Microstructure measurements and heat flux calculations of a triple‐diffusive process in a lake within the diffusive layer convection regime

Sanchez, Xavier; Roget, Elena

doi:10.1029/2006jc003750

Cited by 23 publications

(44 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is about 5-8 m, which is much larger than those observed in laboratory experiments (Turner, 1968;Huppert and Linden, 1979;Fernando, 1987), lakes (Sánchez and Roget, 2007;Schmid et al, 2010) and other ocean regions (Voorhis and Dorson, 1975;Larson and Gregg, 1983;Padman and Dillon, 1987;Anschutz and Blanc, 1996). Associated with the temperature difference across the interface, θ ∼ 1.3×10 −3 • C, and other fluid properties, as listed in Table 1 below, the thermal Rayleigh number of the interface, Ra TI , is on the order of 10 9 , which is much larger than the typical value reported in the literature (Turner, 1968(Turner, , 1973Sánchez and Roget, 2007). Therefore, additional understanding is needed to elucidate the difference between the result in the deep Arctic Ocean and those in previous studies.…”

Section: Introductionmentioning

confidence: 61%

“…On the other hand, many studies follow the classical boundary layer definition in diffusive convection (Turner, 1968(Turner, , 1973Padman and Dillon, 1989;Sánchez and Roget, 2007;Zaussinger and Spruit, 2013), which is similar to that in Rayleigh-Bénard convection. In Rayleigh-Bénard convection, two thermal boundary layers exist near the top and bottom ends.…”

Section: Diffusive Interfacementioning

confidence: 96%

“…As the interface is the boundary of two adjacent convecting layers, the thermal Rayleigh number of the interface, Ra TI , is proposed to be on the same order as the critical Rayleigh number of convection, which is on the order of 1000 (Turner, 1968(Turner, , 1973. This argument has been found to work well in DC staircases in Lake Banyoles (Sánchez and Roget, 2007 characteristics. One of them is the thick diffusive interface.…”

Section: Introductionmentioning

confidence: 96%

See 2 more Smart Citations

The instability of diffusive convection and its implication for the thermohaline staircases in the deep Arctic Ocean

Zhou

et al. 2014

Ocean Sci.

View full text Add to dashboard Cite

Abstract. In the present study, the classical description of diffusive convection is updated to interpret the instability of diffusive interfaces and the dynamical evolution of the bottom layer in the deep Arctic Ocean. In the new consideration of convective instability, both the background salinity stratification and rotation are involved. The critical Rayleigh number of diffusive convection is found to vary from 10 3 to 10 11 in the deep Arctic Ocean as well as in other oceans and lakes. In such a wide range of conditions, the interfaceinduced thermal Rayleigh number is shown to be consistent with the critical Rayleigh number of diffusive convection. In most regions, background salinity stratification is found to be the main hindrance to the occurrence of convecting layers. With the new parameterization, it is predicted that the maximum thickness of the bottom layer is 1051 m in the deep Arctic Ocean, which is close to the observed value of 929 m. The evolution time of the bottom layer is predicted to be ∼ 100 yr, which is on the same order as that based on 14 C isolation age estimation.

show abstract

Section: Introductionmentioning

confidence: 61%

Section: Diffusive Interfacementioning

confidence: 96%

Section: Introductionmentioning

confidence: 96%

See 1 more Smart Citation

The instability of diffusive convection and its implication for the thermohaline staircases in the deep Arctic Ocean

Zhou

et al. 2014

Ocean Sci.

