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Instability Of An Idealized Tidal Mixing Front: Symmetric Instabilities And Frictional Effects, K. H. Brink, Deepak A. Cherian Jan 2013

Instability Of An Idealized Tidal Mixing Front: Symmetric Instabilities And Frictional Effects, K. H. Brink, Deepak A. Cherian

Journal of Marine Research

Finite amplitude instability of an idealized tidal mixing front is considered for cases where there is an active symmetric instability during the early stages of evolution. This can happen either when the initial front is sharp, or when a bottom stress leads to a well-mixed bottom boundary layer under the front. In either case, there is an initial phase, several days long, of slantwise convection, after which a much more energetic and spatially distributed baroclinic or barotropic instability dominates. The presence of an initial symmetrically unstable phase has no obvious effect on the subsequent eddy evolution. Bottom friction does lead …

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Recycling And Burial Of Phosphorus In Sediments Of An Anoxic Fjord—The By Fjord, Western Sweden, Lena Viktorsson, Mikhail Kononets, Per Roos, Per O. J. Hall Jan 2013

Recycling And Burial Of Phosphorus In Sediments Of An Anoxic Fjord—The By Fjord, Western Sweden, Lena Viktorsson, Mikhail Kononets, Per Roos, Per O. J. Hall

Journal of Marine Research

Recycling and burial of sediment phosphorus were studied in the By Fjord, western Sweden, during the years 2009 to 2010 using autonomous benthic landers and sediment sampling. The By Fjord is a small fjord with a shallow sill at its narrow mouth, which limits water exchange of the fjord's basin water. The water in the basin is exchanged only every 3 to 5 years and the water below sill level is anoxic or sulfidic between water renewals. Five sites were examined in the By Fjord; three shallow sites above the sill level with oxic bottom waters and two deeper sites …

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Seasonal, 2-D Sedimentary Extracellular Enzyme Activities And Controlling Processes In Great Peconic Bay, Long Island, Zhenrui Cao, Qingzhi Zhu, Robert C. Aller, Josephine Y. Aller, Stuart Waugh Jan 2013

Seasonal, 2-D Sedimentary Extracellular Enzyme Activities And Controlling Processes In Great Peconic Bay, Long Island, Zhenrui Cao, Qingzhi Zhu, Robert C. Aller, Josephine Y. Aller, Stuart Waugh

Journal of Marine Research

Extracellular enzymes (EE) initiate heterotrophic remineralization by hydrolyzing high-molecularweight organic matter to substrates that are sufficiently small (approximately 600 Da) to be transported across cell membranes. An accurate understanding of EE associated remineralization processes in sedimentary deposits requires measuring patterns of extracellular enzyme activity (EEA) with minimal disturbance of natural sediment structure. In this study, two-dimensional patterns of extracellular enzyme (leucine aminopeptidase) activity in shallow-water, marine sediments from Great Peconic Bay, Long Island, New York were examined seasonally at sub-millimeter resolution by using a newly developed EE planar fluorosensor. Comparisons of spatially averaged, vertical enzyme activity profiles measured using this …

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Influence Of Larval Behavior On Transport And Population Connectivity In A Realistic Simulation Of The California Current System, Patrick T. Drake, Christopher A. Edwards, Steven G. Morgan, Edward P. Dever Jan 2013

Influence Of Larval Behavior On Transport And Population Connectivity In A Realistic Simulation Of The California Current System, Patrick T. Drake, Christopher A. Edwards, Steven G. Morgan, Edward P. Dever

Journal of Marine Research

Using an implementation of the Region Ocean Modeling System, we investigate the influence of larval vertical swimming on spring dispersal for nearshore invertebrate species in the California Current System (CCS), with a focus on central California and the Bodega Bay area. Larvae are given a suite of idealized behaviors designed to reveal the importance of the surface boundary layer (SBL) to transport and settlement. Larvae remain near 5 m, 30 m, or transition between these depths using various strategies, including diel vertical migration (DVM) and ontogenetic vertical migration. Some behaviors result in modeled densities qualitatively similar to observed cross-shelf larval …

