ALBERT

Description: Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C01027, doi:10.1029/2003JC001877.

Description: Vertical flow structure and turbulent dissipation in the swash zone are estimated using cross-shore fluid velocities observed on a low-sloped, fine-grained sandy beach [Raubenheimer, 2002] with two stacks of three current meters located about 2, 5, and 8 cm above the bed. The observations are consistent with an approximately logarithmic vertical decay of wave orbital velocities within 5 cm of the bed. The associated friction coefficients are similar in both the uprush and downrush, as in previous laboratory results. Turbulent dissipation rates estimated from velocity spectra increase with decreasing water depth from O(400 cm2/s3) in the inner surf zone to O(1000 cm2/s3) in the swash zone. Friction coefficients in the swash interior estimated with the logarithmic model and independently estimated by assuming that turbulent dissipation is balanced by production from vertical shear of the local mean flow and from wave breaking are between 0.02 and 0.06. These values are similar to the range of friction coefficients (0.02–0.05) recently estimated on impermeable, rough, nonerodible laboratory beaches and to the range of friction coefficients (0.01–0.03) previously estimated from field observations of the motion of the shoreward edge of the swash (run-up).

Description: This research was supported by ONR and NSF.

Description: Author Posting. © American Meteorological Society, 2010. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 40 (2010): 2605–2623, doi:10.1175/2010JPO4132.1.

Description: Steady scale-invariant solutions of a kinetic equation describing the statistics of oceanic internal gravity waves based on wave turbulence theory are investigated. It is shown in the nonrotating scale-invariant limit that the collision integral in the kinetic equation diverges for almost all spectral power-law exponents. These divergences come from resonant interactions with the smallest horizontal wavenumbers and/or the largest horizontal wavenumbers with extreme scale separations. A small domain is identified in which the scale-invariant collision integral converges and numerically find a convergent power-law solution. This numerical solution is close to the Garrett–Munk spectrum. Power-law exponents that potentially permit a balance between the infrared and ultraviolet divergences are investigated. The balanced exponents are generalizations of an exact solution of the scale-invariant kinetic equation, the Pelinovsky–Raevsky spectrum. A small but finite Coriolis parameter representing the effects of rotation is introduced into the kinetic equation to determine solutions over the divergent part of the domain using rigorous asymptotic arguments. This gives rise to the induced diffusion regime. The derivation of the kinetic equation is based on an assumption of weak nonlinearity. Dominance of the nonlocal interactions puts the self-consistency of the kinetic equation at risk. However, these weakly nonlinear stationary states are consistent with much of the observational evidence.

Description: This research is supported by NSF CMG Grants 0417724, 0417732 and 0417466. YL is also supported by NSF DMS Grant 0807871 and ONR Award N00014-09-1-0515.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1993

