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Multi-Year Current Time Series In The Eastern North Atlantic Ocean, Thomas J. Müller, Gerold Siedler

Journal of Marine Research

Time series of currents from an array of 22 subsurface moorings in the Canary and Iberian Basins of the North Atlantic are analyzed with respect to low-frequency variability. The record lengths are usually 1 to 2 years but almost 9 years (site KIEL276, 33N, 22W) in one case. Maximal energies are observed at periods between 50 and 500 days, and high-energy events are found from time to time. The 9-year long series indicates changes in currents with a 3-4 year period, primarily in the zonal component, and anisotropic energy distributions are found for both current components at periods around 200 …

A Thermocline Model For Ocean-Climate Studies, Sheng Zhang, Charles A. Lin, Richard J. Greatbatch

Journal of Marine Research

A 3-dimensional planetary geostrophic (PG) ocean general circulation model in spherical coordinates is formulated to examine the thermocline structure and thermohaline circulation of an idealized ocean basin. The model equations consist of full prognostic temperature and salinity equations and diagnostic momentum equations. A simple linear friction is used to close the barotropic circulation at the western boundary. An extensive sensitivity study is conducted with different model parameters and processes. The results are also compared with those obtained using the Bryan-Cox primitive equation model. For the steady state case, the PG model can reproduce the primitive equation model results, and displays …

The Measurement Of Sediment Irrigation Rates: A Comparison Of The Br- Tracer And 222rn/226ra Disequilibrium Techniques, W. R. Martin, G. T. Banta

Journal of Marine Research

We have carried out a series of experiments designed to allow comparison of sediment irrigation rates determined simultaneously using two methods: the measurement of ²²²Rn/²²⁶Ra disequilibrium in pore waters, and the measurement of distributions of a tracer, Br⁻, which was added to the water overlying sediments at the start of incubation experiments. The experiments were carried out on fine-grained sediments from Buzzards Bay, MA. We made irrigation rate measurements on sediments in their natural state, as well as on sediments that had been treated to alter macrofaunal abundance and diversity. The range of irrigation rates …

Water Characteristics, Mixing And Circulation In The Bay Of Bengal During Southwest Monsoon, V. S. N. Murty, Y. V. B. Sarma, D. P. Rao, C. S. Murty

Journal of Marine Research

Influence of the freshwater influx, the wind forcing and the Indian Ocean monsoon drift current on the property distributions and the circulation in the Bay of Bengal during southwest monsoon has been quantified. At the head of the Bay, waters of low salinity, affected by the freshwater influx, occupy the upper 90 m water column. The isohaline 34.0 × 10⁻³ separating these waters from those of underlying saline waters shoals southward gradually and outcrops around 14N, 10N and 6N in the western, central and southeastern regions of the Bay respectively. The wind-stress-curl-induced upwelling effect is confined to depth limits …

Benthic Community Metabolism And The Role Of Deposit-Feeding Callianassid Shrimp, Richard C. Murphy, James N. Kremer

Journal of Marine Research

In temperate and tropical seas, bioturbation resulting from the burrowing and feeding activities of deposit-feeding callianassid shrimp can have an important impact on the ecosystem. In Gorda Sound, British Virgin Islands, 97 μmol NH₄ ˙ m⁻² ˙ d⁻¹ and 0.2 μmol PO₄ ˙ m⁻² ˙ d⁻¹ were released to the water column from burrows of callianassid shrimps (Callianassa rathbunae and Calliax Jonesi). Benthic gross primary production was 288 mg C ˙ m⁻² ˙ d⁻¹ and the ratio of gross production to total community 24-hr. respiration was 0.86. The flux of …

Surface-Intensified Rossby Waves Over Rough Topography, R. M. Samelson

Journal of Marine Research

Observations and numerical experiments that suggest that sea-floor roughness can enhance the ratio of thermocline to abyssal eddy kinetic energy, motivate the study of linear free wave modes in a two layer quasi-geostrophic model for several eases of idealized variable bottom topography. The foeus is on topography with horizontal seale comparable to that of the waves, that is, on "rough" small-amplitude topography. Surface-intensified modes are found to exist at frequencies greater than the flat-bottom baroclinic cut-off frequency. These modes exist for topography that varies in both one and two horizontal dimensions. An approximate bound indicates that the maximum frequency of …