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Antimicrobial Resistance To 14 Antimicrobials In Marine Coastal Waters Around Northern Ireland: Use Of The Novel Relative Resistance Index As A Marker Of Ecological Status, Peter J. A. Moore, Juluri R. Rao, B. Cherie Millar, Colin E. Goldsmith, Wilson A. Coulter, John E. Moore Jan 2013

Antimicrobial Resistance To 14 Antimicrobials In Marine Coastal Waters Around Northern Ireland: Use Of The Novel Relative Resistance Index As A Marker Of Ecological Status, Peter J. A. Moore, Juluri R. Rao, B. Cherie Millar, Colin E. Goldsmith, Wilson A. Coulter, John E. Moore

Journal of Marine Research

Relatively little work has been published on the incidence of antibiotic resistance (ABR) in the marine microbiological environment, which is of importance to animal (fish, mammals, birds) health, zoonotic transmission, distribution of ABR bacteria with oceanic drift, and ultimately human health. A study was performed to determine the diversity of total ABR (intrinsic and acquired resistance) in marine bacteria in shallow coastal waters surrounding Northern Ireland through the use of a novel Relative Resistance Index (RRI) as a surrogate marker for ecological change, particularly in comparing marine water in commercial versus non-commercial sites. Total antibiotic resistance was observed to varying …

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Circulation And Cross-Shelf Transport In The Florida Big Bend, Austin C. Todd, Steven L. Morey, Eric P. Chassignet Jan 2013

Circulation And Cross-Shelf Transport In The Florida Big Bend, Austin C. Todd, Steven L. Morey, Eric P. Chassignet

Journal of Marine Research

The Florida Big Bend region in the northeastern Gulf of Mexico contains both spawning sites and nursery habitats for a variety of economically valuable marine species. One species, the gag grouper (Mycteroperca microlepis), relies on the shelf circulation to distribute larvae from shelf-break spawning grounds to coastal sea-grass nurseries each spring. Therefore, identifying the dominant circulation features and physical mechanisms that contribute to cross-shelf transport during the springtime is a necessary step in understanding the variation of the abundance of this reef fish. The mean circulation features and onshore transport pathways are investigated using a numerical ocean model …

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Eddy Induced Kuroshio Intrusions Onto The Continental Shelf Of The East China Sea, Pedro Vélez-Belchí, Luca R. Centurioni, Dong-Kyu Lee, Sen Jan, Pearn P. Niiler Jan 2013

Eddy Induced Kuroshio Intrusions Onto The Continental Shelf Of The East China Sea, Pedro Vélez-Belchí, Luca R. Centurioni, Dong-Kyu Lee, Sen Jan, Pearn P. Niiler

Journal of Marine Research

The Kuroshio is known to intrude onto the continental shelf in the southern East China Sea (ECS) northeast of Taiwan. Two types of intrusions are observed: large and small, depending on how far the Kuroshio penetrates onto the ECS continental shelf, and on the location where it crosses the shelf break. This study demonstrates that cyclonic eddies from the western Pacific induce some of these large Kuroshio intrusions. The large intrusions are identified from more than 20 years of drifter tracks archived in the Global Drifter Program historical database and from weekly and biweekly drifter deployments carried out between April …

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Numerical Study Of Cold Dome Variability Induced By Typhoon Morakot (2009) Off Northeastern Taiwan, Yaling Tsai, Ching-Sheng Chern, Sen Jan, Joe Wang Jan 2013

Numerical Study Of Cold Dome Variability Induced By Typhoon Morakot (2009) Off Northeastern Taiwan, Yaling Tsai, Ching-Sheng Chern, Sen Jan, Joe Wang

Journal of Marine Research

The ocean response to the passage of Typhoon Morakot (2009) near the continental shelf of the East China Sea off northeastern Taiwan was evaluated using a numerical ocean model to clarify how the permanent upwelling feature in this region was changed during this storm event. Several studies have identified the presence of the Kuroshio subsurface water in this Cold Dome region, which results from the interactions among the monsoon, the Kuroshio and the shelf topography. This study shows how tropical cyclone Morakot's passage quickly disturbed the circulation around Taiwan and induced a short-period intrusion of the Kuroshio water onto the …

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Spatial Distribution Of Alitta Virens And Clymenella Torquata With Respect To Rigid Boundaries In Mud And Sand, Kevin T. Du Clos, Sara M. Lindsay, Peter A. Jumars Jan 2013