Description: Breaking waves charge the surface layer of the ocean with small air bubbles which play an important role in air-sea gas transfer and in underwater acoustics near the ocean surface. This work reports on a series of laboratory and field experiments on the measurement on air entrainment by breaking waves. The first part of this thesis addresses the measurement of high volumetric concentrations of air (0.3% to 100% void-fraction) found immediately beneath breaking waves. Instrumentation based on the change of electrical impedance of the bubbly mixture with change in void-fraction is developed. Laboratory measurements are conducted in a wave channel and in a large three-dimensional wave basin. Maps of the evolution of the void-fraction distribution in bubble plumes generated by various size breaking waves are presented. Moments of the void-fraction field are shown to scale with the initially enclosed air volume at breaking and the energy dissipated by breaking. A significant fraction (30 to 50%) of the energy dissipated by breaking is found to be expanded in entraining bubbles against their buoyancy. The results reveal that the bubble plumes experience rapid transformations within the first wave period after the onset of breaking. In particular, the plumes loose 95% of the initially entrained air volume during the fust wave period. Predictions of the low-frequency resonant oscillations of the bubble plumes from measurements of the void-fraction compare well with acoustic measurements. Measurements near the ocean surface show high void-fractions up to 24% immediately beneath breaking waves. These are several orders of magnitude greater than previously reported time-averaged measurements. The second part addresses the measurement of very low void-fractions. Instrumentation based on the propagation velocity of low-frequency acoustic pulses is developed. Simultaneous measurements of the sound-speed (and thus the void-fraction) at several depths are conducted during two field experiments. Time-series of sound-speed and attenuation show dramatic fluctuations over time periods on the order of minutes or less. These are attributed to the formation of bubble plumes or passage of bubble clouds. Frequent occurences of sound-speed anomalies greater than 1 OOrnls and attenuation greater than 30dB/m are observed for moderate wind conditions (8m/s). The signals at various depths are highly correlated and mostly coherent at frequencies below 0.05Hz. The time-averaged (20min) sound-speed profile is found to be significantly more pronounced and shallower than previously reported. Simultaneous measurements at several acoustic frequencies show that the sound-speed is non-dispersive below 20kHz for moderate wind conditions. Bubble size distributions are inferred from the soundspeed and attenuation measurements.

Description: This research was funded by the Office of Naval Research (Ocean Acoustics and Oceanography) and the National Science Foundation.

Description: Author Posting. © American Meteorological Society, 2013. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 43 (2013): 2132–2141, doi:10.1175/JPO-D-12-0182.1.

Description: Repeated occupations of two hydrographic sections in the southwest Pacific basin from the 1990s to 2000s track property changes of Antarctic Bottom Water (AABW). The largest property changes—warming, freshening, increase in total carbon, and decrease in oxygen—are found near the basin’s deep western boundary between 50° and 20°S. The magnitude of the property changes decreases with increasing distance from the western boundary. At the deep western boundary, analysis of the relative importance of AABW (γn 〉 28.1 kg m−3) freshening, heating, or isopycnal heave suggests that the deep ocean stratification change is the result of both warming and freshening processes. The consistent deep ocean changes near the western boundary of the southwest Pacific basin dispel the notion that the deep ocean is quiescent. High-latitude climate variability is being directly transmitted into the deep southwest Pacific basin and the global deep ocean through dynamic deep western boundary currents.

Description: BMS, SEW, and BT were supported by the Australian Climate Change Science Program, funded jointly by the Department of Climate Change and Energy Efficiency and CSIRO. Funding for AM was provided through NOAA GrantNA110AR4310063.

Description: 2014-04-01

Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): C03016, doi:10.1029/2005JC003004.

Description: Waves have many effects on near-surface dynamics: Breaking waves enhance mixing, waves are associated with a Lagrangian mean drift (the Stokes drift), waves act on the mean flow by creating Langmuir circulations and a return flow opposite to the Stokes drift, and, last but not least, waves modify the atmospheric surface roughness. A realistic ocean model is proposed to embrace all these aspects, focusing on near-surface mixing and surface drift associated with the wind and generated waves. The model is based on the generalized Lagrangian mean that separates the momentum into a wave pseudomomentum and a quasi-Eulerian momentum. A wave spectrum with a reasonably high frequency range is used to compute the Stokes drift. A turbulent closure scheme based on a single evolution equation for the turbulent kinetic energy includes the mixing due to breaking wave effects and wave-turbulence interactions. The roughness length of the closure scheme is adjusted using observations of turbulent kinetic energy near the surface. The model is applied to unstratified and horizontally uniform conditions, showing good agreement with observations of strongly mixed quasi-Eulerian currents near the surface when waves are developed. Model results suggest that a strong surface shear persists in the drift current because of the Stokes drift contribution. In the present model the surface drift only reaches 1.5% of the wind speed. It is argued that stratification and the properties of drifting objects may lead to a supplementary drift as large as 1% of the wind speed.

