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Arrested Fronts, William K. Dewar
Arrested Fronts, William K. Dewar
Journal of Marine Research
A theory of fronts within the general circulation is discussed. These fronts and their associated jets differ from the more classical picture of boundary jets and their extensions (an example being the Gulf Stream system) in that they occur in the interior of the general circulation. The mechanism at the heart of the frontogenesis is nonlinear beta steepening, which arises from geostrophy in the presence of continuity. Such dynamics have been used in the past in a study of planetary shock waves. It is here argued that these dynamics result in stationary shock fronts in the general circulation. An equation …
Separation And Recirculation Of The North Brazil Current, Scott A. Condie
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
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 …
Nonlinear General Circulation Of An Ocean Model Driven By Wind With A Stochastic Component, Annalisa Griffa, Sergio Castellari
Nonlinear General Circulation Of An Ocean Model Driven By Wind With A Stochastic Component, Annalisa Griffa, Sergio Castellari
Journal of Marine Research
The effects of the stochastic component of the large-scale wind on the climatological mean of the nonlinear ocean circulation are studied, using a set of numerical solutions for the single-layer, quasi-geostrophic equation in a closed basin with a flat bottom. In the absence of a steady wind, the purely stochastic wind is found to drive the solutions toward a nonlinear mean flow similar to that of the free system (i.e. without forcing and dissipation). This equilibrium mean flow (Fofonoff flow), is predicted by statistical mechanics and is characterized by a westward interior closed by inertial boundary layers along the coast. …
Micropatchiness, Turbulence And Recruitment In Plankton, Cabell S. Davis, Glenn R. Flierl, P. H. Wiebe, P. J. S. Franks
Micropatchiness, Turbulence And Recruitment In Plankton, Cabell S. Davis, Glenn R. Flierl, P. H. Wiebe, P. J. S. Franks
Journal of Marine Research
A series of models are presented which examine the relative importance of microscale patchiness and turbulence to growth and recruitment in planktonic consumers. The analyses apply over scales from centimeters to meters (e.g. from copepods to fish larvae), and we assume food-limited conditions, since, otherwise, patchiness would not affect growth. A model of individual growth response to fluctuating food is developed which shows that growth is approximately exponential and is linearly related to food concentration. A random walk model reveals that the swimming process can be approximated as a simple diffusion term which, when included in the exponential growth model, …
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
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 …
Tidal Stirring And Phytoplankton Bloom Dynamics In An Estuary, James E. Cloern
Tidal Stirring And Phytoplankton Bloom Dynamics In An Estuary, James E. Cloern
Journal of Marine Research
A decade of observation in South San Francisco Bay demonstrates that estuarine phytoplankton biomass fluctuates at the time scale of days to weeks, and that much of this variability is associated with fluctuations in tidal energy. During the spring seasons of every year from 1980–1990, episodic blooms occurred in which phytoplankton biomass rose from a baseline of 2–4 mg chlorophyll a m–3, peaked at 20–40 mg chlorophyll a m–3, and then returned to baseline values, all within several weeks. Each episode of biomass increase occurred during neap tides, and each bloom decline coincided with spring tides. …
A Model Of The Diel Vertical Migration Of Zooplankton Based On Euphausiids, Valérie Andersen, Paul Nival
A Model Of The Diel Vertical Migration Of Zooplankton Based On Euphausiids, Valérie Andersen, Paul Nival
Journal of Marine Research
A detailed model of the diel vertical migration of euphausiids, particularly that of Meganyctiphanes norvegica adults in the northwestern Mediterranean Sea, is presented. It simulates the temporal and vertical variation of the euphausiid biomass over the diel cycle in the water column from 0 to 700 m depth. Migration is influenced by two external factors: food (phyto- and zooplankton) and light. Light is assumed to influence migration both by its intensity with the occurrence of an optimal value, and by its relative change in intensity, which affects the ascent or descent of the organisms. The general features of the diel …
Similarity Solutions Of The Thermocline Equations, Rick Salmon, Rainer Hollerbach
Similarity Solutions Of The Thermocline Equations, Rick Salmon, Rainer Hollerbach
Journal of Marine Research
