Enhanced diapycnal mixing by salt fingers in the thermocline of the tropical Atlantic.
Diapycnal mixing plays a significant role in the ocean's circulation and uptake of heat and carbon dioxide, but has not been quantified in salt finger-driven thermohaline staircases. We recently performed a tracer release experiment in the western tropical Atlantic staircase at approximately 400 m depth. The observed dispersion implies an effective diapycnal diffusivity for tracer and salt of 0.8 to 0.9 x 10(-4) m2/s. Temperature microstructure data interpreted in terms of a vertical production-dissipation balance yields a smaller effective diffusivity for heat of 0.45 (+/- 0.2) x 10(-4) m2/s, consistent with salt fingers and well above the mixing ascribable to mechanical turbulence.
Schmitt
R W
RW
Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
Ledwell
J R
JR
Montgomery
E T
ET
Polzin
K L
KL
Toole
J M
JM