Deep water formation, the subpolar gyre, and the meridional overturning circulation in the subpolar North Atlantic

Rhein, Monika; Kieke, Dagmar; Hüttl-Kabus, Sabine; Roessler, Achim; Mertens, Christian; Meißner, Robert H.; Klein, Birgit; Böning, Claus W.; Yashayaev, Igor

doi:10.1016/j.dsr2.2010.10.061

Cited by 132 publications

(165 citation statements)

References 59 publications

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“…less dense) version of the LSW (e.g. Rhein et al, 2011;Steinfeldt et al, 2009). Thus the deep version of the LSW only experience limited ventilation during this time, i.e.…”

Section: Discussionmentioning

confidence: 99%

“…Since the resulting coverage is very sparse in most regions, we focus on the two northernmost regions (A -the western part of the SPNA, and B -the eastern portion of the SPNA) where more data is available, and where significant changes in deep water formation has occurred over time (e.g. Rhein et al, 2011). The data for the 3 time periods are displayed in Figs.…”

Section: Temporal Variationsmentioning

confidence: 99%

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Changes in column inventories of carbon and oxygen in the Atlantic Ocean

Tanhua

2012

Biogeosciences

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Abstract. Increasing concentrations of dissolved inorganic carbon (DIC) in the interior ocean are expected as a direct consequence of increasing concentrations of CO 2 in the atmosphere. This extra DIC is often referred to as anthropogenic carbon (C ant ), and its inventory, or increase rate, in the interior ocean has previously been estimated by a multitude of observational approaches. Each of these methods is associated with hard to test assumptions since C ant cannot be directly observed. Results from a simpler concept with fewer assumptions applied to the Atlantic Ocean are reported on here using two large data collections of carbon relevant bottle data. The change in column inventory on decadal time scales, i.e. the storage rate, of DIC, respiration compensated DIC and oxygen is calculated for the Atlantic Ocean. We report storage rates and the confidence intervals of the mean trend at the 95 % level (CI), reflecting the mean trend but not considering potential biasing effects of the spatial and temporal sampling. For the whole Atlantic Ocean the mean trends for DIC and oxygen are non-zero at the 95 % confidence level: DIC: 0.86 (CI: 0.72-1.00) and oxygen: −0.24 (CI: −0.41-(−0.07)) mol m −2 yr −1 . For oxygen, the whole Atlantic trend is dominated by the subpolar North Atlantic, whereas for other regions the O 2 trends are not significant. The storage rates are similar to changes found by other studies, although with large uncertainty. For the subpolar North Atlantic the storage rates show significant temporal and regional variation of all variables. This seems to be due to variations in the prevalence of subsurface water masses with different DIC and oxygen concentrations leading to sometimes different signs of storage rates for DIC compared to published C ant estimates. This study suggest that accurate assessment of the uptake of CO 2 by the oceans will require accounting not only for processes that influence C ant but also additional processes that modify CO 2 storage.

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“…less dense) version of the LSW (e.g. Rhein et al, 2011;Steinfeldt et al, 2009). Thus the deep version of the LSW only experience limited ventilation during this time, i.e.…”

Section: Discussionmentioning

confidence: 99%

Section: Temporal Variationsmentioning

confidence: 99%

Changes in column inventories of carbon and oxygen in the Atlantic Ocean

Tanhua

2012

Biogeosciences

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“…The Flemish Cap mooring array (Figure 8) was installed with the aim of measuring strength and variability of the export of deep water from the subpolar North Atlantic and to compare the observed variability with measurements of the North Atlantic Current transport west of the Mid-Atlantic Ridge (Rhein et al, 2011).…”

Section: The Flemish Cap Array At 47°nmentioning

confidence: 99%

“…The Cape Farewell region appears to be a region with a complex deep circulation, including recirculating pathways (Holliday et al, 2009). 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).…”

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

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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...

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“…The deep convection processes there behave as a driving mechanism for the Meridional Overturning Circulation (Kuhlbrodt et al, 2007;Rhein et al, 2011;Sarafanov et al, 2012), which transports heat to high latitudes in the North Atlantic and is predicted to slow down at the end of the present century (IPCC, 2007). Additionally, the SPNA presents the highest anthropogenic CO 2 storage rate of all oceans (Khatiwala et al, 2013) due to both the advection of surface waters enriched with anthropogenic CO 2 in the subtropical North Atlantic (Pérez et al, 2013;Zunino et al, 2015) and their deep injection in the subpolar gyre (Pérez et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

The GEOVIDE cruise in May–June 2014 reveals an intense Meridional Overturning Circulation over a cold and fresh subpolar North Atlantic

et al. 2017

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Abstract. The GEOVIDE cruise was carried out in the subpolar North Atlantic (SPNA) along the OVIDE section and across the Labrador Sea in May-June 2014. It was planned to clarify the distribution of the trace elements and their isotopes in the SPNA as part of the GEOTRACES international program. This paper focuses on the state of the circulation and distribution of thermohaline properties during the cruise. In terms of circulation, the comparison with the 2002-2012 mean state shows a more intense Irminger Current and also a weaker North Atlantic Current, with a transfer of volume transport from its northern to its central branch. However, those anomalies are compatible with the variability already observed along the OVIDE section in the 2000s. In terms of properties, the surface waters of the eastern SPNA were much colder and fresher than the averages over 2002-2012. In spite of negative temperature anomalies in the surface waters, the heat transport across the OVIDE section estimated at 0.56 ± 0.06 PW was the largest measured since 2002. This relatively large value is related to the relatively strong Meridional Overturning Circulation measured across the OVIDE section during GEOVIDE (18.7 ± 3.0 Sv). By analyzing the air-sea heat and freshwater fluxes over the eastern SPNA in relation to the heat and freshwater content changes observed during 2013 and 2014, we concluded that on a short timescale these changes were mainly driven by air-sea heat and freshwater fluxes rather than by ocean circulation.

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Deep water formation, the subpolar gyre, and the meridional overturning circulation in the subpolar North Atlantic

Cited by 132 publications

References 59 publications

Changes in column inventories of carbon and oxygen in the Atlantic Ocean

Changes in column inventories of carbon and oxygen in the Atlantic Ocean

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

The GEOVIDE cruise in May–June 2014 reveals an intense Meridional Overturning Circulation over a cold and fresh subpolar North Atlantic

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