Packets of nonlinear internal waves (NLIWs) in a small area of the Mid-Atlantic Bight were 10 times more energetic during a local neap tide than during the preceding spring tide. This counterintuitive result cannot be explained if the waves are generated near the shelf break by the local barotropic tide...
Internal tide generation, propagation, and dissipation are investigated in Luzon Strait, a system of two quasi-parallel ridges situated between Taiwan and the Philippines. Two profiling moorings deployed for about 20 days and a set of nineteen 36-h lowered ADCP-CTD time series stations allowed separate measurement of diurnal and semidiurnal internal...
Turbulence controls the composition of river plumes through mixing and alters the plume's trajectory by diffusing its momentum. While believed to play a crucial role in decelerating river-source waters, the turbulence stress in a near-field river plume has not previously been observationally quantified. In this study, finely resolved density, velocity,...
A complex superposition of locally forced and shoaling remotely generated semidiurnal internal tides occurs on the Oregon continental slope. Presented here are observations from a zonal line of five profiling moorings deployed across the continental slope from 500 to 3000 m, a 24-h expendable current profiler (XCP) survey, and five...
Energy flux is a fundamental quantity for understanding internal wave generation, propagation, and dissipation. In this paper, the estimation of internal wave energy fluxes <u′p′> from ocean observations that may be sparse in either time or depth are considered. Sampling must be sufficient in depth to allow for the estimation...
Observations of turbulence, internal waves, and subinertial flow were made over a steep, corrugated continental slope off Virginia during May–June 1998. At semidiurnal frequencies, a convergence of low-mode, onshore energy flux is approximately balanced by a divergence of high-wavenumber offshore energy flux. This conversion occurs in a region where the...
Direct determination of the irreversible turbulent flux of salinity in the ocean has not been possible because of the complexity of measuring salinity on the smallest scales over which it mixes. Presented is an analysis of turbulent salinity microstructure from measurements using a combined fast-conductivity/temperature probe on a slowly falling...
Time‐dependent buoyant plumes form at the outflow of tidally dominated estuaries. When estuary discharge velocity exceeds plume internal wave speed c, a sharp front forms at the plume’s leading edge that expands from the time‐dependent source. Using observations of the Columbia River tidal plume from multiple tidal cycles we characterize...
Observations of currents, hydrography, and turbulence provide unambiguous evidence for hydraulic control of flow over an isolated three-dimensional topographic feature on Oregon’s continental shelf. The flow becomes critical at the crest of the bank, forming a strong supercritical downslope flow in the lower layer. Farther downstream, internal hydraulic jumps form...
Lateral stirring is a basic oceanographic phenomenon affecting the distribution of physical, chemical, and biological fields. Eddy stirring at scales on the order of 100 km (the mesoscale) is fairly well understood and explicitly represented in modern eddy-resolving numerical models of global ocean circulation. The same cannot be said for...
Lateral stirring is a basic oceanographic phenomenon affecting the distribution of physical, chemical, and biological fields. Eddy stirring at scales on the order of 100 km (the mesoscale) is fairly well understood and explicitly represented in modern eddy-resolving numerical models of global ocean circulation. The same cannot be said for...
Lateral stirring is a basic oceanographic phenomenon affecting the distribution of physical, chemical, and biological fields. Eddy stirring at scales on the order of 100 km (the mesoscale) is fairly well understood and explicitly represented in modern eddy-resolving numerical models of global ocean circulation. The same cannot be said for...
Internal gravity waves, the subsurface analogue of the familiar
surface gravity waves that break on beaches, are ubiquitous in
the ocean. Because of their strong vertical and horizontal currents,
and the turbulent mixing caused by their breaking, they affect a
panoply of ocean processes, such as the supply of nutrients...
The authors present inferences of diapycnal diffusivity from a compilation of over 5200 microstructure
profiles. As microstructure observations are sparse, these are supplemented with indirect measurements of
mixing obtained from (i) Thorpe-scale overturns from moored profilers, a finescale parameterization applied to
(ii) shipboard observations of upper-ocean shear, (iii) strain as...