A Two-Layer Gulf Stream Over A Continental Slope, Rick Salmon

Journal of Marine Research

We consider the two-layer form of the planetary geostrophic equations, in which a simple Rayleigh friction replaces the inertia, on a western continental slope. In the frictionless limit, these equations can be written as characteristic equations in which the potential vorticities of the top and bottom layers play the role of Riemann invariants. The general solution is of two types. In the first type, the characteristics can cross, and friction is required to resolve the resulting shocks. In the second type, one of the two Riemann invariants is uniform, the remaining characteristic is a line of constant f/H, and …

Models Of Abyssal Flow In Basins Separated By Amid-Ocean Ridge, Scott A. Condie, Mitsuhiro Kawase

Journal of Marine Research

Numerical and laboratory models have been used to study source-driven flows in a system consisting of two basins (with sloping sidewalls) separated by a mid-ocean ridge. Numerical spin-up occurs via topographically modified Kelvin waves which propagate away from the source region around the outer perimeter of the model ocean. Energy is then carried along the ridge by topographic waves and westward by planetary waves. The resulting flow eventually concentrates in strong cyclonic circulation patterns, defined by regions of closed geostrophic contours in the lower latitude portion of each basin. When the deep water source is located at the latitude of …

Circulation And Water Mass Balance In The Brazil Basin, Huai-Min Zhang, Nelson G. Hogg

Journal of Marine Research

Analysis of data from the Levitus (1982) atlas shows that the application of the Montgomery streamfunction to the potential density surfaces induces an error which cannot be ignored in some regions in the ocean. The error arises from the variation of the specific volume anomaly along isopycnal surfaces. By including the major part of this effect, new streamfunctions, named the "pressure anomaly" and "mean pressure" streamfunctions, are suggested for use in potential density coordinates. By including the variations of specific volume anomaly and pressure along isopycnal surfaces, the inverse model proposed by Hogg (1987) is modified for increased accuracy and …

Modelling The Deep-Chlorophyll Maximum: A Coupled Physical-Biological Approach, Ramiro A. Varela, Antonio Cruzado, Joaquín Tintoré, Emilio García Ladona

Journal of Marine Research

The Deep Chlorophyll Maximum (DCM) is simulated in two oligotrophic regions (SW Sargasso Sea and NW Mediterranean) using a physical/biological model that couples an upper ocean turbulent model to a nutrient/phytoplankton model. The biological model considers two types of primary producers, heterotrophs and atmospheric in addition to internal nitrate inputs. Model results appear to adequately reproduce the DCM structure in those regions. The DCM depth and magnitude is mainly determined by the vertical eddy diffusion and light extinction. The grazing parameters mainly affect the intensity of the DCM. This suggest the DCM is primarily the result of a balance between …

Inertial Gyres In Decaying And Forced Geostrophic Turbulence, Patrick F. 0

Journal of Marine Research

Numerical simulations of the motion of a turbulent homogeneous fluid in a rectangular beta-plane ocean basin are conducted to examine the influence of lateral boundary conditions on the development of inertial circulations. Three different boundary conditions are considered. Firstly, with a condition of zero vorticity gradient normal to the boundary, inertial Fofonoff gyres, which coincide with the maximum entropy solution of statistical mechanics, develop from the release of an initial random eddy field. Secondly, under a condition of no-stress (free-slip) at the boundary, inertial gyres resembling the Fofonoff flow develop. However, in this case, the linear relationship between potential vorticity …

Deposit And Suspension Feeding In Oscillatory Flows And Sediment Fluxes, Douglas C. Miller, Michael J. Bock, Elizabeth J. Turner

Journal of Marine Research

We present a survey of feeding behavior of benthic organisms in oscillatory flow and sediment fluxes. These results are based on seventeen species from five phyla and several feeding guilds from an intertidal sandflat and the continental shelf of the Mid-Atlantic coast, U.S.A. General responses to oscillatory flows are: (1) nearly immediate change in feeding behavior or position of feeding appendage when flow is initiated, (2) decrease in feeding area for surface deposit feeders, often (3) alteration of feeding mode, and when anatomically permitted (4) rotation of feeding appendages to track flow direction. At high sediment fluxes, responses are functional …

Active Habitat Selection By Capitella Sp. I Larvae. Ii. Multiple-Choice Experiments In Still Water And Flume Flow, Judith P. Grassie, Cheryl Ann Butman, Suan W. Mills

