Near the bottom, the velocity profile in the bottom boundary layer over the continental
shelf exhibits a characteristic law-of-the-wall that is consistent with local estimates of
friction velocity from near-bottom turbulence measurements. Farther from the bottom, the
velocity profile exhibits a deviation from the law-of-the-wall. Here the velocity gradient
continues...
A reexamination of turbulence dissipation measurements from the equatorial Pacific shows that the turbulence diffusivities are not a simple function of the gradient Richardson number. A widely used mixing scheme, the K-profile parameterization, overpredicts the turbulent vertical heat flux by roughly a factor of 4 in the stably stratified region...
An integrated analysis of turbulence observations from four unique instrument platforms obtained over
the Hawaiian Ridge leads to an assessment of the vertical, cross-ridge, and along-ridge structure of turbulence
dissipation rate and diffusivity. The diffusivity near the seafloor was, on average, 15 times that in the
midwater column. At 1000-m...
Direct numerical simulations of turbulence resulting from Kelvin–Helmholtz instability in stably
stratified shear flow are used to study sources of anisotropy in various spectral ranges. The set of
simulations includes various values of the initial Richardson and Reynolds numbers, as well as
Prandtl numbers ranging from 1 to 7. We...
The upwelling-driven coastal jet off Oregon is in geostrophic balance to first order.
The accompanying thermal wind shear is stable to shear instability. Yet enhanced
turbulence is observed in the upwelling jet, typically as long, thin patches with horizontal
to vertical aspect ratios of 10² to 10³ (median value ~300)....
A sequence of three internal solitary waves of
elevation were observed propagating shoreward along a
near-bottom density interface over Oregon’s continental
shelf. These waves are highly turbulent and coincide with
enhanced optical backscatter, consistent with increased
suspended sediments in the bottom boundary layer. Nonlinear
solitary wave solutions are employed to...
Detailed and repeated measurements of nitrate across the Oregon shelf, made
coincident with turbulence measurements, reveal the importance of cross-isopycnal
mixing via turbulence in providing nitrate to the upper water column. Spatial distributions
of vertical gradients and turbulent fluxes in the Oregon coastal ocean reveal variability that
could not have...
Preliminary results are presented from an analysis of mid-frequency acoustic transmission data collected at range 550m during the Shallow Water 2006 Experiment. The acoustic data were collected on a vertical array immediately before, during, and after the passage of a nonlinear internal wave on 18 August, 2006. Using oceanographic data...
Horizontal tow measurements of internal waves are rare and have been largely supplanted in recent
decades by vertical profile measurements. Here, estimates of isotherm displacements and turbulence dissipation
rate from a towed vehicle deployed near Hawaii are presented. The displacement data are interpreted
in terms of horizontal wavenumber spectra of...
Isopycnal slope spectra were computed from thermistor data obtained using a microstructure platform
towed through turbulence generated by internal tidal motions near the Hawaiian Ridge. The spectra were
compared with turbulence dissipation rates ε that are estimated using shear probes. The turbulence subrange
of isopycnal slope spectra extends to surprisingly...
Since the end of the Cold War, the US Navy has had an increasing interest in continental shelves and slopes as
operational areas. To work in such areas
requires a good understanding of ocean
acoustics, coastal physical oceanography,
and, in the modern era, autonomous
underwater vehicle (AUV) operations.
Each area...
Varied observations over Oregon’s continental shelf illustrate the
beauty and complexity of geophysical flows in coastal waters. Rapid, creative, and
sometimes fortuitous sampling from ships and moorings has allowed detailed looks
at boundary layer processes, internal waves (some extremely nonlinear), and coastal
currents, including how they interact. These processes drive...
The initial composition of a river plume depends on the cumulative turbulent
entrainment within the estuary and how this dilutes the supplied freshwater. Here we
examine the relative roles of turbulence and freshwater input using observations from the
Columbia River estuary and plume during two periods with contrasting river flow....