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Model Behavior And Sensitivity In An Application Of The Cohesive Bed Component Of The Community Sediment Transport Modeling System For The York River Estuary, Va, Usa, Kelsey A. Fall, Courtney K. Harris, Carl T. Friedrichs, J. Paul Rineheimer, Christopher R. Sherwood

VIMS Articles

The Community Sediment Transport Modeling System (CSTMS) cohesive bed sub-model that accounts for erosion, deposition, consolidation, and swelling was implemented in a three-dimensional domain to represent the York River estuary, Virginia. The objectives of this paper are to (1) describe the application of the three-dimensional hydrodynamic York Cohesive Bed Model, (2) compare calculations to observations, and (3) investigate sensitivities of the cohesive bed sub-model to user-defined parameters. Model results for summer 2007 showed good agreement with tidal-phase averaged estimates of sediment concentration, bed stress, and current velocity derived from Acoustic Doppler Velocimeter (ADV) field measurements. An important step in implementing …

A Hydrodynamic And Sediment Transport Model For The Waipaoa Shelf, New Zealand: Sensitivity Of Fluxes To Spatially-Varying Erodibility And Model Nesting, Julia M. Moriarty, Courtney K. Harris, Mark G. Hadfield

VIMS Articles

Numerical models can complement observations in investigations of marine sediment transport and depositional processes. A coupled hydrodynamic and sediment transport model was implemented for the Waipaoa River continental shelf offshore of the North Island of New Zealand, to complement a 13-month field campaign that collected seabed and hydrodynamic measurements. This paper described the formulations used within the model, and analyzed the sensitivity of sediment flux estimates to model nesting and seabed erodibility. Calculations were based on the Regional Ocean Modeling System—Community Sediment Transport Modeling System (ROMS-CSTMS), a primitive equation model using a finite difference solution to the equations for momentum …

Introduction To Special Section On The U.S. Ioos Coastal And Ocean Modeling Testbed, Richard A. Luettich Jr, L. Donelson Wright, Richard Signell, Carl T. Friedrichs, Marjorie A.M. Friedrichs, John Harding, Katja Fennel, Eoin Howlett, Sara Graves, Elizabeth Smith, Gary Crane, Rebecca Baltes

VIMS Articles

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 …

Us Ioos Coastal And Ocean Modeling Testbed: Inter-Model Evaluation Of Tides, Waves, And Hurricane Surge In The Gulf Of Mexico, Pc Kerr, As Donahue, Jj Westerliink, Ra Luettich, Ly Zheng, Rh Weisberg, Y Huang, Harry V. Wang, Y Teng, David R. Forrest, Et Al

VIMS Articles

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 …

Progress Of Regional Oceanography Study Associated With Western Boundary Current In The South China Sea, Dongxiao Wang, Qinyan Liu, Qiang Xie, Zhigang He, Wei Zhuang, Yeqiang Shu, Xianjun Xiao, Bo Hong, Xiangyu Wu, Dandan Sui

VIMS Articles

Recent progress of physical oceanography in the South China Sea (SCS) associated with the western boundary current (WBC) and eddies is reviewed in this paper. It includes Argo observations of the WBC, eddy detection in the WBC based on satellite images, cross-continental shelf exchange in the WBC, eddy-current interaction, interannual variability of the WBC, air-sea interaction, the SCS throughflow (SCSTF), among others. The WBC in the SCS is strong, and its structure, variability and dynamic processes on seasonal and interannual time scales are yet to be fully understood. In this paper, we summarize progresses on the variability of the WBC, …

Simulated Tsunami Inundation For A Range Of Cascadia Megathrust Earthquake Scenarios At Bandon, Oregon, Usa, Rc Witter, Yinglong J. Zhang, Kl Wang, Gr Priest, C Goldfinger

VIMS Articles

Characterizations of tsunami hazards along the Cascadia subduction zone hinge on uncertainties in megathrust rupture models used for simulating tsunami inundation. To explore these uncertainties, we constructed 15 megathrust earthquake scenarios using rupture models that supply the initial conditions for tsunami simulations at Bandon, Oregon. Tsunami inundation varies with the amount and distribution of fault slip assigned to rupture models, including models where slip is partitioned to a splay fault in the accretionary wedge and models that vary the updip limit of slip on a buried fault. Constraints on fault slip come from onshore and offshore paleoseismological evidence. We rank …

