Internal waves Research Papers - Academia.edu (original) (raw)

A coastal acoustic tomography (CAT) experiment with seven acoustic stations was successfully carried out to measure multisubtidal internal modes, generated in Hiroshima Bay, Japan, in spite of severe data gaps due to many oyster... more

A coastal acoustic tomography (CAT) experiment with seven acoustic stations was successfully carried out to measure multisubtidal internal modes, generated in Hiroshima Bay, Japan, in spite of severe data gaps due to many oyster aquaculture rafts, accompanied by an array of vertical wire strings for growing oysters and distributed widely over the bay. The travel-time data acquired along five transmission lines with better data acquisition rates in one-way or reciprocal directions are analyzed, focusing on subtidal variations of sound speed (proportional to temperature). Significant multisubtidal internal modes are observed in the period range of 1.0-4.0 h. To specify the source region of internal modes and to estimate their propagation speed and direction, the power-spectral and cross-spectral analyses are applied to the time-series data of range-averaged sound speed along the successful transmission lines. Waves of period ranges 3.8-4.2, 2.0-2.3, and 1.4-1.5 h are identified as the second, third, and fourth modes of long internal waves, respectively, and the first internal mode is attributed to the semidiurnal tide. It is suggested that the source region of internal modes is located in the narrow channel at the northeastern corner of the tomography site and the modes radiate out from the source region, satisfying the propagation parameters (period, phase speed, and propagation direction) determined by this study. The propagation parameters of the subtidal internal modes can also be measured by point temperature sensors, attached to aquaculture rafts with an appropriate arrangement. However, it should be noted that the tomographic technique can confirm temperature variations through a spatial average along each ray path.

The peculiar mixing processes at the pycnocline and deep regions of the Black Sea are reviewed. In addition to the wind stirring and convective mixing, active in the upper pycnocline, the other important mechanism that results in limited... more

The peculiar mixing processes at the pycnocline and deep regions of the Black Sea are reviewed. In addition to the wind stirring and convective mixing, active in the upper pycnocline, the other important mechanism that results in limited ventilation of the anoxic waters of the Black Sea is the Mediterranean dense water inflow from the Bosphorus, modified by the entrainment of surface and intermediate waters, introduced into the interior through double-diffusive intrusions. This inflow, aided by the surface Ekman flux divergence, boundary processes and internal wave breaking, is the main mechanism for the mixing and renewal of the sub-pycnocline waters in the Black Sea interior. A review of these mixing processes is complemented by results from isotope measurements with improved accuracy and reduced noise compared to earlier experiments. Measurements of the stable isotopes oxygen-18 ( 18 O) and deuterium ( 2 H) confirm the origin of the water masses in the Black Sea and in the Turkish Straits, including the sea of Marmara, to be a continuous mixture with variable fractions of salty Mediterranean waters with inflowing fresh waters. Tritium ( 3 H) measurements confirm very little penetration of the transient signal to the sub-pycnocline and deep waters of the Black Sea, in comparison to the better ventilated Mediterranean waters filling the lower layer of the Marmara Sea. The comparison of stable and transient tracer isotopes shows the effects of fresh waters originating from the north-western shelf, and the difference between the renewal mechanisms of the Marmara and Black seas, as well as those between the upper and lower pycnocline of the Black Sea.

Laser Doppler anemometry (LDA) was used to measure the instantaneous downstream and vertical velocities in a series of simple and reflected saline density currents in a lock-exchange flume tank. All the currents were turbulent and... more

Laser Doppler anemometry (LDA) was used to measure the instantaneous downstream and vertical velocities in a series of simple and reflected saline density currents in a lock-exchange flume tank. All the currents were turbulent and subcritical. Mean downstream fluid velocities were in excess of the head velocity by up to 30%, and instantaneous velocities were greater by up to 50%. Turbulence intensities were highest within the head, and generally greatest in the middle part of the current, but did not correspond with the level of highest mean velocities. The maximum Reynolds stress also occurred within the head; large negative values were associated with shear along the upper boundary of the current. Peaks of turbulence, Reynolds stress and shear velocity occurred in association with the arrival of reflections. In large-scale turbidity currents, suc!a reflections would be capable of re-entraining and resuspending sediment deposited by the forward current. Some reflections take the form of solitary waves within a residual flow with a velocity vector in the opposite direction. In nature, these could produce symmetrical ripples in environments below storm-wave base.

Reflecting internal gravity waves in a stratified fluid preserve their frequency and thus their angle with the gravitational directi on. This leads to a focusing or defocus- ing of the waves at boundaries that are neither hor izontal nor... more

Reflecting internal gravity waves in a stratified fluid preserve their frequency and thus their angle with the gravitational directi on. This leads to a focusing or defocus- ing of the waves at boundaries that are neither hor izontal nor vertical. Previous theoreti- cal and experimental work has demonstrated how this can result in the internal wave en- ergy being focused

Acoustic transmission loss (TL) and supporting ocean environmental data collected during the Asian Seas International Acoustics Experiment (ASIAEX) on June 3, 2001, in the East China Sea (ECS), in a water depth of approximately 100 m are... more

Acoustic transmission loss (TL) and supporting ocean environmental data collected during the Asian Seas International Acoustics Experiment (ASIAEX) on June 3, 2001, in the East China Sea (ECS), in a water depth of approximately 100 m are presented. Objectives of the data analysis are to explore the stochastic nature of TL in terms of the mean (TL) and the fluctuations around the mean (as described by the standard deviation (TL) and higher order statistics). In particular, we conjecture that TL robustly reflects the macrostate of the ocean, including the bottom, whereas uncertainties in TL as measured by TL are related to the microstate of the ocean, again including the bottom. Comparisons are made to TL data at a similar location, 200 km from the ASIAEX site, in waters of the same depth, by the Harsh Environment Program in September 1997. The TL is shown to be approximately horizontally isotropic with exception to a discrete anisotropic feature likely caused by internal waves. Various mechanisms of uncertainty are discussed to describe the microstate. These were not sufficiently resolved to identify the primary cause of variability.

