Date of Award

Winter 2010

Project Type


Program or Major

Mechanical Engineering

Degree Name

Master of Science

First Advisor

Gregory P Chini


Comparably little is known about the impact of lateral density gradients associated with, e.g., submesoscale fronts on Langmuir circulation in the ocean surface mixed layer. In this investigation, two-dimensional pseudospectral numerical simulations of the laterally stratified Craik--Leibovich (CL) equations are performed to elucidate the effect of an imposed horizontal density gradient on Langmuir cells. The dominant instability mode is found to consist of counter-rotating cells with up- and downwelling jets inclined to the vertical. Linear stability analysis confirms that, although no instability occurs in the absence of the CL vortex torque, the dominant instability mode exhibits growth rates exceeding those realized in a constant density fluid. An energy budget is used to gain insight into the physics of this cooperative instability. The fully nonlinear numerical simulations reveal a secondary instability, in which the tilted cells are laterally sheared, and a subsequent energy cascade to fine scales.