View full text Add to dashboard Cite

show abstract

“…The Ra bl condition of Linden & Shirtcliffe (1978) represents a plausible control on the growth of the boundary layer, and has received some tentative support from field observations (Padman & Dillon 1989;Sanchez & Roget 2007), although these observations lack sufficient knowledge of the S-field. It is possible to determine Ra bl (t) in the simulations, and this is shown in figure 14.…”

Section: Boundary Layer Stabilitymentioning

confidence: 99%

Simulations of a double-diffusive interface in the diffusive convection regime

2012

View full text Add to dashboard Cite

Three-dimensional direct numerical simulations are performed that give us an in-depth account of the evolution and structure of the double-diffusive interface. We examine the diffusive convection regime, which, in the oceanographically relevant case, consists of relatively cold fresh water above warm salty water. A 'double-boundary-layer' structure is found in all of the simulations, in which the temperature (T) interface has a greater thickness than the salinity (S) interface. Therefore, thin gravitationally unstable boundary layers are maintained at the edges of the diffusive interface. The TS-interface thickness ratio is found to scale with the diffusivity ratio in a consistent manner once the shear across the boundary layers is accounted for. The turbulence present in the mixed layers is not able to penetrate the stable stratification of the interface core, and the TS-fluxes through the core are given by their molecular diffusion values. Interface growth in time is found to be determined by molecular diffusion of the S-interface, in agreement with a previous theory. The stability of the boundary layers is also considered, where we find boundary layer Rayleigh numbers that are an order of magnitude lower than previously assumed.

show abstract

“…in Lake Lugano (Wüest et al, 1992) or in the strongly meromictic Brenda Mines pit lake (Stevens and Lawrence, 1998), few reports on the explicit appearance of characteristic double-diffusive steps or staircases as a result of local convective mixing for lakes in temperate climates exist so far. Sánchez et al (2007) present microstructure profiles of temperature and salinity and particle concentration data from the ∼1 m thick bottom water body in the ∼35 m deep carstic Lake Banyoles in Spain, where a triple diffusive staircase was sustained. España et al (2009) give another example of step-like structures in the bottom-heated monimolimnion of a mining lake in Spain.…”

Section: Introductionmentioning

confidence: 99%

Evidence for double diffusion in temperate meromictic lakes

Rohden

Boehrer

Ilmberger

2010

Hydrol. Earth Syst. Sci.

View full text Add to dashboard Cite

Abstract. We present CTD-measurements from two shallow meromictic mining lakes. The lakes, which differ in size and depth, show completely different seasonal mixing patterns in their mixolimnia. However, the measurements document the occurrence of similar seasonal convective mixing in discrete layers within their monimolimnia. This mixing is induced by double diffusion and can be identified by the characteristic step-like structure of the temperature and electrical conductivity profiles. The steps develop in the upper part of the monimolimnion, when in autumn cooling mixolimnion temperatures have dropped below temperatures of the underlying monimolimnion. The density gradient across the chemocline due to solutes overcompensates the destabilizing temperature gradient, and moreover, keeps the vertical transport close to molecular level. In conclusion, preconditions for double diffusive effects are given on a seasonal basis. At in general high local stabilities N 2 in the monimolimnia of 10 −4 −10 −2 s −2 , the stability ratio R ρ was in the range of 1-20. This quantitatively indicates that double diffusion can become visible. Between 1 and 6 sequent steps, with sizes between 1 dm and 1 m, were visually identified in the CTDprofiles. In the lower monimolimnion of the deeper lake, the steps systematically emerge at a time delay of more than half a year, which matches with the progression of the mixolimnetic temperature changes into the monimolimnion. In none of the lakes, the chemocline interface is degraded by these processes. However, double diffusive convection is essential for the redistribution of solutes in the inner parts of the monimolimnion at longer time scales, which is crucial for the assessment of the ecologic development of such lakes.

show abstract

Microstructure measurements and heat flux calculations of a triple‐diffusive process in a lake within the diffusive layer convection regime

Cited by 23 publications

References 54 publications

The instability of diffusive convection and its implication for the thermohaline staircases in the deep Arctic Ocean

The instability of diffusive convection and its implication for the thermohaline staircases in the deep Arctic Ocean

Simulations of a double-diffusive interface in the diffusive convection regime

Evidence for double diffusion in temperate meromictic lakes

Contact Info

Product

Resources

About