Spatial Distribution Of Alitta Virens And Clymenella Torquata With Respect To Rigid Boundaries In Mud And Sand, Kevin T. Du Clos, Sara M. Lindsay, Peter A. Jumars

Journal of Marine Research

Recent advances in understanding of sediment material properties and of burrowing mechanics suggest likely differences in the behavior of organisms burrowing in mud and sand. The path of least resistance in the mud may lead an infaunal organism to burrow along a rigid wall. By contrast, in sand, force chains may prevent a burrowing organism from reaching a rigid wall. Burrowing in mud occurs primarily by the propagation of cracks. Cracks, and hence burrows, tend to propagate along rigid walls. In sand, force chains comprise collections of particles that experience much more stress than their neighbors. Stress chains tend to …

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Instability Of A Tidal Mixing Front In The Presence Of Realistic Tides And Mixing, K. H. Brink Jan 2013

Instability Of A Tidal Mixing Front In The Presence Of Realistic Tides And Mixing, K. H. Brink

Journal of Marine Research

Instability and lateral eddy fluxes associated with a tidal mixing front are studied using idealized primitive equation numerical model runs. The front itself develops as a result of turbulence associated with imposed tidal currents over a sloping bottom. Thus, the model includes realistic levels of turbulence and time-dependence in the base-state conditions. In all of the 21 configurations considered, the front is unstable to fluctuations that usually draw energy primarily from the potential energy pool. Scalings are developed to parameterize a) the location of the tidal mixing front; b) the eddy kinetic energy; and c) the lateral eddy coefficients. In …

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Nutrient Supply In The Southern East China Sea After Typhoon Morakot, Chin-Chang Hung, Chih-Ching Chung, Gwo-Ching Gong, Sen Jan, Yaling Tsai, Kuo-Shu Chen, Wen Chen Chou, Ming-An Lee, Yi Chang, Meng-Hsien Chen, Wen-Rong Yang, Chiung-Jung Tseng, Glen Gawarkiewicz Jan 2013

Nutrient Supply In The Southern East China Sea After Typhoon Morakot, Chin-Chang Hung, Chih-Ching Chung, Gwo-Ching Gong, Sen Jan, Yaling Tsai, Kuo-Shu Chen, Wen Chen Chou, Ming-An Lee, Yi Chang, Meng-Hsien Chen, Wen-Rong Yang, Chiung-Jung Tseng, Glen Gawarkiewicz

Journal of Marine Research

Recent studies show that typhoons have profound effects on phytoplankton assemblages along their tracks, but it is difficult to quantitatively estimate nutrient supply after a typhoon's passage due to a lack of nutrient information before and after the arrival of a typhoon. During the passage of Typhoon Morakot (July 22 to Aug. 26, 2009), we conducted pre- and post-typhoon field cruises to study nutrient supply in the Southern East China Sea (SECS). The results showed nitrate and phosphate supplies to the water column in the SECS after the typhoon's passage were 5.6 × 1011 g-N/day and 7.8 × 10 …

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Relative Sensitivity Of Two Marine Bivalves For Detection Of Genotoxic And Cytotoxic Effects: A Field Assessment In The Tamar Estuary, South West England., Lorna J. Dallas, Victoria V. Cheung, Andrew S. Fisher, Awadhesh N. Jha Jan 2013

Relative Sensitivity Of Two Marine Bivalves For Detection Of Genotoxic And Cytotoxic Effects: A Field Assessment In The Tamar Estuary, South West England., Lorna J. Dallas, Victoria V. Cheung, Andrew S. Fisher, Awadhesh N. Jha

School of Geography, Earth and Environmental Sciences

The input of anthropogenic contaminants to the aquatic environment is a major concern for scientists, regulators and the public. This is especially relevant in areas such as the Tamar valley in SW England, which has a legacy of contamination from industrial activity in the nineteenth and twentieth centuries. Following on from previous laboratory validation studies, this study aimed to assess the relationship between genotoxic and cytotoxic responses and heavy metal concentrations in two bivalve species sampled from locations along the Tamar estuary. Adult cockles, Cerastoderma edule, and blue mussels, Mytilus edulis, were sampled from five locations in the Tamar and …