Chlorophyll A In Antarctic Sea Ice From Historical Ice Core Data, Km Meiners, M Vancoppenolle, S Thanassekos, Gs Dieckmann, Dn Thomas, .. .., Walker O. Smith Jr., Et Al

VIMS Articles

Sea ice core chlorophyll a data are used to describe the seasonal, regional and vertical distribution of algal biomass in Southern Ocean pack ice. The Antarctic Sea Ice Processes and Climate - Biology (ASPeCt - Bio) circumpolar dataset consists of 1300 ice cores collected during 32 cruises over a period of 25 years. The analyses show that integrated sea ice chlorophyll a peaks in early spring and late austral summer, which is consistent with theories on light and nutrient limitation. The results indicate that on a circum-Antarctic scale, surface, internal and bottom sea ice layers contribute equally to integrated biomass, …

High Rates Of Ammonium Recycling Drive Phytoplankton Productivity In The Offshore Mississippi River Plume, B Wawrik, Jh Paul, Da Bronk, Et Al

VIMS Articles

As part of an integrated study of the regulation of carbon fixation in the offshore Mississippi River plume, we measured the rates of N-15-labeled ammonium and nitrate uptake in the surface plume waters from offshore to nearshore along the plume axis towards the Mississippi Delta. Concentrations of nitrate in the plume ranged from 0.19 to 2.5 muM with the highest concentrations primarily in the shoreward stations, while ammonium ranged from 0.17 to 0.44 muM, showing little spatial variability. Rates of ammonium uptake ranged from 16.5 to 260 nM h(-1), and showed a strong trend of increasing values from offshore towards …

Phytoplankton Assemblage Structure And Primary Productivity Along 170 Degrees W In The South Pacific Ocean, Gr Ditullio, Me Greesey, Dr Jones, Kl Daly, L Campbell, Walker O. Smith Jr.

VIMS Articles

Phytoplankton pigments were measured using HPLC during non-ENSO conditions in mid-summer along a South Pacific transect from 67degreesS to the equator along 170degreesW. Highest concentrations of chlorophyll a (chl a) occurred in the Polar and the Subtropical Fronts (PF and STF, respectively) with concentrations exceeding 500 ng l(-1). In the STF, there was a distinct subsurface chl a maximum (SCM) at 40 m, which gradually deepened northward to 120 m in the Subtropical Convergence Zone. Northwards, the SCM shoaled to about 30 m in the Equatorial Zone (EZ). Relatively high concentrations of fucoxanthin and 19'-butanoyloxyfucoxanthin occurred in the nutrient-rich waters …

Hydrography, Nutrients, And Carbon Pools In The Pacific Sector Of The Southern Ocean: Implications For Carbon Flux, Kendra L. Daly, Walker O. Smith Jr., Gregory C. Johnson, Et Al

VIMS Articles

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Abstract

We investigated the hydrography, nutrients, and dissolved and particulate carbon pools in the western Pacific sector of the Antarctic Circumpolar Current (ACC) during austral summer 1996 to assess the region's role in the carbon cycle. Low f CO₂ values along two transects indicated that much of the study area was a sink for atmospheric CO₂. The f CO₂ values were lowest near the Polar Front (PF) and the Subtropical Front (STF), concomitant with maxima of chlorophyll a and particulate and dissolved organic carbon. The largest biomass accumulations did not occur at fronts, …

A Balanced Nitrogen Budget Of The Surface Layer Of The Southern Ross Sea, Antarctica, Walker O. Smith Jr.