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... more

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. The spectra span scales from 5 km to 0.1 m, encompassing both internal waves and turbulence. The turbulence subrange is identified using a standard turbulence fit, and the rest of the motions are deemed to be internal waves. The remaining subrange has a slightly red slope ( ϳ k Ϫ1/2 x ) and vertical coherences compatible with internal waves, in agreement with previous towed measurements. However, spectral amplitudes in the internal wave subrange exhibit surprisingly little variation despite a four-order-of-magnitude change in turbulence dissipation rate observed at the site. The shape and amplitude of the horizontal spectra are shown to be consistent with observations and models of vertical internal wave spectra that consist of two subranges: a "linear" subrange ( ϳ k 0 z ) and a red "saturated" subrange ( ϳ k Ϫ1 z ). These two subranges are blurred in the transformation to horizontal spectra, yielding slopes close to those observed. The saturated subrange does not admit amplitude variations in the spectra yet is an important component of the measured horizontal spectra, explaining the poor correspondence with the dissipation rate.

The long term goals of our research are to:

Proteus mirabilis colonies exhibit striking geometric regularity. Basic microbiological methods and imaging techniques were used to measure periodic macroscopic events in swarm colony morphogenesis. We distinguished three initial phases... more

Proteus mirabilis colonies exhibit striking geometric regularity. Basic microbiological methods and imaging techniques were used to measure periodic macroscopic events in swarm colony morphogenesis. We distinguished three initial phases (lag phase, first swarming phase, and first consolidation phase) followed by repeating cycles of subsequent swarming plus consolidation phases. Each Proteus swarm colony terrace corresponds to one swarming-plus-consolidation cycle. The duration of the lag phase was dependent upon inoculation density in a way that indicated the operation of both cooperative and inhibitory multicellular effects. On our standard medium, the second and subsequent swarm phases displayed structure in the form of internal waves visible with reflected and dark-field illumination. These internal waves resulted from organization of the migrating bacteria into successively thicker cohorts of swarmer cells. Bacterial growth and motility were independently modified by altering th...

Mesophotic coral reefs, reefs at depths of 30 m to 150 m, are receiving renewed interest from coral reef scientists and managers because they are linked physically and biologically to their shallow water counterparts, have the potential... more

Mesophotic coral reefs, reefs at depths of 30 m to 150 m, are receiving renewed interest from coral reef scientists and managers because they are linked physically and biologically to their shallow water counterparts, have the potential to be refugia for shallow coral reef taxa such as coral and sponges, and can be a source of larvae that could contribute to the resiliency of shallow water reefs. Here we review what is currently known about how mesophotic reef communities are structured and identify critical areas where new information is needed. The review covers two primary taxa, coral and sponges, where a majority of the ecological work on mesophotic coral reefs has been done, and physical processes (e.g., the attenuation of visible irradiance and internal waves) that exert significant abiotic control on the structure of these deep fore reef communities. Understanding the ecology of mesophotic coral reefs, and the connectivity between them and their shallow water counterparts, should be a primary focus of future reef studies as the worldwide degradation of shallow coral reefs, and the ecosystem services they provide, continues.

Localized patches of turbulence frequently occur in geophysics, such as in the atmosphere and oceans. The effect of rotation, Ω, on such a region (a 'turbulent cloud') is governed by inhomogeneous dynamics. In contrast, most... more

Localized patches of turbulence frequently occur in geophysics, such as in the atmosphere and oceans. The effect of rotation, Ω, on such a region (a 'turbulent cloud') is governed by inhomogeneous dynamics. In contrast, most investigations of rotating turbulence deal with the homogeneous case, although inhomogeneous turbulence is more common in practice. In this paper, we describe the results of 512 3 direct numerical simulations (DNS) of a turbulent cloud under rotation at three Rossby numbers (Ro), namely 0.1, 0.3 and 0.5. Using a spatial filter, fully developed homogeneous turbulence is vertically confined to the centre of a periodic box before the rotation is turned on. Energy isosurfaces show that columnar structures emerge from the cloud and grow into the adjacent quiescent fluid. Helicity is used as a diagnostic and confirms that these structures are formed by inertial waves. In particular, it is observed that structures growing parallel to the rotation axis (upwards) have negative helicity and those moving antiparallel (downwards) to the axis have positive helicity, a characteristic typical of inertial waves. Two-dimensional energy spectra of horizontal wavenumbers, k ⊥ , versus dimensionless time, 2Ωt, confirm that these columnar structures are wavepackets which travel at the group velocities of inertial waves. The kinetic energy transferred from the turbulent cloud to the waves is estimated using Lagrangian particle tracking to distinguish between turbulent and 'wave-only' regions of space. The amount of energy transferred to waves is 40 % of the initial at Ro = 0.1, while it is 16 % at Ro = 0.5. In both cases the bulk of the energy eventually resides in the waves. It is evident from this observation that inertial waves can carry a significant portion of the energy away from a localized turbulent source and are therefore an efficient mechanism of energy dispersion.

In the summer of 1993, a number of chemical parameters (H2S, 02, pH, TA, TCO2, NH +, pO34 -, SiO2, Mn 2+ and Fe 2+) were measured in the Framvaren Fjord, a permanently super-anoxic fjord in southern Norway. The extremely steep gradient of... more

In the summer of 1993, a number of chemical parameters (H2S, 02, pH, TA, TCO2, NH +, pO34 -, SiO2, Mn 2+ and Fe 2+) were measured in the Framvaren Fjord, a permanently super-anoxic fjord in southern Norway. The extremely steep gradient of sulfide near the interface suggests that other than downward flux of oxygen, three other possible oxidants, particulate manganese and iron oxides, phototrophic sulfur oxidation bacteria and horizontally transported oxygen account for the oxidation of the upward flux of H2S. Water intrusion through the sill accounts for the temperature inflection above the interface, which, together with internal waves (Stigerbrandt and Molvaer, 1988), may cause fluctuations of the depth of interface. Significant gradients of hydrographic properties and chemical species between 80-100 m suggest that there is a "second interface" at about 90 m that separates the deep and older bottom waters. A stoichiometric model is applied to examine the biogeochemical cycles of S, C, N and P in the Framvaren. High C:S, C:N and C:P ratios are found while the nutrients (N, P) have Redfield ratio. Based on the C:N:P ratio of 155:16:1 in organic matter, about 30% of sulfide produced by sulfate reduction is estimated to be removed by processes such as oxidation, formation of FeS2, degassing and incorporation into organic matter. The rates of oxidation of H2S by Mn and Fe oxides in the water near the interface were slightly faster than the observed values in the laboratory, probably due to the presence of bacteria. 12 15 WENSHENG YAO AND FRANK J. MILLERO Salinity 18 21 24 T S , I r I , I , 9 12 15 T (°C),