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A Centennial Record Of Paleosalinity Change In The Tidal Reaches Of The Potomac And Rappahannock Rivers, Tributaries To Chesapeake Bay, Neil E. Tibert, Lindsay J. Walker, William P. Patterson, J. Bradford Hubeny, Emma Jones, Olivia R. Cooper Oct 2012

A Centennial Record Of Paleosalinity Change In The Tidal Reaches Of The Potomac And Rappahannock Rivers, Tributaries To Chesapeake Bay, Neil E. Tibert, Lindsay J. Walker, William P. Patterson, J. Bradford Hubeny, Emma Jones, Olivia R. Cooper

Virginia Journal of Science

Gravity and push cores from the Potomac and Rappahannock Rivers (Virginia Tidewater) were collected from central and proximal estuarine zones with known seasonal salinity stratification. The lowermost microfossil associations in the cores comprise alternating ostracode populations of Cyprideis salebrosa and Cytheromorpha. This microfossil association gives way to an oligohaline association dominated by the freshwater ostracode Darwinula stevensoni. Stable oxygen isotope values (δ18O) of Rapphannock Cyprideis salebrosa are highly variable ranging between -6.6 to -3.2‰ VPDB. δ18O values for Potomac Cytheromorpha fuscata range from -8.2 to -3.2‰ VPDB. Positive excursions in δ18O values …

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The Breathing Of The Bays, Jamie Vaudrey, Margaret (Peg) A. Van_Patten (Editor) Aug 2012

The Breathing Of The Bays, Jamie Vaudrey, Margaret (Peg) A. Van_Patten (Editor)

Wrack Lines

Bays in Long Island Sound and beyond have natural rhythms like breathing. Stress can impact the health of these natural ecosystems. While Long Island Sound has been examined for the extent of hypoxia in the summer, small embayments have not been examined carefully. In this article, two researchers investigate the oxygen, or lack of, in small bays of Long Island Sound.

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The Air-Sea Transformation And Residual Overturning Circulation Within The Nordic Seas, Pål Erik Isachsen, Ole Anders Nøst Jan 2012

The Air-Sea Transformation And Residual Overturning Circulation Within The Nordic Seas, Pål Erik Isachsen, Ole Anders Nøst

Journal of Marine Research

The residual diapycnal overturning circulation through interior regions of the Nordic Seas is diagnosed. The mean flow is estimated from Ekman dynamics and from the thermal wind relation with reference level velocities deduced from observations and from simplified theory. Eddy-induced transport is estimated from a GM-type parameterization which includes top and bottom boundary layers. The contributions from the Eulerian mean and eddy-induced transport are then compared to the annual-mean air – sea density transformation over the Nordic Seas. The calculations suggest that the mean flow overturning may explain up to 25% of the observed air – sea transformation in the …

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The Impact Of Ambient Stratification On Freshwater Transport In A River Plume, Yan Jia, Alexander Yankovsky Jan 2012

The Impact Of Ambient Stratification On Freshwater Transport In A River Plume, Yan Jia, Alexander Yankovsky

Journal of Marine Research

The influence of ambient stratification on the river plume dynamics is studied using the Regional Ocean Modeling System (ROMS). The shelf flow is thermally stratified and retains a 15-m deep upper mixed layer. A buoyant inflow into the model domain is systematically varied so that both surface-advected and bottom-advected buoyant plumes are formed. The resulting buoyant plumes are compared with the corresponding numerical solutions when the ambient shelf flow is not stratified. Surface-advected plumes spread on top of the thermocline and are not affected by the ambient stratification. Bottom-advected plumes on the other hand interact with the ambient stratification by …

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Deep Circulation Within The Argentine Basin, Joseph L. Reid Jan 2012

Deep Circulation Within The Argentine Basin, Joseph L. Reid

Journal of Marine Research

The total transport in the South Atlantic Ocean (Fig. 1) consists of an anticyclonic gyre that reaches from the equator to about 50°S, and south of 40°S two cyclonic turns from the Circumpolar Current and Weddell Sea, west and east of the anticyclonic gyre. This figure has been changed very slightly between 40°S and 50°S from the figure shown in Reid (1994)...