Description: Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1997

Description: A series of numerical experiments is conducted in order to examine the role of topographic irregularities in generation of subinertial cross-channel barotropic currents and to obtain quantitative estimates of the offshore flow amplitude, its ratio to the magnitude of the alongshore currents and the alongshore correlation scale. A periodic (along the coast) channel with geometry representative of continental margins is considered. Topographic disturbances have multiple alongshore wavenumber contributions, kT, and the amplitude proportional to kT-2 (except one experiment). The motion is forced by spatially uniform and temporally varying alongshore wind stress, which drives the background current along the channel. The background current adjusts to topographic disturbances and, in particular, Barotropic Shelf Waves (BSW) result. That gives rise to the offshore currents. The amplitude of the cross-channel flow is shown to increase with kT in the long wave limit (order of 100 km in the model) and, in contrast, to decrease with kT in the short wave limit (less than 20 km in the model). As a rule, the strongest response is attained on the intermediate scales where lee waves form most efficiently. Hart's {1990} quasi-geostrophic solution provided quantitative parameters to explain the scale dependence and helped to interpret the results of simulations meant to examine sensitivity of the cross-channel flow characteristics to variation of the governing parameters. It is shown that the structure of the resonant wave is established by the combination of spatial properties of the bottom bumps, and by the period and amplitude of the fluctuating background current. On the basis of this analysis, it is demonstrated how the BSW dispersion diagram can be used for diagnostic purposes. The averaged (in time and along the channel) amplitude of subinertial cross-channel currents ranged from negligible values to about 5.5 cm/sec, indicating that, indeed, rather substantial offshore flow can be generated due to the effect of the topographic irregularities. The alongshore correlation scale was no smaller than about 5 km and in a few simulations (for instance, with lee-wave-favourable mean wind included) reached 30 - 50 km.

Description: This work was supported by the Office of Naval Research, Coastal Science Program, Grant N00014-95-1-0580.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution October 1987

Description: A two-layer shallow water equation model is used to investigate the linear stability of a coastal upwelling front. The model features a surface front near a coastal boundary and bottom topography which is an arbitrary function of the cross-shelf coordinate. By combining the various conservation statements for the global properties of the system, a general stability theorem is established which allows the a priori determination of the stability of a coastal upwelling front. Unstable waves are found for the modelled coastal upwelling front. The unstable wave motions are frontally-trapped and dominant in the upper layer. The wave propagates phase in the direction of the basic state flow and the primary energy conversion is via baroclinic instability. The effect of varying the model parameters is presented. Moving the front closer than ~ 2 Rossby radii to the coastal boundary results in a decrease in the growth rate of the fastest growing wave. Increasing the overall vertical shear of the basic state flow, by either decreasing the lower layer depth or increasing the steepness of the interface, results in an increase in the growth of the fastest growing wave. A bottom sloping in the same sense as the interface results in a decrease of the growth rates and alongfront wavenumbers of the unstable waves in the system. Linearized bottom friction is included in the stability model and results in a decrease in the growth rates of the unstable waves by extracting energy from the system. Since the unstable mode is strongest in the upper layer, bottom friction will not stabilize the upwelling front. A comparison between the predictions from the simple two-layer model and observed alongfront variability for three areas of active upwelling is presented. Reasonable agreement is found, suggesting that observed alongfront variability can be interpreted in terms of the instability of a coastal upwelling front.

Description: This study was supported by the National Science Foundation Grant OCE 84-08563 and the Office of Naval Research Coastal Ocean Sciences Program 10/1984.37.

