Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network™

Open Access. Powered by Scholars. Published by Universities.®

Estuaries

Discipline
Institution
Publication Year
Publication
Publication Type

Articles 811 - 840 of 2567

Full-Text Articles in Entire DC Network

Mechanisms Of Infaunal Polychaete Dispersal And Colonization In An Intertidal Sandflat, David H. Shull Jan 1997

Mechanisms Of Infaunal Polychaete Dispersal And Colonization In An Intertidal Sandflat, David H. Shull

Journal of Marine Research

Changes in benthic infaunal population densities following disturbance may be influenced by colonization mechanisms. Accordingly, this study experimentally examined the relative importance of four colonization mechanisms for seven numerically dominant polychaete species in an intertidal estuarine sandflat in Connecticut, USA. The colonization mechanism an organism used depended upon species characteristics including larval developmental mode and depth distribution within the sediment. A spionid polychaete with planktonic larval development, Polydora cornuta, colonized experimental disturbance treatments primarily by larval settlement. A surface-dwelling syllid polychaete with nonplanktonic development, Streptosyllis arenae, colonized mainly by bedload transport. Two syllid polychaetes developmentally and morphologically similar …

Go to article

Analysis Of The Mean Annual Cycle Of The Dissolved Oxygen Anomaly In The World Ocean, Raymond G. Najjar, Ralph F. Keeling Jan 1997

Analysis Of The Mean Annual Cycle Of The Dissolved Oxygen Anomaly In The World Ocean, Raymond G. Najjar, Ralph F. Keeling

Journal of Marine Research

A global climatology of the dissolved oxygen anomaly (the excess over saturation) is created with monthly resolution in the upper 500 m of the ocean. The climatology is based on dissolved oxygen, temperature and salinity data archived at the National Oceanographic Data Center. Examination of this climatology reveals statistically significant annual cycles throughout the upper 500 m of the World Ocean, though seasonal variations are most coherent in the North Atlantic, where data density is greatest. Vertical trends in the phase and amplitude of the annual cycle are noted. The cycle in surface waters is characterized by a summer maximum …

Go to article

Phytoplankton Patches At Fronts: A Model Of Formation And Response To Wind Events, Peter J. S. Franks, Leonard J. Walstad Jan 1997

Phytoplankton Patches At Fronts: A Model Of Formation And Response To Wind Events, Peter J. S. Franks, Leonard J. Walstad

Journal of Marine Research

A subsurface patch of chlorophyll is a feature common to many fronts. The dynamics underlying the patch formation are not well understood; however, there appears to be a strong link between the biological and physical dynamics. Here we test the hypothesis that patch formation is a result of wind-forced motions of the front. Frontal responses to transient wind events include acceleration of the surface layers, changes in mixed-layer depth, and excitation of nonlinear oscillations at the front. Such dynamics can affect nutrient fluxes across the pycnocline and the coupling between trophic levels. To test this hypothesis, we developed a two-dimensional …

Go to article

Current Structure In The Rhine Region Of Freshwater Influence, A. J. Souza, J. H. Simpson, F. Schirmer Jan 1997

Current Structure In The Rhine Region Of Freshwater Influence, A. J. Souza, J. H. Simpson, F. Schirmer

Journal of Marine Research

Observation with HF radar, ADCPs and conventional current meters in the Rhine ROFI system in the North Sea indicate that the dominant currents are due to tidal flow, with important contributions from winds and density-driven circulation. The tidal currents are dominated by the semidiurnal components, principally the M2, with tidal ellipses parallel to the coast and a semimajor axis of the order of 1 m s−1 at the surface. The wind-driven flow varies between 1 and 3% of the wind speed and the rotation varies with depth in qualitative agreement with Ekman theory. After removal of the tidal and …

Go to article

Describing Additional Fluxes To Deep Sediment Traps And Water-Column Decay In A Coastal Environment, David A. Timothy, Stephen Pond Jan 1997