In this review paper, state-of-the-art observational and numerical modeling methods for small scale turbulence and mixing with applications to coastal oceans are presented in one context. Unresolved dynamics and remaining problems of... more

In this review paper, state-of-the-art observational and numerical modeling methods for small scale turbulence and mixing with applications to coastal oceans are presented in one context. Unresolved dynamics and remaining problems of field observations and numerical simulations are reviewed on the basis of the approach that modern process-oriented studies should be based on both observations and models. First of all, the basic dynamics of surface and bottom boundary layers as well as intermediate stratified regimes including the interaction of turbulence and internal waves are briefly discussed. Then, an overview is given on just established or recently emerging mechanical, acoustic and optical observational techniques. Microstructure shear probes although developed already in the 1970s have only recently become reliable commercial products. Specifically under surface waves turbulence measurements are difficult due to the necessary decomposition of waves and turbulence. The methods to apply Acoustic Doppler Current Profilers (ADCPs) for estimations of Reynolds stresses, turbulence kinetic energy and dissipation rates are under further development. Finally, applications of well-established turbulence resolving particle image velocimetry (PIV) to the dynamics of the bottom boundary layer are presented. As counterpart to the field methods the state-of-the-art in numerical modeling in coastal seas is presented. This includes the 0079-6611/$ -see front matter Ó application of the Large Eddy Simulation (LES) method to shallow water Langmuir Circulation (LC) and to stratified flow over a topographic obstacle. Furthermore, statistical turbulence closure methods as well as empirical turbulence parameterizations and their applicability to coastal ocean turbulence and mixing are discussed. Specific problems related to the combined wave-current bottom boundary layer are discussed. Finally, two coastal modeling sensitivity studies are presented as applications, a two-dimensional study of upwelling and downwelling and a three-dimensional study for a marginal sea scenario (Baltic Sea). It is concluded that the discussed methods need further refinements specifically to account for the complex dynamics associated with the presence of surface and internal waves.

A small (50-kg, 2-m long) underwater vehicle with operating speeds of 20-30 cm/s and ranges up to 6000 km has been developed and field tested. The vehicle is essentially an autonomous profiling float that uses a buoyancy engine to cycle... more

A small (50-kg, 2-m long) underwater vehicle with operating speeds of 20-30 cm/s and ranges up to 6000 km has been developed and field tested. The vehicle is essentially an autonomous profiling float that uses a buoyancy engine to cycle vertically and wings to glide horizontally while moving up and down. Operational control and data relay is provided by GPS navigation and two-way communication through ORBCOMM low-earth-orbit satellites. Missions are envisioned with profile measurements repeated at a station or spaced along a transect. The initial instrument complement of temperature, conductivity, and pressure sensors was used to observe internal waves and tides in the Monterey underwater canyon.

Hummocky cross-stratification (HCS) is considered a diagnostic structure of surface storm activity at the shoreface–offshore transition. However, the origin of HCS is still debated. Laboratory experiments have not yet reproduced it and... more

Hummocky cross-stratification (HCS) is considered a diagnostic structure of surface storm activity at the shoreface–offshore transition. However, the origin of HCS is still debated. Laboratory experiments have not yet reproduced it and direct observations on the continental shelves do not exist. Most hydrodynamic interpretations invoke pure oscillatory flows, unidirectional-dominated combined flows and oscillatory-dominated flows, but they all share the assumption of HCS to reflect the combined action of surface storm waves and related currents. Within this context of uncertainties, internal waves (gravity waves propagating along the pycnocline) provide an alternative mechanism to explain the origin of HCS. Internal waves breaking on the shelf create episodic high-turbulence events and induce upslope- and downslope currents as well as oscillatory flows at the depth where the pycnocline intersects the sea floor. In this scenario, both the oscillatory- and the unidirectional components needed for HCS to form are not necessarily linked to surface storm waves, but can occur at various depth as far and near there is a pycnocline where internal waves can form.

Nonlinear dynamics of surface and internal waves in a stratified ocean under the influence of the Earth's rotation is discussed. Attention is focussed upon guided waves long compared to the ocean depth. The effect of rotation on... more

Nonlinear dynamics of surface and internal waves in a stratified ocean under the influence of the Earth's rotation is discussed. Attention is focussed upon guided waves long compared to the ocean depth. The effect of rotation on linear processes is reviewed in detail as well as the existing nonlinear models describing weakly and strongly nonlinear dynamics of long waves. The

The vertical mixing in the transition area from the North Sea to the Baltic Sea is dominated by entrainment processes of the inflowing saline water within near bottom layers. The hot spots of these processes are located at the Darss Sill... more

The vertical mixing in the transition area from the North Sea to the Baltic Sea is dominated by entrainment processes of the inflowing saline water within near bottom layers. The hot spots of these processes are located at the Darss Sill and the Bornholm Channel in the western Baltic Sea. In the central Baltic Sea temporal changes and associated transports are dominated by the horizontal advection of saline water in deep layers below the permanent halocline. This is accompanied by the turbulent vertical transport through the halocline into the surface layers. The related vertical salt transport into the entire surface mixed layer is estimated by various methods to be around values slightly above 30 kg/(m² a). During so-called stagnation periods the corresponding residence time of the deep water in the Eastern Gotland Basin drastically increases roughly by a factor of five. Therefore vertical mixing through the halocline seems to be drastically reduced when inflows are lacking. The potential processes of diapycnal mixing are discussed to the present knowledge. The turbulent motion resulting from breaking internal waves seems to be capable of turbulent transports through the halocline corresponding to the estimates of the salt transport into the surface mixed layer. The actual knowledge about boundary mixing due to internal waves in the Baltic Sea is found to be poor. Mesoscale eddies are evaluated to be able to contribute to the vertical mixing, but it is not known if they really do and which of the possible direct and indirect mixing mechanisms is most effective. Near bottom currents induced by inflow events are found to be likely to enhance vertical mixing. Coastal upwelling certainly contributes to the vertical transport, but the depth of its origin and the volume transport are hard to determine for large-scale quantifications. The short spatiotemporal scale of turbulent transports through the halocline resulting in a weakening of the halocline during summer and the mixing of the entire surface layer down to the halocline in winter are combined to a consistent description of the vertical salt transport. The longer residence time of the deep water during stagnation periods is hypothesised to be attributed to the lack of energy imported by the inflows and directly or indirectly feeding the diapycnal mixing processes. The discussion about consequences of vertical mixing processes crossing the seasonal thermocline and affecting the embedded ecosystem arrives at the conclusion that the vertical transport of nutrients such as the phosphate is quantitatively not sufficiently understood and needs further interdisciplinary research activities.