We apply symmetry group methods to find the group of transformations of the dependent and independent variables that leave the thermocline equations unchanged, These transformations lead to an optimal subset of sixteen forms of similarity solution, Each form obeys an equation with one fewer dependent variable than the original thermocline equations. Previously obtained similarity solutions, which are based solely upon scaling symmetries, are special cases of just three of these forms. Two of the sixteen forms lead to linear, two-dimensional, advection-diffusion equations for the temperature, Bernoulli functional or potential vorticity. Simple exact solutions contain "internal boundary layers" that resemble the …
The Effect Of East River On The Barotropic Motions In Long Island Sound, Kuo-Chuin Wong
The Effect Of East River On The Barotropic Motions In Long Island Sound, Kuo-Chuin Wong
Journal of Marine Research
A linearized, frequency-dependent analytical model is developed to examine the effect of East River on the barotropic motions in Long Island Sound. At tidal frequencies, East River creates a slightly imperfect reflecting wall at the western end of Long Island Sound, resulting in moderate reduction in the resonance of the M2 tide. At subtidal frequencies the presence of East River permits a significant amount of volume exchange through the western end of Long Island Sound, causing large scale adjustments in both the amplitude and the phase of the barotropic flow well into the interior of the Sound. It appears …
The Accumulation Of Barium By Marine Phytoplankton Grown In Culture, Nicholas S. Fisher, Robert R. L. Guillard, Donald C. Bankston
The Accumulation Of Barium By Marine Phytoplankton Grown In Culture, Nicholas S. Fisher, Robert R. L. Guillard, Donald C. Bankston
Journal of Marine Research
Marine phytoplankton have been implicated as potentially important vectors for the vertical transport of barium in the oceans. To better assess the extent to which phytoplankton can influence the geochemical cycling of barium, its bioconcentration was studied in 21 clones of 19 species of marine phytoplankters belonging to 9 algal classes. Barium levels in the ash ranged from less than 2 μg g–1 for the coccolithophore Emiliania huxleyi and the red alga Porphyridium cruenturn to 589 μg g–1 for the flagellate Tetraselmis levis. Concentrations ≥4000 μg g–1, previously reported for certain samples of diatom ash were …
Geostrophic Transport Of The South Equatorial Current In The Atlantic, Lothar Stramma
Geostrophic Transport Of The South Equatorial Current In The Atlantic, Lothar Stramma
Journal of Marine Research
Geostrophic transport calculations from historical data of the equatorial South Atlantic are presented for the investigation of the flow field in the South Equatorial Current region. On the basis of water mass distribution, the potential density surface of σ1 = 32.15 kg m–3 is used as a reference for geostrophic shears. This reference surface is located at a depth of 1000 to 1200 m and represents the boundary between the upper branch of the Circumpolar Deep Water and the Upper North Atlantic Deep Water. The southern band of the South Equatorial Current (SSEC) is fed by the Benguela …
Buoyancy-Driven Circulation As Horizontal Convection On Β-Plane, Nobuo Suginohara, Shigeaki Aoki
Buoyancy-Driven Circulation As Horizontal Convection On Β-Plane, Nobuo Suginohara, Shigeaki Aoki
Journal of Marine Research
The nature of the steady buoyancy-driven circulation is investigated using multi-level numerical models. An ocean which extends over the northern and southern hemispheres is forced by cooling in a confined region and heating in the rest of the ocean through the sea surface. As is already known, the circulation and associated thermal structure strongly depend upon the effect of the vertical diffusivity. This nature of the buoyancy-driven circulation is found in the thermodynamic balance. The vertical diffusion plays an essential role in the whole ocean domain. In counterbalancing the vertical diffusion, the horizontal advection at the deepest levels and the …
Seasonal Variations Of Surface Dynamic Topography In The Tropical Atlantic: Observational Uncertainties And Model Testing, Christine Duchène, Claude Frankignoul
Seasonal Variations Of Surface Dynamic Topography In The Tropical Atlantic: Observational Uncertainties And Model Testing, Christine Duchène, Claude Frankignoul
Journal of Marine Research
A new analysis of the historical temperature and salinity profiles in the tropical Atlantic is done in order to estimate quantitatively the uncertainties in the climatological seasonal variations of 0/400 db dynamic topography. The uncertainties are described by an error covariance matrix which takes into account aliasing and measurement errors, the effect of data gaps and interpolation, as well as the uncertainty of the T-S method that was used to calculate the dynamic height. The standard deviation of the monthly means is found to range between 2 and 10 dyn cm, depending on the data density and the level of …