Journal of Marine Research

Experiments on larval settlement of the opportunistic polychaete, Capitella sp. I, using three natural sediment treatments from the Buzzards Bay area (organic-rich mud from Sippewissett Marsh, organic-rich mud from New Bedford Harbor and low-organic sand from off the Weepecket Islands), and a glass bead mixture similar in grain size distribution to the New Bedford Harbor mud, were carried out in still water and two flume flows (near-surface velocities of 5 cm s⁻¹ and 15 cm s⁻¹; boundary-shear velocities of 0.26 cm s⁻¹ and 0.64 cm s⁻¹). For all three flow conditions the larvae settled …

Active Habitat Selection By Capitella Sp. I Larvae. I. Two-Choice Experiments In Still Water And Flume Flow, Cheryl Ann Butman, Judith P. Grassie

Journal of Marine Research

Sediment selection by settling larvae of the opportunistic polychaete Capitella sp. I was determined in laboratory still-water and flume experiments, where larvae were given a choice between two highly contrasting sediment treatments. In most cases, 2-h experiments were conducted with a natural, organic-rich mud and an abiotic, glass-bead mixture with a grain-size distribution similar to the mud, as the sediment treatments. Spatial settlement patterns were also determined in sediment arrays containing mud only. Two types of flume flows were tested, both with a near-surface velocity of ∼5 cm s⁻¹, but one flow was cyclical, varying between about 2 …

Effects Of Polychaetes On Silicate Dynamics And Fluxes In Sediments: Importance Of Species, Animal Activity And Polychaete Effects On Benthic Diatoms, Roberta L. Marinelli

Journal of Marine Research

Laboratory experiments tested the effects of two polychaetes, a surface deposit feeder Eupolymnia heterobranchia, and a head-down deposit feeder Abarenicola pacifica, on silicate dynamics in sediment porewaters and overlying waters. Experimental chambers of sediment containing an individual deposit feeder, and controls with no macrofauna, were studied over a one month period during the summers of 1989 and 1990. Measurements included temporal changes in vertical depth profiles of pore water silicate concentrations, concurrent determinations of silicate accumulation in the water column, and the activities of experimental. organisms. A diffusion-nonlocal exchange-reaction model was devised to determine, from the pore water profiles, both …

Nutrient And Biogenic Particulate Distributions, Primary Productivity And Nitrogen Uptake In The Weddell-Scotia Sea Marginal Ice Zone During Winter, Glenn F. Cota, Walker O. Smith Jr., David M. Nelson, Robin D. Muench, Louis I. Gordon

Journal of Marine Research

During austral winter of 1988, we determined the distributions of inorganic nutrients (nitrate, silicic acid, phosphate, nitrite and ammonium) and particulate materials (chlorophyll, biogenic silica, particulate organic carbon and particulate organic nitrogen), as well as primary productivity and rates of nutrient (NO₃⁻ and NH₄⁺) uptake in the upper 150 m of the marginal ice zone of the Weddell-Scotia Sea. Nutrient concentrations were high and particulate matter levels were low throughout the study area, but occasionally nutrient minima and particulate maxima occurred near the ice edge associated with warm-core eddies. Chlorophyll concentrations and primary productivity averaged …

A Model For Death Assemblage Formation: Can Sediment Shelliness Be Explained?, Eric N. Powell

Journal of Marine Research

A numerical model for carbonate (shell) accumulation in marine sediments is proposed. Sediment shelliness is controlled by carbonate addition, taphonomic loss, carbonate reorganizing processes, and sedimentation rate. Using representative rates of carbonate production, taphonomic loss, and sedimentary carbonate content, the model shows that insufficient carbonate is produced today in many environments to explain sedimentary carbonate content and that most produced carbonate must be preseIVed despite a generally high capacity for taphonomic loss. An anthropogenically-produced decrease in carbonate production over the last ∼100 yr may explain the former. Representative rates of burial and sedimentation, and a temporal and spatial offset between …

The Dynamic Changes Of Stable Isotopic Ratios Of Carbon And Nitrogen In Suspended And Sedimented Particulate Organic Matter During A Phytoplankton Bloom, Takeshi Nakatsuka, Nobuhiko Handa, Eitaro Wada, Chi Shing Wong

