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Modeling The Antarctic Circumpolar Current: A Comparison Of Fram And Equivalent Barotropic Model Results, V. O. Ivchenko, A. E. Krupitsky, V. M. Kamenkovich, N. C. Wells Jan 1999

Modeling The Antarctic Circumpolar Current: A Comparison Of Fram And Equivalent Barotropic Model Results, V. O. Ivchenko, A. E. Krupitsky, V. M. Kamenkovich, N. C. Wells

Journal of Marine Research

Analyzing the FRAM simulations, Killworth (1992) noticed a strong tendency for self-similarity in the vertical structure of the velocity field of the Antarctic Circumpolar Current (ACC). By assuming the self-similarity as a hypothesis, Krupitsky et al. (1996) developed an equivalent barotropic (EB) model of the ACC capable of describing the horizontal structure of the ACC. Compared to the multi-level-primitive-equation GCM, the EB model appeared substantially simpler and therefore useful in pilot process-oriented and sensitivity studies. In the present study dynamical and kinematical comparisons of the EB and FRAM outputs are given.

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Formation And Circulation Of The Water Masses Between The Southern Indian Ocean And Antarctica: Results From Δ18o, Michael P. Meredith, Karen J. Heywood, Russell D. Frew, Paul F. Dennis Jan 1999

Formation And Circulation Of The Water Masses Between The Southern Indian Ocean And Antarctica: Results From Δ18o, Michael P. Meredith, Karen J. Heywood, Russell D. Frew, Paul F. Dennis

Journal of Marine Research

We present measurements of the stable isotopes of oxygen (18O and 16O) from seawater samples collected during the Antarctic Deep Outflow Experiment (ADOX) cruises in the Southern Ocean and southern Indian Ocean, February to March, 1993 and 1994. The data are used in conjunction with hydrographic data to infer characteristics of the formation and circulation of water masses found in the region. The waters on the continental shelf of Antarctica (adjacent to the Princess Elizabeth Trough; PET) are isotopically the lightest found due to the injection of about 1% of glacial meltwater, and are probably advected to …

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On The Chaotic Evolution Of Baroclinic Instability Of Wave-Wave Interactions With Topography, John Kroll Jan 1999

On The Chaotic Evolution Of Baroclinic Instability Of Wave-Wave Interactions With Topography, John Kroll

Journal of Marine Research

De Szoeke (1986) developed an asymptotic solution for the nonlinear evolution of a type of baroclinic instability of a two-layer quasi-geostrophic model over topography. He found that under certain conditions pairs of hybrid modes interacting with topography could become unstable in the linearized model. He also found that the addition of the nonlinearity stabilized the flow which he analyzed using an expansion in small ε, a measure of the topographic height. This work is extended and modified by first considering a slightly varying mean flow (time dependent parametric forcing) which produces chaotic behavior, and then considering friction which allows chaos …

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Temporal Variations Of Mixed-Layer Oceanic Co2 At Jgofs-Kerfix Time-Series Station: Physical Versus Biogeochemical Processes, Ferial Louanchi, Diana P. Ruiz-Pino, Alain Poisson Jan 1999

Temporal Variations Of Mixed-Layer Oceanic Co2 At Jgofs-Kerfix Time-Series Station: Physical Versus Biogeochemical Processes, Ferial Louanchi, Diana P. Ruiz-Pino, Alain Poisson

Journal of Marine Research

The seasonal and interannual variations in mixed-layer carbon dioxide in the Southern Ocean are analyzed from January 1990 to March 1995 at KERFIX time-series station (50°40S-69°25E). The temperature, salinity and chlorophyll time series are used as constraints on a simple box model to extrapolate total dissolved inorganic carbon (DIC), total alkalinity (TA) and oceanic CO2 fugacity (fCO2) over the five years of the monitoring. Results of the simulation are compared to all available observations. Both measured and simulated DIC and TA give seasonal signals of 25 µmol/kg and 8 µeq/kg, respectively. In spite of a …