Direct Measurement Of Dissolved Inorganic Nitrogen Exchange And Denitrification In Individual Polychaete (Nereis Virens) Burrows, Erik Kristensen, Mikael Hjorth Jensen, Robert C. Aller
Direct Measurement Of Dissolved Inorganic Nitrogen Exchange And Denitrification In Individual Polychaete (Nereis Virens) Burrows, Erik Kristensen, Mikael Hjorth Jensen, Robert C. Aller
Journal of Marine Research
The burrows of macroinfauna are significant sites of sediment-water nitrogen exchange and associated microbial activity. In this study, the exchange of dissolved inorganic nitrogen (DIN) and nitrogen cycle reaction rates were quantified in individual burrows of the estuarine polychaete Nereis virens. Burrow ventilation rate and DIN (NH4+, NO2−, NO3− and N2O) exchange were determined at 22°C in individual, inhabited burrows with and without the presence of C2H2 (an NH4+ oxidation, N2O reduction block). Ventilation cycles were unaffected by C2H2, …
Early Diagenesis Of Chlorophyll-A In Long Island Sound Sediments: A Measure Of Carbon Flux And Particle Reworking, Mingyi Sun, Robert C. Aller, Cindy Lee
Early Diagenesis Of Chlorophyll-A In Long Island Sound Sediments: A Measure Of Carbon Flux And Particle Reworking, Mingyi Sun, Robert C. Aller, Cindy Lee
Journal of Marine Research
Sedimentary chlorophyll distributions reflect supply from primary production in overlying waters, transport during sedimentation/bioturbation, and alteration due to decomposition/transformation reactions. In Long Island Sound sediments, seasonal depth profiles of chlorophyll-a (Chl-a) often decreased exponentially within a few centimeters of the sediment-water interface, implying that initial decomposition rates of Chl-a were faster than surface sediment mixing rates. The highest surface sediment concentrations of Chl-a occurred in early spring, shortly after the spring bloom; the lowest concentrations occurred in summer. Chl-a was more concentrated at the shallow station (∼15 m) than at the deeper station (∼40 …
A Subsurface Cyclonic Eddy In The Bay Of Bengal, M. T. Babu, Prasanna Kumar, D. P. Rao
A Subsurface Cyclonic Eddy In The Bay Of Bengal, M. T. Babu, Prasanna Kumar, D. P. Rao
Journal of Marine Research
CTD data collected from the northwestern Bay of Bengal during late July 1984 reveal the existence of a cold core subsurface eddy centered at 17°40'N and 85°19'E. The thermal structure observed across the eddy indicates that it was confined to a level well below the mixed layer, between 50 and 300 db, and that it had a diameter of about 200 km. A temperature drop of 4–5°C as compared with the surroundings was observed at the center of the eddy. A plausible mechanism for the eddy generation is baroclinic instability at the interface of two opposing boundary currents present along …
Bubbles And The Air-Sea Exchange Of Gases In Near-Saturation Conditions, David K. Woolf, S. A. Thorpe
Bubbles And The Air-Sea Exchange Of Gases In Near-Saturation Conditions, David K. Woolf, S. A. Thorpe
Journal of Marine Research
The net air-sea transfer of gases is not simply proportional to the surface gradient of gas concentration as is widely assumed but, when proper account of bubbles is taken, is asymmetrical with a net invasion of gas at 100% saturation. The nitrogen and oxygen saturation levels and the variation of the composition of a bubble during its lifetime affect the transfer of all gases. The net transfer of gases is not a function of the size and depth of the bubbles and the concentration of dissolved gases alone, but is dependent on the composition of the bubbles and thus the …
The Climatological Seasonal Circulation Of The Mediterranean Sea, Eli Tziperman, Paola Malanotte-Rizzoli
The Climatological Seasonal Circulation Of The Mediterranean Sea, Eli Tziperman, Paola Malanotte-Rizzoli
Journal of Marine Research
The horizontal circulation of the upper 800 m of the Mediterranean Sea is calculated from a seasonal climatological hydrographic data set using a simple inverse model. The results show a fairly steady surface circulation in the western Mediterranean and a somewhat stronger seasonal signal in the surface circulation of the eastern Mediterranean. The deep flow field can be calculated for most of the Mediterranean, except for the Levantine basin east of Crete, where the high noise level in the data masks the deep circulation. The calculated deep velocity field (below 500 m) shows some interesting features, including several steady cyclonic …
Time Scales Of Mesoscale Variability And Their Relationship With Space Scales In The North Atlantic, P. Y. Le Traon
