  We present experimental measurements of a wall-bounded gravity current,
motivated by characterizing natural gravity currents such as oceanic overflows.
We use particle image velocimetry and planar laser-induced fluorescence to
simultaneously measure the velocity and density fields as they evolve
downstream of the initial injection from a turbulent channel flow onto a plane
inclined at 10$^\circ$ with respect to horizontal. The turbulence level of the
input flow is controlled by injecting velocity fluctuations upstream of the
output nozzle. The initial Reynolds number based on Taylor microscale of the
flow, R$_\lambda$, is varied between 40 and 120, and the effects of the initial
turbulence level are assessed. The bulk Richardson number $Ri$ for the flow is
about 0.3 whereas the gradient Richardson number $Ri_g$ varies between 0.04 and
0.25, indicating that shear dominates the stabilizing effect of stratification.
Kelvin-Helmholtz instability results in vigorous vertical transport of mass and
momentum. We present baseline characterization of standard turbulence
quantities and calculate, in several different ways, the fluid entrainment
coefficient $E$, a quantity of considerable interest in mixing parameterization
for ocean circulation models. We also determine properties of mixing as
represented by the flux Richardson number $Ri_f$ as a function of $Ri_g$ and
diapycnal mixing parameter $K_\rho$ versus buoyancy Reynolds number $Re_b$. We
find reasonable agreement with results from natural flows.