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Lagrangian Statistics In Unforced Barotropic Flows, J. H. Lacasce, K. G. Speer Jan 1999

Lagrangian Statistics In Unforced Barotropic Flows, J. H. Lacasce, K. G. Speer

Journal of Marine Research

We consider the dispersion of particles in potential vorticity (PV)-conserving flows. Because particle drift is preferentially along the mean PV contours, Lagrangian dispersion is strongly anisotropic. If the mean PV field moreover is spatially variable, as when there is topography, the anisotropy is more clearly visible in the dispersion of displacements along and across the mean PV field itself. We examine several numerical examples of unforced barotropic flows; in all cases, this "projected" dispersion is more anisotropic than that in cartesian (x, y) coordinates. What differs is the rate at which spreading occurs, both along and across …

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The Effects Of Multiple Trap Spacing, Baffles And Brine Volume On Sediment Trap Collection Efficiency, Scott D. Nodder, Bridget L. Alexander Jan 1999

The Effects Of Multiple Trap Spacing, Baffles And Brine Volume On Sediment Trap Collection Efficiency, Scott D. Nodder, Bridget L. Alexander

Journal of Marine Research

The hydrodynamic effects on trapping efficiency of sediment trap cross-frame position, baffles and brine volume were evaluated in three short-term (<1 week) experiments in a temperate shallow marine environment (Evans Bay, Wellington Harbour, New Zealand). The effects of trap position and brine were further investigated during two open ocean, free-floating sediment trap deployments (1-2 days) near the Subtropical Front (STF), east of New Zealand. In the Evans Bay experiments (numbered I-III), cross-frames, each holding 12 cylindrical traps (inside diameter 9 cm, height 95 cm), were moored 3 meters above the seafloor in 15-18 m water depths at three randomly selected inner harbor sites. Triplicate subsamples from each cylinder were analyzed for total dry weight and mass fluxes calculated. The STF deployments utilized JGOFS MULTI-traps (inside diameter 7 cm, height 58 cm) attached to cross-frames moored at three depths (120, 300 and 550 m) on drifting arrays (Experiments IV and V). MULTI-trap samples were analyzed for total particulate mass, carbon and nitrogen. Results from Experiments I and V indicate that a spacing of about 3-trap diameters was sufficient to minimize inter-trap interactions and maintain trapping efficiency among traps suspended on a cross-frame at the same depth. Furthermore, baffles had no effect on trapping efficiency and an undetectable impact on zooplankton "swimmer" populations also collected in traps (Experiment II). In Experiment III, traps that were filled completely with high-density salt brine (50‰ excess NaCl) collected 2-3 times less material than traps with a basal brine height equivalent to 1- and 2.5-trap diameters. In contrast, high levels of inter-site variability confounded the STF MULTI-trap deployments during Experiment IV. However, variability in flux measurements from both Experiments III and IV increased 2 to 3-fold in brine-filled traps. Thus, the potential for brine-filled traps to undercollect material with higher levels of variability could possibly explain previously reported inaccuracies in the sediment trap method.

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Distributions Of Nuclear Fuel-Reprocessing Tracers In The Arctic Ocean: Indications Of Russian River Influence, Lee W. Cooper, Tom Beasley, Knut Aagaard, James M. Kelley, L. L. Larsen, Jacqueline M. Grebmeier Jan 1999

Distributions Of Nuclear Fuel-Reprocessing Tracers In The Arctic Ocean: Indications Of Russian River Influence, Lee W. Cooper, Tom Beasley, Knut Aagaard, James M. Kelley, L. L. Larsen, Jacqueline M. Grebmeier

Journal of Marine Research

Radionuclide sampling in 1986 and 1993 in the Canada Basin, and in 1993 in the Amundsen Basin and on the adjacent Laptev shelf, provides new insights into the origin, timing, pathways, and mechanisms for dispersal of non-fallout radioactive tracers in the Arctic Ocean. First, samples from the Beaufort Sea shelf, slope, and adjacent basin show a four-fold increase in 129I concentrations from 1986 to 1993. Second, anthropogenic non-fallout radionuclide concentrations in the Beaufort Sea increase with proximity to slope boundary currents. Third, there is evidence for riverine contributions of anthropogenic radionuclides to surface waters of the Amundsen Basin and …

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On The Predictability Of Regional Oceanic Jet Stream: The Impact Of Model Errors At The Inflow Boundary, Shi Jiang, Paola Malanotte-Rizzoli Jan 1999

On The Predictability Of Regional Oceanic Jet Stream: The Impact Of Model Errors At The Inflow Boundary, Shi Jiang, Paola Malanotte-Rizzoli

Journal of Marine Research

When a jet is simulated in a fine-resolution regional model with inflow and outflow boundaries, its dynamical behavior depends crucially on the specified inflow boundary condition (IBC). Our primary goals are (1) to explore the model's ability to simulate the jet when the IBC is approximately known, (2) to examine the dynamical propagation and growth of the IBC errors in both space and time, and (3) to assess the relative usefulness of different types of data used to specify the IBC. This paper represents the results of an ensemble of 30 IBC-perturbed experiments derived from the Semi-Spectral Primitive Equation Model …

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Strange Encounters Of Eddies With Walls, Doron Nof Jan 1999

Strange Encounters Of Eddies With Walls, Doron Nof

Journal of Marine Research

The impingement of a westward drifting lens-like anticyclonic ring on a meridional boundary is examined analytically and numerically using an (inviscid) layer-and-a-half model. A nonlinear analytical solution is constructed with the aid of a slowly varying perturbation expansion and numerical simulations are performed with the Bleck and Boudra model. It is found that, in contrast to conventional wisdom which implies that an anticyclonic ring encountering a wall moves poleward due to the image effect, the ring stays roughly in a fixed latitude. As it slowly moves into the wall due to β, it gradually leaks fluid toward the equator until …

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Lattice Boltzmann Solutions Of The Three-Dimensional Planetary Geostrophic Equations, Rick Salmon Jan 1999

Lattice Boltzmann Solutions Of The Three-Dimensional Planetary Geostrophic Equations, Rick Salmon

Journal of Marine Research

We use the lattice Boltzmann method as the basis for a three-dimensional, numerical ocean circulation model in a rectangular basin. The fundamental dynamical variables are the populations of mass- and buoyancy-particles with prescribed discrete velocities. The particles obey collision rules that correspond, on the macroscopic scale, to planetary geostrophic dynamics. The advantages of the model are simplicity, stability, and massively parallel construction. By the special nature of its construction, the lattice Boltzmann model resolves upwelling boundary layers and unsteady convection. Solutions of the model show many of the features predicted by ocean circulation theories.

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Frontogenesis In The North Pacific Oceanic Frontal Zones--A Numerical Simulation, Michael S. Dinniman, Michele M. Rienecker Jan 1999

Frontogenesis In The North Pacific Oceanic Frontal Zones--A Numerical Simulation, Michael S. Dinniman, Michele M. Rienecker

CCPO Publications

A primitive equation model [Geophysical Fluid Dynamics Laboratory's (GFDL's) MOM 2] with one degree horizontal resolution is used to simulate the seasonal cycle of frontogenesis in the subarctic frontal zone (SAFZ) and the subtropical frontal zone (STFZ) of the North Pacific Ocean. The SAFZ in the model contains deep (greater than 500 m in some places) regions with seasonally varying high gradients in temperature and salinity. The gradients generally weaken toward the east. The STFZ consists of a relatively shallow (less than 200 m in most places) region of high gradient in temperature that disappears in the summer/fall. The high …

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Enhanced Dispersion Of Near-Inertial Waves In An Idealized Geostrophic Flow, N. J. Balmforth, Stefan G. Llewellyn Smith, W. R. Young Jan 1998

Enhanced Dispersion Of Near-Inertial Waves In An Idealized Geostrophic Flow, N. J. Balmforth, Stefan G. Llewellyn Smith, W. R. Young

Journal of Marine Research

This paper presents a simplified model of the process through which a geostrophic flow enhances the vertical propagation of near-inertial activity from the mixed layer into the deeper ocean. The geostrophic flow is idealized as steady and barotropic with a sinusoidal dependence on the north-south coordinate; the corresponding streamfunction takes the form ψ = - Ψ cos (2αy). Near-inertial oscillations are considered in linear theory and disturbances are decomposed into horizontal and vertical normal modes. For this particular flow, the horizontal modes are given in terms of Mathieu functions. The initial-value problem can then be solved by projecting …

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The Malin Cascade In Winter 1996, A. E. Hill, A. J. Souza, K. Jones, J. H. Simpson, G. I. Shapiro, R. Mccandliss, H. Wilson, J. Leftley Jan 1998

The Malin Cascade In Winter 1996, A. E. Hill, A. J. Souza, K. Jones, J. H. Simpson, G. I. Shapiro, R. Mccandliss, H. Wilson, J. Leftley

Journal of Marine Research

We report evidence for cascading of shelf-edge water down the continental slope northwest of Ireland at 55N in February 1996. The measured surface density contrast between shelf-edge and slope waters was 0.01 kg m-3 and the resulting dense plume was 20-50 m thick over the continental slope and penetrated to a depth of 500 m. Cascade waters were warmer but saltier than overlying slope waters and their shelf-edge origin was confirmed by relatively higher chlorophyll concentrations and a distinctive nutrient signature. Other cross-slope transects 100 km north and south of the cascade site showed dense water at the shelf …

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The Influence Of The Ambient Flow On The Spreading Of Convected Water Masses, Sonya Legg, John Marshall Jan 1998

The Influence Of The Ambient Flow On The Spreading Of Convected Water Masses, Sonya Legg, John Marshall

Journal of Marine Research

We investigate the influence of a cyclonic vortical flow on the lateral spreading of newly mixed fluid generated through localized deep convection. Localized open ocean deep convection often occurs within such a cyclonic gyre circulation, since the associated upwardly domed isopycnals and weaker stratification locally precondition the ocean for deeper convection. In the absence of ambient flow, localized convection has been shown to result in strong lateral fluxes of buoyancy generated by baroclinic instability, sufficient to offset the local surface buoyancy loss and limit the density anomaly of the convectively generated water mass. Here we examine the consequences of a …

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The Southern Flux Of Sea Ice In The Tatarskiy Strait, Japan Sea And The Generation Of The Liman Current, Seelye Martin, Mitsuhiro Kawase Jan 1998

The Southern Flux Of Sea Ice In The Tatarskiy Strait, Japan Sea And The Generation Of The Liman Current, Seelye Martin, Mitsuhiro Kawase

Journal of Marine Research

The circulation in the surface waters of the Japan Sea is driven in part by thermohaline forcing associated with the flux of cold, low-salinity water from the Tatarskiy Strait. Existing numerical models suggest that this water contributes to the Liman Current, which flows from northeast to southwest along the Russian coast. The major source of Japan Sea freshwater is the Amur River, which flows into the sea through Tatarskiy Strait, but has a near-zero minimum during January to March. As an alternate source of freshwater to the surface layer, we derive from meteorological and remote sensing data for the 1992-1994 …

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Corrigendum To Surface-Intensified Rossby Waves Over Rough Topography (J. Mar. Res., 50, 367–384), R. M. Samelson Jan 1998

Corrigendum To Surface-Intensified Rossby Waves Over Rough Topography (J. Mar. Res., 50, 367–384), R. M. Samelson

Journal of Marine Research

In Samelson (1992), Eq. (13) should be changed to… respectively. The same error appears in the Abstract.

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Tidal Resuspension And Deposition Of Particulate Matter In The Oyster Grounds, North Sea, Wim Van Raaphorst, Hans Malschaert, Hans Van Haren Jan 1998

Tidal Resuspension And Deposition Of Particulate Matter In The Oyster Grounds, North Sea, Wim Van Raaphorst, Hans Malschaert, Hans Van Haren

Journal of Marine Research

Moored current meters, fluorom eters and transmissometers were used in combination with sediment traps (aspect ratio >4) and shipborne sampling to determine fluxes of deposition and resuspension of total suspended matter (TSM) under tidal action in the 45 m deep Oyster Grounds, North Sea. Here, we present data from the mixed layer below the major thermocline at about 20 m above the bottom (mab) as obtained during a 14-day period of calm weather in July 1994. Around neap tide near-bottom current velocities remained smaller than 0.15 m s-1 and TSM was dominated by particles advected from a relatively turbid …

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Under-Ice Observations Of Water Column Temperature, Salinity And Spring Phytoplankton Dynamics: Eastern Bering Sea Shelf, P. J. Stabeno, J. D. Schumacher, R. F. Davis, J. M. Napp Jan 1998

Under-Ice Observations Of Water Column Temperature, Salinity And Spring Phytoplankton Dynamics: Eastern Bering Sea Shelf, P. J. Stabeno, J. D. Schumacher, R. F. Davis, J. M. Napp

Journal of Marine Research

The inundation of two moored platforms by sea ice in late winter and early spring of 1995 provided unique time series of water column temperature, salinity, estimated chlorophyll-a, and phytoplankton fluorescence under advancing and retreating sea ice. One platform was located at 72 m in the weakly advective middle shelf regime. Here, chlorophyll-a concentrations began increasing shortly after the arrival of the ice (arch) during the period of weak stratification and continued to increase while wind actively mixed the water column to >60 m. Changes in water column structure and properties resulted from an event of strong …

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Deep Water Properties, Velocities, And Dynamics Over Ocean Trenches, Gregory C. Johnson Jan 1998

Deep Water Properties, Velocities, And Dynamics Over Ocean Trenches, Gregory C. Johnson

Journal of Marine Research

Observations of water properties and deep currents over several trenches in the Pacific Ocean central basins give consistent evidence for recent ventilation of water below the trench sills and cyclonic sense of circulation over the trenches. A dynamical argument for this pattern is advanced. First, a review of previous analyses of hydrographic data shows that the trenches are well ventilated by dense bottom water, that within the trenches this bottom water generally spreads away from its source, and that a cyclonic sense of circulation is suggested over some trenches. Then, this cyclonic sense of circulation over the trenches is further …

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A Numerical Study Of Layer Formation Due To Fingers In Double-Diffusive Convection In A Vertically-Bounded Domain, Tamay M. Özgökmen, Oleg E. Esenkov, Donald B. Olson Jan 1998

A Numerical Study Of Layer Formation Due To Fingers In Double-Diffusive Convection In A Vertically-Bounded Domain, Tamay M. Özgökmen, Oleg E. Esenkov, Donald B. Olson

Journal of Marine Research

The evolution of fingers in a double-diffusive system is investigated using numerical integration of two-dimensional equations of motion for an incompressible, Boussinesq fluid. The computational domain is periodic in the horizontal direction and is closed with no-flux boundary conditions in the vertical direction. The main result of this study is the evolution of the system from initially linear profiles for both fast and slow diffusing components to a layered state characterized by a finger zone sandwiched between two mixed layers. The horizontal boundaries in this system play an important role in the development of the layered state. At the top …

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The Rectification Of Wind-Driven Flow Due To Its Instabilities, Caroline A. Katsman, Henk A. Dijkstra, Sybren S. Drijfhout Jan 1998

The Rectification Of Wind-Driven Flow Due To Its Instabilities, Caroline A. Katsman, Henk A. Dijkstra, Sybren S. Drijfhout