Description: Submitted in partial fulfillment of the requirements for the degree of Ocean Engineer at the Massachusetts Institute of Technology and Woods Hole Oceanographic Institution September 1994

Description: This paper presents a method for estimating the spectra of water wave disturbances on five of the six axes of a stationary, slender body underwater vehicle in an inertia dominated wave force regime, both in head seas and in beam seas. Inertia dominated wave forces are typical of those encountered by a 21 inch diameter, torpedo shaped underwater vehicle operating in coastal waters and sea state 2. Strip theory is used to develop transfer function phase and magnitude between surface water waves and the slender body pitch, heave, and surge forces and moment for the vehicle in head seas, and for pitch, heave, yaw, and sway forces and moments in beam seas. Experiments are conducted which verify this method of transfer function calculation, and demonstrate the effects of vehicle forward motion in the head seas case. Using known sea spectra and linear time invariant systems theory allows for estimation of the water wave disturbance spectra for these forces and moments. Application of sliding control techniques are then developed for the underwater vehicle longitudinal plane equations of motion. Computer simulations are used to demonstrate the dependence of underwater vehicle depth control upon the pitch control, and adaptive pitch control is shown to provide good performance in the presence of substantial parametric uncertainty. Pitch disturbance rejection properties of variations of the sliding controller are investigated. Both single frequency and stochastic disturbances are used, and the stochastic disturbance is developed using the results of the earlier investigation.

Description: This research was sponsored in part by ONR Contract N00014-90-J-1912.

Description: Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 39 (2012): L24604, doi:10.1029/2012GL054034.

Description: Eddies and vortices associated with breaking waves rapidly disperse pollution, nutrients, and terrestrial material along the coast. Although theory and numerical models suggest that vorticity is generated near the ends of a breaking wave crest, this hypothesis has not been tested in the field. Here we report the first observations of wave-generated vertical vorticity (e.g., horizontal eddies), and find that individual short-crested breaking waves generate significant vorticity [O(0.01 s−1)] in the surfzone. Left- and right-handed wave ends generate vorticity of opposite sign, consistent with theory. In contrast to theory, the observed vorticity also increases inside the breaking crest, possibly owing to onshore advection of vorticity generated at previous stages of breaking or from the shape of the breaking region. Short-crested breaking transferred energy from incident waves to lower frequency rotational motions that are a primary mechanism for dispersion near the shoreline.

Description: Funding was provided by a National Security Science and Engineering Faculty Fellowship, the Office of Naval Research, and a Woods Hole Oceanographic Institution Postdoctoral Fellowship.

Description: 2013-06-21

Description: Submitted to the Joint Program in Physical Oceanography in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2006

Description: Ocean surface infragravity waves (periods from 20 to 200 s) observed along the southern California coast are shown to be sensitive to the bottom topography of the shelf region, where propagation is linear, and of the nearshore region, where nonlinearity is important. Infragravity waves exchange energy with swell and wind waves (periods from 5 to 20 s) via conservative nonlinear interactions that approach resonance with decreasing water depth. Consistent with previous results, it is shown here that as waves shoal into water less than a few meters deep, energy is transfered from swell to infragravity waves. In addition, it is shown here that the apparent dissipation of infragravity energy observed in the surfzone is the result of nonlinear energy transfers from infragravity waves back to swell and wind waves. The energy transfers are sensitive to the shallow water bottom topography. On nonplanar beach profiles the transfers, and thus the amount of infragravity energy available for reflection from the shoreline, change with the tide, resulting in the tidal modulation of infragravity energy observed in bottom-pressure records on the continental shelf. The observed wave propagation over the shelf topography is dominated by refraction, and the observed partial reflection from, and transmission across, a steep-walled submarine canyon is consistent with long-wave theory. A generalized regional model incorporating these results predicts the observed infragravity wave amplitudes over variable bottom topography.

