Salinity-driven Thermocline Transients in a Wind- and Thermohaline-forced Isopycnic Coordinate Model of the North Atlantic

Bleck, Rainer; Rooth, Claes; Hu, Dingming; Smith, Linda Tombras

doi:10.1175/1520-0485(1992)022<1486:sdttia>2.0.co;2

Cited by 479 publications

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“…We consider a hindcast simulation of the North Atlantic Ocean using a regional version of the Nansen Center version (Bentsen et al 2004) of the Miami Isopycnic Coordinate Ocean Model (MICOM, Bleck et al 1992. Detailed descriptions of the model, its circulation and water property characteristics have been previously published (e.g., Drange et al, 2005;Hatun et al 2005a and b;Mauritzen et al 2006;Deshayes et al 2007;DF08).…”

Section: The Simulationmentioning

confidence: 99%

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: The Simulationmentioning

confidence: 99%

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

2009

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“…This model is well documented in the literature. For a review, the reader is referred to Bleck et al [1992] and Bleck and Chassignet [1994]. The fundamental reason for modeling ocean flow in density coordinates is that this system suppresses the diapycnal component of numerically caused dispersion of material and thermodynamic properties, such as temperature and salinity.…”

Section: ¦¤mentioning

confidence: 99%

Pathways and variability at intermediate depths in the tropical Atlantic

Schmid

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Johns

et al. 2003

Interhemispheric Water Exchange in the Atlantic Ocean

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¤ is present, which can not be resolved by the spectral analysis. In the time space the spectral analysis for the zonal and meridional velocity reveals coinciding peaks at periods of 45 days, 66 days and one year. For the latter two periods the energy for the two velocity components are quite similar. An analytical planetary wave solution shows that a superposition of a mesoscale and an annual planetary wave is sufficient to reproduce a large part of the variability found in the observations and the model. The wave with an annual period is most likely due to the annual cycle of the wind field.

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“…Various implicit models have been developed and used by many researchers (e.g. Backhaus, 1983Backhaus, , 1985Backhaus, , 1987Blumberg and Mellor, 1987;Davies, 1987;Bleck et al, 1992;Davies and Lawrence, 1994;Ip and Lynch, 1994;Song and Haidvogel, 1994).…”

Section: Introductionmentioning

confidence: 99%

Barotropic response in a lake to wind-forcing

2001

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Abstract.We report results gained with a three-dimensional, semi-implicit, semi-spectral model of the shallow water equations on the rotating Earth that allowed one to compute the wind-induced motion in lakes. The barotropic response to unidirectional, uniform winds, Heaviside in time, is determined in a rectangular basin with constant depth, and in Lake Constance, for different values and vertical distributions of the vertical eddy viscosities. It is computationally demonstrated that both the transitory oscillating, as well as the steady state current distribution, depends strongly upon the absolute value and vertical shape of the vertical eddy viscosity. In particular, the excitation and attenuation in time of the inertial waves, the structure of the Ekman spiral, the thickness of the Ekman layer, and the exact distribution and magnitude of the upwelling and downwelling zones are all significantly affected by the eddy viscosities. Observations indicate that the eddy viscosities must be sufficiently small so that the oscillatory behaviour can be adequately modelled.Comparison of the measured current-time series at depth in one position of Lake Constance with those computed on the basis of the measured wind demonstrates fair agreement, including the rotation-induced inertial oscillation.

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Salinity-driven Thermocline Transients in a Wind- and Thermohaline-forced Isopycnic Coordinate Model of the North Atlantic

Cited by 479 publications

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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

Pathways and variability at intermediate depths in the tropical Atlantic

Barotropic response in a lake to wind-forcing

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