Interior pathways of the North Atlantic meridional overturning circulation

Bower, Amy S.; Lozier, M. Susan; Gary, Stefan F.; Böning, Claus W.

doi:10.1038/nature07979

Cited by 253 publications

(296 citation statements)

References 48 publications

Supporting

Mentioning

249

Contrasting

Unclassified

Order By: Relevance

“…LSW classes can even reach the European ocean margin van Aken, 2000;Yashayaev et al, 2007aYashayaev et al, , 2007b. This supports the ideas, expressed by Bower et al (2009), that interior pathways of the cold branch of the AMOC may be at least as important as the deep western boundary current.…”

Section: Discussionsupporting

confidence: 73%

“…Entering the deep western boundary current along the American continental slope via such indirect pathways (Bower et al, 2009) LSW contributes to the south flowing North Atlantic Deep Water in the cold branch of the Atlantic meridional overturning circulation (AMOC). Because of the relatively high near-surface salinities outside the Labrador Sea, e.g.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Decadal and multi-decadal variability of Labrador Sea Water in the north-western North Atlantic Ocean derived from tracer distributions: Heat budget, ventilation, and advection

Aken

Jong

Yashayaev

2011

Deep Sea Research Part I: Oceanographic Research Papers

View full text Add to dashboard Cite

a b s t r a c tTime series of profiles of potential temperature, salinity, dissolved oxygen, and planetary potential vorticity at intermediate depths in the Labrador Sea, the Irminger Sea, and the Iceland Basin have been constructed by combining the hydrographic sections crossing the sub-arctic gyre of the North Atlantic Ocean from the coast of Labrador to Europe, occupied nearly annually since 1990, and historic hydrographic data from the preceding years since 1950. The temperature data of the last 60 years mainly reflect a multi-decadal variability, with a characteristic time scale of about 50 years. With the use of a highly simplified heat budget model it was shown that this long-term temperature variability in the Labrador Sea mainly reflects the long-term variation of the net heat flux to the atmosphere. However, the analysis of the data on dissolved oxygen and planetary potential vorticity show that convective ventilation events, during which successive classes of Labrador Sea Water (LSW) are formed, occurring on decadal or shorter time scales. These convective ventilation events have performed the role of vertical mixing in the heat budget model, homogenising the properties of the intermediate layers (e.g. temperature) for significant periods of time. Both the long-term and the near-decadal temperature signals at a pressure of 1500 dbar are connected with successive deep LSW classes, emphasising the leading role of Labrador Sea convection in running the variability of the intermediate depth layers of the North Atlantic. These signals are advected to the neighbouring Irminger Sea and Iceland Basin. Advection time scales, estimated from the 60 year time series, are slightly shorter or of the same order as most earlier estimates, which were mainly based on the feature tracking of the spreading of the LSW 94 class formed in the period 1989

show abstract

Section: Discussionsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Decadal and multi-decadal variability of Labrador Sea Water in the north-western North Atlantic Ocean derived from tracer distributions: Heat budget, ventilation, and advection

Aken

Jong

Yashayaev

2011

Deep Sea Research Part I: Oceanographic Research Papers

View full text Add to dashboard Cite

show abstract

“…From Cape Farewell, the DWBC then travels around the Labrador Sea as the deep part of the West Greenland Current, passing through the 53°N array (Fischer et al, 2010 off southern Labrador in the Deep Labrador Current (DLC) and entering the open subpolar North Atlantic at Flemish Cap (Rhein et al, 2011) and finally (for this investigation) exits the subpolar regime at the tail of the Grand Banks . Besides the DWBC there also are interior routes along which North Atlantic Deep Water (NADW) either recirculates in the subpolar basin or is exported into the subtropics (Bower et al, 2009). However, in a comparative analysis of the currents and transports in a high resolution (0.08° grid) isopycnic HYCOM model, Xu et al (2013) show that the boundary flow at 53°N is correlated with the Meridional Overturning Circulation (MOC) transport across WOCE Line AR19 off the Grand Banks, and in an earlier study by Böning et al (2006) it has been shown that the deep water export from the Labrador Sea is correlated with the mid-latitude Meridional Overturning Circulation (MOC).…”

Section: ) Introduction and Objectivesmentioning

confidence: 99%

Intra-seasonal variability of the DWBC in the western subpolar North Atlantic

Fischer

Karstensen

Zantopp

et al. 2015

Progress in Oceanography

View full text Add to dashboard Cite

The Deep Western Boundary Current (DWBC) along the western margin of the subpolar North Atlantic is an important component of the deep limb of the Meridional Overturning near its northern origins. A network of moored arrays from Denmark Strait to the tail of the Grand Banks has been installed for almost two decades to observe the boundary currents and transports of North Atlantic Deep Water as part of an internationally coordinated Observatory for the Atlantic Meridional Overturning Circulation. The dominant variability in all of the moored velocity time series is in the week-to-month period range. While the temporal characteristics of this variability changes only gradually between Denmark Strait and Flemish Cap, a broad band of longer term variability is present farther along the path of the DWBC at the Grand Banks and in the interior basins (Labrador and Irminger Seas). The vigorous intraseasonal variability may well mask possible interannual to decadal variability that is typically an order of magnitude smaller than the high-frequency fluctuations. Here, the intra-seasonal variability at key positions along the DWBC path using both, observations and high resolution model data is quantified. The results are used to evaluate the model circulation, and in turn the model is used to relate the discrete measurements to the overall pattern of the subpolar circulation. Topographic waves are found to be trapped by the steep topography all around the western basins, the Labrador and Irminger Seas. In the Labrador Sea, the high intra-seasonal variability of the boundary current regime is separated by a region of extremely low variability in narrow recirculation cells from the basin interior. There, the variability is also on intra-seasonal timescales, but at much longer periods around 50 days. We would like to thank reviewer #2 for his/her very careful evaluation of our manuscript, the constructive criticism and the recommendations for corrections and suggestions. Below, recommendations by the reviewer are in blue and our response in black.Review of "Intra-seasonal variability of the Deep Western Boundary Current in the western subpolar North Atlantic", Manuscript Number: PROOCE-D-13-00096 1 General comments: Using long current meter records in the western margin of the subpolar gyre, the authors investigate the intra-seasonal variability in the Deep Western Boundary Current. From the Denmark Strait to the Grand Banks they show -that the dominant variability is in the week-to-month period range -that 10 day periods dominate the variance, which they attribute to topographic Rossby waves -that at Flemish Cap and farther south, there is also variability at longer periods -that in the basin centers (Labrador and Irminger) the variance dominate at 50 day period and there is almost no variance at 10 days. Using a long time series in the DWBC at 53°N they also find seasonality in the intra-seasonal variability, with an offset of 6 months between the surface and the bottom. Then to validate a new high resolu...

show abstract

“…The data presented in Bower et al (2009) suggest that the horizontally curving slopes around the GB and Flemish Cap (FC) are associated with increased eddy generation relative to less curved portions. The curvature, convex or concave, we refer to is of isobaths, horizontal lines of constant bottom depth.…”

Section: Introductionmentioning

confidence: 99%

“…The task of measuring and characterizing eddy generation mechanisms is more challenging for deep (sub-surface intensified) boundary currents, since they are much less amenable to remote sensing, and since even after decades of oceanographic expeditions, in situ measurements are quite sparse. A prominent example is the variability associated with the Deep Western Boundary Current (DWBC) in the Grand Banks (GB) area, where eddy shedding and interior flow pathways are prevalent, as observational campaigns using deep Lagrangian floats have revealed (Lavender et al 2000(Lavender et al , 2005Bower et al 2009). …”

Section: Introductionmentioning

confidence: 99%

Baroclinic instability of axially symmetric flow over sloping bathymetry

2016

View full text Add to dashboard Cite

Observations and models of deep ocean boundary currents show that they exhibit complex variability, instabilities and eddy shedding, particularly over continental slopes that curve horizontally, for example around coastal peninsulas. In this article the authors investigate the source of this variability by characterizing the properties of baroclinic instability in mean flows over horizontally curved bottom slopes. The classical 2-layer quasi-geostrophic solution for linear baroclinic instability over sloping bottom topography is extended to the case of azimuthal mean flow in an annular channel. To facilitate comparison with the classical straight channel instability problem of uniform mean flow, the authors focus on comparatively simple flows in an annulus, namely uniform azimuthal velocity and solid-body rotation. Baroclinic instability in solid-body rotation flow is analytically analogous to the instability in uniform straight channel flow due to several identical properties of the mean flow, including vanishing strain rate and vorticity gradient. The instability of uniform azimuthal flow is numerically similar to straight channel flow instability as long as the mean barotropic azimuthal velocity is zero. Nonzero barotropic flow generally suppresses the instability via horizontal curvatureinduced strain and Reynolds stresses work. An exception occurs when the ratio of the bathymetric to isopycnal slopes is close to (positive) one, as is often observed in the ocean, in which case the instability is enhanced. A non-vanishing mean barotropic flow component also results in a larger number of growing eigenmodes and in increased non-normal growth. The implications of these findings for variability in deep western boundary currents are discussed.

show abstract

Interior pathways of the North Atlantic meridional overturning circulation

Cited by 253 publications

References 48 publications

Decadal and multi-decadal variability of Labrador Sea Water in the north-western North Atlantic Ocean derived from tracer distributions: Heat budget, ventilation, and advection

Decadal and multi-decadal variability of Labrador Sea Water in the north-western North Atlantic Ocean derived from tracer distributions: Heat budget, ventilation, and advection

Intra-seasonal variability of the DWBC in the western subpolar North Atlantic

Baroclinic instability of axially symmetric flow over sloping bathymetry

Contact Info

Product

Resources

About