Circulation characteristics in three eddy-permitting models of the North Atlantic

Willebrand, Jürgen; Barnier, Bernard; Böning, Claus W.; Dieterich, Christian; Killworth, Peter D.; Provost, C. Le; Jia, Yanli; Molines, Jean‐Marc; New, Adrian L.

doi:10.1016/s0079-6611(01)00003-9

Cited by 217 publications

(177 citation statements)

References 70 publications

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“…In the deep layers, the simulated density and salinity structure reflect the difficulties of isopycnal coordinate models in reproducing the processes of overflow and entrainment that ventilate these deep basins (e.g., Willebrand et al 2001). The volume of dense waters (σ θ > 27.80 kgm -3 ) corresponding to the overflows is significantly reduced and the salinity maximum observed below 2 km is replaced by a small salinity increase down to the bottom.…”

Section: Mean Fieldsmentioning

confidence: 86%

The role of salinity in the decadal variability of the North Atlantic meridional overturning circulation

2009

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An OGCM hindcast is used to investigate the linkages between North Atlantic Ocean salinity and circulation changes during . The focus is on the eastern subpolar region consisting of the Irminger Sea and the eastern North Atlantic where a careful assessment shows that the simulated interannual to decadal salinity changes in the upper 1500 m reproduce well those derived from the available record of hydrographic measurements. In the model, the variability of the Atlantic meridional overturning circulation (MOC) is primarily driven by changes in deep water formation taking place in the Irminger Sea and, to a lesser extent, the Labrador Sea. Both are strongly influenced by the North Atlantic Oscillation (NAO). The modeled interannual to decadal salinity changes in the subpolar basins are mostly controlled by circulation-driven anomalies of freshwater flux convergence, although surface salinity restoring to climatology and other boundary fluxes each account for approximately 25% of the variance. The NAO plays an important role: a positive NAO phase is associated with increased precipitation, reduced northward salt transport by the wind-driven intergyre gyre, and increased southward flows of freshwater across the Greenland-Scotland ridge. Since the NAO largely controlled deep convection in the subpolar gyre, fresher waters are found near the sinking region during convective events. This markedly differs from the active influence on the MOC that salinity exerts at decadal and longer timescales in most coupled models. The intensification of the MOC that follows a positive NAO phase by about 2 years does not lead to an increase in the northward salt transport into the subpolar domain at low frequencies because it is cancelled by the concomitant intensification of the subpolar gyre which shifts the subpolar front eastward and reduces the northward salt transport by the North Atlantic Current waters. This differs again from most coupled models, where the gyre intensification precedes that of the MOC by several years.3

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Section: Mean Fieldsmentioning

confidence: 86%

The role of salinity in the decadal variability of the North Atlantic meridional overturning circulation

2009

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“…The model intercomparison study carried out in the Dynamics of North Atlantic Models (DYNAMO) project (Willebrand et al 2001) showed that the proper representation of the mixing depends much on the choice of the vertical coordinate. Most climate OGCMs are formulated on depth coordinates and obtain far too much mixing for dense overflows at a sill.…”

Section: Parameterization Of Dense Outflow and Bottom Boundary Layer mentioning

confidence: 99%

Modelling the Overflows Across the Greenland–Scotland Ridge

Jungclaus

Macrander

Käse

2008

Arctic–Subarctic Ocean Fluxes

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“…Most of the models use geopotential coordinate surfaces, however, H€ a akkinen (1999) uses terrainfollowing r-coordinates and Holland (2001) uses isopycnic coordinates. These three basic choices were the focus of the Atlantic model comparison in the European Union project DY-NAMO (DYNAMO group, 1999;Willebrand et al, 2001). The DYNAMO project found that considerable differences in model results could be due to the choice of the vertical coordinate system.…”

Section: Introductionmentioning

confidence: 99%

Comparing modeled streamfunction, heat and freshwater content in the Arctic Ocean

Steiner¹,

Holloway²,

Gerdes

et al. 2004

Ocean Modelling

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Within the framework of the Arctic Ocean Model Intercomparison Project results from several coupled sea ice-ocean models are compared in order to investigate vertically integrated properties of the Arctic Ocean. Annual means and seasonal ranges of streamfunction, freshwater and heat content are shown. For streamfunction the entire water column is integrated. For heat and freshwater content integration is over the upper 1000 m. The study represents a step toward identifying differences among model approaches and will serve as a base for upcoming studies where all models will be executed with common forcing. In this first stage only readily available outputs are compared, while forcing as well as numerical parameterizations differ.The intercomparison shows streamfunctions differing in pattern and by several Sverdrups in magnitude. Differences occur as well for the seasonal range, where streamfunction is subject to large variability.Annual mean heat content, referenced to 0°C, in the Canada Basin varies from )3.5 to +1.8 GJ m À2 among the models, representing both colder and warmer solutions compared to the climatology. Seasonal range is highest in regions with seasonal or no ice cover.Corresponding freshwater content, referenced to 34.8 ppt, shows differences most obviously in the Beaufort Sea and Canada Basin where maximum values vary between 6 and 24 m for the individual models. Maxima in the seasonal range are related to river inflow.In the current stage of the project, applied windstress contributes significantly to the differences. However differences due to model resolutions and model parameterizations can already be detected.

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Circulation characteristics in three eddy-permitting models of the North Atlantic

Cited by 217 publications

References 70 publications

The role of salinity in the decadal variability of the North Atlantic meridional overturning circulation

The role of salinity in the decadal variability of the North Atlantic meridional overturning circulation

Modelling the Overflows Across the Greenland–Scotland Ridge

Comparing modeled streamfunction, heat and freshwater content in the Arctic Ocean

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