Journal of Marine Research

Within a quasi-geostrophic two-layer model of the wind-driven ocean circulation, an idealized symmetric double gyre flow is considered. When lateral friction is large enough, this flow is steady and characterized by a motionless lower layer. As friction is decreased, the flow undergoes a transition to time-dependence through a Hopf bifurcation, associated with a mixed barotropic/baroclinic instability. It is shown that the nonlinear self-interaction of this oscillatory unstable mode induces a nonzero time mean response in the lower layer. The origin of this deep flow is clarified through a weakly nonlinear analysis near critical conditions. It is explained how the perturbation …

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Process-Specific Cues For Recruitment In Sedimentary Environments: Geochemical Signals?, Sarah A. Woodin, Roberta L. Marinelli, Sara M. Lindsay Jan 1998

Process-Specific Cues For Recruitment In Sedimentary Environments: Geochemical Signals?, Sarah A. Woodin, Roberta L. Marinelli, Sara M. Lindsay

Journal of Marine Research

The most biologically and geochemically active marine sediments are characterized by steep chemical gradients within the top centimeters of sediment (Berner, 1980). A common feature of these environments is disruptions of surface sediments by both physical and biotic forces. Growth and mortality rates for new recruits are affected by many of these surface perturbations. At the same time, these disturbances also impose a discontinuity in concentration across the sediment-water interface, and accordingly, a change in surface chemistry. In this paper we present evidence that the cue used by juveniles to distinguish between recently disturbed and undisturbed surfaces may be disruption …

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Seabed Drag Coefficient Over Natural Beds Of Horse Mussels (Atrina Zelandica), Malcolm O. Green, Judi E. Hewitt, Simon F. Thrush Jan 1998

Seabed Drag Coefficient Over Natural Beds Of Horse Mussels (Atrina Zelandica), Malcolm O. Green, Judi E. Hewitt, Simon F. Thrush

Journal of Marine Research

Measurements of seabed drag coefficient, C100, were made under tidal currents at four sites in Mahurangi Harbour, New Zealand. At the first three sites the dominant roughness element was the pinnid bivalve, Atrina zelandica (horse mussel). At the fourth site, which was devoid of horse mussels but covered in cockle shells, patches of seaweed and crab burrows, C100 was smallest (0.0055), but still twice as large as the value typically applied to abiotic, flat, cohesionless seabeds (0.0025). The mean drag coefficient plus-or-minus standard error at the three sites with horse mussels was: 0.0082 ± 0.0010 (site 1); …

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Three-Dimensional Stirring Of Thermohaline Fronts, Patrice Klein, Anne-Marie Treguier, Bach Lien Hua Jan 1998

Three-Dimensional Stirring Of Thermohaline Fronts, Patrice Klein, Anne-Marie Treguier, Bach Lien Hua

Journal of Marine Research

This study investigates the stirring of the thermohaline anomalies in a fully turbulent quasigeostrophic stratified flow. Temperature and salinity fields are permanently forced at large scales and are related to density by a linear equation of state. We show, using some inherent properties of quasi-geostrophic turbulence, that the 3-D ageostrophic circulation is the key dynamical characteristic that governs the strength and the spatial distribution of small-scale thermohaline fronts that are strongly density compensated. The numerical simulations well illustrate the formation by the mesoscale eddy field of sharp thermohaline fronts that are mainly located in the saddle regions and around the …

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Temporal Variability And Composition Of Settling Particle Fluxes On The Barcelona Continental Margin (Northwestern Mediterranean), P. Puig, A. Palanques Jan 1998

Temporal Variability And Composition Of Settling Particle Fluxes On The Barcelona Continental Margin (Northwestern Mediterranean), P. Puig, A. Palanques

Journal of Marine Research

The results of a year-long sediment-trap experiment provide the first direct observations of sediment fluxes to the seafloor on the Barcelona continental margin. Time-series of vertical particle fluxes and major constituents (organic carbon, biogenic silica, calcium carbonate and aluminosilicates) were determined inside and in the vicinity of the Foix submarine canyon from May 1993 to April 1994. The spatial and temporal variability of bi-weekly total mass fluxes indicate significant high frequency variability related to physical and biological processes at this site. The Foix submarine canyon acts as an actual conduit for transport of sediment from the shelf to the slope, …

