Salt Fingers Observed in the Mediterranean Outflow Region (34°N, 11°W) Using a Towed Sensor

Magnell, Bruce

doi:10.1175/1520-0485(1976)006<0511:sfoitm>2.0.co;2

Cited by 49 publications

(13 citation statements)

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“…inhibited by shears. In support of this we note that observations of salt fingers in the ocean have been made by Williams [1975] qn d Magnell [1976] and that Gargett [1976] has found increased microstructure activity where double-diffusive processes a[.e possible. We feel that fingers must be nearly ubiquitous in the central waters and make a substantial contribution to the vertical fluxes of heat and mass.…”

supporting

confidence: 83%

An estimate of the vertical mixing due to salt fingers based on observations in the North Atlantic central water

Schmitt¹,

Evans²

1978

J. Geophys. Res.

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Recent theoretical work suggests that salt fingers have sufficiently rapid growth rates in much of the thermocline to produce significant vertical fluxes of heat and mass, even in an active internal wave field. Using laboratory determinations of the power law for the salt flux we have estimated the salt flux at depth for several CTD stations in the central water of the North Atlantic by assuming the fingers to be intermittently active on the high‐gradient sheets in the thermocline. The flux is found to be comparable to the surface input of salt due to evaporation. This implies a release of energy by the falling out of salt, comparable to the rate of work done by the wind on the mean circulation, and supports the model of Stern (1969b). Salt fingers transport heat and mass at different rates, and thus the usual concept of an ‘eddy diffusivity’ is invalid when salt fingers make a major contribution to the vertical mixing processes.

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supporting

confidence: 83%

An estimate of the vertical mixing due to salt fingers based on observations in the North Atlantic central water

Schmitt¹,

Evans²

1978

J. Geophys. Res.

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“…Thermohaline staircases represent the most dramatic manifestation of double-diffusive convection in the ocean. For finger-driven staircases, the majority of observations have come from three locations: the western tropical Atlantic (Schmitt et al 1987(Schmitt et al , 2005, Tyrrhenian Sea (Zodiatis and Gasparini 1996), and the Mediterranean outflow in the Northeast Atlantic (Tait andHowe 1968, 1971;Magnell 1976). Common to these regions are anomalously low values of the density ratio:…”

Section: Introductionmentioning

confidence: 74%

Double-Diffusive Recipes. Part I: Large-Scale Dynamics of Thermohaline Staircases

Radko

Bulters

Flanagan

et al. 2014

Journal of Physical Oceanography

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Three-dimensional dynamics of thermohaline staircases are investigated using a series of basin-scale staircase-resolving numerical simulations. The computational domain and forcing fields are chosen to reflect the size and structure of the North Atlantic subtropical thermocline. Salt-finger transport is parameterized using the flux-gradient formulation based on a suite of recent direct numerical simulations. Analysis of the spontaneous generation of thermohaline staircases suggests that thermohaline layering is a product of the gamma instability, associated with the variation of the flux ratio g with the density ratio R r . After their formation, numerical staircases undergo a series of merging events, which systematically increase the size of layers. Ultimately, the system evolves into a steady equilibrium state with pronounced layers 20-50 m thick. The size of the region occupied by thermohaline staircases is controlled by the competition between turbulent mixing and double diffusion. Assuming, in accordance with observations, that staircases form when the density ratio is less than the critical value of R cr ' 1:7, the authors arrive at an indirect estimate of the characteristic turbulent diffusivity in the subtropical thermocline.

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“…It is strongest when the salinity gradient almost compensates the temperature gradient. Fingering-favorable conditions are found in the subtropical Atlantic and Indian pycnoclines (Schmitt, 1981(Schmitt, , 2003You, 2002), below salt tongues originating from the Mediterranean and Red seas (e.g., Williams, 1974;Magnell, 1976), and in double-diffusive intrusions that form at density-compensated water-mass fronts (Toole and Georgi, 1981;Ruddick and Richards, 2003). Of principal interest to the general oceanographic community is their heatand salt-fluxes as these can lead to water-mass modification and lower the available potential energy of the water column.…”

Section: Introductionmentioning

confidence: 99%

Evaluating salt-fingering theories

Inoue¹,

Kunze²,

Laurent³

et al. 2008

J Mar Res

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The NATRE fine-and microstructure data set is revisited to test salt-finger amplitude theories. Dependences of the mixing efficiency ⌫, microscale buoyancy Reynolds number Re and thermal Cox number Cx T on 5-m density ratio R and gradient Richardson number Ri are examined. The observed mixing efficiency is too high to be explained by linear fastest-growing fingers but can be reproduced by wavenumbers 0.5-0.9 times lower than the fastest-growing wavenumber. Constraining these fingers with a hybrid wave/finger Froude number or a finger Reynolds number cannot reproduce the observed trends with R or Ri, respectively. This suggests that background shear has no influence on finger amplitudes. Constraining average amplitudes of these lower-wavenumber fingers with finger Richardson number Ri f ϳ 0.2 reproduces the observed dependence of Re and Cx T on density ratio R and Ri at all but the lowest observed density ratio (R ϭ 1.3). Separately relaxing the assumptions of viscous control, dominance of a single mode and tall narrow fingers does not explain the difference between theory and data at low R for a critical Ri f ϳ 0.2.

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Salt Fingers Observed in the Mediterranean Outflow Region (34°N, 11°W) Using a Towed Sensor

Cited by 49 publications

References 0 publications

An estimate of the vertical mixing due to salt fingers based on observations in the North Atlantic central water

An estimate of the vertical mixing due to salt fingers based on observations in the North Atlantic central water

Double-Diffusive Recipes. Part I: Large-Scale Dynamics of Thermohaline Staircases

Evaluating salt-fingering theories

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