Description: Support from the Office of Naval Research (Coastal Geosciences Program, N00014-02-10145), the National Science Foundation (Physical Oceanography, OCE-0115850),

Description: Submitted in partial fulfillment of the requirements for the degree of Ocean Engineer at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1991

Description: A model is developed for the prediction of the seismo-acoustic noise spectrum in the microseism peak region (0.1 to 0.7 Hz). The model uses a theory developed by Cato [J. Acoust. Soc. Am., 89 , 1096-1112 (1991)] for an infinite depth ocean in which the surface orbital motion caused by gravity waves may produce acoustic waves at twice the gravity wave frequency. Using directional wave spectra as inputs, acoustic source levels are computed and incorporated into a more realistic environment consisting of a horizontally stratified ocean with an elastic bottom. Noise predictions are made using directional wave spectra obtained from the SWADE surface buoys moored off the coast of Virginia and the SAFARI sound propagation code, with a bottom model derived using wave speeds measured in the EDGE deep seismic reflection survey. The predictions are analyzed for noise level variations with frequency, wave height, wind direction, and receiver depth. These predictions are compared to noise measurements made in ECONOMEX using near-bottom receivers located close to the surface buoys. Good agreement is found between the predictions and observations under a variety of environmental conditions.

Description: Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 118 (2013): 6319–6328, doi:10.1002/2013JC008939.

Description: Strong and strategic collaborations among experts from academia, federal operational centers, and industry have been forged to create a U.S. IOOS Coastal and Ocean Modeling Testbed (COMT). The COMT mission is to accelerate the transition of scientific and technical advances from the coastal and ocean modeling research community to improved operational ocean products and services. This is achieved via the evaluation of existing technology or the development of new technology depending on the status of technology within the research community. The initial phase of the COMT has addressed three coastal and ocean prediction challenges of great societal importance: estuarine hypoxia, shelf hypoxia, and coastal inundation. A fourth effort concentrated on providing and refining the cyberinfrastructure and cyber tools to support the modeling work and to advance interoperability and community access to the COMT archive. This paper presents an overview of the initiation of the COMT, the findings of each team and a discussion of the role of the COMT in research to operations and its interface with the coastal and ocean modeling community in general. Detailed technical results are presented in the accompanying series of 16 technical papers in this special issue.

Description: This project was supported by NOAA via the IOOS Office, award NA10NOS0120063 and NA11NOS0120141, and used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant OCI- 1053575.

Description: Wave power spectra from four waverider buoys on the New England Shelf and wind velocity records from three of those buoys and a fixed platform were analyzed. The data span the period from May 1987 through August 1988. Time series plots of significant wave height, mean wave period and modal (peak) period and distribution histograms of significant wave height, mean frequency and modal frequency are presented for the two buoys nearest to Martha's Vineyard. Time series plots of wind speed and vector velocity and distribution histograms of speed and direction are plotted for one buoy and the platform. For all stations, monthly and seasonal mean and extreme values of significant wave height, mean and modal wave periods, wind speed and mean weighted and unweighted values of wind direction are provided in tabular form. Five and ten year extreme wave height predictions are also calculated.

Description: Funding was provided by the Office of Naval Research through contract Number N00014-86-K-0715 under the University Research Initiative Program.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September, 1970

Description: A series of laboratory experiments were conducted in a glass wave tank to investigate the propagation of internal gravity waves up a sloping bottom in a fluid with constant Brunt-Vaisala frequency. Measurements of the wave motion in the fluid interior were primarily taken with electrical conductivity probes; measurements in the boundary layer were made with dye streaks and neutrally buoyant particles. The results indicate that, outside of the breaking zone, the amplitude and horizontal wave number of the high-frequency waves increase lineariy with decreasing depth; this is shown to agree with existing linear, inviscid solutions. A zone of breaking or runup is induced by these high-frequency waves well upslope. Shadowgraph observations show that, if the wave characteristics are coincident, or nearly so, with the bottom slope, the upslope propagation of the low-frequency waves causes a line of regularly spaced vortices to form along the slope. Subsequent mixing in the vortex cells creates thin horizontal laminae that are more homogeneous than the adjacent layers. These laminae slowly penetrate the fluid interior, creating a step-like vertical density structure. Available linear theoretical solutions for the velocity in the viscous boundary layer, determined to be valid for certain experimental conditions, are used to develop a criterion for incipient motion of bottom sediment induced by shoaling internal waves. The maximum sediment sizes that can be placed into motion, according to this criterion, are larger than certain mean sediment sizes on the continental margin off New England. This suggests that internal waves might induce initial sediment movement. Speculation about the geological effects of breaking and vortex instabilities is also given. These processes, not definitely measured in the field as yet, might also be conducive to sediment movement.