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Excretion Of Trace Elements By Marine Copepods And Their Bioavailability To Diatoms, Wen-Xiong Wang, Nicholas S. Fisher Jan 1998

Excretion Of Trace Elements By Marine Copepods And Their Bioavailability To Diatoms, Wen-Xiong Wang, Nicholas S. Fisher

Journal of Marine Research

We measured the physiological turnover rate (= excretion rate) of five trace elements (Ag, Cd, Co, Se and Zn) in the marine copepod Temora longicornis following feeding on radiolabeled diatoms. The turnover rate constants of trace elements in copepods were high (0.05 to 0.38 d-1) and were comparable to published values for N and P excretion. Ag, Cd and Co were excreted at higher rates than Se and Zn. Turnover rate constants of Ag, Cd, and Co also increased with increasing food concentration, whereas excretion of Se and Zn was not affected by food concentration. There was little …

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The Non-Wavelike Response Of A Continental Shelf To Wind, G. T. Csanady Jan 1998

The Non-Wavelike Response Of A Continental Shelf To Wind, G. T. Csanady

Journal of Marine Research

An overlooked aspect of continental shelf wave generation by wind is that a non-wavelike flow field may accompany the waves. To explore this possibility, we calculate the response of an inclined plane shelf to suddenly applied alongshore wind, affecting a finite portion of the coast. The calculations are based on the classical theory of continental shelf waves, supposing low frequency motions and invoking the boundary layer approximation (alongshore scales much longer than cross-shore ones). The results reveal non-wavelike circulations, with or without bottom friction, on a shelf of finite or unlimited width, unaffected by changing offshore boundary conditions. In the …

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Nonlinear Limits To Ocean Thermal Structure, N. P. Fofonoff Jan 1998

Nonlinear Limits To Ocean Thermal Structure, N. P. Fofonoff

Journal of Marine Research

The nonlinear volume changes associated with diffusion and mixing of different seawater types produce significant conversions of gravitational potential energy to kinetic energy to maintain and enhance mixing processes and to limit the magnitudes of temperature gradients that can persist in the ocean. Several examples are given to illustrate these critical temperature gradients beyond which conversion exceeds local energy consumption by mixing. The vertical temperature gradients in the Gulf Stream reduce downstream from Cape Hatteras to the critical limit found in the North Atlantic thermocline. The limiting gradients are also seen in surface thermoclines and in "staircase" structures. Although the …

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Linear Ocean Circulation Theory With Realistic Bathymetry, Rick Salmon Jan 1998

Linear Ocean Circulation Theory With Realistic Bathymetry, Rick Salmon

Journal of Marine Research

The linear equations governing stratified, wind-driven flow in an ocean of arbitrary shape may be combined into a single "advection-diffusion" equation for the pressure , in which the "flow" advecting  includes a delta-function contribution at the ocean bottom in the sense of southward "advection" of  along western continental slopes. This interpretation of the -equation helps to explain numerical solutions obtained with a finite-element model incorporating realistic North Atlantic bathymetry.

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On The Stability Of The Wind-Driven Circulation, P. Berloff, S. P. Meacham Jan 1998

On The Stability Of The Wind-Driven Circulation, P. Berloff, S. P. Meacham

Journal of Marine Research

This work examines the instabilities of steady circulations driven by stationary single-gyre wind forcing in closed rectangular basins with different aspect ratios. The stratified ocean is modeled with quasi-geostrophic 1.5-layer (equivalent-barotropic) and two-layer models. As friction is reduced, a stability threshold is encountered. In the vicinity of this threshold, unstable steady states and their unstable eigenmodes are determined. The structures of the eigenmodes and their associated energy conversion terms allow us to characterize the instabilities. In each case, the loss of stability is associated with an oscillatory instability. Several different instability mechanisms are observed. Which of these is responsible for …

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