VIMS Articles

To understand marine biogeochemical cycles, it is critical to quantitatively balance organic matter transformations within the euphotic zone. Such an assessment for nitrogen is difficult because of lateral advection, uncertainties in individual measurements, the complexity of elemental transformations (including nitrification and denitrification), and the difficulty of collecting data on appropriate space and time scales. Two cruises were conducted to the southern Ross Sea, Antarctica, to understand the time-varying fluxes of nitrogen into its various pools. From these data a balanced inventory was constructed. Nitrate removal in the upper 200 m was balanced by particulate and dissolved organic nitrogen production, ammonification, …

Seawifs Satellite Ocean Color Data From The Southern Ocean, Jk Moore, Mr Abbott, Rg Richman, Walker O. Smith Jr., Et Al

VIMS Articles

SeaWiFS estimates of surface chlorophyll concentrations are reported for the region of the U.S. JGOFS study in the Southern Ocean (similar to 170 degrees W, 60 degrees S). Elevated chlorophyll was observed at the Southern Ocean fronts, near the edge of the seasonal ice sheet, and above the Pacific-Antarctic Ridge. The elevated chlorophyll levels associated with the Pacific-Antarctic Ridge are surprising since even the crest of the ridge is at depths > 2000 m. This elevated phytoplankton biomass is likely the result of mesoscale physical-biological interactions where the Antarctic Circumpolar Current (ACC) encounters the ridge. Four cruises surveyed this region between …

Measurements Of The Shape Of Sand Ripples, Jerome P-Y Maa, S-H Ou, C-J Huang

VIMS Articles

Laboratory experiments have been conductef. for determining what would be the correct selection of acoustic devices for measuring the shape of sand ripples. The results reveal that a toneburst type signal generator with I or 2 watts will be sufficient to drive the transducer. A transducer with focus and reasonable size would be the best choice. While measuring, the ratio of measuring distance (between the transducer and sea floor) and the transducer's focus length should be maintained at a ratio between 90% and II 0% for best results.

Hydrodynamics And Equilibrium Sediment Dynamics Of Shallow, Funnel-Shaped Tidal Estuaries, Carl T. Friedrichs, Bruce A. Armbrust, H. E. Deswart

VIMS Books and Book Chapters

No abstract provided.

Storm Surges In The Region Of Western Alaska, Warren Blier, Stanley Keefe, Wilson Shaffer, Sung C. Kim

VIMS Articles

Within the period of the historical record there have been several occurrences of extensive damage from storm-surge-related coastal flooding in the region of Nome, Alaska. The most recent of these events, although by no means the most destructive, occurred in association with the storm of 5–6 October 1992. Despite the small population of Nome (approximately 4000 people), total damage costs exceeded $6 million. The research into the nature and causes of such flooding events has focused on this October 1992 case. The authors have, however, also examined a weaker, shorter-duration event that occurred on 20 August 1993 and, for contrast, …

Storm Surges In The Region Of Western Alaska, Warren Blier, Stanley Keefe, Wilson A. Shaffer, Sung C. Kim

VIMS Articles

Within the period of the historical record there have been several occurrences of extensive damage from storm-surge-related coastal flooding in the region of Nome, Alaska. The most recent of these events, although by no means the most destructive, occurred in association with the storm of 5–6 October 1992. Despite the small population of Nome (approximately 4000 people), total damage costs exceeded $6 million.

The research into the nature and causes of such flooding events has focused on this October 1992 case. The authors have, however, also examined a weaker, shorter-duration event that occurred on 20 August 1993 and, for contrast, …

Effects Of Channel Geometry On Cross Sectional Variation In Along Channel Velocity In Partially Stratified Estuaries, Carl T. Friedrichs, John M. Hamrick

VIMS Books and Book Chapters

Analytic solutions for along‐channel velocity through an estuarine cross‐section with laterally varying depth are compared to observations from an array of current meters deployed over a nearly triangular cross‐section of the James River estuary. Analytic results suggest that the transverse structure of along‐channel velocity at this cross‐section is primarily due to simple density‐driven circulation modified by bathymetry. Comparisons of analytic solutions for the amplitude and phase of tidal velocity to observations suggest that linear models which include realistic lateral depth variation should also incorporate across‐channel variation in eddy viscosity. Solutions for various contributions to mean velocity are then derived which …

Temporal And Spatial Patterns In The Ross Sea: Phytoplankton Biomass, Elemental Composition, Productivity And Growth Rates, Walker O. Smith Jr., David Nelson, Giacomo R. Ditullio, Amy R. Leventer