Describing Additional Fluxes To Deep Sediment Traps And Water-Column Decay In A Coastal Environment, David A. Timothy, Stephen Pond

Journal of Marine Research

Sediment traps were moored at three stations in Sechelt Inlet, a fjord in southern British Columbia, Canada, for five one-month deployment periods from late January to late June, 1991. On each mooring were traps at three depths; total and constituent fluxes often increased with depth. We present the flux data and describe an analytical model that is based on a set of simultaneous equations for which two unknowns are the decay rate of material representatively caught by two vertically-separated sediment traps and the composition of material causing observed increases in flux with depth. The unknowns are solved in a least-squares …

Go to article

Estimation Of Vertical Mixing In The Upper Ocean At Station P From Chlorofluorcarbons, R. J. Matear, C. S. Wong Jan 1997

Estimation Of Vertical Mixing In The Upper Ocean At Station P From Chlorofluorcarbons, R. J. Matear, C. S. Wong

Journal of Marine Research

Vertical mixing (Kv) in the upper ocean is estimated from chlorofluorocarbons (CFC's) F-11 and F-12 data collected on 5 cruises (1982, 1985, 1992, 1993, 1995) near Station P (50N, 145W). A one-dimensional advection-diffusion model was fitted to the data from each cruise to estimate vertical mixing (Kv) and upwelling velocity (w). With constant Kv and w, the average value of Kv and w was 0.4 ± 0.1 cm2 s−1 and 1.2 ± 0.4 m yr−1 respectively for the depth range 0–900 m below the base of …

Go to article

The Dynamics Of An Equivalent-Barotropic Model Of The Wind-Driven Circulation, Pavel S. Berloff, Stephen P. Meacham Jan 1997

The Dynamics Of An Equivalent-Barotropic Model Of The Wind-Driven Circulation, Pavel S. Berloff, Stephen P. Meacham

Journal of Marine Research

Various steady and time-dependent regimes of a quasi-geostrophic 1.5 layer model of an oceanic circulation driven by a steady wind stress are studied. After being discretized as a numerical model, the quasi-geostrophic equations of motion become a dynamical system with a large dimensional phase space. We find that, for a wide range of parameters, the large-time asymptotic regimes of the model correspond to low-dimensional attractors in this phase space. Motion on these attractors is significant in determining the intrinsic time scales of the system. In two sets of experiments, we explore the dependence of solutions on the viscosity coefficient and …

Go to article

Effect Of A Freshwater Pulse On Mesoscale Circulation And Phytoplankton Distribution In The Lower St. Lawrence Estuary, Claude Savenkoff, Alain F. Vézina, Yves Gratton Jan 1997

Effect Of A Freshwater Pulse On Mesoscale Circulation And Phytoplankton Distribution In The Lower St. Lawrence Estuary, Claude Savenkoff, Alain F. Vézina, Yves Gratton

Journal of Marine Research

As part of a multidisciplinary program to study the physical-biological interactions regulating carbon flows in the lower St. Lawrence Estuary (LSLE), three cruises were conducted in June–July 1990 during a neap-spring tidal cycle when biological production was expected to be maximal. Nutrient (nitrates and silicates), phytoplankton biomass (chlorophyll), oxygen, temperature, salinity, and current fields were used to elucidate the effect of a freshwater pulse produced by the discharge of the St. Lawrence and Saguenay rivers on the current fields and the biological variability and productivity of the LSLE. A simple Rossby adjustment model is presented to explain the temporal (3–5 …

Go to article

On The Eddy Transfer Of Tracers: Advective Or Diffusive?, Mei-Man Lee, David P. Marshall, Richard G. Williams Jan 1997

On The Eddy Transfer Of Tracers: Advective Or Diffusive?, Mei-Man Lee, David P. Marshall, Richard G. Williams