The ocean circulation is a cause and consequence of fluid scale interactions ranging from millimeters to more than 10,000 km. Although the wind field produces a large energy input to the ocean, all but approximately 10% appears to be... more

The ocean circulation is a cause and consequence of fluid scale interactions ranging from millimeters to more than 10,000 km. Although the wind field produces a large energy input to the ocean, all but approximately 10% appears to be dissipated within about 100 m of the sea surface, rendering observations of the energy divergence necessary to maintain the full watercolumn flow difficult. Attention thus shifts to the physically different kinetic energy (KE) reservoirs of the circulation and their maintenance, dissipation, and possible influence on the very small scales representing irreversible molecular mixing. Oceanic KE is dominated by the geostrophic eddy field, and depending on the vertical structure (barotropic versus low-mode baroclinic), direct and inverse energy cascades are possible. The pathways toward dissipation of the dominant geostrophic eddy KE depend crucially on the direction of the cascade but are difficult to quantify because of serious observational difficulties for wavelengths shorter than approximately 100-200 km. At high frequencies, KE is dominated by internal waves with near-inertial frequencies (frequencies near the local Coriolis parameter), whose shears appear to be a major source of wave breaking and mixing in the ocean interior. 253 Annu. Rev. Fluid Mech. 2009.41:253-282. Downloaded from arjournals.annualreviews.org by 65.96.167.244 on 01/19/09. For personal use only. Click here for quick links to Annual Reviews content online, including: • Other articles in this volume • Top cited articles • Top downloaded articles • Our comprehensive search Further ANNUAL REVIEWS 254 Ferrari · Wunsch Annu. Rev. Fluid Mech. 2009.41:253-282. Downloaded from arjournals.annualreviews.org by 65.96.167.244 on 01/19/09. For personal use only. www.annualreviews.org • Ocean Circulation Kinetic Energy 256 Ferrari · Wunsch Annu. Rev. Fluid Mech. 2009.41:253-282. Downloaded from arjournals.annualreviews.org by 65.96.167.244 on 01/19/09. For personal use only. 4 Geostrophic eddies are commonly called mesoscale eddies, which is a misnomer (in the atmospheric literature, they are referred to as synoptic scale eddies), but we sometimes use the terminology. www.annualreviews.org • Ocean Circulation Kinetic Energy 257 Annu. Rev. Fluid Mech. 2009.41:253-282. Downloaded from arjournals.annualreviews.org by 65.96.167.244 on 01/19/09. For personal use only. LITERATURE CITED Alford MH. 2003. Improved global maps and 54-year history of wind-work on ocean inertial motions. Geophys. Res. Lett. 30:1424 Alford MH, Whitmont M. 2007. Seasonal and spatial variability of near-inertial kinetic energy from historical moored velocity records. J. Phys. Oceanogr. 37:2022-37 Arbic BK, Flierl GR. 2004. Baroclinically unstable geostrophic turbulence in the limits of strong and weak bottom Ekman friction: application to mid-ocean eddies. J. Phys. Oceanogr. 34:2257-73 Arbic B, Flierl GR, Scott RB. 2007. Cascade inequalities for forced-dissipated geostrophic turbulence.

We present analyses of fluctuations seen in acoustic signals transmitted by two 400-Hz sources moored as part of the ASIAEX 2001 South China Sea (SCS) experiment. One source was near the bottom in 350-m deep water 31.3 km offshore from... more

We present analyses of fluctuations seen in acoustic signals transmitted by two 400-Hz sources moored as part of the ASIAEX 2001 South China Sea (SCS) experiment. One source was near the bottom in 350-m deep water 31.3 km offshore from the receiving array, and the other was near the bottom in 135-m deep water 20.6 km alongshore from the array. Time series of signal intensity measured at individual phones of a 16-element vertical line array are analyzed, as well as time series of intensity averaged over the array. Signals were recorded from 2 May to 17 May 2001. Fluctuations were observed at periods ranging from subtidal (days) to the shortest periods resolved with our signaling (10 s). Short-period fluctuations of depth-and time-averaged intensity have scintillation indexes (computed within 3-h long windows) which peak at values near 0.5 during an interval of numerous high-amplitude internal gravity waves, and which are lower during intervals with fewer internal waves. The decorrelation times of the averaged intensity (energy level) are also closely related to internal wave properties. Scintillation indexes computed for unaveraged pulses arriving at individual phones often exceed unity. Index Terms-Acoustic intensity fluctuation, underwater acoustic propagation.

The Labani Channel is one of the entry passages of Indonesian Throughflow (ITF) in Makassar Strait. The Channel has strong internal tidal energy which is released due to narrowing passage of the strait. Internal tide is one of the main... more

The Labani Channel is one of the entry passages of Indonesian Throughflow (ITF) in Makassar Strait. The Channel has strong internal tidal energy which is released due to narrowing passage of the strait. Internal tide is one of the main energy sources which causes mixing processes in the oceans. The purpose of this research is to estimate the turbulent mixing by using the Thorpe scale approach. Field observation was carried out on 7-8 of June, 2013 in the Labani Channel, Makassar Strait. A CTD (an instrument with conductivity, temperature and depth sensors) wase cast twelve times during one tidal cycle (24 hours). The results showed that the Labani Channel has an internal tide with a semidiurnal period. The average value of Kρ in the Labani Channel is 2.44 x 10-3 ± 4.73 x 10-3 m2 s-1 and the highest value is found in the deep layer, 2.61 x 10-3 ± 1.67 x 10-3 m2 s-1. This is presumably due to a strong internal tide there. The strong effect of the internal tide occurred particularly during the low tide when the water mass was induced to the deep layer.

Our long-term scientific goal is to understand the mechanisms by which mixing occurs in the ocean and thereby help develop improved parameterizations of mixing for ocean models. Mixing within the stratified ocean is our particular focus... more

Our long-term scientific goal is to understand the mechanisms by which mixing occurs in the ocean and thereby help develop improved parameterizations of mixing for ocean models. Mixing within the stratified ocean is our particular focus as the complex interplay of internal waves from a variety of sources and turbulence makes this a current locus of uncertainty. In this study, our broad focus is on the energy sources of nonlinear internal waves (NLIWs) in a complex environment of strong internal tides and abrupt topography (continental shelf and slope). We expect a rapid evolution of internal tides and NLIWs, and we aim to understand their dynamics, energy cascade, and role in mixing. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Tropical cyclones (TCs) often change intensity as they move over mesoscale oceanic features, as a function of the oceanic mixed layer (OML) thermal response (cooling) to the storm's wind stress. For example, observational evidence... more

Tropical cyclones (TCs) often change intensity as they move over mesoscale oceanic features, as a function of the oceanic mixed layer (OML) thermal response (cooling) to the storm's wind stress. For example, observational evidence indicates that TCs in the Gulf of Mexico rapidly weaken over cyclonic cold core eddies (CCEs) where the cooling response is enhanced, and they rapidly intensify over anticyclonic warm features such as the Loop Current (LC) and Warm Core Eddies (WCEs) where OML cooling is reduced. Understanding this contrasting thermal response has important implications for oceanic feedback to TCs' intensity in forecasting models. Based on numerical experimentation and data acquired during hurricanes Katrina and Rita, this dissertation delineates the contrasting velocity and thermal response to TCs in mesoscale oceanic eddies. Observational evidence and model results indicate that, during the forced stage, the wind-driven horizontal current divergence under the sto...

Two techniques have been developed for estimating statistics of inertial oscillations from satellitetracked drifters. These techniques overcome the difficulties inherent in estimating such statistics from data dependent upon space... more

Two techniques have been developed for estimating statistics of inertial oscillations from satellitetracked drifters. These techniques overcome the difficulties inherent in estimating such statistics from data dependent upon space coordinates that are a function of time. Application of these techniques to tropical surface drifter data collected during the NORPAX, EPOCS, and TOGA programs reveals a latitude-dependent, statistically significant "blue shift" of inertial wave frequency. The latitudinal dependence of the blue shift is similar to predictions based on "global" internal wave spectral models, with a superposition of frequency shifting due to modification of the effective local inertial frequency by the presence of strongly sheared zonal mean currents within 12 ø of the equator.

An analytical model has been developed to describe the generation of a linear interfacial wave over a steep ocean margin by a barotropic tide propagating toward the shelf break with a variable angle of incidence. The stratification is... more

An analytical model has been developed to describe the generation of a linear interfacial wave over a steep ocean margin by a barotropic tide propagating toward the shelf break with a variable angle of incidence. The stratification is reduced to a two-layer system, and the model uses step-like shelf geometry. In both shallow and deep regions an open boundary is assumed (this implies particularly that there is no reflection at the coast). The model is forced with the amplitude and direction of an incident barotropic Poincar6 wave propagating toward the shelf break. With this forcing, the model gives the amplitude, direction of propagation, and wavenumber of both barotropic and baroclinic Poincar6 waves transmitted onto the shelf and reflected into the deep region in the vicinity of the shelf break. After comparison with Baines' [1973] model, our model is compared with internal tide observations made in July 1996 on the Malin Shelf within the U.K. Land Ocean Interaction Study-Shelf Edge Study program. The observations are from moored thermistor chains and acoustic Doppler current profilers sited at two locations, one near the shelf break and the other 47.5 km onto the shelf. Observations at this latter mooring are not described by the generation model because of nonlinear changes and damping as the internal wave propagates through shallow water. Baroclinic displacements of the thermocline of 8 m amplitude were observed close to the shelf break, and total baroclinic energy was estimated at 2.4 J/m 3 during neap tide and 3 J/m 3 during spring tide. Both amplitude and energy of the shoreward propagating internal tide waves are compared with the model. Using a barotropic forcing taken from bibliographical data, good agreement with observations is found during neap tide (when the density structure is close to being two-layer) for an incident barotropic tide of 1 m amplitude and propagation direction on a bearing of 23øT (T means from True North in a clockwise sense).

During July and August of 1996, the summer component of the New England Shelfbreak Front PRIMER Experiment was fielded in the Mid-Atlantic Bight, at a site due south of Martha's Vineyard, MA. This study produced acoustic transmission data... more

During July and August of 1996, the summer component of the New England Shelfbreak Front PRIMER Experiment was fielded in the Mid-Atlantic Bight, at a site due south of Martha's Vineyard, MA. This study produced acoustic transmission data from a network of moored sources and receivers in conjunction with very-high-resolution oceanography measurements. This paper analyzes receptions at the northeast array receiver from two 400-Hz acoustic tomography sources, with the transmission paths going from the continental slope onto the continental shelf. These data, along with forward acoustic-propagation modeling based on moored oceanographic data, SeaSoar hydrography measurements, and bottom measurements, reveal many new and interesting aspects of acoustic propagation in a complicated slope-shelf environment. For example, one sees that both the shelfbreak front and tidally generated soliton internal wave packets produce stronger mode coupling than previously expected, leading to an interesting time-and-range-variable population of the acoustic normal modes. Additionally, the arrival time wander and the signal spread of acoustic pulses show variability that can be attributed to the presence of a frontal meander and variability in the soliton field. These and other effects are discussed in this paper, with an emphasis on creating a strong connection between the environmental measurements and the acoustic field characteristics.

Li mn ologischcs In stitU t, Uni ve rsity of Konstanz, Germ any Nih ar.Sa mal@uni-konsta nz.de, nih arw re@s ify.co m IAq uatic M icrob iologyll nstitutc for Bi odi vcrsity an d Ecosystem Dy nam ics Uni ve rsi ty of Amsterdam, Th e Neth... more

Li mn ologischcs In stitU t, Uni ve rsity of Konstanz, Germ any Nih ar.Sa mal@uni-konsta nz.de, nih arw re@s ify.co m IAq uatic M icrob iologyll nstitutc for Bi odi vcrsity an d Ecosystem Dy nam ics Uni ve rsi ty of Amsterdam, Th e Neth erlands 2\ Vasscransichten, Ge rm any JSc ho ol of ' Vater Resou rces Engin ee rin g, Jadavp ur Un iversity, Kolkata, India

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and... more

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to the Department of Defense, Executive Services end Communications Directorate (0704-0188). Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Generation of semi-diurnal internal tides at high latitudes is investigated theoretically and on the basis of in situ data, collected in the Barents Sea. The experimental data had revealed evidence of semi-diurnal internal tides in... more

