Skip to main content Accessibility help

Heat, salt and momentum transport in a laboratory thermohaline staircase



Flow characteristics and fluxes in thermohaline staircases are measured in two tanks differing in aspect ratio A, where A is the ratio of tank width to fluid depth. In one tank (the ‘1 × 1’ tank) which is 30 cm deep and 30 cm wide, a staircase of one salt-finger layer and one convecting layer develops for a certain setting of the control parameters. The convecting layer has A ≃ 2. Shadowgraphs show convecting plumes that appear disorganized, and a large-scale flow never develops. Instead, the finger layer grows in height, overtakes the convecting layer and within a few days becomes one finger layer. The second tank (the ‘1 × 5’ tank) is also 30 cm deep but is 150 cm wide. For the same control parameter setting a similar staircase with a finger layer 20 cm deep and a convecting layer 10 cm deep develop. The convecting layer, with A = 15, has quite a different character. A large-scale flow develops so that the convecting layer has one cell, 10 cm deep and 150 cm wide. In this flow are large plumes which are transient and tilted; particle image velocimetry measurements of Reynolds stresses show they help to maintain the large-scale flow against viscous dissipation. Shadowgraphs show all the finger tips swept in the direction of the large-scale flow adjacent to the finger layer. Measurements show that the large-scale flow ‘collects’ the salt delivered by the many fingers so that the accumulated negative buoyancy leads to deep convection. This is a more stable arrangement, with the configuration lasting to the order of 102 days.


Corresponding author

Email address for correspondence:


Hide All
Castaign, B.Gunrantne, G., Heslot, F., Kadanoff, L., Libchaber, A., Thomae, S., Wu, X.-Z., Zaleski, S. & Zanetti, G. 1989 Scaling of hard thermal turbulence in Rayleigh–Bénard convection. J. Fluid Mech. 204, 130.
Christiansen, K. T., Soloff, S. M. & Adrian, R. J. 2001 PIV Sleuth: integrated particle image velocimetry (PIV) interrogation/validation software. Tech Rep. 943. Department of Theoretical and Applied Mechanics, University of Illinois at Urbana-Champaign.
Griffiths, R. W. & Ruddick, B. R. 1980 Accurate fluxes across a salt-sugar finger interface deduced from direct density measurements. J. Fluid Mech. 99, 8595.
Krishnamurti, R. 2005 Double-diffusive interleaving on horizontal gradients. J. Fluid Mech. 558, 113131.
Krishnamurti, R. 2003 Double-diffusive transport in laboratory thermohaline staircases. J.Fluid Mech. 483, 287314.
Krishnamurti, R. 1995 Low-frequency oscillations in turbulent Rayleigh–Bénard convection: laboratory experiments. Fluid Dyn. Res. 16, 87108.
Krishnamurti, R. & Howard, L. N. 1981 Large-scale flow generation in turbulent convection. Proc. Natl Acad. Sci. 78, 19811985.
Lambert, R. B. & Demenkow, J. W. 1972 On the vertical transport due to fingers in double-diffusive convection. J. Fluid Mech. 54, 627640.
Oster, G. 1965 Density gradients. Scient. Am. 213, 7076.
Radko, T. 2005 What determines the thickness of layers in a thermohaline staircase? J. Fluid Mech. 253, 7998.
Ruddick, B. R. & Shirtcliffe, T. G. L. 1979 Data for double-diffusers: Physical properties of aqueous salt-sugar solutions. Deep-Sea Res. 26A, 7757873.
Schmitt, R. W. 1979 Flux measurements at an interface. J. Mar. Res. 37, 419436.
MathJax is a JavaScript display engine for mathematics. For more information see

Heat, salt and momentum transport in a laboratory thermohaline staircase



Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed