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Central Equatorial Pacific Zonal Currents. I: The Sverdrup Balance, Nonlinearity And Tropical Instability Waves. Annual Mean Dynamics, D. E. Harrison, R. D. Romea, S. H. Hankin Jan 2001

Central Equatorial Pacific Zonal Currents. I: The Sverdrup Balance, Nonlinearity And Tropical Instability Waves. Annual Mean Dynamics, D. E. Harrison, R. D. Romea, S. H. Hankin

Journal of Marine Research

Several recent observational studies of central Pacific equatorial current dynamics have suggested that, in the vertical integral between the surface and the thermocline, the linear equatorial Sverdrup balance holds. However, in a high vertical resolution ocean general circulation model, we find that nonlinearity is an order (1) element of the local and the vertically integrated balances on and near the equator at 140W. Although this OGCM has been used in many studies of the tropical Pacific, its equatorial zonal momentum equation balances have never been described in detail and compared with observations. We describe the annual mean balances here, identify …

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The Impact Of Model-Error Correlation On Regional Data Assimilative Models And Their Observational Arrays, Philip S. Bogden Jan 2001

The Impact Of Model-Error Correlation On Regional Data Assimilative Models And Their Observational Arrays, Philip S. Bogden

Journal of Marine Research

Data assimilative models often minimize a penalty functional that measures model adjustment and model-data misfit. The penalty functional builds assumptions about model error into the analysis. Usually, errors from different parts of the model (e.g., dynamics and boundary conditions) are presumed to be uncorrelated. This is clearly not a valid assumption in regional models where uncertain large-scale forcing affects open-ocean boundary conditions. In this study, calculations with a regional wind-driven inverse model provide a specific example where model error from uncertain wind stress is correlated with model error from uncertain open boundary conditions. This physically realistic scenario motivates development of …

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The Near-Surface Velocity And Potential Vorticity Structure Of The Gulf Stream, T. Rossby, H. M. Zhang Jan 2001

The Near-Surface Velocity And Potential Vorticity Structure Of The Gulf Stream, T. Rossby, H. M. Zhang

Journal of Marine Research

Using Acoustic Doppler Current Profiler and XBT data between 1992 and 1999 from a container vessel that crosses the Gulf Stream twice weekly near 70W, we examine the near-surface velocity, thermal and vorticity structure of the current. These data come from an ongoing sampling program that has as its overall objective to measure the currents between New York and Bermuda to provide a high-quality database for studies of variability and long-term trends in the region. These Gulf Stream sections, when averaged in natural or stream coordinates, exhibit a remarkable double-exponential structure. The scale-widths of the lateral shear north and south …

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Effects Of Topography On The Beta-Drift Of A Baroclinic Vortex, Georgi Sutyrin Jan 2001

Effects Of Topography On The Beta-Drift Of A Baroclinic Vortex, Georgi Sutyrin

Journal of Marine Research

The propagation of compact, surface-intensified vortices over a topographic slope on the beta-plane is studied in the framework of a two-layer model. A perturbation theory is derived for a circular vortex in the upper layer with the lower layer at rest as a basic state. An integral momentum balance for the upper layer is used to obtain expressions for the velocity of the vortex center assuming the flow is quasi-stationary to leading order. This approach allows the calculation of the lower-layer flow pattern as a function of the interface shape and the slope orientation. The essential part of the lower-layer …

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Modeling Water Column Structure And Suspended Particulate Matter On The Middle Atlantic Continental Shelf During The Passages Of Hurricanes Edouard And Hortense, Alejandro J. Souza, Tommy D. Dickey, Grace C. Chang Jan 2001

Modeling Water Column Structure And Suspended Particulate Matter On The Middle Atlantic Continental Shelf During The Passages Of Hurricanes Edouard And Hortense, Alejandro J. Souza, Tommy D. Dickey, Grace C. Chang

Journal of Marine Research

The present contribution is motivated by the desire to elucidate the processes that contributed to the evolution of observed thermal structure and resuspension of particulate matter during and after the passages of two hurricanes, Edouard and Hortense, within a two-week period in late-summer 1996. A unique set of high temporal frequency measurements of the vertical structures of physical and optical properties was obtained at a mooring site near the Middle Atlantic Bight continental shelf-break (70 m water depth). These data provided insight and initial conditions for the physical model used for this study. The model accounted for wind and bottom …

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Particle Trapping In A Stratified Flood-Dominated Estuary, Robert J. Chant, Allan W. Stoner Jan 2001

Particle Trapping In A Stratified Flood-Dominated Estuary, Robert J. Chant, Allan W. Stoner

Journal of Marine Research

Observations in the Navesink River estuary in northern New Jersey demonstrate that buoyancy augments the particle trapping tendencies of flood-dominated systems because these estuaries heighten tidal period asymmetries in stratification. During the long and slow ebb which typifies flood-dominated systems, a positive feedback between tidal straining and weak vertical mixing stratifies the estuary. In contrast, during flood, turbulence generated by the stronger tidal currents augments overstraining of the density field and the water column becomes well mixed. The tidal period asymmetries in stratification have profound effects on the vertical structure and transport of suspended matter. During ebb, weak vertical mixing …

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Performance Of Cages As Large Animal-Exclusion Devices In The Deep Sea, James E. Eckman, David Thistle, William C. Burnett, Gordon L. J. Paterson, Charles Y. Robertson, P. John D. Lambshead Jan 2001

Performance Of Cages As Large Animal-Exclusion Devices In The Deep Sea, James E. Eckman, David Thistle, William C. Burnett, Gordon L. J. Paterson, Charles Y. Robertson, P. John D. Lambshead

Journal of Marine Research

Sedimentary, deep-sea communities include megafaunal animals (e.g., sea cucumbers, brittle stars, crabs) and demersal fishes, collectively termed the large, motile epifauna (LME). Individuals of the LME are common, and their biomass approximates that of the macrofauna. Based on analogies with shallow-water animals, they are likely to be sources of mortality for the infauna and to create spatial and temporal heterogeneity in the community. Given present theories of deep-sea community organization, such effects could be important. Unfortunately, this hypothesis has not been tested because of the difficulty of conducting experiments in the deep sea and because tools for manipulating the LME …

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Assessing The Dispersal And Exchange Of Brachyuran Larvae Between Regions Of San Diego Bay, California And Nearshore Coastal Habitats Using Elemental Fingerprinting, Claudio Dibacco, D. Bart Chadwick Jan 2001

Assessing The Dispersal And Exchange Of Brachyuran Larvae Between Regions Of San Diego Bay, California And Nearshore Coastal Habitats Using Elemental Fingerprinting, Claudio Dibacco, D. Bart Chadwick

Journal of Marine Research

Marine benthic invertebrate populations found in estuarine or coastal habitats often exchange larvae. However, the dynamics of larval exchange are poorly understood because of difficulties in (1) making synoptic assessments of horizontal and vertical larval distribution patterns over large areas for extended periods of time and (2) determining the origins of field-sampled larvae. This study examines how temporal changes in the vertical and horizontal distribution of crab larvae (i.e., Pachygrapsus crassipes and Lophopanopeus spp.) affect larval transport. Larval concentration and water velocity data were collected concurrently and were used to estimate larval exchange between regions of San Diego Bay (SDB) …

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A Particle Introduction Experiment In Santa Catalina Basin Sediments: Testing The Age-Dependent Mixing Hypothesis, William L. Fornes, David J. Demaster, Craig R. Smith Jan 2001

A Particle Introduction Experiment In Santa Catalina Basin Sediments: Testing The Age-Dependent Mixing Hypothesis, William L. Fornes, David J. Demaster, Craig R. Smith

Journal of Marine Research

The occurrence of "age-dependent mixing," a process by which recently deposited, food-rich particles undergo more intense bioturbation than older, food-poor particles, could dramatically alter patterns of organic-matter diagenesis in deep-sea sediments. To explicitly test for age-dependent mixing, an in-situ particle introduction experiment was conducted on the bathyal Santa Catalina Basin floor. Mixtures of radioisotope-tagged particles representing a food quality gradient were dispersed in small amounts on the seafloor and sampled over periods of 0 to 594 days. Introduced particle types were all similar in size and included fresh diatoms ("young" particles), surface sediments ("intermediate-age" particles), and particles from 30-cm deep …

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Dynamics Of The Makassar Strait, Jorina M. Waworuntu, Silvia L. Garzoli, Donald B. Olson Jan 2001

Dynamics Of The Makassar Strait, Jorina M. Waworuntu, Silvia L. Garzoli, Donald B. Olson

Journal of Marine Research

Data collected as part of the Arlindo Project ("Arlindo" is an acronym for Arus Lintas Indonesia, meaning "throughflow" in Bahasa Indonesia) from October 1996 to March 1998 are analyzed to study the characteristics of the flow through the Makassar Strait. Analysis of inverted echo sounders (IES) and bottom pressure data (PIES) combined with TOPEX/POSEIDON satellite-derived sea height anomaly suggest that a minimum of three-layer approximation is necessary to explain the dynamics of the flow in the Makassar Strait. The simple two-layer model used in several studies of the throughflow is rejected based on total incompatibility with the data sets. A …

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Salt Fingers In An Unbounded Thermocline, Melvin E. Stern, Timour Radko, Julian Simeonov Jan 2001

Salt Fingers In An Unbounded Thermocline, Melvin E. Stern, Timour Radko, Julian Simeonov

Journal of Marine Research

Numerical solutions for salt fingers in an unbounded thermocline with uniform overall vertical temperature-salinity gradients are obtained from the Navier-Stokes-Boussinesq equations in a finite computational domain with periodic boundary conditions on the velocity. First we extend previous two-dimensional (2D) heat-salt calculations [Prandtl number Pr = ν/kT = 7 and molecular diffusivity ratio τ = kS/kT = 0.01] for density ratio R = 2; as R decreases we show that the average heat and salt fluxes increase rapidly. Then three-dimensional (3D) calculations for R = 2.0, Pr = 7, and the numerically "accessible" values of τ …

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Observations Of The Wind-Induced Exchange At The Entrance To Chesapeake Bay, Arnoldo Valle-Levinson, Kuo-Chuin Wong, Kathryn T. Bosley Jan 2001

Observations Of The Wind-Induced Exchange At The Entrance To Chesapeake Bay, Arnoldo Valle-Levinson, Kuo-Chuin Wong, Kathryn T. Bosley

Journal of Marine Research

Water density and velocity data from two ~75-day deployments across the entrance to the Chesapeake Bay were used in conjunction with wind velocity and sea level records to describe the transverse structure of wind-induced subtidal exchange. Acoustic Doppler current profilers, electromagnetic current meters, and conductivity-temperature-depth recorders were deployed at the entrance to the bay from mid-April to early July of 1999 and from early September to mid-November of 1999. Three main scenarios of wind-induced exchange were identified: (1) Northeasterly (NE) winds consistently drove water from the coast toward the lower Chesapeake Bay as well as water from the upper bay …

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Horizontal Dispersion Of Near-Inertial Oscillations In A Turbulent Mesoscale Eddy Field, Patrice Klein, Stefan Llewellyn Smith Jan 2001

Horizontal Dispersion Of Near-Inertial Oscillations In A Turbulent Mesoscale Eddy Field, Patrice Klein, Stefan Llewellyn Smith

Journal of Marine Research

We study the dispersion of wind-induced near-inertial oscillations (NIOs) in a fully turbulent baroclinic mesoscale eddy field characterized by a continuous wavenumber spectrum. The influence of the eddy field on the horizontal dispersion of the different NIO modes is analyzed using a vertical normal mode expansion. Previous studies have identified two dispersion regimes: trapping and strong dispersion. We examine the modes in physical and spectral space to assess which regime prevails. Numerical and analytical results show the prevalence of a trapping regime. For each NIO mode, there exists a critical horizontal wavenumber, kc, that separates large-scale NIO structures, …

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Central Equatorial Pacific Zonal Currents. Ii: The Seasonal Cycle And The Boreal Spring Surface Eastward Surge, D. E. Harrison, R. D. Romea, G. A. Vecchi Jan 2001

Central Equatorial Pacific Zonal Currents. Ii: The Seasonal Cycle And The Boreal Spring Surface Eastward Surge, D. E. Harrison, R. D. Romea, G. A. Vecchi

Journal of Marine Research

The seasonally averaged zonal momentum equation tendencies at 140W are studied in a high-resolution primitive equation ocean general circulation model simulation of the tropical Pacific. The model experiment, forced by climatological monthly average wind-stress, reproduces well the observed boreal springtime eastward surge of the normally westward surface flow, as well as many features of the acceleration and deceleration between the surface and 200 m between January and October. We present each of the zonal momentum equation tendency terms for the depth range 0-160 m, but our discussion focuses on the behavior of the boreal springtime near-surface flow, perhaps the most …

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Effects Of Macrofauna On Acoustic Backscatter From The Seabed: Field Manipulations In West Sound, Orcas Island, Washington, U.S.A., Robert F. L. Self, Patrick A'Hearn, Peter A. Jumars, Darrell R. Jackson, Michael D. Richardson, Kevin B. Briggs Jan 2001

Effects Of Macrofauna On Acoustic Backscatter From The Seabed: Field Manipulations In West Sound, Orcas Island, Washington, U.S.A., Robert F. L. Self, Patrick A'Hearn, Peter A. Jumars, Darrell R. Jackson, Michael D. Richardson, Kevin B. Briggs

Journal of Marine Research

Previous observations with a bottom-mounted, radially scanning sonar (BAMS) at 40 kHz suggested that macrofaunal activities influence low-angle, acoustic backscatter from seafloor sediments. In order to test that possibility experimentally, we measured and modeled time series of backscatter strength at both 40 and 300 kHz prior to manipulation and then introduced several macrofaunal species at known abundances to randomly selected locations within the ensonified area. We worked in West Sound, Orcas Island, Washington, at a water depth of 20.4 m and for the more frequently recorded 40-kHz series extracted effects by the time-series method known as "intervention analysis," wherein the …

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New Observations Of The Intermediate Depth Circulation In The Tropical Atlantic, Claudia Schmid, Robert L. Molinari, Silvia L. Garzoli Jan 2001

New Observations Of The Intermediate Depth Circulation In The Tropical Atlantic, Claudia Schmid, Robert L. Molinari, Silvia L. Garzoli

Journal of Marine Research

The intermediate depth (around 1000 m) circulation in the interior tropical Atlantic has been described as several narrow flow bands. Due to a lack of data, these currents have previously been poorly resolved in space and time. Recent observations, obtained during the mid-1997 Seward Johnson cruise and from PALACE floats which cover the period Summer 1997 to Spring 2000, allow a more detailed description of the intermediate depth circulation in the tropical Atlantic. The PALACE trajectories display several well defined currents between the equator and 4N at 800 to 1100 m. Two regimes separated by the eastern edge of the …

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Prominent Renewal Of Weddell Sea Deep Water From A Remote Source, Mario Hoppema, Olaf Klatt, Wolfgang Roether, Eberhard Fahrbach, Klaus Bulsiewicz, Christian Rodehacke, Gerd Rohardt Jan 2001

Prominent Renewal Of Weddell Sea Deep Water From A Remote Source, Mario Hoppema, Olaf Klatt, Wolfgang Roether, Eberhard Fahrbach, Klaus Bulsiewicz, Christian Rodehacke, Gerd Rohardt

Journal of Marine Research

Three transient tracer sections of CFC-11 across the Weddell Sea are presented, collected during "Polarstern" cruises ANT X/4 (July 1992), ANT XIII/4 (May 1996) and ANT XV/4 (April 1998). The corresponding sections of silicate, a quasi-steady-state tracer, are displayed for comparison and as a supplement. Two distinct CFC-11 maximum layers are found in the deep water, one centered near 2200 m and another near 3500 m. These layers, previously observed by other investigators, represent recently ventilated Weddell Sea Deep Water. The deeper, more pronounced core, occurs along the southern continental slope, whereas the shallower core occurs in the northern Weddell …

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Bioirrigation Modeling In Experimental Benthic Mesocosms, Yoko Furukawa, Samuel J. Bentley, Dawn L. Lavoie Jan 2001

Bioirrigation Modeling In Experimental Benthic Mesocosms, Yoko Furukawa, Samuel J. Bentley, Dawn L. Lavoie

Journal of Marine Research

Burrow irrigation by benthic infauna affects chemical mass transfer regimes in marine and estuarine sediments. The bioirrigation facilitates rapid exchange of solutes between oxygenated overlying water and anoxic pore water, and thus promotes biogeochemical reactions that include degradation of sedimentary organic matter and reoxidation of reduced species. A comprehensive understanding of chemical mass transfer processes in aquatic sediments thus requires a proper treatment of bioirrigation. We investigated bioirrigation processes during early diagenesis using laboratory benthic mesocosms. Bioirrigation was carried out in the mesocosms by Schizocardium sp., a funnel-feeding enteropneust hemichordate that builds and ventilates a U-shaped burrow. Interpretation of the …

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Size-Selective Downward Particle Transport By Cirratulid Polychaetes, David H. Shull, Michie Yasuda Jan 2001

Size-Selective Downward Particle Transport By Cirratulid Polychaetes, David H. Shull, Michie Yasuda

Journal of Marine Research

The deposition of surficial sediments many centimeters below the sediment-water interface due to the reworking activities of organisms is a potentially important but easily overlooked process in marine sediments. This kind of downward particle transport is difficult to observe in the laboratory or in the field but it has important consequences for bioturbation rates and sediment geochemistry. It is also much more likely to be size dependent than other sediment-mixing mechanisms, such as conveyor-belt feeding, and may also explain some subsurface maxima observed in sediment chemical profiles. We examined the mechanisms behind downward particle transport in Boston Harbor. Laboratory observations …

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Adult Macrofauna Effects On Capitella Sp. I Larval Settlement: A Laboratory Flume Study, Paul V. R. Snelgrove, Judith P. Grassle, Cheryl Ann Zimmer Jan 2001

Adult Macrofauna Effects On Capitella Sp. I Larval Settlement: A Laboratory Flume Study, Paul V. R. Snelgrove, Judith P. Grassle, Cheryl Ann Zimmer

Journal of Marine Research

The opportunistic, deposit-feeding polychaete Capitella sp. I is the overwhelming numerical dominant in disturbed and enriched sediments and rarely co-occurs in appreciable numbers with other abundant mud-dwelling macrofauna. Rapid colonization and population increase in organicrich sediments is typically followed by subsequent sharp decline. The mechanistic basis for these characteristics was explored in flume-flow experiments that tested whether settling Capitella sp. I larvae avoid sediments inhabited by macrofaunal adults or sediments reworked by them. The first set of experiments consisted of four treatments: conspecific adults or no adults in reworked or non-reworked sediment. Capitella sp. I settlement was significantly altered (depressed) …

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Geostrophy Via Potential Vorticity Inversion In The Yucatan Channel, J. Ochoa, J. Sheinbaum, A. Badan, J. Candela, D. Wilson Jan 2001

Geostrophy Via Potential Vorticity Inversion In The Yucatan Channel, J. Ochoa, J. Sheinbaum, A. Badan, J. Candela, D. Wilson

Journal of Marine Research

It has become common practice to measure ocean current velocities together with the hydrography by lowering an ADCP on typical CTD casts. The velocities and densities thus observed are considered to consist mostly of a background contribution in geostrophic balance, plus internal waves and tides. A method to infer the geostrophic component by inverting the linearized potential vorticity (Pv) provides plausible geostrophic density and velocity distributions. The method extracts the geostrophic balance closest to the measurements by minimizing the energy involved in the difference, supposed to consist of Pv-free anomalies. The boundary conditions and the …

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Diffusion In A Lattice-Automaton Model Of Bioturbation By Small Deposit Feeders, Bernard P. Boudreau, Jae Choi, Filip Meysman, Fréderique François-Carcaillet Jan 2001

Diffusion In A Lattice-Automaton Model Of Bioturbation By Small Deposit Feeders, Bernard P. Boudreau, Jae Choi, Filip Meysman, Fréderique François-Carcaillet

Journal of Marine Research

The mixing of 210Pb and tagged particles is examined in a lattice-automaton model for bioturbation containing small deposit feeders. The values of the biodiffusion coefficient, DB, calculated using typical biological parameter values, i.e., size, abundance, feeding and locomotion rates, are similar to those expected from marine sediments of a given sedimentation rate. Most biological parameters appear to exert primarily linear effects on DB values, while most nonlinearities seem to be model artifacts or failures of the assumptions in the basic DB model. The model highlights the importance of ingestion-egestion, over simple particle displacement, as an …

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Early Diagenesis Of Calcium Carbonate In Long Island Sound Sediments: Benthic Fluxes Of Ca2+ And Minor Elements During Seasonal Periods Of Net Dissolution, Mark A. Green, Robert C. Aller Jan 2001

Early Diagenesis Of Calcium Carbonate In Long Island Sound Sediments: Benthic Fluxes Of Ca2+ And Minor Elements During Seasonal Periods Of Net Dissolution, Mark A. Green, Robert C. Aller

Journal of Marine Research

The present study confirms the quantitative significance of carbonate dissolution for associated major and minor element solute fluxes in shelf deposits of temperate regions. Multiple measurement techniques all demonstrate that net dissolution of CaCO3 dominates during winter in Long Island Sound sediments and results in large fluxes of Ca2+, Sr2+, and F- out of the seafloor. Ca2+ fluxes averaged from 4 independent methods range from ~5 to ~13 mmol m-2 d-1 with highest flux occurring when surface deposits are most undersaturated with respect to common biogenic carbonates. A significant proportion of …

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The Stability Of An Npz Model Subject To Realistic Levels Of Vertical Mixing, Christopher A. Edwards, Thomas A. Powell, Harold P. Batchelder Jan 2000

The Stability Of An Npz Model Subject To Realistic Levels Of Vertical Mixing, Christopher A. Edwards, Thomas A. Powell, Harold P. Batchelder

Journal of Marine Research

The linear stability of a vertically-distributed, Nutrient-Phytoplankton-Zooplankton (NPZ) ocean ecosystem model is analyzed to understand how vertical mixing influences biological dynamics. In the absence of vertical diffusion, the model generally exhibits both stable fixed point and limit cycle behavior, depending on the depth and choice of parameters. Diffusion couples the dynamics of nearby levels and can induce stable profiles as well as oscillatory dynamical trajectories that become vertically phase-locked for large mixing levels. Calculations of the Lyapunov exponent reveal that vertical diffusion can drive this model into a chaotic state, though this occurs only for levels of diffusion …

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Circulation And Volume Flux Of The North Atlantic Using Synoptic Hydrographic Data In A Bernoulli Inverse, Stuart A. Cunningham Jan 2000

Circulation And Volume Flux Of The North Atlantic Using Synoptic Hydrographic Data In A Bernoulli Inverse, Stuart A. Cunningham

Journal of Marine Research

A new formulation of the Bernoulli inverse is used to determine the circulation and flux of the North Atlantic from synoptic CTD observations. The inverse assumes that the compressible Bernoulli function, modified potential temperature and salinity are conserved on streamlines in steady, geostrophic, hydrostatic, mass and density conserving flow. Crossings between CTD stations in the distribution of modified potential temperature versus salinity define a set of streamlines. The Bernoulli function is conserved along streamlines and the difference in the Bernoulli function at each crossing is related to the contribution of the unknown sea-surface height (SSH) to the Bernoulli function. These …

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Generation Of Strong Mesoscale Eddies By Weak Ocean Gyres, Michael A. Spall Jan 2000

Generation Of Strong Mesoscale Eddies By Weak Ocean Gyres, Michael A. Spall

Journal of Marine Research

The generation of strong mesoscale variability through instability of the large-scale circulation in the interior of oceanic gyres is addressed. While previous studies have shown that eddies generated from weakly sheared zonal flows are generally weak, the present results demonstrate that weakly sheared meridional flows typical of wind-forced gyres can generate very strong mesoscale variability. Meridional flows are effective at generating strong eddies because the reduced influence of the planetary vorticity gradient allows the potential energy stored in the zonal potential vorticity gradient to be converted to eddy kinetic energy. A simple scaling theory based on a balance between turbulent …