Generation of semi-diurnal internal tides at high latitudes is investigated theoretically and on the basis of in situ data, collected in the Barents Sea. The experimental data had revealed evidence of semi-diurnal internal tides in records obtained at the critical latitude and above it, whilst the existing theories of baroclinic tides (linear or nonlinear) predict a suppression of tidal activity in the vicinity of the critical latitudes. The analytical solution for linear internal tides excited over the oceanic ridges predicts a substantial reduction of the efficiency of their generation. A similar result was obtained also in the frame of a fully nonlinear, nonhydrostatic model, developed and applied for typical conditions of the Barents Sea: weakly nonlinear baroclinic tides at high latitudes are suppressed by the Earth's rotation and have characteristics inherent to linear tides (small amplitude, large wavelength and small group speed). However, when applied to conditions of the southern slope of the Spitsbergen Bank, where the nonlinearity of the generated waves was estimated to be sufficiently strong, the mathematical model demonstrated generation of topography-scale short internal waves with characteristics close to those of unsteady lee waves. Propagating away from their source these waves produce wave patterns which may be considered as nonlinear internal tides of relatively short wavelength, although their genesis and features significantly differ from common internal tides. In particular, under conditions of strong nonlinearity and rotation the energy transfer from the barotropic tidal flux to the baroclinic modes leads to an effective generation of multiple tidal harmonics. r

In order to understand the fluctuations imposed upon low frequency ͑50 to 500 Hz͒ acoustic signals due to coastal internal waves, a large multilaboratory, multidisciplinary experiment was performed in the Mid-Atlantic Bight in the summer... more

In order to understand the fluctuations imposed upon low frequency ͑50 to 500 Hz͒ acoustic signals due to coastal internal waves, a large multilaboratory, multidisciplinary experiment was performed in the Mid-Atlantic Bight in the summer of 1995. This experiment featured the most complete set of environmental measurements ͑especially physical oceanography and geology͒ made to date in support of a coastal acoustics study. This support enabled the correlation of acoustic fluctuations to clearly observed ocean processes, especially those associated with the internal wave field. More specifically, a 16 element WHOI vertical line array ͑WVLA͒ was moored in 70 m of water off the New Jersey coast. Tomography sources of 224 Hz and 400 Hz were moored 32 km directly shoreward of this array, such that an acoustic path was constructed that was anti-parallel to the primary, onshore propagation direction for shelf generated internal wave solitons. These nonlinear internal waves, produced in packets as the tide shifts from ebb to flood, produce strong semidiurnal effects on the acoustic signals at our measurement location. Specifically, the internal waves in the acoustic waveguide cause significant coupling of energy between the propagating acoustic modes, resulting in broadband fluctuations in modal intensity, travel-time, and temporal coherence. The strong correlations between the environmental parameters and the internal wave field include an interesting sensitivity of the spread of an acoustic pulse to solitons near the receiver.

A field program to measure acoustic propagation characteristics and physical oceanography was undertaken in April and May 2001 in the northern South China Sea. Fluctuating ocean properties were measured with 21 moorings in water of 350to... more

A field program to measure acoustic propagation characteristics and physical oceanography was undertaken in April and May 2001 in the northern South China Sea. Fluctuating ocean properties were measured with 21 moorings in water of 350to 71-m depth near the continental slope. The sea floor at the site is gradually sloped at depths less than 90 m, but the deeper area is steppy, having gradual slopes over large areas that are near critical for diurnal internal waves and steep steps between those areas that account for much of the depth change. Large-amplitude nonlinear internal gravity waves incident on the site from the east were observed to change amplitude, horizontal length scale, and energy when shoaling. Beginning as relatively narrow solitary waves of depression, these waves continued onto the shelf much broadened in horizontal scale, where they were trailed by numerous waves of elevation (alternatively described as oscillations) that first appeared in the continental slope region. Internal gravity waves of both diurnal and semidiurnal tidal frequencies (internal tides) were also observed to propagate into shallow water from deeper water, with the diurnal waves dominating. The internal tides were at times sufficiently nonlinear to break down into bores and groups of high-frequency nonlinear internal waves.

A perturbation analysis of the Lagrangian equations of motion is used to examine the diffusion induced by a random field of internal waves. At second order there is a random field of shearing motion in the horizontal plane. We calculate... more

A perturbation analysis of the Lagrangian equations of motion is used to examine the diffusion induced by a random field of internal waves. At second order there is a random field of shearing motion in the horizontal plane. We calculate the single-particle, two-particle, and patch diffusivities that result from this motion. Patch and two-particle diffusivity both increase as scale raised to the power of 4/3 for an internal wave field in which the spectrum of horizontal velocity varies as o•-2

The Formosa Satellite-3 and Constellation Observing System for the Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) radio occultation (RO) mission has been successfully launched on April 14, 2006. The FORMOSAT-3/ COSMIC mission... more

The Formosa Satellite-3 and Constellation Observing System for the Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) radio occultation (RO) mission has been successfully launched on April 14, 2006. The FORMOSAT-3/ COSMIC mission uses global positioning system (GPS) signals to study the atmosphere and the ionosphere with global coverage. Receivers that are installed onboard of the six small FORMOSAT-3/COSMIC satellites register the phase and the amplitude of radio waves at two GPS frequencies. We give a preliminary analysis of the first RO measurements that are provided by the FORMOSAT-3/COSMIC mission. The geographical distribution of the first FORMOSAT-3/COSMIC RO experiments is shown. We demonstrate that the performance of the first measurements allows obtaining the vertical profiles of the refractivity, temperature, and pressure for the considered FORMOSAT-3/COSMIC RO events with expected accuracy, which is quite similar to the accuracy of the previous Challenging Mini-Satellite Payload and Gravity Recovery and Climate Experiment RO missions. New elements in the RO technology are suggested for further improving the accuracy and broadening the application range of the RO method. We emphasize new directions in applying the RO method to measure the vertical gradients of the refractivity in the atmosphere, to determine the temperature regime in the upper stratosphere, and to investigate the internal wave activity in the atmosphere. We find a significant correlation between the phase acceleration and the intensity variations in the RO signals that are emitted by GPS satellites and registered by the FORMOSAT-3/ COSMIC satellites. This correlation opens a way to locate the layered structures in the propagation medium based on simultaneous observations of the radio wave intensity and the phase variations in trans-ionospheric satellite-to-satellite links.