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Long-Term Patterns Of An Estuarine Pathogen Along A Salinity Gradient, David Bushek, Susan E. Ford, Iris Burt Jan 2012

Long-Term Patterns Of An Estuarine Pathogen Along A Salinity Gradient, David Bushek, Susan E. Ford, Iris Burt

Journal of Marine Research

Parasitic, disease-causing pathogens can exert strong control over marine populations yet few long-term studies exist that describe these relationships. Understanding the connections to long-term large-scale processes relative to local short-term processes should facilitate better planning for disease impacts in the management of marine resources. We describe a 21-yr dataset of dermo disease (Perkinsus marinus) in eastern oysters (Crassostrea virginica) in Delaware Bay, USA. Analyses indicated (1) a strong positive association between disease and mortality that was non-linear and defined by thresholds, (2) a clear spatial gradient of increasing disease and mortality with increasing salinity, (3) an …

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An Introduction To Ecology Of Infectious Diseases – Oysters And Estuaries, Eileen E. Hofmann, Susan E. Ford Jan 2012

An Introduction To Ecology Of Infectious Diseases – Oysters And Estuaries, Eileen E. Hofmann, Susan E. Ford

Journal of Marine Research

Infectious diseases are recognized as an important factor regulating marine ecosystems (Harvell et al., 1999, 2002, 2004; Porter et al., 2001; McCallum et al., 2004; Ward and Lafferty, 2004; Stewart et al., 2008; Bienfang et al., 2011). Many of the organisms affected by marine diseases have important ecological roles in estuarine and coastal environments and some are also commercially important. Outbreaks of infectious diseases in these environments, referred to as epizootics, can produce significant population declines and extinctions, both of which threaten biodiversity, food web interactions, and ecosystem productivity (Harvell et al., 2002, 2004)...

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Can Oysters Crassostrea Virginica Develop Resistance To Dermo Disease In The Field: The Impediment Posed By Climate Cycles, Eric N. Powell, John M. Klinck, Ximing Guo, Eileen E. Hofmann, Susan E. Ford, David Bushek Jan 2012

Can Oysters Crassostrea Virginica Develop Resistance To Dermo Disease In The Field: The Impediment Posed By Climate Cycles, Eric N. Powell, John M. Klinck, Ximing Guo, Eileen E. Hofmann, Susan E. Ford, David Bushek

Journal of Marine Research

Populations of eastern oysters, Crassostrea virginica, are commonly limited by mortality from dermo disease. Little development of resistance to Perkinsus marinus, the dermo pathogen, has occurred, despite the high mortality rates and frequency of epizootics. Can the tendency of the parasite to exhibit cyclic epizootics limit the oyster's response to the disease despite the presence of alleles apparently conferring disease resistance? We utilize a gene-based population dynamics model to simulate the development of disease resistance in Crassostrea virginica populations exposed to cyclic mortality encompassing periodicities expected of dermo disease over the geographic range at which epizootics have been …

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Circulation And Water Properties And Their Relationship To The Oyster Disease Msx In Delaware Bay, Zhiren Wang, Dale B. Haidvogel, David Bushek, Susan E. Ford, Eileen E. Hofmann, Eric N. Powell, John Wilkin Jan 2012

Circulation And Water Properties And Their Relationship To The Oyster Disease Msx In Delaware Bay, Zhiren Wang, Dale B. Haidvogel, David Bushek, Susan E. Ford, Eileen E. Hofmann, Eric N. Powell, John Wilkin

Journal of Marine Research

We apply a high-resolution hydro-dynamical model to investigate the role of physical factors influencing infection prevalence of Haplosporidium nelsoni, causative agent of MSX disease in the eastern oyster (Crassostrea virginica), in Delaware Bay, USA. Validation studies conducted for the years 2000 and 2010–2011 confirm that the model, based upon the Regional Ocean Modeling System, has significant skill in the recovery of observed water level, temperature, salinity, and velocity. Multi-year simulations are performed for periods representing temporal and spatial variations in H. nelsoni infection prevalence (1974–76, 1979–81, 1984–86, 1990–92, and 2006–09) to assess the degree to which the …

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Spatial And Temporal Variability Of Disease Refuges In An Estuary: Implications For The Development Of Resistance, Susan E. Ford, Emily Scarpa, David Bushek Jan 2012