Description: This work was supported by the Office of Naval Research.

Description: © The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Coral Reefs 30 (2011): 23-38, doi:10.1007/s00338-010-0705-3.

Description: Sediment traps are commonly used as standard tools for monitoring “sedimentation” in coral reef environments. In much of the literature where sediment traps were used to measure the effects of “sedimentation” on corals, it is clear from deployment descriptions and interpretations of the resulting data that information derived from sediment traps has frequently been misinterpreted or misapplied. Despite their widespread use in this setting, sediment traps do not provide quantitative information about “sedimentation” on coral surfaces. Traps can provide useful information about the relative magnitude of sediment dynamics if trap deployment standards are used. This conclusion is based first on a brief review of the state of knowledge of sediment trap dynamics, which has primarily focused on traps deployed high above the seabed in relatively deep water, followed by our understanding of near-bed sediment dynamics in shallow-water environments that characterize coral reefs. This overview is followed by the first synthesis of near-bed sediment trap data collected with concurrent hydrodynamic information in coral reef environments. This collective information is utilized to develop nine protocols for using sediment traps in coral reef environments, which focus on trap parameters that researchers can control such as trap height (H), trap mouth diameter (D), the height of the trap mouth above the substrate (z o ), and the spacing between traps. The hydrodynamic behavior of sediment traps and the limitations of data derived from these traps should be forefront when interpreting sediment trap data to infer sediment transport processes in coral reef environments.

Description: This paper is not subject to U.S. copyright. The definitive version was published in Continental Shelf Research 24 (2004): 1397-1419, doi:10.1016/j.csr.2004.02.010.

Description: The fringing coral reef off the south coast of Molokai, Hawaii is currently being studied as part of a US Geological Survey (USGS) multi-disciplinary project that focuses on geologic and oceanographic processes that affect coral reef systems. For this investigation, four instrument packages were deployed across the fringing coral reef during the summer of 2001 to understand the processes governing fine-grained terrestrial sediment suspension on the shallow reef flat (h=1 m) and its advection across the reef crest and onto the deeper fore reef. The time–series measurements suggest the following conceptual model of water and fine-grained sediment transport across the reef: Relatively cool, clear water flows up onto the reef flat during flooding tides. At high tide, more deep-water wave energy is able to propagate onto the reef flat and larger Trade wind-driven waves can develop on the reef flat, thereby increasing sediment suspension. Trade wind-driven surface currents and wave breaking at the reef crest cause setup of water on the reef flat, further increasing the water depth and enhancing the development of depth-limited waves and sediment suspension. As the tide ebbs, the water and associated suspended sediment on the reef flat drains off the reef flat and is advected offshore and to the west by Trade wind- and tidally- driven currents. Observations on the fore reef show relatively high turbidity throughout the water column during the ebb tide. It therefore appears that high suspended sediment concentrations on the deeper fore reef, where active coral growth is at a maximum, are dynamically linked to processes on the muddy, shallow reef flat.

Description: This paper is not subject to U.S. copyright. The definitive version was published in Marine Geology 264 (2009): 140-151, doi:10.1016/j.margeo.2009.05.002.