The three-dimensional (3D) double-ridge internal tide interference in the Luzon Strait in the South China
Sea is examined by comparing 3D and two-dimensional (2D) realistic simulations. Both the 3D simulations
and observations indicate the presence of 3D first-mode (semi)diurnal standing waves in the 3.6-km-deep
trench in the strait. As in...
Abstract: Tide-topography interactions dominate the transfer of tidal energy from large to small scales. At present, it is poorly understood how low-mode internal tides reflect and scatter along the continental margins. Here, the coupling equations for linear tides model (CELT) are derived to determine the independent modal solutions to Laplace's...
Sea surface temperature (SST) is a critical control on the atmosphere(1), and numerical models of atmosphere-ocean circulation emphasize its accurate prediction. Yet many models demonstrate large, systematic biases in simulated SST in the equatorial 'cold tongues' (expansive regions of net heat uptake from the atmosphere) of the Atlantic(2) and Pacific(3)...
As currents flow over rough topography, the pressure difference between the up-and downstream sides results in form drag-a force that opposes the flow. Measuring form drag is valuable because it can be used to estimate the loss of energy from currents as they interact with topography. An array of bottom...
Observations of breaking internal tides on the Oregon continental slope during a 40-day deployment of 5 moorings along 43°12'N are presented. Remotely generated internal tides shoal onto the slope, steepen, break, and form turbulent bores that propagate upslope independently of the internal tide. A high-resolution snapshot of a single bore...
Intensive sampling of the deep Mediterranean outflow 70 km W of the Strait of Gibraltar reveals a strong, tidally modulated gravity current embedded with large-amplitude oscillations and energetic turbulence. The flow appears to be hydraulically controlled at a small topographic constriction, with turbulence and internal waves varying together and increasing...
The linear transfer of tidal energy from large to small scales is quantified for small tidal excursion over a near-critical continental slope. A theoretical framework for low-wavenumber energy transfer is derived from “flat bottom” vertical modes and evaluated with observations from the Oregon continental slope. To better understand the observations,...
Internal waves are often observed to break close to the seafloor topography that generates them, or from which they scatter. This breaking is often spectacular, with turbulent structures observed hundreds of meters above the seafloor, and driving turbulence dissipations and mixing up to 10,000 times open-ocean levels. This article provides...
Surface tides are the heartbeat of the ocean. Because they are controlled by Earth's motion relative to other astronomical objects in our solar system, surface tides act like clockwork and generate highly deterministic ebb and flow familiar to all mariners. In contrast, baroclinic motions at tidal frequencies are much more...
Internal tide generation, propagation, and dissipation are investigated in Luzon Strait, a system of two quasi-parallel ridges situated between Taiwan and the Philippines. Two profiling moorings deployed for about 20 days and a set of nineteen 36-h lowered ADCP–CTD time series stations allowed separate measurement of diurnal and semidiurnal internal...
At the smallest length scales, conductivity measurements include a contribution from salinity fluctuations in
the inertial–convective and viscous–diffusive ranges of the turbulent scalar variance spectrum. Interpreting these
measurements is complicated because conductivity is a compound quantity of both temperature and salinity.
Accurate estimates of the dissipation rate of salinity variance...
A fast-response chromel–constantan thermocouple sensor was constructed for use on the microstructure profiler Chameleon and used for 60 ocean profiles off the coast of Oregon. The stability of the thermocouple was compared to that of an FP07 microbead thermistor, and its frequency response was compared to a high-resolution microconductivity probe....
Repeat transects of full-depth density and velocity are used to quantify generation and radiation of the semidiurnal internal tide from Kaena Ridge, Hawaii. A 20-km-long transect was sampled every 3 h using expendable current profilers and the absolute velocity profiler. Phase and amplitude of the baroclinic velocity, pressure, and vertical...
Full-depth velocity and density profiles taken along the 3000-m isobath characterize the semidiurnal
internal tide and bottom-intensified turbulence along the Hawaiian Ridge. Observations reveal baroclinic
energy fluxes of 21 ± 5 kW m⁻¹ radiating from French Frigate Shoals, 17 ± 2.5 kW m⁻¹ from Kauai
Channel west of Oahu, and...
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...
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...
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...