Journal of Marine Research

The dynamic changes of carbon and nitrogen stable isotopic ratios in suspended and sedimented particulate matter were observed together with many other chemical and biological properties during a phytoplankton bloom induced by nutrient addition in a controlled ecosystem enclosure (CEE, about 70 m³) in Saanich Inlet, British Columbia, Canada. Both of the stable isotopic ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) in suspended particulate organic matter showed characteristic patterns of variations in surface water during the bloom. The δ¹³C of suspended particulate matter increased with the growth of phytoplankton population and decreased …

The Radiolarian Fauna At The Ice Edge In The Greenland Sea During Summer, 1988, N. R. Swanberg, L. K. Eide

Journal of Marine Research

Radiolaria were sampled from the plankton at 18 stations during two cruises in the Greenland Sea during summer, 1988. A total of 43 species or categories of radiolaria was found, but over 90% of the radiolarian fauna was dominated by adults or juveniles of 4 species: the spumellarian, Actinomma leptodermum and the nassellaria, Amphimelissa setosa, Pseudodictyophimus gracilipes, and Peridium longispinum. The stations sampled ranged from ice-covered areas high in nutrients to open water areas which were depleted in nutrients. These stations encompassed a gradient in the composition of the radiolarian fauna from an assemblage dominated by juveniles and adults …

The Rise Of Bubbles In A Glass Tube And The Spectrum Of Bubbles Produced By A Splash, P. A. Bowyer

Journal of Marine Research

Bubbles produced by a volume of 500 cc of water falling through a distance of 1.07 m into a water-filled basin were allowed to rise into an adjacent water-filled tube whose top was sealed at a level of 1.7 m above the level of water in the basin. The rise of these bubbles was recorded on video at a height of 1.5 m above the level of the splash: larger bubbles were recorded first. A model has been devised to describe the rise of such bubbles. The rise speed of the bubbles at the level of the video camera decreased …

Upwelling And Outwelling Effects On The Benthic Regime Of The Continental Shelf Off Galicia, Nw Spain, E. López-Jamar, R. M. Cal, G. González, R. B. Hanson, J. Rey, G. Santiago, K. R. Tenore

Journal of Marine Research

The benthic regime off the Galician coast of NW Spain was surveyed to assess biogenic enrichment from coastal upwelling and detritus outwelling from the rías, large coastal embayments: the Rías Altas along the northern and the Rías Bajas along the western coast, which have intense mussel aquaculture. Sediment samples were collected from 1984 to 1986 and used for geological, microbiological, and macrofaunal studies. Sub-bottom acoustic profiler records and grab and core samples identified two main mud deposits on the western shelf that were aligned north to south and parallel with the coastline. The major axis of the mud deposit, which …

The Equatorial Basin Response To A Rossby Wave Packet: The Effects Of Nonlinear Mechanism, Hong Ma

Journal of Marine Research

Responses of the equatorial ocean to a Rossby wave packet, which assumes the form of either a cyclonic or an anticyclonic vortex pair, are simulated with the spectral element shallow water equation model (reduced gravity). We found that during the course of the western boundary reflection of an incoming equatorial Rossby wave packet, strong wave-wave interaction has significant influence on local dynamic and kinetic structures in the western tropical ocean. In the case of the western boundary reflection of a cyclonic Rossby wave vortex pair, the nonlinear effect tends to induce a strong, long-lasting eastward equatorial current; while in the …

The Stability Of A Canonical Front, John Kroll

Journal of Marine Research

The stability of a geostrophic frontal current of constant slope over a stratified ocean is investigated using asymptotic techniques for large horizontal wavenumber and a small Burger number. The front is called canonical because it should approximate the edges of eddies or boundary currents. Results show that the front is unstable for an along the front wavenumber greater than f/V₀ where V₀ is the current velocity. But the instability is confined to a region near the vertex of the front of horizontal extent 0(V₀/f). The flow becomes more unstable for increasing …

Integral Equation Approach To Tropical Ocean Dynamics: Part Ii-Rossby Wave Scattering From The Equatorial Atlantic Western Boundary, Paulo R. Holvorcem, Marcio L. Vianna

Journal of Marine Research

We develop a linear theory for the scattering of equatorial waves of a fixed frequency ω by islands and continental margins of arbitrary geometry by use of the boundary integral equation (BIE) method of Vianna and Holvorcem (Part I of this work). All the solutions of the equatorial β-plane dispersion relations at frequency ω are treated explicitly through the extensive use of exact Green's functions, so that the approach is more general and more rigorous than previous attempts to solve equatorial scattering problems, many of which employ the low-frequency and long-wave approximations. The numerical solution of the HIE is obtained …

