Shipboard current measurements in the equatorial Indian Ocean in October and November of 2011 revealed oscillations in the meridional velocity with amplitude ~0.10 m/s. These were clearest in a layer extending from ~300 to 600 m depth and had periods near 3 weeks. Phase propagation was upward. Measurements from two...
Deep cycle mixing in the cold tongue of the equatorial
Pacific Ocean is associated with a mean flow regime
in which the gradient Richardson number Ri (a ratio of
stratification to shear that affects the evolution of turbulence)
fluctuates about a critical value near 1/4. This is the state
of...
A new theory of shear instability in a turbulent environment is applied to eight days of velocity and density profiles from the upper-equatorial Pacific. This period featured a regular diurnal cycle of surface forcing, together with a clear response in upper-ocean mixing. During the day, a layer of stable stratification...
The effect of non-zero, but small, viscosity and diffusivity on the marginal stability
of a stably stratified shear flow is examined by making perturbations around the
neutral solution for an inviscid and non-diffusive flow. The results apply to turbulent
flows in which horizontal and vertical turbulent transports of momentum and...
Mixing due to sheared salt fingers is studied by means of direct numerical simulations (DNS) of a double-diffusively unstable shear layer. The focus is on the “moderate shear” case, where shear is strong enough to produce Kelvin–Helmholtz (KH) instability but not strong enough to produce the subharmonic pairing instability. This...
The Taylor–Goldstein (T–G) equation is extended to include the effects of small-scale
turbulence represented by non-uniform vertical and horizontal eddy viscosity and
diffusion coefficients. The vertical coefficients of viscosity and diffusion, A[subscript V] and K[subscript V],
respectively, are assumed to be equal and are expressed in terms of the buoyancy...
Measurements of velocity, hydrography, surface meteorology, and microstructure were made through several squall events during a westerly wind burst that occurred in the Western Pacific warm pool in December 1992. Sustained wind forcing generated a weakly stratified turbulent surface layer that extended to the top of the main thermocline. Following...
Direct simulations are used to study turbulence and mixing in Holmboe waves. Previous results showing that mixing in Holmboe waves is comparable to that found in the better-known Kelvin–Helmholtz (KH) billows are extended to cover a range of stratification levels. Mixing efficiency is discussed in detail, as are effective diffusivities...
The linear theory of double diffusive interleaving is extended to take account of baroclinic effects. This study goes beyond previous studies by including the possibility of modes with nonzero tilt in the alongfront direction, which allows for advection by the baroclinic frontal flow. This requires that the stability equations be...
The response of the upper ocean to westerly wind forcing in the western equatorial Pacific was modeled by means of large-eddy simulation for the purpose of comparison with concurrent microstructure observations. The model was initialized using currents and hydrography measured during the Coupled Ocean–Atmosphere Response Experiment (COARE) and forced using...