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Articles 901 - 930 of 2516
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Dense Overflow Into A Large Silled Embayment: Tidal Modulation, Fronts And Basin Modes, M. White, Alex E. Hay
Dense Overflow Into A Large Silled Embayment: Tidal Modulation, Fronts And Basin Modes, M. White, Alex E. Hay
Journal of Marine Research
A dense bottom overflow into a 100-km scale silled embayment has been observed for a 70-day period using a coherent array of current meters and thermistor chains. As the internal Rossby radius is less than the width of the bay, the overflow is controlled by rotational dynamics. The flow is strongly modulated by the tide at diurnal, semi-diurnal and fortnightly periods. This causes a series of cold temperature fronts, associated with separate overflow events, to pass through the mooring array. The overflow is also modulated at periods of 2–3 days. This appears to be associated with the interaction of the …
The Recruitment Patterns Of An Estuarine Copepod: A Biological-Physical Model, Sanjay Gupta, Darcy J. Lonsdale, Dong-Ping Wang
The Recruitment Patterns Of An Estuarine Copepod: A Biological-Physical Model, Sanjay Gupta, Darcy J. Lonsdale, Dong-Ping Wang
Journal of Marine Research
A biological-physical model was developed to study the population growth of Coullana canadensis (Willey), a meroplanktonic copepod, in the Saco River estuary, Maine. The biological processes were derived from extensive laboratory and field data, and the physical processes were based on a comprehensive estuarine hydrodynamic model. The study found that the physical environment significantly altered the seasonal pattern of population growth from that predicted from the biological model. Nauplii were lost from the estuary due to flushing in spring and early summer, and thus, the timing of the peak in copepod recruitment was delayed until late summer. A …
Phytoplankton Dynamics Associated With A Geostrophic Front: Ecological And Biogeochemical Implications, Hervé Claustre, Philippe Kerhervé, Jean Claude Marty, Louis Prieur, Christianne Videau, Jean-Henri Hecq
Phytoplankton Dynamics Associated With A Geostrophic Front: Ecological And Biogeochemical Implications, Hervé Claustre, Philippe Kerhervé, Jean Claude Marty, Louis Prieur, Christianne Videau, Jean-Henri Hecq
Journal of Marine Research
Using phytoplankton pigments as biomarkers, we investigated the relationship between the physical forcing and the resulting biological, ecological and biogeochemical properties of the geostrophic front of the Eastern Alboran Sea. (1) Typical frontal sites present biomass levels averaging 60 mg chl a m−2 (up to 100 mg m−2), whereas the adjacent zones (typical Atlantic and Mediterranean) are characterized by an average integrated chlorophyll biomass of 20 mg chl a m−2. (2) The phytoplankton biomass at front is diatom-dominated and differs markedly from the adjacent zones (typical Atlantic and Mediterranean), flagellate- and cyanobacteria-dominated. Therefore, high biomasses …
Species Assemblages Of Leptocephali In The Subtropical Convergence Zone Of The Sargasso Sea, Michael J. Miller, James D. Mccleave
Species Assemblages Of Leptocephali In The Subtropical Convergence Zone Of The Sargasso Sea, Michael J. Miller, James D. Mccleave
Journal of Marine Research
Species assemblages of leptocephali are described in relation to density in the Subtropical Convergence Zone (STCZ) of the Sargasso Sea. Seven transects across fronts were made during four cruises in the late winter or early spring of 1983, 1985 and 1989. About 50 species from 13 families of eels were collected at 66 stations, but fewer than 10 species were abundant in all transects. Four oceanic species, two Anguilla species and Conger oceanicus appeared to be spawning in the STCZ. Leptocephali of most species whose adults inhabit the continental shelf were consistently large in size and were more abundant at …
Parameter Space Exploration Of An Ocean General Circulation Model Using An Isopycnal Mixing Parameterization, William A. Gough, William J. Welch
Parameter Space Exploration Of An Ocean General Circulation Model Using An Isopycnal Mixing Parameterization, William A. Gough, William J. Welch
Journal of Marine Research
In this study we have employed statistical methods to efficiently design experiments and analyze output of an ocean general circulation model that uses an isopycnal mixing parameterization. Full ranges of seven inputs are explored using 51 numerical experiments. Fifteen of the cases fail to reach satisfactory equilibria. These are attributable to numerical limitations specific to the isopycnal model. Statistical approximating functions are evaluated using the remaining cases to determine the dependency of each of the six scalar outputs on the inputs. With the exception of one output, the approximating functions perform well. Known sensitivities, particularly the importance of diapycnal (vertical) …
Generalized Two-Layer Models Of Ocean Circulation, Rick Salmon
Generalized Two-Layer Models Of Ocean Circulation, Rick Salmon
Journal of Marine Research
The assumption that surfaces of constant temperature and potential vorticity coincide leads to an exact, time-dependent reduction of the ideal thermocline equations in an ocean basin of arbitrary shape. After modifications to include forcing, dissipation, and the presence of the equator, these reduced equations form the basis for numerical models that are both more realistic and easier to solve than the conventional two-layer model.