VIMS Articles

The temporal and spatial patterns of phytoplankton biomass, productivity, and particulate matter composition in the Ross Sea were assessed during cruises in January 1990 and February 1992. Biomass and primary productivity in the southern Ross Sea were greatest during mid-January, with surface chlorophyll concentrations, particulate organic carbon levels, and integrated primary productivity averaging 4.9 Ixg L 'l, 0.54 mg L-•, and 2.63 g C m"• d '•, respectively. Comparable mean concentrations and rates for February were 1.1 Ixg L 'l, 0.29 mg L 'l, and 0.78 g C m '•- d '• (decreases of 76, 46, and 70%, respectively), indicative …

Linking Sediment Transport And Stratigraphy On The Continental Shelf, Pl Wilberg, Da Cacchione, Rw Sternberg, L. Donelson Wright

VIMS Articles

The goal of the shelf sediment dynamics component of STRATAFORM is to link sediment transport processes active on the continental shelf to the formation and preservation of event beds in shelf sediment deposits. An approach combining shelf sediment-transport models with high-resolution measurements of water-column and bed properties over periods from several months to several years allows us to make quantitative estimates of bed modification caused by sediment resuspension during episodic transport events. These modifications include erosion and deposition of bed material, formation of graded storm beds, and changes in small-scale bed surface morphology. The characteristics of the resulting “event bed” …

Linking Sediment Transport And Stratigraphy On The Continental Shelf, Patrica Wiberg, David Cacchione, Richard Sternberg, L. Donelson Wright

VIMS Articles

The goal of the shelf sediment dynamics component of STRATAFORM is to link sediment transport processes active on the continental shelfto the formation and preservation of event beds inshelf sediment deposits. An approach combining
shelf sediment-transport models with high-resolution measurements of water-column and bed properties over periods from several months to several
years allows us to make quantitative estimates of bed modification caused by sediment resuspension during episodic transport events.

Introduction, Carl T. Friedrichs, D. G. Aubrey

VIMS Books and Book Chapters

No abstract provided.

Calcium Carbonate Sedimentation In The Global Ocean: Linkages Between The Neritic And Pelagic Environments, John D. Milliman, Andre W. Droxler

VIMS Articles

Other than fluvial sediment, calcium carbonate (CaCO3) is the greatest source of sediment in the present-day ocean. Interest in carbonate sedimentation extends beyond geologists because the carbonate system involves biologic and geochemical
processes. Carbonate production, for example, releases CO2 but its accumulation becomes a major sink for inorganic carbon.

Unlike fluvial sediments, modern carbonates accumulate more or less equally in the neritic and pelagic environments. Neritic carbonates (benthic) are characterized by rapid production of (mostly) metastable aragonite and magnesian calcite:pelagic production of (primarily) calcite in the open ocean occurs at much slower rates but overmuch larger areas than does neritic …

Tidal Propagation In Strongly Convergent Channels, Carl T. Friedrichs, David G. Aubrey

VIMS Articles

Simple first‐ and second‐order analytic solutions, which diverge markedly from classical views of cooscillating tides, are derived for tidal propagation in strongly convergent channels. Theoretical predictions compare well with observations from typical examples of shallow, “funnel‐shaped” tidal estuaries. A scaling of the governing equations appropriate to these channels indicates that at first order, gradients in cross‐sectional area dominate velocity gradients in the continuity equation and the friction term dominates acceleration in the momentum equation. Finite amplitude effects, velocity gradients due to wave propagation, and local acceleration enter the equations at second order. Applying this scaling, the first‐order governing equation becomes …

Hydrodynamical Modeling Of A Multiple‐Inlet Estuary/Barrier System: Insight Into Tidal Inlet Formation And Stability, Carl T. Friedrichs, David G. Aubrey, Graham S. Giese, Paul E. Speer

VIMS Books and Book Chapters

Two specific questions are addressed concerning the role of tidal hydrodynamics in determining the long‐term morphologic evolution of the Nauset Beach‐Monomoy Island barrier system and the Chatham Harbor‐Pleasant Bay tidal estuary, Massachusetts: (1) why do the barrier and estuary exhibit a long‐term (∼150 yr) cycle of new inlet formation, and (2) once a new inlet forms, why is the resulting multiple inlet system unstable? To address these questions, a branched 1‐d numerical model is used to recreate the basic flow patterns in the tidal estuary at ten‐year intervals during the last half century and also to recreate flow conditions shortly …