Journal of Marine Research

Geostrophic eddies have traditionally been viewed within oceanography as diffusing water masses and tracers in a down-gradient manner. However, eddies also have an advective role that may lead to an up-gradient transfer of tracers, as has been recognized in atmospheric tracer studies and recent eddy parameterizations developed for the ocean. Eddies provide an advective transfer or “bolus” velocity through the secondary circulation formed by the slumping of density surfaces in baroclinic instability. Here we use an eddy-resolving isopycnal ocean model to investigate the meridional transfer across a zonal jet. The jet undergoes baroclinic instability, forming a vibrant eddy field and …

Go to article

Rapid Subduction Of Organic Matter By Maldanid Polychaetes On The North Carolina Slope, L. Levin, N. Blair, D. Demaster, G. Plaia, W. Fornes, C. Martin, C. Thomas Jan 1997

Rapid Subduction Of Organic Matter By Maldanid Polychaetes On The North Carolina Slope, L. Levin, N. Blair, D. Demaster, G. Plaia, W. Fornes, C. Martin, C. Thomas

Journal of Marine Research

In situ tracer experiments conducted on the North Carolina continental slope reveal that tube-building worms (Polychaeta: Maldanidae) can, without ingestion, rapidly subduct freshly deposited, algal carbon (13C-labeled diatoms) and inorganic materials (slope sediment and glass beads) to depths of 10 cm or more in the sediment column. Transport over 1.5 days appears to be nonselective but spatially patchy, creating localized, deep hotspots. As a result of this transport, relatively fresh organic matter becomes available soon after deposition to deep-dwelling microbes and other infauna, and both aerobic and anaerobic processes may be enhanced. Comparison of tracer subduction with estimates …

Go to article

Solitary Rossby Waves With Baroclinic Modes, Z. Kizner Jan 1997

Solitary Rossby Waves With Baroclinic Modes, Z. Kizner

Journal of Marine Research

A class of exact solutions of the equation of conservation of the quasi-geostrophic vorticity in a continuously stratified ocean on the β-plane is studied. These are stationary solitary waves traveling east and having horizontal scale comparable with the Rossby deformation radius, which exist due to the balance between the nonlinearity and β-effect. The solutions look like a sum of a barotropic modon and a number of axially symmetric baroclinic components. The baroclinicity, represented in the form of vertical normal modes, introduces an extra “degree of freedom” into the problem (as compared with the barotropic model) and allows for the construction …

Go to article

Analysis Of Diel Variability In Chlorophyll Fluorescence, John Marra Jan 1997

Analysis Of Diel Variability In Chlorophyll Fluorescence, John Marra

Journal of Marine Research

Examples of the diel variability in chlorophyll and beam attenuation are presented using data from moored in situ fluorometers and transmissometers, and from profiles of the beam attenuation coefficient and fluorescence. The data are discussed in terms of the three primary processes thought to influence the diel variability in chlorophyll: (1) fluorescence yield per unit chlorophyll a, (2) chlorophyll a changes per cell (or, carbon), and (3) changes in phytoplankton carbon (growth). A simple, provisional, model is presented which incorporates these three biological processes, under the assumption that the corresponding diel variability in particle attenuation represents the change in …

Go to article

Propagation Of Near-Inertial Oscillations Through A Geostrophic Flow, W. R. Young, Mahdi Ben Jelloul Jan 1997

Propagation Of Near-Inertial Oscillations Through A Geostrophic Flow, W. R. Young, Mahdi Ben Jelloul

Journal of Marine Research

The method of multiple time scales is used to obtain an approximate description of the linear propagation of near-inertial oscillations (NIOs) through a three-dimensional geostrophic flow. This ‘NIO equation’ uses a complex field, M(x, y, z, t), related to the demodulated horizontal velocity by Mz = exp (if0t)(u + iv), where f0 is the inertial frequency. The three processes of wave dispersion, advection by geostrophic velocity and refraction (geostrophic vorticity slightly shifts the local inertial frequency) are all included in the formulation. The NIO equation has an energy conservation …

Go to article

A One-Dimensional Physical-Biological Model Study Of The Pelagic Nitrogen Cycling During The Spring Bloom In The Northern North Sea (Flex ‘76), Wilfried Kuhn, Günther Radach Jan 1997

