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Biological oceanography

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Multiple Thermoclines Are Barriers To Vertical Exchange In The Subarctic Pacific During Super, May 1984, K. L. Denman, A. E. Gargett Jan 1988

Multiple Thermoclines Are Barriers To Vertical Exchange In The Subarctic Pacific During Super, May 1984, K. L. Denman, A. E. Gargett

Journal of Marine Research

As part of the Subarctic Pacific Ecosystem Research program, we made observations of upper ocean physical and biological properties at 50N; 145W during 12–21 May 1984 from a drifting buoy, instrumented with a thermistor chain and meteorological sensors; a CTD/rosette bottle profiler; a shipboard solar radiometer; and a microstructure profiler equipped with a fast response thermistor and two airfoil velocity probes. At that time, the ocean above the seasonal thermocline was divided by a shallow thermocline step (∼0.5°C) into two layers with different turbulence characteristics and dynamics. The surface layer thermal structure (even in wind speeds up to 14 m …

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Organic Geochemistry Of Particulate Matter In The Eastern Tropical North Pacific Ocean: Implications For Particle Dynamics, Stuart G. Wakeham, Elizabeth A. Canuel Jan 1988

Organic Geochemistry Of Particulate Matter In The Eastern Tropical North Pacific Ocean: Implications For Particle Dynamics, Stuart G. Wakeham, Elizabeth A. Canuel

Journal of Marine Research

Samples of marine particulate matter were collected in sediment traps and by in-situ filtration to depths of 1500 m during VERTEX II and III cruises in the eastern tropical North Pacific. Wax esters, triacylglycerols, fatty acids, sterols and steroidal ketones were analyzed in these samples to compare the compositions of organic matter associated with large sinking particulate aggregates sampled by sediment traps and with fine suspended material obtained by in-situ filtration. Distributions of specific compounds indicated that the organic chemical composition of large sinking particles and small suspended particles both in the euphotic zone and at mid-depth result from very …

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Phytoplankton Species Composition And Abundance In A Gulf Stream Warm Core Ring. Ii. Distributional Patterns, Richard W. Gould Jr., Greta A. Fryxell Jan 1988

Phytoplankton Species Composition And Abundance In A Gulf Stream Warm Core Ring. Ii. Distributional Patterns, Richard W. Gould Jr., Greta A. Fryxell

Journal of Marine Research

During the spring and summer of 1982, Gulf Stream warm core ring (WCR) 82B was sampled during four cruises from April to August to investigate phytoplankton distributional patterns. Discrete water samples from 28 stations were collected for identification and enumeration of phytoplankton. In April, when the water column was well mixed to 350 m, quantitative samples clustered by station when the 100 most frequently observed taxa were used as variables, indicating fairly unique assemblages at each station that were consistent with depth. Two transects across the ring in June showed a symmetrical diatom abundance maximum, dominated by Chaetoceros cf. vixvisibilis …

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The Coupling Of Wave Drift And Wind Velocity Profiles, John A. T. Bye Jan 1988

The Coupling Of Wave Drift And Wind Velocity Profiles, John A. T. Bye

Journal of Marine Research

The Stokes drift velocity profile due to Toba's equilibrium wave spectrum is shown to consist of a surface constant shear layer, an intermediate logarithmic layer and a deep exponentially decaying tail. On identifying the logarithmic layer with a wall boundary layer (which is justified a posteriori by showing that the major part of the energy dissipation by wave breaking occurs in the roughness sublayer), for a range of directionality (p) of the wave spectrum ½–2, Toba's constant (α) lies in the range 0.12–0.10 in good agreement with data. The roughness length for water (z0 …

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A Numerical Model Of Instabilities In The Florida Current, Douglas B. Boudra, Rainer Bleck, Friedrich Schott Jan 1988

A Numerical Model Of Instabilities In The Florida Current, Douglas B. Boudra, Rainer Bleck, Friedrich Schott

Journal of Marine Research

An isopycnic coordinate numerical model is configured as an infinitely long channel with the width and bottom topography of the Straits of Florida at 27N to investigate the possibility that Florida Current meanders are due to dynamical instabilities. One mass/flow configuration with which to initialize the model is developed primarily from theoretical considerations, a second from the analysis of ST ACS observations (Leaman et al., 1987). To ascertain the effect of the bottom topography, flat bottom experiments are first examined. The current is found to be baroclinically unstable in the classical sense (Eady, 1949) to perturbations with wavelengths greater …