Marine Ecosystem Research At The Weddell Sea Ice Edge: The Ameriez Program, Walker O. Smith Jr., Dl Garrison

VIMS Articles

The explorers and naturalists who first visited Antarctica were struck by the large numbers of whales, seals and seabirds in such a harsh environment (summarized in Everson, 1977). Scientific expeditions in the twentieth century confirmed these observations, and also established that an even greater abundance of many different trophic levels occurred at the ice edge. Hart (1942) noted that phytoplankton were more abundant near the ice edge mad suggested that there was a distinct ice-edge flora, and Marr (1962) noted that krill (Euphausia superba) were concentrated at the interface between pack ice and open water. Routh (1949) observed …

The Formation Of Longitudinal Fronts In A Coastal Plain Estuary, Linda M. Huzzey, John M. Brubaker

VIMS Articles

Longitudinal estuarine fronts, aligned parallel to the axis of the estuary, are characteristic of the York River. Their time scale for genesis and decay is of the order of hours; they are usually located at the inner edge of the shoals or over the main channel. Field measurements have shown marked intratidal differences in density and current speeds across this estuary. These can be correlated with changes in depth and the strength of the advective processes. Differential advection between the channel and shoal regions, when acting upon a constant longitudinal density gradient, is shown to be of sufficient magnitude to …

Mid‐Level Intrusions At The Continental Shelf Edge, Christopher S. Welch

VIMS Articles

Observations across the continental shelf offshore from New Jersey in late summer 1976 show an intrusion of saline water at the mid level of the water column across the shelf edge front, which appears in density only as an offshore thickening of the pycnocline. This internal density field produces horizontal pressure gradient forces within the pycnocline in the onshore direction. These forces, in the linearized equation of motion with a constant eddy viscosity, drive a circulation which resembles a double Ekman spiral for internal pressure vertical distributions which are thin with respect to the Ekman depth. For thick pressure distributions, …

Groundwater Flow In A Sandy Tidal Beach 2. Two-Dimensional Finite Element Analysis., C. S. Fang, S. N. Wang, W. Harrison

VIMS Articles

Two-dimensional finite element techniques are described that model closely the complicated fluctuations osbserved in the water table of an ocean beach. The use of triangular elements permits the specification of more realistic boundary conditions than the use of line elements in a one-dimensional model. Also, results obtained from the two-dimensional model for the region closet o the ocean compare more favorably with field data than results obtained from the one-dimensional finite element model.

Groundwater Flow In A Sandy Tidal Beach 1. One-Dimensional Finite Element Analysis, W. Harrison, C. S. Fang, S. N. Wang

VIMS Articles

A 31-day time series of observations of beach water table and tidal fluctuations was obtained from 13 wells along a profile perpendicular to the shoreline at Virginia Beach, Virginia. Finite element techniques were applied to solve the one-dimensional, unsteady state, nonlinear equation for groundwater movement. For the finite element analysis, the semi-infinite mass (unconfined aquifer) had to be replaced by a finite mass. The boundary conditions were found from the field data by directly solving the flow equation with a finite difference technique. The finite element method, using the variational principle, provided a reasonable solution and afforded economy in computer …

Predictor Equations For Beach Processes And Responses, W. Harrison, N. A. Pore, D. R. Tuck Jr.

VIMS Articles

A stepwise (linear) multiple regression procedure is applied to 11 environmental variables (or predictors) in the beach-ocean-atmosphersey stema t Virginia Beach, Virginia, for the following five predictands: mean longshore current velocity, mean bottom slope in the shoaling-wave zone, average mean grain size in the shoaling-wave zone, and beach deposition and beach erosion on the lower foreshore. Predictors consist of variables related to beach geometry, local water properties, local wind conditions, tidal fluctuations, and wave characteristics The resultant equations are tested against a set of independent data and, with one exception, agree reasonably. It is believed that if the data set …