Multichannel seismic data acquired in the Lesser Antilles in the western tropical North Atlantic indicate that the seismic reflection method has imaged an oceanic thermohaline staircase. Synthetic acoustic modeling using measured density... more

Multichannel seismic data acquired in the Lesser Antilles in the western tropical North Atlantic indicate that the seismic reflection method has imaged an oceanic thermohaline staircase. Synthetic acoustic modeling using measured density and sound speed profiles corroborates inferences from the seismic data. In a small portion of the seismic image, laterally coherent, uniform layers are present at depths ranging from 550-700 m and have a separation of Published by Copernicus Publications on behalf of the European Geosciences Union.

The Columbia River plume is typical of large-scale, high discharge, mid-latitude plumes. In the absence of strong upwelling winds, freshwater from the river executes a rightward turn and forms an anticyclonic bulge before moving north... more

The Columbia River plume is typical of large-scale, high discharge, mid-latitude plumes. In the absence of strong upwelling winds, freshwater from the river executes a rightward turn and forms an anticyclonic bulge before moving north along the Washington coast. In addition to the above dynamics, however, the river plume outflow is subject to large tides, which modify the structure of the plume in the region near the river mouth. Observations based on data acquired during a summer 2005 cruise indicate that the plume consists of four distinct water masses; source water at the lift-off point, and the tidal, re-circulating and far-field plumes. In contrast to most plume models that describe the discharge of low-salinity estuary water into ambient high-salinity coastal water, we describe the Columbia plume as the superposition of these four plume types. We focus primarily on a conceptual summary of the dynamics and mutual interaction of the tidal and recirculating plumes. The new tidal plume flows over top of the re-circulating plume and is typically bounded by strong fronts. Soon after the end of ebb tide, it covers roughly 50-100% of the re-circulating plume surface area. The fronts may penetrate well below the re-circulating plume water and eventually spawn internal waves that mix the re-circulating plume further. The re-circulating plume persists throughout the tidal cycle and corresponds to a freshwater volume equivalent to 3-4 days of river discharge. Finally, the plume water masses are distinguished from one another in term of surface chlorophyll concentration, suggesting that the above classification may also describe different biological growth regimes. The low-salinity re-circulating plume serves as an extension of the estuary into the coastal ocean, or an "estuary at sea", because residence times during periods of high river flow are greater than those in the estuary.

We have investigated the barotropic tides in the Tunisian shelf and the Strait of Sicily using the Regional Ocean Modelling System (ROMS) with very high-resolution. Model performance was evaluated with respect to tide gauge, satellite... more

We have investigated the barotropic tides in the Tunisian shelf and the Strait of Sicily using the Regional Ocean Modelling System (ROMS) with very high-resolution. Model performance was evaluated with respect to tide gauge, satellite data, and current meter measurements. The model fields faithfully reproduced the major feature of the barotropic tidal currents and agreed well with existing tidal elevation and phase observations. General features for the various semidiurnal constituents are nearly similar to each other with maximum amplitude in the Gulf of Gabes. The larger tidal currents occur over the continental shelves. In the Adventure Bank, the current is essentially of diurnal type whereas in the Gulf of Gabes it is of semidiurnal type.

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1] An array of instruments air-deployed ahead of Hurricane Frances measured the three-dimensional, time dependent response of the ocean to this strong (60 ms À1 ) storm. Sea surface temperature cooled by up to 2.2°C with the greatest... more

1] An array of instruments air-deployed ahead of Hurricane Frances measured the three-dimensional, time dependent response of the ocean to this strong (60 ms À1 ) storm. Sea surface temperature cooled by up to 2.2°C with the greatest cooling occurring in a 50-km-wide band centered 60 -85 km to the right of the track. The cooling was almost entirely due to vertical mixing, not air-sea heat fluxes. Currents of up to 1.6 ms À1 and thermocline displacements of up to 50 m dispersed as near-inertial internal waves. The heat in excess of 26°C, decreased behind the storm due primarily to horizontal advection of heat away from the storm track, with a small contribution from mixing across the 26°C isotherm. SST cooling under the storm core (0.4°C) produced a 16% decrease in air-sea heat flux implying an approximately 5 ms À1 reduction in peak winds.

Slope sand deposits have accumulated from at least the Neogene to the Present on the southeastern Brazilian continental margin (Campos Basin area). This region shows sand accumulations concentrated on the upper portion and on the base of... more

Slope sand deposits have accumulated from at least the Neogene to the Present on the southeastern Brazilian continental margin (Campos Basin area). This region shows sand accumulations concentrated on the upper portion and on the base of the continental slope with a middle to lower slope bypass zone. A synthesis of preliminary results, supported by recent cores, high-resolution geophysical surveys, geotechnical investigations and environmental research, is presented and permits a prelitrdnary analysis of the sedimentological mechanisms operational in this area. These point toward a temporal and spatial multiscale set of phenomena responsible for sand deposits. At any sea-level stand these deposits are dependent on: (1) a suitable sediment source; (2) offshelf transport mechanisms; (3) a morphostructural and hydrodynamic context responsible figr the deposition of these sands in the upper portion of continental slopes. The proposed scenario of depositional processes concerns: (1) a set of hydrological processes such as surface currents and counter-currents, waves, tides and eddies with sufficient energy to form submarine sand dune fields at the outer shelf; (2) the offshelf export of this sediment under a combined action of spillover, internal waves, eddies 'seafloor polishing effect' and gravity processes (turbidity currents); and (3) the slope sand deposits and their distribution controlled by the action of contour currents, mass movements and the morphological context, such as canyons, gullies or scarps.