Description: Oceanographic measurements and sediment samples were collected during the summer of 2006 as part of a multi-year study of coastal circulation and the fate of terrigenous sediment on coral reefs in Hanalei Bay, Kauai. The goal of this study was to better understand sediment dynamics in a coral reef-lined embayment where winds, ocean surface waves, and river floods are important processes. During a summer period that was marked by two wave events and one river flood, we documented significant differences in sediment trap collection rates and the composition, grain size, and magnitude of sediment transported in the bay. Sediment trap collection rates were well correlated with combined wave-current near-bed shear stresses during the non-flood periods but were not correlated during the flood. The flood's delivery of fine-grained sediment to the bay initially caused high turbidity and sediment collection rates off the river mouth but the plume dispersed relatively quickly. Over the next month, the flood deposit was reworked by mild waves and currents and the fine-grained terrestrial sediment was advected around the bay and collected in sediment traps away from the river mouth, long after the turbid surface plume was gone. The reworked flood deposits, due to their longer duration of influence and proximity to the seabed, appear to pose a greater long-term impact to benthic coral reef communities than the flood plumes themselves. The results presented here display how spatial and temporal differences in hydrodynamic processes, which result from variations in reef morphology and orientation, cause substantial variations in the deposition, residence time, resuspension, and advection of both reef-derived and fluvial sediment over relatively short spatial scales in a coral reef embayment.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution November 1990

Description: One and two layer models are used to study flow over axisymmetric isolated topography. Inviscid or nearly inviscid flow in which non-linear effects have order one importance is considered, and both the effects of β and finite topography are included. A one-layer quasi-geostrophic model is used to find the shape of Taylor columns on both the f-plane and the β-plane in the inviscid limit of the frictional problem. In this limit, the boundary of the Taylor column is a streamline, and the velocity in both directions vanishes on the boundary. The fluid within the Taylor column is stagnant, corresponding to the solution that Ingersoll (1969) found for flow over a right circular cylinder on the f-plane. In this case, the Taylor column is circular. An iterative boundary integral technique is used to find the solutions for flow over a cone on the f-plane. In this case the Taylor column has a tear drop shape. Solutions are also found for flow on the β-plane over a cylinder, and the Taylor column is approximately elliptical for westward flow with the major axis in the x direction, while it is slightly elongated in the y direction for eastward flow. The stagnation point of the Taylor column is located on the edge of the topography for all the solutions found. It was not possible to find solutions for smooth topographic shapes. Steady solutions for flow over a right circular cylinder of finite height are studied when the quasi-geostrophic approximation no longer applies. The solution consists of two parts, one which is similar to the quasi-geostrophic solution and is driven by the potential vorticity anomaly over the topography and the other which is similar to the solution of potential flow around an cylinder and is driven by the matching conditions on the edge of the topography. When the effect of β is large, the transport over the topography is enhanced as the streamlines follow lines of constant background potential vorticity. For eastward flow, the Rossby wave drag can be much larger than predicted from quasi-geostrophic theory. A two-layer model over finite topography using the quasi-geostrophic approximation is developed. The topography is a right circular cylinder which goes all of the way through the lower layer and an order Rossby number amount into the upper layer, so that the quasi-geostrophic approximation can be applied consistently. This geometry allows description of flow in which an isopycnal intersects the topography. The model is valid for a different regime than existing models of steady flow over finite topography in a continuously stratified fluid in which the bottom boundary is an isopycnal surface. The solutions contain the two components that are found in the the barotropic model of flow over finite topography. The model breaks down when the interface goes above the topography which occurs more easily when the stratification is weak. Closed streamlines occur more readily over the topography when the stratification is weak, whereas in traditional quasi-geostrophic theory they occur more readily when the stratification is strong. Near the topography, the interface is depressed to the right and raised to the left (looking downstream). A hierarchy of time-dependent models is used to examine the initial value problem of flow initiation over topography on the f-plane. A modified contour dynamics method is developed that extends the range of problems to which contour dynamics can be applied. The method allows boundary and matching conditions to be applied on a circular boundary. A one-layer quasi-geostrophic model is used to show that more fluid that originates over the topography remains there when the flow is turned on slowly than when it is turned on quickly. Flow over finite topography in a one-layer model shows a variety of different behaviors depending on the topographic height. When the topography has moderate height, two cyclonic eddies are created; when the topography fills up most of the water column, the fluid oscillates on and off the topography as it moves around the topography in a clockwise direction, and none of the fluid is shed downstream. Two quasi-geostrophic stratified models are considered, one in which the topography is small, and the other in which it is finite. In the small topography model, an eddy is shed which is cyclonic, warm-core, and bottom-trapped. In contrast, the shed eddy is cyclonic, cold-core, and surfaceintensified in the finite depth model using the geometry described above.