A One-Dimensional Physical-Biological Model Study Of The Pelagic Nitrogen Cycling During The Spring Bloom In The Northern North Sea (Flex ‘76), Wilfried Kuhn, Günther Radach

Journal of Marine Research

A one-dimensional model of the pelagic ecosystem was developed and applied to the spring bloom in the northern North Sea making use of the data set obtained during the Fladenground experiment FLEX '76. The physical submodel is the second-order turbulence closure model of level 2 type developed by Mellor and Yamada (1974, 1982). The biological submodel is a depth-resolved version of the nitrogen flux model of the lower trophic levels in the pelagic proposed by Fasham et al. (1990). The parameter set employed by Fasham et al. did not yield satisfying results. However, using a parameter set adapted …

Go to article

Digestive Environments Of Benthic Macroinvertebrate Guts: Enzymes, Surfactants And Dissolved Organic Matter, Lawrence M. Mayer, Linda L. Schick, Robert F. L. Self, Peter A. Jumars, Robert H. Findlay, Zhen Chen, Stephen Sampson Jan 1997

Digestive Environments Of Benthic Macroinvertebrate Guts: Enzymes, Surfactants And Dissolved Organic Matter, Lawrence M. Mayer, Linda L. Schick, Robert F. L. Self, Peter A. Jumars, Robert H. Findlay, Zhen Chen, Stephen Sampson

Journal of Marine Research

Hydrolytic enzyme activity, surfactancy, and dissolved organic matter in the digestive lumens of 19 benthic echinoderm and polychaete species were examined, using consistent and quantifiable methods. Enzyme activities were compared with those of extracellular enzymes from ambient sediments. Enzyme activities ranged over five orders of magnitude, with averages decreasing in the order polychaetes > echinoderms > sediment. Highest activities in animals were usually associated with the fluid phase in midgut sections, with posteriorward decreases indicating little export to the external environment. At some phyletic levels, activity correlated inversely with animal size. Hydrolase patterns reflected food type; for example, high lipase:protease ratios in …

Go to article

Instabilities Of A Steady, Barotropic, Wind-Driven Circulation, S. P. Meacham, P. S. Berloff Jan 1997

Instabilities Of A Steady, Barotropic, Wind-Driven Circulation, S. P. Meacham, P. S. Berloff

Journal of Marine Research

We explore the stability characteristics of a single, barotropic, wind-driven gyre as a function of the strength of the wind forcing and the size and shape of the basin. We find steady solutions for the barotropic flow in a basin driven by a steady wind stress over a range of values of the Reynolds number and the strength of the wind stress. For those solutions that are close to the stability boundary, we examine the form of the most unstable normal mode. We find that for sufficiently weak forcing, the form of the first instability seen is an instability of …

Go to article

Agulhas Ring Dynamics From Topex/Poseidon Satellite Altimeter Data, Gustavo J. Goni, Silvia L. Garzoli, Andreas J. Roubicek, Donald B. Olson, Otis B. Brown Jan 1997

Agulhas Ring Dynamics From Topex/Poseidon Satellite Altimeter Data, Gustavo J. Goni, Silvia L. Garzoli, Andreas J. Roubicek, Donald B. Olson, Otis B. Brown

Journal of Marine Research

The transfer of warm water from the Indian Ocean into the South Atlantic subtropical gyre takes place in the form of rings and filaments formed when the Agulhas Current retroflects south of Africa between 15 and 25E. A survey of the rings formed from September 1992 until December 1995 in the Retroflection region was carried out using TOPEX/POSEIDON altimeter data. A two-layer model was used to estimate the upper layer thickness from the altimeter-derived sea-surface height anomaly data. An objective analysis scheme was used to construct a map of upper layer thickness every ten days. Seventeen rings and their trajectories …

Go to article

A Sediment Trap Experiment In The Vema Channel To Evaluate The Effect Of Horizontal Particle Fluxes On Measured Vertical Fluxes, Wilford D. Gardner, Pierre E. Biscaye, Mary Jo Richardson Jan 1997

A Sediment Trap Experiment In The Vema Channel To Evaluate The Effect Of Horizontal Particle Fluxes On Measured Vertical Fluxes, Wilford D. Gardner, Pierre E. Biscaye, Mary Jo Richardson

Journal of Marine Research

Sediment traps are used to measure fluxes and collect samples for studies in biology, chemistry and geology, yet we have much to learn about factors that influence particle collection rates. Toward this end, we deployed cylindrical sediment traps on five current meter moorings across the Vema Channel to field-test the effect of different horizontal particle fluxes on the collection rate of the traps— instruments intended for the collection of vertically settling particles. The asymmetric flow of Antarctic Bottom Water through the Vema Channel created an excellent natural flume environment in which there were vertical and lateral gradients in the distribution …

Go to article

The Effect Of Brine On The Collection Efficiency Of Cylindrical Sediment Traps, Wilford D. Gardner, Youcheng Zhang Jan 1997

The Effect Of Brine On The Collection Efficiency Of Cylindrical Sediment Traps, Wilford D. Gardner, Youcheng Zhang

Journal of Marine Research

Cylindrical sediment traps are frequently used to measure the downward flux of particles in the upper ocean. Some protocols recommend filling these traps with brine (50 psu in excess of ambient) before deployment to better retain the collected sample. However, this also changes the aspect ratio of the traps—a critical parameter affecting the trapping efficiency. We conducted controlled experiments in a flume that demonstrate filling traps with a 5 psu brine decreases their trapping efficiency to 54% at a velocity of 5 cm sec−1, and to 75% at 15 cm sec−1 relative to the same trap with …

Go to article

On The Development Of Thermohaline Correlations As A Result Of Nonlinear Diffusive Parameterizations, Raffaele Ferrari, W. R. Young Jan 1997

On The Development Of Thermohaline Correlations As A Result Of Nonlinear Diffusive Parameterizations, Raffaele Ferrari, W. R. Young

Journal of Marine Research

Some oceanographic mixing parameterizations assume that transports depend nonlinearly on the buoyancy gradient; e.g., diffusivities are proportional to some power of the buoyancy gradient. In this paper we examine the consequences of these nonlinear-diffusion parameterizations by solving an initial value problem in which the t = 0 thermohaline fields are prepared as random and uncorrelated distributions of temperature and salinity. Solutions of the nonlinear diffusion equation as a ‘rundown’ problem show that correlations develop between the temperature and salinity. These correlations are such that the evolving thermohaline gradients tend to be strongly compensating in their joint effect on buoyancy.

Go to article

On The Parameterization Of Eddy Transfer Part I. Theory, Peter D. Killworth Jan 1997

On The Parameterization Of Eddy Transfer Part I. Theory, Peter D. Killworth

Journal of Marine Research

This is the first of three linked papers which develop an eddy parameterization scheme for mean flows which are wide compared with a deformation radius. The scheme is partly based on the behavior of potential vorticity and thickness fluxes in linear instability, where the former are downgradient (apart from a turning matrix, not present in channel models) and the latter are not precisely downgradient, except on an f-plane. The scheme leads to a diffusivity which varies quite strongly with depth and is smallest at surface and floor. Intrinsic delta-function fluxes also occur at surface and floor, and these are …

Go to article

Irregular Flow Of Persian (Arabian) Gulf Water To The Arabian Sea, Karl Banse Jan 1997

Irregular Flow Of Persian (Arabian) Gulf Water To The Arabian Sea, Karl Banse

Journal of Marine Research

The bottom outflow from the Persian (Arabian) Gulf, which intrudes in the Gulf of Oman as an intermediate salinity maximum and spreads in the northern Arabian Sea, was inferred to be seasonal. Also, based on particular expedition, single values of temperatures, salinities, and oxygen concentrations were assumed as end members for this core layer. From historical data it is shown here that the salinity of the water exiting at depth from the Gulf is first reduced to <40 ppt by mixing with Gulf of Oman water in the shallow Strait of Hormuz with its strong tides. The core layer acquires its characteristics when the mixing product descends the outer shelf at the head of the Gulf of Oman and entrains upper-thermocline water with an intermediate to low oxygen content above the outflow. After leaving the seabed, when mixing with water also below the intrusion begins, the maximal values observed in the core layer for salinity, density (sigma-t), and oxygen saturation ranged between 37.5 and 38.0 ppt, 26.30 and 26.95 g dm−3, and approximately 20 and 60%, …

Go to article

Parameterization Of Mesoscale Eddy Fluxes In Zonal Ocean Flows, Vladimir O. Ivchenko, Kelvin J. Richards, Bablu Sinha, Jörg-Olaf Wolff Jan 1997

Parameterization Of Mesoscale Eddy Fluxes In Zonal Ocean Flows, Vladimir O. Ivchenko, Kelvin J. Richards, Bablu Sinha, Jörg-Olaf Wolff

Journal of Marine Research

Quasi-geostrophic dynamics in an eddy-resolving zonal re-entrant channel in the Southern Hemisphere have been studied for east- and westward wind forcing scenarios. The main difference is seen in the zonally averaged velocity profiles. In the case of eastward forcing, transient eddies strongly intensify the flow in the channel center into a jet, a feature totally absent in the westward forcing cases. The free jet is associated with a five times higher available potential energy compared to the westward flow. We have used these two distinctly different flow regimes to investigate possible parameterizations of the eddy fluxes in both situations. Parameterizations …

Go to article

Circulation Around Islands And Ridges, Joseph Pedlosky, Lawrence J. Pratt, Michael A. Spall, Karl R. Helfrich Jan 1997

Circulation Around Islands And Ridges, Joseph Pedlosky, Lawrence J. Pratt, Michael A. Spall, Karl R. Helfrich

Journal of Marine Research

The circulation in an ocean basin containing an island is studied under nearly geostrophic, beta plane dynamics. The model is a fluid of uniform density driven by wind forcing or sources and sinks of mass at the upper boundary of the flow. The circulation is studied analytically, numerically, as well as in the laboratory through the device of the “sliced cylinder” model for the ocean circulation. Of particular interest is the estimate of the transport between the island and the oceanic basin's boundary. The model is conceived as relevant to both the wind-driven circulation as well as the circulation of …

Go to article

Influences Of River Discharge On Biological Production In The Inner Shelf: A Coupled Biological And Physical Model Of The Louisiana-Texas Shelf, Changsheng Chen, Denis A. Wiesenburg, Liusen Xie Jan 1997

Influences Of River Discharge On Biological Production In The Inner Shelf: A Coupled Biological And Physical Model Of The Louisiana-Texas Shelf, Changsheng Chen, Denis A. Wiesenburg, Liusen Xie

Journal of Marine Research

A coupled biological and physical model was applied to study the influence of river discharge on biological variability on the Louisiana-Texas (LATEX) continental shelf. The physical part included a primitive-equation turbulent closure model, and the biological part was a simple phytoplankton (P), zooplankton (Z), and nutrient (N) model. The model was forced by freshwater discharge from the river and ran prognostically under initial conditions of springtime water stratification and a steady-state solution of the P-Z-N model with no horizontal dependence. A nutrient source was included at the mouth of the river. The model predicted …

Go to article

Subduction Of Water Masses In An Eddying Ocean, David Marshall Jan 1997

Subduction Of Water Masses In An Eddying Ocean, David Marshall

Journal of Marine Research

Mesoscale eddies modify the rate at which a water mass transfers from the surface mixed layer of the ocean into the interior thermocline, in particular in regions of intense baroclinic instability such as the Antarctic Circumpolar Current, open-ocean convective chimneys, and ocean fronts. Here, the time-mean subduction of a water mass, evaluated following the meandering surface density outcrops, is found to incorporate a rectified contribution from eddies, arising from correlations between the area over which the water mass is outcropped at the sea surface and the local subduction rate. Alternatively, this eddy subduction can be interpreted in terms of an …

