”

Section: Instabilities Of the Dwbcmentioning

confidence: 99%

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Why Does the Deep Western Boundary Current “Leak” around Flemish Cap?

Solodoch

McWilliams

Stewart

et al. 2020

Journal of Physical Oceanography

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Abstract The southward-flowing deep limb of the Atlantic meridional overturning circulation is composed of both the deep western boundary current (DWBC) and interior pathways. The latter are fed by “leakiness” from the DWBC in the Newfoundland Basin. However, the cause of this leakiness has not yet been explored mechanistically. Here the statistics and dynamics of the DWBC leakiness in the Newfoundland Basin are explored using two float datasets and a high-resolution numerical model. The float leakiness around Flemish Cap is found to be concentrated in several areas (hot spots) that are collocated with bathymetric curvature and steepening. Numerical particle advection experiments reveal that the Lagrangian mean velocity is offshore at these hot spots, while Lagrangian variability is minimal locally. Furthermore, model Eulerian mean streamlines separate from the DWBC to the interior at the leakiness hot spots. This suggests that the leakiness of Lagrangian particles is primarily accomplished by an Eulerian mean flow across isobaths, though eddies serve to transfer around 50% of the Lagrangian particles to the leakiness hot spots via chaotic advection, and rectified eddy transport accounts for around 50% of the offshore flow along the southern face of Flemish Cap. Analysis of the model’s energy and potential vorticity budgets suggests that the flow is baroclinically unstable after separation, but that the resulting eddies induce modest modifications of the mean potential vorticity along streamlines. These results suggest that mean uncompensated leakiness occurs mostly through inertial separation, for which a scaling analysis is presented. Implications for leakiness of other major boundary current systems are discussed.

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Section: B Eulerian Characterization Of Leakinesssupporting

confidence: 79%

Section: Introductionmentioning

confidence: 90%

Section: Instabilities Of the Dwbcmentioning

confidence: 99%

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Why Does the Deep Western Boundary Current “Leak” around Flemish Cap?

Solodoch

McWilliams

Stewart

et al. 2020

Journal of Physical Oceanography

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“…This (¼)° mean product includes data from 1997 to 2016 and is made available through the Asia‐Pacific Data Research Center (APDRC). The Argo‐derived baroclinic shear is interpolated to (¼)° and referenced to the 1,000‐m Argo drift displacement data to resolve Argo‐based mean velocities throughout the upper 2,000‐m water column (Bilo, 2019; Bilo & Johns, 2019). These data are also used in transport calculations along a number of sections across the ERRC (e.g., Figure 8) by integrating all velocities shallower than σ θ = 27.8 kg m −3 that are within the domain and direction of the ERRC (see Figure 9).…”

Section: Methodsmentioning

confidence: 99%

Transport and Evolution of the East Reykjanes Ridge Current

2020

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This study of the first continuous multiyear observations of the East Reykjanes Ridge Current (ERRC) reveals a highly variable, mostly barotropic southwestward flow with a mean transport of 10-13 Sv. The ERRC effectively acts as a western boundary current in the Iceland Basin on the eastern flank of the Reykjanes Ridge. As part of the Overturning in the Subpolar North Atlantic Program (OSNAP), continuous measurements of the ERRC have been maintained for the first time using acoustic Doppler current profilers, current meters, and dynamic height moorings at six mooring sites near 58°N since 2014. Together with satellite altimetry and Argo profile and drift data, the mean transport, synoptic variability, water mass properties, and upstream and downstream pathways of the ERRC are examined. Results show that the ERRC forms in the northeastern Iceland Basin at the convergence of surface waters from the North Atlantic Current and deeper Icelandic Slope Water formed along the Iceland-Faroe Ridge. The ERRC becomes denser as it cools and freshens along the northern and western topography of the Basin before retroflecting over the Reykjanes Ridge near 59°N into the Irminger Current. Analysis of the flow-weighted density changes along the ERRC's path reveals that it is responsible for about one third of the net potential density change of waters circulating around the rim of the subpolar gyre. Plain Language Summary The East Reykjanes Ridge Current (ERRC) is an important but poorly studied flow in the Iceland Basin of the northern North Atlantic Ocean. This study investigates the ERRC using underwater floats, satellites, and 4 years of continuous mooring data to determine the current's pathways, water properties, and the strength of its transport. From its formation to the south of Iceland near 62°N, 18°W, the ERRC travels westward along the Icelandic slope before turning to the southwest as it follows the eastern flank of a shallow portion of the Mid-Atlantic Ridge, known as the Reykjanes Ridge. As the Reykjanes Ridge deepens, the ERRC eventually reaches its termination as it crosses westward over the ridge into the next basin. Results of this study show that the ERRC is approximately 900 km in length and has an average transport of 10-13 Sv (1 Sv = 1,000,000 m 3 /s). Significant water densification occurs along the ERRC's path, which makes it an important component in the broader picture of the Earth's climate system.

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“…Another part of the LSW joins the LC, flowing south along the continental shelf and around Grand Banks into the subtropics to join the Deep Western Boundary Current (DWBC). As the LC splits near Flemish Cap, some LSW is entrained into the North Atlantic Current (NAC), which, in turn, splits to flow eastward crossing the mid-Atlantic ridge (Biló & Johns, 2019) and to finally mix with the warm and saline Mediterranean Water (MW). The remaining NAC flows to the north into the Irminger Sea and then to the LS via the Irminger Current (IC; see Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Kinematic Subduction Rate Of Labrador Sea Water From an Eddy‐Permitting Numerical Model

Courtois

Garcia‐Quintana

et al. 2020

JGR Oceans

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We use an eddy‐permitting, 1/12° regional configuration of the Nucleus for European Modelling of the Ocean (NEMO) model to examine water mass subduction rates in the Labrador Sea for the 2002–2013 period. An instantaneous kinematic subduction approach is implemented to calculate the subduction rate of Labrador Sea Water (LSW). By following the outcrop positions of a given isopycncal range, we calculate the vertical transport of a water mass from the mixed layer into the permanent thermocline over the course of a year. We examine the importance of the various terms in this approach, including the evolution of the Mixed Layer Depth (MLD), the advection across the base of the Mixed Layer (ML), and the vertical velocity at the base of the ML. We find that the subduction rate is not greatly affected by the definition of the MLD, as long as the integration time is long enough for the subduction‐obduction processes to balance each other. The total LSW subduction rate is ∼4–5 Sv, with similar rates for both Upper (ULSW) and Classical LSWs (CLSW), (∼2–2.5 Sv). After 2008, a shift in the LSW density is found in the simulation. CLSW reaches a maximum rate of 6 Sv in 2008, which is mainly inferred by the instantaneous ML change.

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Interior Pathways of Labrador Sea Water in the North Atlantic From the Argo Perspective

Cited by 26 publications

References 44 publications

Why Does the Deep Western Boundary Current “Leak” around Flemish Cap?

Why Does the Deep Western Boundary Current “Leak” around Flemish Cap?

Transport and Evolution of the East Reykjanes Ridge Current

Kinematic Subduction Rate Of Labrador Sea Water From an Eddy‐Permitting Numerical Model

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