Spatial And Temporal Variability Of Disease Refuges In An Estuary: Implications For The Development Of Resistance, Susan E. Ford, Emily Scarpa, David Bushek

Journal of Marine Research

Although the concept of genetic refuge has long been employed in ecological and paleoecological context, it has only rarely been used to identify regions where organisms are protected from diseases that affect the rest of a population. The refuges harbor individuals that have not been exposed to selective mortality and remain susceptible to the disease. They represent a reservoir of susceptibility alleles that can mix with those from resistant survivors of disease and can retard the development of resistance in the population as a whole. Two water-borne protistan parasites affect oysters along the east coast of the United States: Haplosporidium …

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Primary And New Production In The Thermocline Ridge Region Of The Southern Indian Ocean During The Summer Monsoon, Naveen Gandhi, R. Ramesh, S. Prakash, Sharon Noronha, N. Anilkumar Jan 2012

Primary And New Production In The Thermocline Ridge Region Of The Southern Indian Ocean During The Summer Monsoon, Naveen Gandhi, R. Ramesh, S. Prakash, Sharon Noronha, N. Anilkumar

Journal of Marine Research

New and primary production, measured using 15N and 13C tracers, integrated over the euphotic zone (mostly upper 80–100 m) varied from 7.5 to 14.1 mmol N m–2d–1(average 10.8 mmol N m–2d–1) and 2.7 to 17.7 mmol C m–2d–1 (average 11.3 mmol C m–2d–1), respectively, in the tropical India Ocean (TIO). Shoaling of thermocline in the thermocline ridge located in the tropical Indian Ocean (TR) influences new and total productivity by supplying nutrients to the upper layers. At the same time, N-limited conditions prevail …

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Geostrophic Ocean Currents And Freshwater Fluxes Across The Canadian Polar Shelf Via Nares Strait, Berit Rabe, Helen L. Johnson, Andreas Münchow, Humfrey Melling Jan 2012

Geostrophic Ocean Currents And Freshwater Fluxes Across The Canadian Polar Shelf Via Nares Strait, Berit Rabe, Helen L. Johnson, Andreas Münchow, Humfrey Melling

Journal of Marine Research

This study discusses geostrophic ocean currents and fluxes through Nares Strait, one of the major straits connecting the Arctic Ocean to the North Atlantic across the Canadian polar shelf. Between 2003 and 2006, instruments were installed on subsea moorings to measure conductivity, temperature, pressure and velocity at high temporal and spatial resolution across the 400-m-deep strait. Here we present estimates of the variable volume and liquid freshwater fluxes, derived by geostrophic calculation, through the fraction of the cross section measured by the array. The array of conductivity-temperature recorders spanned 30 km of a 38-km-wide section between 30- and 200-m depth. …

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Solar Warming Of Near-Bottom Water Over A Fringing Reef, Judith R. Wells, Jonathan P. Fram, Geno Pawlak Jan 2012

Solar Warming Of Near-Bottom Water Over A Fringing Reef, Judith R. Wells, Jonathan P. Fram, Geno Pawlak

Journal of Marine Research

The Kilo Nalu Observatory is located on the foreslope of a fringing reef on the south shore of Oahu, Hawaii. A cabled node at 12-m depth has enabled continuous real-time temperature observations from a thermistor chain extending from 1 to 7 m above bottom. Data from a 27-month deployment in 2007–2009 reveal repeated instances of subsurface temperature inversions. The usual diurnal pattern shows increases in temperature throughout the water column after sunrise, peaking in the early afternoon. Bottom waters typically warm faster than those at mid-depth, driving an inversion in the thermal profile. The onset and evolution of the inversions …

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Experimental Assessment Of Particle Mixing Fingerprints In The Deposit-Feeding Bivalve Abra Alba (Wood), Guillaume Bernard, Antoine Grémare, Olivier Maire, Pascal Lecroart, Filip J. R. Meysman, Aurélie Ciutat, Bruno Deflandre, Jean Claude Duchêne Jan 2012

Experimental Assessment Of Particle Mixing Fingerprints In The Deposit-Feeding Bivalve Abra Alba (Wood), Guillaume Bernard, Antoine Grémare, Olivier Maire, Pascal Lecroart, Filip J. R. Meysman, Aurélie Ciutat, Bruno Deflandre, Jean Claude Duchêne

