Origin of Thermohaline Staircases

Abstract

Hypotheses concerning the origin of thermohaline staircases in salt fingering regions are reviewed and assessed. One such hypothesis, that staircases arise from thermohaline intrusions, is developed into a quantitative theory. It is shown that growing intrusions evolve toward staircases when the background density ratio lies below a threshold value, and nonlinear computations confirm that staircases are viable intrusion equilibria. Staircase properties such as step heights, lateral density ratios, and layer slopes lie closest to observed values when salt fingers are assumed not to contribute to shear stress and when turbulent mixing rates are smaller than usual thermocline values.