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The Linkage Between Upper Circumpolar Deep Water (Ucdw) And Phytoplankton Assemblages On The West Antarctic Peninsula Continental Shelf, Barbara B. Prézelin, Eileen E. Hofmann, Claudia Mengelt, John H. Klinck Jan 2000

The Linkage Between Upper Circumpolar Deep Water (Ucdw) And Phytoplankton Assemblages On The West Antarctic Peninsula Continental Shelf, Barbara B. Prézelin, Eileen E. Hofmann, Claudia Mengelt, John H. Klinck

Journal of Marine Research

Intrusion of Upper Circumpolar Deep Water (UCDW), which was derived from the Antarctic Circumpolar Current (ACC), onto the western Antarctic Peninsula (WAP) shelf region in January 1993 provided a reservoir of nutrient-rich, warmer water below 150 m that subsequently upwelled into the upper water column. Four sites, at which topographically-induced upwelling of UCDW occurred, were identified in a 50 km by 400 km band along the outer WAP continental shelf. One additional site at which wind-driven upwelling occurred was also identified. Diatom-dominated phytoplankton assemblages were always associated with a topographically-induced upwelling site. Such phytoplankton communities were not detected at any …

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On The Influence Of Bottom Topography And The Deep Western Boundary Current On Gulf Stream Separation, Claire E. Tansley, David P. Marshall Jan 2000

On The Influence Of Bottom Topography And The Deep Western Boundary Current On Gulf Stream Separation, Claire E. Tansley, David P. Marshall

Journal of Marine Research

The Gulf Stream separates abruptly from the North American coastline at Cape Hatteras. The absence of significant seasonal and interannual variability in the separation point, compared with that of other separating boundary currents, suggests that Gulf Stream separation is locally controlled. In this paper we consider the possible influence of bottom topography and the Deep Western Boundary Current (DWBC), which descends underneath the Gulf Stream at Cape Hatteras. The path of the DWBC is strongly constrained by bottom topography. At Cape Hatteras, the continental shelf widens and the DWBC is forced to swing offshore and pass beneath the Gulf Stream. …

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Circulation And Water Masses Of The Southwest Pacific: Woce Section P11, Papua New Guinea To Tasmania, Serguei Sokolov, Stephen Rintoul Jan 2000

Circulation And Water Masses Of The Southwest Pacific: Woce Section P11, Papua New Guinea To Tasmania, Serguei Sokolov, Stephen Rintoul

Journal of Marine Research

The circulation near the western boundary of the South Pacific is described on the basis of water properties and geostrophic velocities measured on a meridional section along 155E through the East Australian and Coral Basins. The section was occupied in winter 1993 as part of the World Ocean Circulation Experiment (WOCE, Section P11S). The primary objective of P11 was to quantify the zonal flows entering and leaving the western boundary of the basin. The primary inflow to the Tasman and Coral seas is supplied by the South Equatorial Current (SEC), which crosses the P11 section as a wide band of …

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Emergence Of Modons From Collapsing Vortex Structures On The Β-Plane, Z. Kizner, D. Berson Jan 2000

Emergence Of Modons From Collapsing Vortex Structures On The Β-Plane, Z. Kizner, D. Berson

Journal of Marine Research

The evolution of unstable barotropic vortices is studied numerically. Exact solutions to the equation of potential vorticity conservation under the "rigid lid" condition, as well as nonsteady-state configurations, are set as initial states in the evolutionary experiments. The examined "shielded modon" structures usually collapse within one to several synoptic periods and radiate vortex pairs propagating westward and eastward. The latter are shown to be modons of Larichev and Reznik. The westward dipoles are identified as "nonlocal modons," that is, vortical cores of stationary nonlinear Rossby waves. In the case of standing Stern modons, some small initial perturbations induce slow westward …

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