A Proposed Flux Constraint For Salt Fingers In Shear, Eric Kunze
A Proposed Flux Constraint For Salt Fingers In Shear, Eric Kunze
Journal of Marine Research
Towed ocean microstructure observations reveal that the temperature Cox number depends inversely on interface temperature-gradient Tz in the fingering-favorable thermohaline staircase east of Barbados. This implies fluxes independent of interface gradients. These conclusions are contrary to theoretical expectations from a finger Froude number stability criterion, |Δw|/N < 1.0: (i) Cox numbers independent of temperature gradient, and (ii) fluxes varying linearly with temperature gradient. We propose a hybrid wave/finger Froude number stability criterion, |(uz − wx)(wy − vz)|N2 ≤ 1.0 which reduces to Uz|Vw|/N2 ≤ 1.0 for salt sheets (δ/δx = 0, | Δw| = wy) aligned with background (internal-wave) shear Uz. …
Calcium Carbonate Dissolution Rates In Hydrothermal Vent Fields Of The Guaymas Basin, Richard A. Lutz, Michael J. Kennish, Alan S. Pooley, Lowell W. Fritz
Calcium Carbonate Dissolution Rates In Hydrothermal Vent Fields Of The Guaymas Basin, Richard A. Lutz, Michael J. Kennish, Alan S. Pooley, Lowell W. Fritz
Journal of Marine Research
Analysis of bivalve shell fragments that were embedded in epoxy blocks, mounted on titanium stakes, and deployed by DSRV Alvin at 5 sites in the Southern Trough of the Guaymas Basin (27°00′N, 111°24.55′W; depth 2012 m) indicates significant variation of calcium carbonate dissolution in in situ exposures of more than 900 days. Arrays of shell fragments of six bivalve species (i.e., Bathymodiolus thermophilus, Calyptogena magnifica, Calyptogena sp., Corbicula fluminea, Crassostrea virginica and Mytilus edulis) were positioned −17 cm, −7 cm and −2.5 cm below the sediment-water interface and 2.5 cm, 7 cm and 17 cm above the sediment-water interface …
Currents Under Land-Fast Ice In The Canadian Arctic Archipelago Part 2: Vertical Mixing, R. F. Marsden, R. G. Ingram, L. Legendre
Currents Under Land-Fast Ice In The Canadian Arctic Archipelago Part 2: Vertical Mixing, R. F. Marsden, R. G. Ingram, L. Legendre
Journal of Marine Research
During an acoustic Doppler current profiler (ADCP) study of the velocity field under land-fast ice, coincident CTD casts showed three instances of pronounced instability in the water column, immediately above and below the pycnocline. In this paper we demonstrate that the density inversions are associated with the passage of high frequency linear internal waves and finite amplitude waves. Contours of ADCP acoustic return intensity display pronounced vertical eddy-like features which may indicate overturning. A Richardson number calculation showed that even the most highly stratified portion of the pycnocline had sufficient vertical velocity shear to promote dynamic instability. Finally, we calculate …
Currents Under Land-Fast Ice In The Canadian Arctic Archipelago Part 1: Vertical Velocities, R. F. Marsden, R. Paquet, R. G. Ingram
Currents Under Land-Fast Ice In The Canadian Arctic Archipelago Part 1: Vertical Velocities, R. F. Marsden, R. Paquet, R. G. Ingram
Journal of Marine Research
A 614 kHz acoustic Doppler current profiler was deployed through land-fast ice in Resolute Passage, in the Canadian Archipelago for 30 days in April and May 1992. It was demonstrated that in the mean, at tidal and at high frequencies the instrument was stable and aligned within 0.5° of vertical, permitting unambiguous measurement of the horizontal, and more importantly, the vertical velocity structure. The flow was dominated by tidal and high frequency (15 min period) oscillations. The K1 and M2 tidal currents were both approximately 10.0 cm s−1, oriented along-channel. The K1 component was constant …
Individual Physiological Responses To Environmental Hypoxia And Organic Enrichment: Implications For Early Soft-Bottom Community Succession, Thomas L. Forbes, Valery E. Forbes, Michael H. Depledge
Individual Physiological Responses To Environmental Hypoxia And Organic Enrichment: Implications For Early Soft-Bottom Community Succession, Thomas L. Forbes, Valery E. Forbes, Michael H. Depledge
Journal of Marine Research
Infaunal inhabitants of coastal marine sediments occupy environments along a continuum from extremely food-rich, low-oxygen regions to food-poor habitats with relatively high levels of available oxygen. In organic-rich sediments, efficient utilization of available organic matter by deposit-feeding macrofauna may often be limited by the supply of oxygen. Specific feeding rate, growth, and production efficiency were measured on single individuals of the polychaete Capitella species 1 to determine whether previously measured declines in growth rates in response to hypoxia were due to decreased feeding, decreased conversion efficiency, or both. Under otherwise constant conditions, feeding rate was determined by the nitrogen content …
Spatial And Temporal Distributions Of Sedimentary Chloropigments As Indicators Of Benthic Processes In Long Island Sound, Ming-Yi Sun, Robert C. Aller, Cindy Lee
Spatial And Temporal Distributions Of Sedimentary Chloropigments As Indicators Of Benthic Processes In Long Island Sound, Ming-Yi Sun, Robert C. Aller, Cindy Lee
Journal of Marine Research
Regular spatial and seasonal distribution patterns of sedimentary chloropigments occurred at 19 subtidal stations located in Long Island Sound (LIS) from MAY 1988 to APR 1989. Inventories of chloropigments were higher (2–10x) in western than central LIS, mirroring patterns of phytoplankton production in surface waters. Shallow water sediments (<25 m) received more chloropigments than deep stations (>25 m). Lateral resuspension and redistribution of particles, as shown by 234Th inventories, are partly responsible for these patterns. Seasonal variations of Chl-a inventories in LIS sediments follow the production pattern in the water column: higher values occur in spring and lower values in summer and fall. A time …
Frictional Decay Of Abyssal Boundary Currents, Parker Maccready
Frictional Decay Of Abyssal Boundary Currents, Parker Maccready
Journal of Marine Research
A theory is presented to explain the observed longevity of abyssal boundary currents flowing along sloping topography. Typically such currents are many Rossby radii wide, and their energy is dominantly potential, residing in the broad upturn of isopycnals near the slope. The rate of decay of energy, on the other hand, is governed by the much smaller kinetic energy of the flow absorbed by the bottom boundary layer. The spin-down time is thus increased by a (possibly large) factor of PE/KE times that required to dissipate the kinetic energy alone. The ratio PE/KE is calculated from data on two sections …
The Effect Of Current-Induced Stress Perturbation In A Coupled Atmosphere-Ocean Model, Lian Xie, Claes Rooth
The Effect Of Current-Induced Stress Perturbation In A Coupled Atmosphere-Ocean Model, Lian Xie, Claes Rooth
Journal of Marine Research
In the presence of surface currents, a stress perturbation at the air-sea interface is induced by the surface currents. It is directly correlated to the surface current pattern, and thus causes a feed-back effect in the sea-air system. This effect is studied for an equatorial sea-air system of the geometry of the equatorial Pacific Ocean by using a simple coupled atmosphere-ocean model. It is shown that the effect of the current-induced stress perturbation appears as a damping mechanism for the ocean circulation in general. However, in the presence of a zonally-asymmetric surface wind field, the stress perturbation associated with the …
Aggregation And Sedimentation Processes During A Spring Phytoplankton Bloom: A Field Experiment To Test Coagulation Theory, Thomas Kiørboe, Claus Lundsgaard, Michael Olesen, Jørgen L. S. Hansen
Aggregation And Sedimentation Processes During A Spring Phytoplankton Bloom: A Field Experiment To Test Coagulation Theory, Thomas Kiørboe, Claus Lundsgaard, Michael Olesen, Jørgen L. S. Hansen
Journal of Marine Research
Spring diatom blooms in temperate waters are often terminated by aggregation of the cells into large flocs and subsequent mass sedimentation of the phytoplankton to the sea floor. The rate of aggregate formation by physical coagulation depends on the concentration of suspended particles, on the turbulent shear that makes particles collide, and on their stickiness (= probability of adhesion upon collision). During a mixed diatom bloom in a shallow Danish fjord, for 3 weeks we monitored the concentration and stickiness of suspended particles and the species composition of the phytoplankton at 2–3 d intervals and we estimated the turbulent shear …
Internal Tidal Bores In The Nearshore: Warm-Water Fronts, Seaward Gravity Currents And The Onshore Transport Of Neustonic Larvae, Jesus Pineda
Journal of Marine Research
Nearshore temperature fluctuations are associated with energetic cross-shore two-way flows that influence the onshore transport of neustonic larvae. Water temperature near the surface and bottom at two nearshore stations off southern California (6 and 15 m water depth, respectively) can drop sharply and subsequently rise. Two or more consecutive drops and rises can occur at diurnal or semidiurnal periodicities. The temperature increases may be accompanied by energetic seaward bottom currents together with sharp-edged warm-water fronts. (Warm-water fronts are defined here as linear seasurface features dividing parcels of water of different temperature.) Shoreward-moving surface fronts divided bodies of water of different …
Flow Along And Across The Aleutian Ridge, R. K. Reed, P. J. Stabeno
Flow Along And Across The Aleutian Ridge, R. K. Reed, P. J. Stabeno
Journal of Marine Research
During a synoptic hydrocast survey in September 1993 near the Aleutian Islands, net northward flow of Alaskan Stream water occurred through deep passes near 180 and 172W. This inflow (≈4 × 106 m3 s−1) was the source of the eastward flow in the Bering Sea north of the islands. The eastward flow, however, was weaker and more convoluted than the stream flow (≈7 × 106 m3 s−1, referred to 1000 db) south of the islands.
Signatures Of Stirring And Mixing Near The Gulf Stream Front, G. L. Hitchcock, T. Rossby, J. L. Lillibridge Iii., E. J. Lessard, E. R. Levine, D. N. Connors, K. Y. Børsheim, M. Mork
Signatures Of Stirring And Mixing Near The Gulf Stream Front, G. L. Hitchcock, T. Rossby, J. L. Lillibridge Iii., E. J. Lessard, E. R. Levine, D. N. Connors, K. Y. Børsheim, M. Mork
Journal of Marine Research
In October, 1986 the surface waters adjacent to the Gulf Stream front were surveyed with an undulating profiler to describe the finescale structure of the mixed layer. The profiler was a Seasoar equipped with a CTD and fluorometer. The survey first defined the structure of a cyclonic eddy which resembled frontal eddies of the South Atlantic Bight in sea surface temperature imagery. The Seasoar transects revealed, however, that the cyclonic eddy lacked a cold dome typically seen in frontal eddies. Farther downstream the Seasoar defined the structure of streamers of Gulf Stream and Shelf water wrapped about the southern edge …
Vortex Pair Model Of Langmuir Circulation, G. T. Csanady
Vortex Pair Model Of Langmuir Circulation, G. T. Csanady
Journal of Marine Research
Accumulating evidence shows spacing and length of surface convergences associated with Langmuir circulation to be random variables, their strength also variable, their lifetime limited. Analysis of several sets of quantitative observations reveals the probability distribution of windrow spacing to be lognormal. This suggests generation of surface convergences at random times and locations on the sea surface. Moving shear stress anomalies, under wind gusts or breaking long waves, are capable of generating surface convergence in their wakes, and are the type of random event likely responsible for the stochastic properties of windrows. The generation mechanism envisaged is a “forced” version of …
Measurements Of Internal Wave Band Eddy Fluxes Above A Sloping Bottom, Hans Van Haren, Neil Oakey, Chris Garrett
Measurements Of Internal Wave Band Eddy Fluxes Above A Sloping Bottom, Hans Van Haren, Neil Oakey, Chris Garrett
Journal of Marine Research
The boundary layer near a sloping bottom may have a major influence on the ocean's interior density structure (due to “boundary mixing”) and on its circulation (because of the arrest of the Ekman layer by buoyancy forces). As a first attempt to measure eddy fluxes of momentum and buoyancy, in order to quantify the mixing in this region, we have carried out a 5-day pilot experiment on a sloping side of Emerald Basin on the Scotian Shelf. A moored upward-looking 1.2 MHz ADCP and a thermistor chain mounted along its vertical axis returned analyzable data between 8 and 17 m …
Set-Down Computations Over An Arbitrarily Inclined Plane Bed, Ulf Torsten Ehrenmark
Set-Down Computations Over An Arbitrarily Inclined Plane Bed, Ulf Torsten Ehrenmark
Journal of Marine Research
A perturbation theory, for waves on a perfect fluid in a wedge-shaped domain, is used to derive integral expressions for set-down valid up to the breaker line for arbitrary wedge angles α. Computations are carried out for a set α = π/2N, (N = 2,3,…,7,15) using a generalized Simpson quadrature and these confirm that existing theory underestimates the set-down by a factor which increases with the wedge angle. Curve fitting techniques are used to deduce a modification of the formula given by Longuet-Higgins and Stewart (1963) which can be universally implemented to estimate set-down just seaward of …
A Modelling Study Of Discontinuous Biological Irrigation, Bernard P. Boudreau, Roberta L. Marinelli
A Modelling Study Of Discontinuous Biological Irrigation, Bernard P. Boudreau, Roberta L. Marinelli
Journal of Marine Research
Irrigation of infaunal dwellings can lead to significant alteration of solute distributions in sediments. As a result, sediment-seawater fluxes of nutrients and dissolved carbon are greatly enhanced, and the biology of benthic communities is affected. The most realistic mathematical representation of irrigation and its effect on sediment geochemistry is Aller's (1980) cylinder model. One critical assumption of this model is that burrows are irrigated continually, and that burrow water solute concentrations are identical to overlying water concentrations at all times. However, the vast majority of infaunal tube- and burrow-dwelling organisms irrigate periodically, i.e. in an on/off cycle. During periodic irrigation, …
Instability Waves In The Gulf Stream Front And Its Thermocline Layer, Sang-Ki Lee, G. T. Csanady
Instability Waves In The Gulf Stream Front And Its Thermocline Layer, Sang-Ki Lee, G. T. Csanady
Journal of Marine Research
We carried out linear instability calculations on a three layer Gulf Stream front model in an attempt to elucidate the interaction of the thermocline layer with surface slopewater shoreward of the front. The basic state is geostrophic balance and constant potential vorticity in the two active layers, but the perturbations are ageostrophic. We found the flow to be unstable to long wave perturbations, the wavelength of the most unstable wave to be of the order of 10 radii of deformation. The instability is mainly baroclinic, 75–85% of the energy supply to the growing perturbation coming from basic flow potential energy. …
On Topographic Pressure Drag In A Zonal Channel, Alexander Krupitsky, Mark A. Cane
On Topographic Pressure Drag In A Zonal Channel, Alexander Krupitsky, Mark A. Cane
Journal of Marine Research
The effect of bottom topography H on the barotropic transport in a periodic zonal channel is studied. An asymptotic approximation is found for the zonal transport on an f-plane and a β-plane when all f/H isolines are blocked by the zonal walls. It is shown that to leading order, the zonal channel transport is independent of friction. In this it is similar to the Sverdrup transport in a basin. To leading order, the transport is proportional to the bottom topographic wavelength, and inversely proportional to the height of the topography and to R, the range of values of …
Lateral Entrainment In Baroclinic Currents, Melvin E. Stern, Jean-Raymond Bidlot
Lateral Entrainment In Baroclinic Currents, Melvin E. Stern, Jean-Raymond Bidlot
Journal of Marine Research
A two layer shear flow model with piecewise uniform potential vorticity is used to show that circulation or free exchange of parcels in an isopycnal layer of uniform potential vorticity can be greatly inhibited by a strong potential vorticity front in another isopycnal layer. On the other hand, a net mass transfer across the edge of a shear flow can be produced by the initial presence of a strong mesoscale eddy. The entrainment resulting from this eddy-shear flow interaction is defined and quantified for an ensemble of initial realizations. It is suggested that dynamically similar entrainment processes, occurring in more …
Water-Mass Distributions In The Western South Atlantic; A Section From South Georgia Island (54s) Northward Across The Equator, Mizuki Tsuchiya, Lynne D. Talley, 0 S. Mccartney
Water-Mass Distributions In The Western South Atlantic; A Section From South Georgia Island (54s) Northward Across The Equator, Mizuki Tsuchiya, Lynne D. Talley, 0 S. Mccartney
Journal of Marine Research
A long CTD/hydrographic section with closely spaced stations was made in February–April 1989 in the western Atlantic Ocean between 0°40′N and South Georgia (54S) along a nominal longitude of 25W. Vertical sections of various properties from CTD and discrete water-sample measurements are presented and discussed in terms of the large-scale circulation of the South Atlantic Ocean. One of the most important results is the identification of various deep-reaching fronts in relation to the large-scale circulation and the distribution of mode waters. Five major fronts are clearly defined in the thermal and salinity fields. These are the Polar (49.5S), Subantarctic (45S), …
Macrofaunal Response To Artificial Enrichments And Depressions In A Deep-Sea Habitat, P. V. R. Snelgrove, J. F. Grassle, R. F. Petrecca
Macrofaunal Response To Artificial Enrichments And Depressions In A Deep-Sea Habitat, P. V. R. Snelgrove, J. F. Grassle, R. F. Petrecca
Journal of Marine Research
To test whether colonizing macrofauna specialize on different types of small-scale patches of food and disturbance in the deep sea, sediment tray and artificial depression colonization experiments were conducted on the deep-sea floor at 900-m depth, south of St. Croix, U.S. Virgin Islands. Trays and depressions were unenriched (Unenriched Controls) or enriched with either Thalassiosira sp. or Sargassum sp. Concurrent deployment of different types of enrichment and disturbance made it possible to evaluate whether macrofauna specialize on different patches, and thus avoid species interactions that might lead to competitive exclusion. Depressions create a hydrodynamic regime that traps passive particles, allowing …
Disturbance Associated With Bait-Collection For Sandprawns (Callianassa Kraussi) And Mudprawns (Upogebia Africana): Long-Term Effects On The Biota Of Intertidal Sandflats, Rachel P. Wynberg, George M. Branch
Disturbance Associated With Bait-Collection For Sandprawns (Callianassa Kraussi) And Mudprawns (Upogebia Africana): Long-Term Effects On The Biota Of Intertidal Sandflats, Rachel P. Wynberg, George M. Branch
Journal of Marine Research
The sandprawn Callianassa kraussi and the mudprawn Upogebia africana are used extensively as fish bait in southern Africa. A holistic analysis of disturbance associated with experimental prawn-collecting was undertaken to determine its repercussions upon the sediment and associated macrofaunal, meiofaunal, microbial and microalgal communities. Patterns of recovery were examined for 18 months following the disturbance. The recovery of both C. kraussi and U. africana was far more protracted than predicted, taking 18 months for completion. Sedimentary compaction, associated with the removal of prawns, could account for these prolonged recoveries. Both C. kraussi and U. africana suffered greater depressions of population …
Circulation, Transport And Bottom Boundary Layers Of The Deep Currents In The Brazil Basin, X. Durrieu De Madron, G. Weatherly
Circulation, Transport And Bottom Boundary Layers Of The Deep Currents In The Brazil Basin, X. Durrieu De Madron, G. Weatherly
Journal of Marine Research
Zonal and meridional hydrographic sections obtained for the South Atlantic Ventilation Experiment are used to study the circulation patterns and estimate the transports of North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) in the Brazil Basin. The NADW Deep Western Boundary Current (DWBC) appears to be a relatively large (≈ 800 km wide by 2 km thick), double core current, separated by counterflowing recirculation. It appears to split, branching seaward at the Cape Saõ Roque near 5S and again at the Columbia-Trinidad Seamount Chain at 21S. As a result of this latter bifurcation, the NADW DWBC flow in …
Wave-Induced Abyssal Recirculations, Michael A. Spall
Wave-Induced Abyssal Recirculations, Michael A. Spall
Journal of Marine Research
The forcing of abyssal recirculation gyres by cross-isopycnal mixing and wave fluxes near the deep western boundary is investigated. A three-layer isopycnal primitive equation model is applied in a series of experiments to an idealized basin with bottom topography. In the absence of deep western boundary current instabilities, cross-isopycnal mixing forces a cyclonic recirculation gyre, modified by topography, which is consistent with the traditional Stommel-Arons model. Instabilities of the boundary current fundamentally alter the mean basin-scale deep flow from a cyclonic recirculation to an anticyclonic recirculation. Bottom topography plays a key role in destabilizing the mean flow. The forcing mechanism …