Time Scales Of Mesoscale Variability And Their Relationship With Space Scales In The North Atlantic, P. Y. Le Traon
Journal of Marine Research
A systematic study of characteristic time scales of mesoscale variability over the North Atlantic was done using two years of Geosat data. Time scales are first characterized by 10° latitude by 10° longitude bins. A more detailed description was obtained by globally mapping the Sea Level Anomaly temporal correlation after one cycle (17.05 days). The scales are shortest in areas of high mesoscale activity (Gulf Stream, North Atlantic Current) while relatively long time scales are observed over the Mid-Atlantic Ridge and in the eastern part of the basin. In general, time scales are not proportional to space scales. Propagation velocities …
Diel Migration And Feeding Patterns Of The Chaetognath, Sagitta Friderici, Off The West Coast Of South Africa, Venetia Stuart, Hans M. Verheye
Diel Migration And Feeding Patterns Of The Chaetognath, Sagitta Friderici, Off The West Coast Of South Africa, Venetia Stuart, Hans M. Verheye
Journal of Marine Research
The vertical distribution patterns of adult and juvenile Sagitta friderici were investigated over a 48 h period, using samples collected at different depth strata with an RMT 1 × 6 net. Juvenile chaetognaths were generally found at depths of less than 50 m throughout the day and night, and exhibited limited diel migration patterns. Adults, on the other hand, migrated more extensively and were generally found below 50 m during the day and scattered throughout the water column or near the surface at night. Using the mean depths at each sampling time, the migration patterns of adult chaetognaths closely followed …
The Influence Of A Changing Bacterial Community On Trace Metal Scavenging In A Deep-Sea Particle Plume, James P. Cowen, Yuan Hui Lui
The Influence Of A Changing Bacterial Community On Trace Metal Scavenging In A Deep-Sea Particle Plume, James P. Cowen, Yuan Hui Lui
Journal of Marine Research
An extensive set of particle samples was collected from the extended (nonbuoyant) hydrothermal plume, the distal remnant plume, and the adjacent waters in a transect across the Southern Juan de Fuca Ridge. Bacterial capsules comprised the primary species of particulate Mn. However, the data also showed significant shifts in the relative abundance of distinctive subpopulations of this bacterial community, as expressed by several consistently recurring capsule morphologies. The data are discussed with respect to distance from plume origins (relative plume age), total bacterial numbers, experimentally determined scavenging rate constants and total particulate and dissolved Mn. The relative distribution of one …
Oxic And Anoxic Decomposition Of Tubes From The Burrowing Sea Anemone Ceriantheopsis Americanus: Implications For Bulk Sediment Carbon And Nitrogen Balance, Erik Kristensen, Robert C. Aller, Josephine Y. Aller
Oxic And Anoxic Decomposition Of Tubes From The Burrowing Sea Anemone Ceriantheopsis Americanus: Implications For Bulk Sediment Carbon And Nitrogen Balance, Erik Kristensen, Robert C. Aller, Josephine Y. Aller
Journal of Marine Research
Many marine infaunal animals form organic tube and burrow linings. The role of these materials in organic matter cycling and preservation in sediments is largely unknown. In the case examined here, the infaunal sea anemone, Ceriantheopsis americanus, (a common component of bottom communities along the east coast of North America) forms a leathery, fibrous tube lining 2–3 mm thick, ∼1 cm in diameter, and typically extending 20–30 cm into deposits. Tube fibers (∼2 mm long, 2–5 μm thick) formed from discharged specialized nematocyst cells, ptychocysts, are composed of a silk-like protein copolymer, cerianthin. Tubes incubated under oxic and anoxic conditions …
Conservative Tracer Study Of Horizontal Sediment Mixing Rates In A Bathyal Basin, California Borderland, Robert A. Wheatcroft
Conservative Tracer Study Of Horizontal Sediment Mixing Rates In A Bathyal Basin, California Borderland, Robert A. Wheatcroft
Journal of Marine Research
In situ tracer (50–125 μm plastic particles) experiments conducted using the DSV Alvin over a two year period in the 1240 m deep Santa Catalina Basin (eastern Pacific) have yielded near-surface (0–1.5 cm) horizontal bioturbation rates of order 1–10 cm2yr–1. Vertical biodiffusivities obtained from the same and similar particulate tracers at the same site are approximately an order of magnitude less. Mixing of near-surface, coarse sediment in Santa Catalina Basin is anisotropic. Deeper within the sediment horizontal bioturbation is not diffusive on a two-year time scale, but would appear to be a form of mixing termed …