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Influences Of Abiotic Factors On The Return, Ocean Abundance, And Maturity Of Sockeye Salmon (Oncorhynchus Nerka) In The Northern North Pacific Ocean, Shinn-Pyng Yeh Apr 1987

Influences Of Abiotic Factors On The Return, Ocean Abundance, And Maturity Of Sockeye Salmon (Oncorhynchus Nerka) In The Northern North Pacific Ocean, Shinn-Pyng Yeh

Fisheries

The fluctuations in return, ocean abundance, and maturity of sockeye salmon (O. nerka) were examined and related to wind stress curl, sea suface temperature (SST), sea level pressure, and cloudiness, in the area between 40$\sp\circ$N-60$\sp\circ$N and 160$\sp\circ$E-140$\sp\circ$W. Historical records, during two periods, 1971-76 and 1955-86, were the primary source of data. Spectral analysis of a 360-month period of mean wind stress curl during 1955-85 showed 3.1- and 5.3-year cycles. The 5.3-year cycle was correlated (r =.32 to.44, P $<$.10) with the return of Bristol Bay sockeye salmon mostly at 0- (the year of spawning migration) and 1-year lag (the first year of lake residence). The relative ocean abundance of sockeye salmon in the northwestern Northern Pacific during 1971-76 was lowest during the three periods: 1961-70, 1971-76, and 1977-85. Mature Kamchatka sockeye salmon were 24% more abundant than mature Bristol Bay sockeye salmon during 1971-76. A significant relationship was found between the May-June mean SST and abundance of sockeye salmon (r =.56 to.66, P $<$.01) during 1961-85. In the northern North Pacific, the SST was positively (r =.73 to.86, P $<$.001) related with the gonad weight of sockeye salmon. The results indicated a close relation between the return, ocean abundance, and maturity of sockeye salmon and most of the abiotic factors.

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The Paradox Of Pelagic Food Webs On The Bering-Chukchi Continental Shelf, Alan M. Springer Apr 1987

The Paradox Of Pelagic Food Webs On The Bering-Chukchi Continental Shelf, Alan M. Springer

Marine Biology

Prolific primary production and spectacular populations of marine birds and mammals in the northern Bering Sea were for many years considered to be a paradox of an environment that should have had low production, as is typical of shallow continental shelves elsewhere. However, a "river" of oceanic water, Anadyr Water, originating along the continental slope of the Bering Sea carries a perpetual supply of nutrients and biota onto this northern shelf that transforms part of the region into one that is extremely productive at all trophic levels. Diatoms grow profusely throughout the ice-free season and, together with oceanic zooplankton advected …

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The Role Of The Higher Shelf Modes In Coastal Hydraulics, Roger L. Hughes Jan 1987

The Role Of The Higher Shelf Modes In Coastal Hydraulics, Roger L. Hughes

Journal of Marine Research

A simple barotropic model is used to establish the basic nature of the hydraulics of the various shelf modes in coastal flows. It shows that there is a major difference in behavior between flows with an even number of subcritical modes and those with an odd number of subcritical modes. It is suggested that a poleward flowing western boundary current exhibiting an odd number of subcritical shelf modes loses contact with the coast at that latitude at which the flow becomes critical to the next higher shelf mode. The East Australian Current and the East Cape Current are discussed as …

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Solutions For Internal Tidal Generation Over Coastal Topography, P. D. Craig Jan 1987

Solutions For Internal Tidal Generation Over Coastal Topography, P. D. Craig

Journal of Marine Research

Internal tides may be described by a hyperbolic equation which, for the case of constant buoyancy frequency, has constant coefficients. The equation is solved by using the characteristic geometry and characteristic functions to establish a set of linear algebraic equations in the modal amplitudes. The accuracy of the solutions can be assessed using energy considerations. The capability of the solution technique is demonstrated by simulating the barotropic generation of internal waves over linear topography, with emphasis on near-critical topography, when the solution exhibits high shears and discontinuous behavior at the critical slope. The structure of the waves is determined by …

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Daily And Seasonal Variations In The Spatial Distribution Of Zooplankton Populations In Relation To The Physical Structure In The Ligurian Sea Front, J. Boucher, F. Ibanez, L. Prieur Jan 1987

Daily And Seasonal Variations In The Spatial Distribution Of Zooplankton Populations In Relation To The Physical Structure In The Ligurian Sea Front, J. Boucher, F. Ibanez, L. Prieur

Journal of Marine Research

Results from five hydrographic and biological surveys at different seasons across the Ligurian Sea front, using horizontal continuous measurements and vertical profiles are presented. The vertical circulation across the front is described, and two divergences and one convergence are identified as permanent features from data. The key to find their location for each survey is given. The spatial patterns of 14 zooplankton taxa along the transect are established using variance analysis, principal component and correspondence analyses. The spatial distribution of each taxon is related to the physical structure, and the convection cells evidenced by the scheme appear as different biotopes. …

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Compositional Changes In Particulate Matter On The Iceland Rise, Through The Water Column, And At The Seafloor, M. J. Richardson, C. D. Hollister Jan 1987

Compositional Changes In Particulate Matter On The Iceland Rise, Through The Water Column, And At The Seafloor, M. J. Richardson, C. D. Hollister

Journal of Marine Research

Local resuspension of sediments along the Iceland Rise was substantiated by the collection in sediment traps of large particles whose source is clearly the seafloor. These resuspended components included benthic foraminifera, iron-oxide coated planktonic foraminifera, the glacial, subpolar assemblage planktonic foraminifera (N. pachyderma (sinistral)), and an increase in the volcanic glass and mineral grain/aggregate component with proximity to the seafloor.The horizontal flux of particulate matter in the near-bottom nepheloid layer through the region was ≃200 kg/s. The apparent vertical flux of sediment calculated from sediment traps at 500 m above bottom (mab) was an order of magnitude less than …

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Observations On The Vertical Structure Of Tidal And Inertial Currents In The Central North Sea, L. R. M. Maas, J. J. M. Van Haren Jan 1987

Observations On The Vertical Structure Of Tidal And Inertial Currents In The Central North Sea, L. R. M. Maas, J. J. M. Van Haren

Journal of Marine Research

Tidal and inertial current ellipses, measured at several locations and depths in the central North Sea during a number of monthly periods in 1980, 1981 and 1982, are decomposed into counterrotating, circular components to which Ekman dynamics are applied to determine Ekman layer depths and vertical phase differences, from which are inferred overall values of the eddy viscosity and drag coefficient. Stratification effects produce an additional vertical phase shift of the anticyclonic rotary component, indicative of an inverse proportionality of the eddy viscosity to the vertical density gradient. From the time variations of the Ekman layer depths of the semidiurnal …

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Subsurface Chlorophyll Maximum And Hydrodynamics Of The Water Column, T. Vandevelde, L. Legendre, J. C. Therriault, S. Demers, A. Bah Jan 1987

Subsurface Chlorophyll Maximum And Hydrodynamics Of The Water Column, T. Vandevelde, L. Legendre, J. C. Therriault, S. Demers, A. Bah

Journal of Marine Research

The vertical distributions of chlorophyll a (in vivo fluorescence) and hydrodynamic properties were monitored in the Gulf of St. Lawrence (Canada) from 6 to 10 August 1983, using an automatic yo-yo profiling system and a chain of 4 current meters. Spectral analyses of temperature and in vivo fluorescence series showed that dominant frequencies were associated with internal waves (∼16 h inertial frequency). A subsurface chlorophyll maximum was continuously observed in the lower part of the 20 m thick photic layer, at a depth corresponding with maximum vertical stability of the water column, just above the nutricline.The depth of maximum …

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Methane Anomalies Over Tag Hydrothermal Field On Mid Atlantic Ridge, J. L. Charlou, P. Rona, H. Bougault Jan 1987

Methane Anomalies Over Tag Hydrothermal Field On Mid Atlantic Ridge, J. L. Charlou, P. Rona, H. Bougault

Journal of Marine Research

Black smoker type hydrothermal venting was discovered in July 1985 at the TAG hydrothermal field in the rift valley of the Mid Atlantic Ridge near 26N. We present here, the first methane profiles in the seawater column over this black smoker along with methane profiles away from the black smokers for comparison. The CH4 plume, spreading over 400 m above the seafloor, shows a maximum concentration of 105 nl/l at 3450 m (238 m above the bottom), correlated with a positive temperature anomaly (0.02°C). CH4 concentrations up to 2422 nl/l, correlated with a huge positive increase of in …

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The Dynamics Of Near-Bed Seston Flux And Suspension-Feeding Benthos, D. K. Muschenheim Jan 1987

The Dynamics Of Near-Bed Seston Flux And Suspension-Feeding Benthos, D. K. Muschenheim