We report a novel and spectacular instability of a fluid surface in a rotating system. In a flow driven by rotating the bottom plate of a partially filled, stationary cylindrical container, the shape of the free surface can spontaneously... more

We report a novel and spectacular instability of a fluid surface in a rotating system. In a flow driven by rotating the bottom plate of a partially filled, stationary cylindrical container, the shape of the free surface can spontaneously break the axial symmetry and assume the form of a polygon rotating rigidly with a speed different from that of the

Internal waves are waves that propagate along the pycnocline, the interface between two density-stratified fluids. Even though internal waves are ubiquitous in oceans and lakes, their impact in the sedimentary record has remained largely... more

Internal waves are waves that propagate along the pycnocline, the interface between two density-stratified fluids. Even though internal waves are ubiquitous in oceans and lakes, their impact in the sedimentary record has remained largely unrecognized. Internal waves can remobilize the sediment from the depth at which the internal waves break onto the sea floor. In shelf, or ramp settings, internal wave deposits (internalites) have to be distinguished from tempestites while in slope and deeper settings internalites require distinction from turbidites. The Upper Kimmeridgian carbonate ramp succession cropping out near Ricla (NE Spain) provides some key evidence to differentiate the depositional processes induced by breaking internal waves from those related to surface storm waves. Sandy-oolitic grainstone eventites, previously interpreted as tempestites, contain evidence of reworking by turbulent events related to breaking internal waves. Underlying rationale are: 1) they occur in distal mid-ramp position, detached from the coeval shallow-water successions; 2) they do not have the characteristic coarsening- and thickening upward trend of storm deposits; 3) they gradually thin-out to disappear both up dip and down dip, interbedded with mid-ramp lime mudstones; and 4) they show little or no erosion towards the shallower areas. A facies model for internalites produced by two sediment populations, sand and mud, on a gently sloping carbonate ramp is proposed. The individual internalites occurring at Ricla include several architectural elements, sequentially organized in dip direction, which can be related to the flows associated with breaking internal waves: erosion in the breaker zone, swash run-up and tractive backwash flow. Individual internalites stack, with down- and up-slope shingling configuration, in dm-thick packages thought to reflect the up-slope and down-slope migration of the breaker zone, in turn related to depth variations of the palaeo-pycnocline. Packages occur in dm- to m-thick clusters suggested to reflect changes in sediment supply and/or variations in water stratification affecting the energy of internal waves.

We studied the cross-shelf variation in hydrography and plankton dynamics off west Thailand, focusing on physical-biological linkages. The overall research programme investigated linkages between physics, chemistry and plankton biology;... more

We studied the cross-shelf variation in hydrography and plankton dynamics off west Thailand, focusing on physical-biological linkages. The overall research programme investigated linkages between physics, chemistry and plankton biology; in the present paper we consider the findings based on the sampling of fish larvae and mesozooplankton. Surveys were carried out during 2 monsoon periods in March and August 1996, using 3 cross-bathymetric transects extending to the deeper part of the shelf slope of the Andaman Sea. Station distances were either 5 or 10 n miles apart, and at each station a series of net tows were carried out, targeting different size ranges of organisms. Plankton were identified to order (invertebrates) or family (fish larvae), and their abundances and biomass estimated. The abundance of both mesozooplankton and fish larvae peaked mid-shelf (50 to 65 m bottom depth) coinciding with a hydrographic front generated where the pycnocline meets the sea-bottom. An internal wave of pronounced amplitude interacts with the shelf slope at ca. 300 m bottom depth, and findings indicated another zone of enhanced abundance in this area. Analysis of the relative abundances of fish larvae within families revealed a marked cross-shelf structuring into a number of larval assemblages. Distinct assemblages were identified in nearshore areas, at midshelf in the area of the hydrographic front, and off the shelf break in oceanic water. Less pronounced variation was seen in the along-shelf direction and between monsoon periods.

Tidal processes are examined that control the water exchange between two basins of the Trondheimsfjord through a narrow channel with sills. For this purpose, a non-hydrostatic numerical model based on the laterally averaged Reynolds... more

Tidal processes are examined that control the water exchange between two basins of the Trondheimsfjord through a narrow channel with sills. For this purpose, a non-hydrostatic numerical model based on the laterally averaged Reynolds equations in the Boussinesq approximation was developed. The model takes into account the real vertical fluid stratification, variable bottom topography and variable cross-section of the fjord. Numerical experiments were performed to investigate tidally generated internal waves and their influence on the water exchange.

Bioptical models are used jointly with hyperspectral imaging in inversion procedures for mapping of benthic habitats. Several algorithms have been described in the literature to remove the effects of the water column and extract... more

Bioptical models are used jointly with hyperspectral imaging in inversion procedures for mapping of benthic habitats. Several algorithms have been described in the literature to remove the effects of the water column and extract information about the sea bottom that only take into consideration the measured hyperspectral image. However the availability of LIDAR derived bathymetry information opens the possibility of using this information for improved retrieval of the bottom properties. We present in this paper a study using simulated and hyperspectral imagery on the improvement in benthic habitat mapping that can be achieved by fusing bathymetry and hyperspectral imagery. Simulation results show that it is possible to obtain accurate bottom abundance estimates 5-10 meters beyond what can be obtained with hyperspectral imaging alone in clear waters. With real data we demonstrate increase in accuracy with respect to ground truth.

The physical context for ocean margin exchange at Goban Spur is described. Observations adjacent to, prior to and during the Ocean Margin EXchange (OMEX) project of 1993-1996 are used. They include currents measured on moorings,... more

The physical context for ocean margin exchange at Goban Spur is described. Observations adjacent to, prior to and during the Ocean Margin EXchange (OMEX) project of 1993-1996 are used. They include currents measured on moorings, drogued-buoy tracks; temperature and other data from CTD profiles, especially as indicators of vertical mixing; evidence from models, particularly for turbulence causing vertical mixing. These data are combined in estimates of (seasonally dependent) mean flow, tidal currents, other current variability, exchange and mixing over the main cross-slope section studied in OMEX and in nearby and contrasted locations (aided by the use of earlier and adjacent measurements). Causative physical processes are discussed: potentially northward flow along the continental slope, effects of Goban Spur

Comparisons are made of L band and X band SAR images with in situ measurements of surface currents and surface wave spectral perturbations for two of the Joint Canada-U.S. Ocean Wave Investigation Project internal wave data sets.... more

Comparisons are made of L band and X band SAR images with in situ measurements of surface currents and surface wave spectral perturbations for two of the Joint Canada-U.S. Ocean Wave Investigation Project internal wave data sets. Predicted and observed perturbations show agreement to within approximately a factor of 2 for L band, while the agreement at X band is much less satisfactory. Comparison of predicted microwave backscatter at X band with near-surface radar measurements indicates large discrepancies even when surface tilt and specular reflection effects are included in the model. Synthetic aperture radar (SAR) X band modulations compare favorably with near-surface radar measurements for range-traveling internal waves, but for other directions, the SAR modulations are smaller than the near-surface radar measurements. Simultaneous X and L band SAR images show comparable internal wave modulations.