Journal of Marine Research

Particle mixing induced by the deposit-feeding bivalve Abra alba was assessed using a new experimental approach allowing for the tracking of individual particle displacements. This approach combines the adaptation of existing image acquisition techniques with new image analysis software that tracks the position of individual particles. This led to measurements of particle mixing fingerprints, namely the frequency distributions of particle waiting times, and of the characteristics (i.e. direction and length) of their jumps. The validity of this new approach was assessed by comparing the so-measured frequency distributions of jump characteristics with the current qualitative knowledge regarding particle mixing in the …

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Eddy Viscosity And Diffusivity In The Modon-Sea Model, Timour Radko Jan 2012

Eddy Viscosity And Diffusivity In The Modon-Sea Model, Timour Radko

Journal of Marine Research

A deterministic model is developed to evaluate and explain the rate of dissipation of momentum in eddying oceanic flows. Theory is based on a classical conceptualization of mesoscale variability – Stern's modon-sea solution – which represents a closely packed array of steady compact dipolar vortices on the barotropic beta-plane. In our model, the periodic modon-sea pattern is subjected to a large-scale perturbation, weakly modulating the amplitude of the individual modons. The asymptotic multiscale analysis makes it possible to explicitly describe the interaction between the modon-sea eddies and the perturbing flow. This interaction results in a systematic weakening of the large-scale …

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Measuring Overturns With Gliders, S. A. Thorpe Jan 2012

Measuring Overturns With Gliders, S. A. Thorpe

Journal of Marine Research

The accuracy of the estimation of the vertical size of eddies in turbulent stratified shear flows in the ocean from measurements obtained by gliders is examined. It is assumed that gliders move along paths inclined at moderate angles to the horizontal. Comparison is made with measurements by probes falling or lowered vertically through billows resulting from Kelvin-Helmholtz (K-H) or Holmboe instability and through the statically unstable regions formed at early stages of convective breaking of internal waves. The probable errors involved in estimating the overturn scale of a K-H billow along the track of a glider are greatest when the …

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Glider Measurements Of Overturning In A Kelvin-Helmholtz Billow Train, W. D. Smyth, S. A. Thorpe Jan 2012

Glider Measurements Of Overturning In A Kelvin-Helmholtz Billow Train, W. D. Smyth, S. A. Thorpe

Journal of Marine Research

The prospects for glider-based measurement of turbulence statistics are assessed using direct numerical simulation data representing breaking Kelvin-Helmholtz (KH) billows in a stratified, parallel shear flow. Transects tilted upstream against the shear tend to produce overestimates of overturning; those tilted with the shear produce underestimates. Low-angle transects can produce illusory overturning as the braid between the KH billows is crossed. Statistical features of the bias in displacement scales are related to geometrical aspects of KH billows. Results are interpreted in the context of a hypothetical effort to characterize overturning in a strongly sheared current (e.g. the Equatorial Undercurrent) using nonvertical …

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Cross-Shelf Mixing And Mid-Shelf Front Dynamics In The Mid-Atlantic Bight Evaluated Using The Radium Quartet, Scott L. Stachelhaus, S. Bradley Moran, David S. Ullman, Roger P. Kelly Jan 2012

Cross-Shelf Mixing And Mid-Shelf Front Dynamics In The Mid-Atlantic Bight Evaluated Using The Radium Quartet, Scott L. Stachelhaus, S. Bradley Moran, David S. Ullman, Roger P. Kelly

Journal of Marine Research

Mid-shelf fronts (MSFs) are thought to be ubiquitous in shelf areas. However, their dynamical role in cross-shelf mixing has yet to be fully characterized. In January, February, and April of 2007, radium isotopes (223Ra, t1/2 = 11 d; 224Ra, t1/2 = 3.7 d; 226Ra, t1/2 = 1600 yr; 228Ra, t1/2 = 5.7 yr) were measured along a transect in the Mid-Atlantic Bight to constrain mixing rates at and around a MSF. Cross-shelf eddy diffusivities (Kx) were determined from 223Ra and 224Ra distributions using a variable-depth model. Two key assumptions …

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