Description: This study was supported by the Office of Naval Research Program N00014- 90-J-1839.

Description: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Geophysical Research: Oceans 118 (2013): 5129–5172, doi:10.1002/jgrc.20376.

Description: A Gulf of Mexico performance evaluation and comparison of coastal circulation and wave models was executed through harmonic analyses of tidal simulations, hindcasts of Hurricane Ike (2008) and Rita (2005), and a benchmarking study. Three unstructured coastal circulation models (ADCIRC, FVCOM, and SELFE) validated with similar skill on a new common Gulf scale mesh (ULLR) with identical frictional parameterization and forcing for the tidal validation and hurricane hindcasts. Coupled circulation and wave models, SWAN+ADCIRC and WWMII+SELFE, along with FVCOM loosely coupled with SWAN, also validated with similar skill. NOAA's official operational forecast storm surge model (SLOSH) was implemented on local and Gulf scale meshes with the same wind stress and pressure forcing used by the unstructured models for hindcasts of Ike and Rita. SLOSH's local meshes failed to capture regional processes such as Ike's forerunner and the results from the Gulf scale mesh further suggest shortcomings may be due to a combination of poor mesh resolution, missing internal physics such as tides and nonlinear advection, and SLOSH's internal frictional parameterization. In addition, these models were benchmarked to assess and compare execution speed and scalability for a prototypical operational simulation. It was apparent that a higher number of computational cores are needed for the unstructured models to meet similar operational implementation requirements to SLOSH, and that some of them could benefit from improved parallelization and faster execution speed.

Description: This project was supported by NOAA via the U.S. IOOS Office (award: NA10NOS0120063 and NA11NOS0120141)

Description: Originally issued as Reference No. 60-20, series later renamed WHOI-.

Description: Six years of field data plus the conclusions of eight published papers, plus two papers 11 in press", are included in this final report. Wherever possible the writer has attempted to sum up significant unpublished data by the use of illustrations, for example (Plates I through XII and Plates XIII to XVI). All other research, whether fruitful or not is summed up as concisely as possible. The format is outlined in the Contents. It may best be considered in three parts, an Introduction, description of the area and a discussion of technique, for one part. A second part wherein Beach and Coastal Regimen is the topic, this includes profile studies, aerial photography and coastal erosion studies; sediment distribution and wave dynamics is part 3. The studies have led to problems which are unsolved and in a sense the data bearing on these problems is more or less "hanging in air". For example, the most interesting conclusion we derived from the sediment sampling along offshore profiles was that deposition of sediment is confined to a thin strip of sand next to the coast and a mud zone far offshore. These sites of deposition are separated by a zone of erosion or non-deposition. We have carried these ideas rather far and have published a model to explain the mechanics of transport (Miller and Zeigler, in press). Yet, the field sampling is inadequate in spite of supplementary efforts made on two cruises, not a part of this contract, to get enough field data. Consequently, a formal discussion of this problem is in the future and surely that discussion will draw heavily on data which is now inadequate. A second example of a problem in progress, but unsolved concerns inlets. The data is included in this report, but it leads to no conclusions. In keeping with instructions for report requirements for Geography Branch contracts, conclusions of published reports are listed, details are not reported.

Description: Geography Branch, Office of Naval Research Under Contract Nonr-1254 {00) (NR-388-018)