Temporal Variability of the Atlantic Meridional Overturning Circulation at 26.5°N

Cunningham, Stuart A.; Kanzow, Torsten; Rayner, Darren; Baringer, Molly O.; Johns, William E.; Marotzke, Jochem; Longworth, Hannah R.; Grant, Elizabeth M.; Hirschi, Joël; Beal, Lisa M.; Meinen, Christopher S.; Bryden, Harry L.

doi:10.1126/science.1141304

Cited by 773 publications

(728 citation statements)

References 13 publications

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“…Observational programs, developed in the last decade, are monitoring the AMOC strength, structure, and variability: the RAPID-MOCHA program (Hirschi et al 2003;Baehr et al 2004;Cunningham et al 2007;Kanzow et al 2007;McCarthy et al 2012) started in 2004 and continuously monitors the AMOC at the 26.58N latitude; the Meridional Overturning Variability Experiment (MOVE) program (Send et al 2002) started in 2000 and is focused on 168N; and the Observatoire de la Variabilité Interannuelle et Décennale en Atlantique Nord (OVIDE) program (Lherminier et al 2007) has been monitoring a section from Greenland to Portugal every other year since 2002. The mechanisms of AMOC variability have also been studied numerically (e.g., Delworth et al 1993;Bentsen et al 2004) throughout the whole basin and on much longer time scales, either from ocean simulations driven by atmospheric reanalyses (in laminar or eddying regimes) or from coupled oceanatmospheric simulations (mostly in the laminar regime).…”

Section: Introductionmentioning

confidence: 99%

Intrinsic Variability of the Atlantic Meridional Overturning Circulation at Interannual-to-Multidecadal Time Scales

Grégorio

Penduff

Sérazin

et al. 2015

Journal of Physical Oceanography

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The low-frequency variability of the Atlantic meridional overturning circulation (AMOC) is investigated from 2, 1 /48, and 1 /128 global ocean-sea ice simulations, with a specific focus on its internally generated (i.e., ''intrinsic'') component. A 327-yr climatological 1 /48 simulation, driven by a repeated seasonal cycle (i.e., a forcing devoid of interannual time scales), is shown to spontaneously generate a significant fraction R of the interannual-to-decadal AMOC variance obtained in a 50-yr ''fully forced'' hindcast (with reanalyzed atmospheric forcing including interannual time scales). This intrinsic variance fraction R slightly depends on whether AMOCs are computed in geopotential or density coordinates, and on the period considered in the climatological simulation, but the following features are quite robust when mesoscale eddies are simulated (at both 1 /48 and 1 /128 resolutions); R barely exceeds 5%-10% in the subpolar gyre but reaches 30%-50% at 348S, up to 20%-40% near 258N, and 40%-60% near the Gulf Stream. About 25% of the meridional heat transport interannual variability is attributed to intrinsic processes at 348S and near the Gulf Stream. Fourier and wavelet spectra, built from the 327-yr 1 /48 climatological simulation, further indicate that spectral peaks of intrinsic AMOC variability (i) are found at specific frequencies ranging from interannual to multidecadal, (ii) often extend over the whole meridional scale of gyres, (iii) stochastically change throughout these 327 yr, and (iv) sometimes match the spectral peaks found in the fully forced hindcast in the North Atlantic. Intrinsic AMOC variability is also detected at multidecadal time scales, with a marked meridional coherence between 358S and 258N (15-30 yr periods) and throughout the whole basin (50-90-yr periods).

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Section: Introductionmentioning

confidence: 99%

Intrinsic Variability of the Atlantic Meridional Overturning Circulation at Interannual-to-Multidecadal Time Scales

Grégorio

Penduff

Sérazin

et al. 2015

Journal of Physical Oceanography

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“…By assuming thermal-wind balance (Marotzke et al 1999), the zonally integrated geostrophic shear can be estimated just from seawater densities at the western and the eastern boundaries of the ocean (ρ w and ρ e , respectively), where they can be measured and reconstructed (e.g., Lynch-Stieglitz 2001;Cunningham et al 2007). One approximation to the zonally averaged velocity component is given by the formula:…”

Section: Amoc Decompositionmentioning

confidence: 99%

Assessing reconstruction techniques of the Atlantic Ocean circulation variability during the last millennium

et al. 2016

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the simulated variability at deep/shallow levels. Density changes responsible for the pseudo-reconstructed FCT are mainly driven by zonal temperature differences; salinity differences oppose but play a minor role. These results thus support the use of the thermal-wind relationship to reconstruct the oceanic circulation past variability, in particular at multidecadal timescales. Yet model-data comparison highlights important differences between the simulated and the proxy-based FCT variability. ECHO-G simulates a prominent weakening in the North Atlantic circulation that contrasts with the reconstructed enhancement. Our model results thus do not support the reconstructed FC minimum during the Little Ice Age. This points to a failure in the reconstruction, misrepresented processes in the model, or an important role of internal ocean dynamics.

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“…Maltrud and McClean, 2005;Kohl and Stammer, 2007;Doos et al, 2008), and to observational estimates in the North Atlantic (e.g. Cunningham et al, 2007).…”

Section: Zonally Averaged Fieldsmentioning

confidence: 99%

Evaluation of a near-global eddy-resolving ocean model

et al. 2013

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Abstract. Analysis of the variability of the last 18 yr (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012) of a 32 yr run of a new near-global, eddy-resolving ocean general circulation model coupled with biogeochemistry is presented. Comparisons between modelled and observed mean sea level (MSL), mixed layer depth (MLD), sea level anomaly (SLA), sea surface temperature (SST), and chlorophyll a indicate that the model variability is realistic. We find some systematic errors in the modelled MLD, with the model generally deeper than observations, which results in errors in the chlorophyll a, owing to the strong biophysical coupling. We evaluate several other metrics in the model, including the zonally averaged seasonal cycle of SST, meridional overturning, volume transports through key straits and passages, zonally averaged temperature and salinity, and El Niño-related SST indices. We find that the modelled seasonal cycle in SST is 0.5-1.5 • C weaker than observed; volume transports of the Antarctic Circumpolar Current, the East Australian Current, and Indonesian Throughflow are in good agreement with observational estimates; and the correlation between the modelled and observed NINO SST indices exceeds 0.91. Most aspects of the model circulation are realistic. We conclude that the model output is suitable for broader analysis to better understand upper ocean dynamics and ocean variability at mid-and low latitudes. The new model is intended to underpin a future version of Australia's operational short-range ocean forecasting system.

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Temporal Variability of the Atlantic Meridional Overturning Circulation at 26.5°N

Cited by 773 publications

References 13 publications

Intrinsic Variability of the Atlantic Meridional Overturning Circulation at Interannual-to-Multidecadal Time Scales

Intrinsic Variability of the Atlantic Meridional Overturning Circulation at Interannual-to-Multidecadal Time Scales

Assessing reconstruction techniques of the Atlantic Ocean circulation variability during the last millennium

Evaluation of a near-global eddy-resolving ocean model

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