Sources And Transport Of Suspended Calcites In Pacific Deep Water, J. C. Brun-Cottan, R. Auger, C. E. Lambert, R. Chesselet
Sources And Transport Of Suspended Calcites In Pacific Deep Water, J. C. Brun-Cottan, R. Auger, C. E. Lambert, R. Chesselet
Journal of Marine Research
Significantly large concentrations of suspended matter, especially calcites, are found at some locations in the Deep Pacific, particularly at the depth of the Pacific Benthic Thermocline. These particle-rich layers cannot be explained by simple classical settling processes nor by resuspension of the underlying sediment. A theoretical approach based on these data, on the hydrodynamic characteristics of the regional circulation and on some known physical and chemical parameters, leads us to postulate two possible mechanisms: the settling of large particles from surface waters and their preferential disaggregation at some specific depth, particularly at the Pacific Benthic Thermocline depth; or alternatively, the …
Generation And Propagation Of Inertial Waves In The Subtropical Front, Dong-Ping Wang
Generation And Propagation Of Inertial Waves In The Subtropical Front, Dong-Ping Wang
Journal of Marine Research
A primitive-equation numerical model is used to examine the generation and propagation of internal-inertial waves in the Subtropical Front. The mesoscale variability in surface inertial currents is induced by radiation of internal-inertial waves out of the surface layer. On the warm side of the front, surface inertial energy is carried away by normal internal-inertial waves. A deep inertial energy maximum exists at the base of the thermocline where the effective local inertial frequency approaches the planetary inertial frequency. On the cold side of the front, the surface inertial energy is carried away by anomalously low frequency internal waves. A subsurface …
Modeling Of Internal Tides In Fjords, V. Tverberg, B. Cushman-Roisin, H. Svendsen
Modeling Of Internal Tides In Fjords, V. Tverberg, B. Cushman-Roisin, H. Svendsen
Journal of Marine Research
A previous model for the distribution of internal tides above irregular topography is generalized to include arbitrary stratification and a radiation condition at the open boundary. Thanks to a small amount of dissipation, this model remains valid in the presence of resonant internal tides, leading to intense wave-energy beams. An application to a Norwegian fjord correctly reproduces the observed energy pattern consisting of two beams both originating at the 60-meter deep entrance sill and extending in-fjord, one upward toward the surface, the other downward toward the bottom. After correction for the varying width of the fjord, the observed and modelled …
Modeling The Variability Of The Somali Current, D. L. T. Anderson, D. J. Carrington, R. Corry, C. Gordon
Modeling The Variability Of The Somali Current, D. L. T. Anderson, D. J. Carrington, R. Corry, C. Gordon
Journal of Marine Research
The dynamics of the Somali Current system during the southwest Monsoon are investigated using a 16 level general circulation model. Solutions are found for a number of model geometries and wind-forcing patterns. The first integrations reported use a model domain exactly equivalent to that of the layer model of McCreary and Kundu allowing a direct comparison between the level and layer models. In the second set of integrations a more realistic Indian Ocean geometry is used, but still with an idealized wind forcing, while in the third, the Hellerman and Rosenstein wind stresses are used to simulate the seasonal cycle. …
Laminar Separation Of Colliding Western Boundary Currents, Paola Cessi
Laminar Separation Of Colliding Western Boundary Currents, Paola Cessi
Journal of Marine Research
A barotropic model is employed to study the dynamics of colliding jets along a western boundary. To isolate the processes at the western wall we use a regional model where two opposing jets are induced by prescribing narrow inflows at the northern and southern edges of the computational domain. The fluid is withdrawn from the domain on the eastern side.
On The Structure And Stability Of The Alaskan Stream, R. K. Reed, F. I. Gonzalez, L. Miller
On The Structure And Stability Of The Alaskan Stream, R. K. Reed, F. I. Gonzalez, L. Miller
Journal of Marine Research
Data from a year-long current mooring in the central region of the Alaskan Stream revealed an extremely stable flow unlike that in typical western boundary currents. Hydrographic and ADCP data also showed a simple flow free of excursions or eddies. These findings are in good agreement with a recent analytical model of the Stream. In addition, GEOSAT altimeter estimates of variability are consistent with the observations, suggesting that the results are valid in spite of the relatively large corrections applied at these high latitudes.