Numerical Modeling Of Larval Settlement In Turbulent Bottom Boundary Layers, Thomas F. Gross, Francisco E. Werner, James E. Eckman

Journal of Marine Research

A time-dependent model of a tidal or wave bottom boundary layer has been developed to quantitatively evaluate the relative influences of vertical advection, turbulent mixing and shear, and near-bed behavior on settlement of planktonic larvae of benthic animals. The settlement behavior of larvae is modeled with a simple flux condition at the bed. This allows full time dependence to be included when determining settlement rates. For tidal oscillations, the model predicts that most settlement will occur at and near periods of slack water, whereas comparatively little settlement will occur during periods of stronger flow. In contrast, there should be little …

Encounter Rate By Turbulent Shear Of Particles Similar In Diameter To The Kolmogorov Scale, P. S. Hill, A. R. M. Nowell, P. A. Jumars

Journal of Marine Research

To clarify the rate at which particles similar in size to the smallest eddies in a turbulent fluid encounter one another via turbulent shear, 3-D video motion analysis was used to make direct measurements of relative velocities between closely spaced, near-neutrally buoyant, 700-μm mean diameter, polystyrene latex spheres suspended in an oscillating-grid turbulence tank. Smallest eddy size, termed the Kolmogorov scale, λ, was estimated as (ν³/ε)^0.25 where ν is fluid viscosity and ε is the dissipation rate of turbulent kinetic energy. For runs made in water, the effective particle diameter examined was ≈ 3–6 times …

Processes Affecting The Behavior Of Redox-Sensitive Elements In Chesapeake Bay, Maria Lourdes San Diego-Mcglone

OES Theses and Dissertations

Several processes can affect variations in the chemical composition of an estuary, including (1) biogeochemical reactions in the water column, (2) advective transport, and (3) diffusion from underlying sediments.

The purpose of the study was to establish whether estuarine redox reactions are controlled by a complex interaction of processes 1 to 3. Short-term and long-term studies were conducted in Chesapeake Bay. Redox species involved in redox cycling include oxygen, iron, manganese, hydrogen sulfide, nitrogen species, arsenic and antimony species, while phosphate is indirectly involved in redox cycles. Silicate was used as a non-redox tracer.

For the short-term study, a Lagrangian …

Separation And Recirculation Of The North Brazil Current, Scott A. Condie

Journal of Marine Research

The North Brazil Current separates from the French Guiana coast in the western tropical North Atlantic and a portion of the flow retroflects to form a recirculation zone known as the Demerara Anticyclone. The remainder of the North Brazil Current continues northwestward to join the Guiana Current. This part of the flow may be particularly significant, since it carries a cross-gyre transport of heat and mass from the tropical Atlantic into the subtropical gyre. An extension of the recirculation model of Cessi (1988), in which a quasi-geostrophic flow was driven by potential vorticity anomalies along a boundary, has been used …

Spectral Time Scales For Mid-Latitude Eddies, William J. Schmitz Jr., James R. Luyten

Journal of Marine Research

A few hundred current meter records of roughly one to two years' duration are now available from diverse locations in the world's oceans, primarily the North Atlantic. The shape of the spectrum for low-frequency ocean current fluctuations is shown to have a geographical distribution related to the general circulation. In the offshore segment of the Gulf Stream and Kuroshio Extension systems along with their recirculations, and near the Agulhas Current as well, normalized frequency distributions of eddy kinetic energy tend to be comparatively depth-independent and peaked at the mesoscale. However, in the immediate vicinity of current axes or fronts, spectral …

Optics Of Heterotrophic Nanoflagellates And Ciliates: A Tentative Assessment Of Their Scattering Role In Oceanic Waters Compared To Those Of Bacterial And Algal Cells, André Morel, Yu-Hwan Ahn

Journal of Marine Research

Heterotrophic nanoflagellates and naked ciliates have been isolated from open sea waters and separately grown by using free living marine bacteria as food. The modal diameters of purified (by differential screening) populations are about 3 and 12.5 μm, respectively. The spectral determination of their absorption and scattering properties have been carried out. By combining these values with the cell number density and size distribution function, simultaneously measured, the efficiency factors for absorption and scattering at the level of individual cells can be derived. From these factors and by using the anomalous diffraction theory, the relative index of refraction can be …