Go to article

Transient Hydrographic And Chemical Conditions Affecting Microplankton Populations In The Coastal Transition Zone Of The Iberian Upwelling System (Nw Spain) In September 1986, C. G. Castro, X. A. Alvarez-Salgado, F. G. Figueiras, F. F. Perez, F. Fraga Jan 1997

Transient Hydrographic And Chemical Conditions Affecting Microplankton Populations In The Coastal Transition Zone Of The Iberian Upwelling System (Nw Spain) In September 1986, C. G. Castro, X. A. Alvarez-Salgado, F. G. Figueiras, F. F. Perez, F. Fraga

Journal of Marine Research

The coastal transition zone and adjacent continental shelf of the Iberian upwelling system was studied in September 1986, during the seasonal transition from upwelling-favored to downwelling-favored winds. The most striking features in the coastal transition zone were: (1) a poleward flow of high salinity Eastern North Atlantic Central Water (subtropical) off the Rías Baixas (Galician western coast); and (2) an anticyclonic eddy off Cape Ortegal (Galician northern coast). Chemical and biological similarities between both structures, clearly different from the surrounding oceanic waters, suggest that the eddy was an isolated and aged parcel of water originating from the poleward flow. The …

Go to article

Long-Term Measurements Of Flow Near The Aleutian Islands, R. K. Reed, P. J. Stabeno Jan 1997

Long-Term Measurements Of Flow Near The Aleutian Islands, R. K. Reed, P. J. Stabeno

Journal of Marine Research

In summer 1995, the Alaskan Stream at 173.5W was very intense; the peak geostrophic speed was ≈125 cm s−1, and the computed volume transport above 1000 db, referred to 1000 db, was 9 × 106 m3 s−1). Flow north of the central Aleutians was shallow, convoluted and weak (2– 3 × 106 m3 s−1). A sequence of CTD casts across Amukta Pass, spaced irregularly in time during 1993–1996, showed a mean northward (southward) geostrophic transport of 1.0 (0.4) × 106 m3 s−1, for a net flow …

Go to article

Large-Scale Circulation With Small Diapycnal Diffusion: The Two-Thermocline Limit, R. M. Samelson, Geoffrey K. Vallis Jan 1997

Large-Scale Circulation With Small Diapycnal Diffusion: The Two-Thermocline Limit, R. M. Samelson, Geoffrey K. Vallis

Journal of Marine Research

The structure and dynamics of the large-scale circulation of a single-hemisphere, closed-basin ocean with small diapycnal diffusion are studied by numerical and analytical methods. The investigation is motivated in part by recent differing theoretical descriptions of the dynamics that control the stratification of the upper ocean, and in part by recent observational evidence that diapycnal diffusivities due to small-scale turbulence in the ocean thermocline are small (≈0.1 cm2 s−1). Numerical solutions of a computationally efficient, three-dimensional, planetary geostrophic ocean circulation model are obtained in a square basin on a mid-latitude β-plane. The forcing consists of a zonal …

Go to article

Time-Dependent Motions And The Nonlinear Bottom Ekman Layer, K. H. Brink Jan 1997

Time-Dependent Motions And The Nonlinear Bottom Ekman Layer, K. H. Brink

Journal of Marine Research

The laminar bottom Ekman layer beneath a flow with finite relative vorticity is studied. First, the case with only a steady interior shear flow is reviewed, and then a case with a spatially uniform oscillating flow is superimposed. In both cases, the problem can be reduced to solving ordinary differential equations. The competition of two effects governs the results. The interior vorticity effectively modifies the rotation rate, but advection (especially vertically, due to Ekman pumping) tends to counteract the vorticity modification. Vertical advection keeps the time-dependent boundary layer well behaved for negative interior vorticities, but a boundary layer singularity can …

Go to article

First Prev Next Last