Journal of Marine Research

Benthic suspension feeders depend on the fluid medium for their supply of edible particles. The horizontal flux of organic seston is a function of the interaction of particles of varying densities with the near-bed velocity field. Analytical and numerical models of this process predict that the shape of the flux profile varies with flow rate, bottom roughness and particle settling velocity. Bulk horizontal particle flux may either decrease or increase with height above the bed. Flume experiments with natural sediments from Eastern Passage, Nova Scotia confirmed the trends predicted by the model. In a complex suspension, denser, inorganic particles have …

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Penetrating Outflows And The Dam-Breaking Problem, Doron Nof Jan 1987

Penetrating Outflows And The Dam-Breaking Problem, Doron Nof

Journal of Marine Research

A new analytical method for computing the speed at which the nose of a rotating intrusion advances along a straight coast is proposed. The nonlinear model includes two active layers; the width of the basin in which the intrusion advances is taken to be finite. Friction is assumed to be small but the motions near the leading edge are not constrained to be quasi-geostrophic.In contrast to previous models (Stern et al., 1982; Kubokawa and Hanawa, 1984a, b) which rely on the assumption that the current head behaves like a long wave and the flow is hydrostatic, the propagation rate …

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A Model For The Inertial Recirculation Of A Gyre, Richard J. Greatbatch Jan 1987

A Model For The Inertial Recirculation Of A Gyre, Richard J. Greatbatch

Journal of Marine Research

This paper considers the "time-mean" circulation of wind-driven ocean gyres in the limit referred to as "inertial" or "almost-free." In this limit, potential vorticity is conserved following the flow with sources and sinks of potential vorticity balancing in an integral sense around the gyre. Approximate analytic solutions are obtained for a continuously stratified quasi-geostrophic ocean by neglecting the relative vorticity in the gyre interiors. The solutions have features similar to those found in the western part of ocean basins both in eddy-resolving numerical models and in observations. In particular, a deep westward recirculation, such as proposed by Worthington (1976) for …

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A Model For The Dynamics Of Nutrients And Oxygen In The Baltic Proper, Anders Stigebrandt, Fredrik Wulff Jan 1987

A Model For The Dynamics Of Nutrients And Oxygen In The Baltic Proper, Anders Stigebrandt, Fredrik Wulff

Journal of Marine Research

A horizontally integrated, time-dependent physical-biogeochemical model of high vertical resolution has been developed for the Baltic Sea proper. A seasonal pycnocline model computes the physical state of the mixed surface layer. Below this is an advective-diffusive model. The vertical advection is caused by a time-dependent, entraining bottom current which transports dense seawater into the system. The vertical distributions of volumes and sediment areas are accounted for by the use of the hypsographic function of the system. The chemical/biological processes controlling the distributions of nitrogen and oxygen are modelled as follows: Primary production is controlled by light, temperature, nutrients and density …

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The Influence Of Planetary Rotation On Oceanic Double-Diffusive Fluxes, Dan Kelley Jan 1987

The Influence Of Planetary Rotation On Oceanic Double-Diffusive Fluxes, Dan Kelley

Journal of Marine Research

Does planetary rotation inhibit double-diffusive fluxes of heat and salt in oceanic thermohaline staircases? The Taylor number Ta, which measures the effect of planetary rotation on convection, is O(1) for laboratory diffusive staircases O(104) for oceanic diffusive staircases. Does this mean that laboratory-based flux laws are inapplicable in the ocean? Lacking flux measurements in double-diffusive systems, these questions are addressed using an analogy between double-diffusive convection and thermal convection. It is shown that Ta is an inappropriate parameter, and that rotating thermal fluxes collapse onto a simple curve when a new Taylor number Tano-slip …

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Temporal Variability And The Relationship Between Benthic Meiofaunal And Microbial Populations Of A Natural Coastal Petroleum Seep, Paul A. Montagna, James E. Bauer, Jon Toal, Dane Hardin, Robert B. Spies Jan 1987

Temporal Variability And The Relationship Between Benthic Meiofaunal And Microbial Populations Of A Natural Coastal Petroleum Seep, Paul A. Montagna, James E. Bauer, Jon Toal, Dane Hardin, Robert B. Spies

Journal of Marine Research

Previous studies of the Isla Vista petroleum seep in the Santa Barbara Channel found much higher abundances of macrofauna and concentrations of adenosine triphosphate (ATP) in sediments near petroleum seepage compared to those from nonseep areas. To further assess the possible effect of petroleum on organisms at the base of benthic food webs, population abundances of meiobenthos and their suspected microbial food (bacteria and diatoms) were measured biweekly for one year at three stations with differing petroleum exposure. Determinations of suspended particulate matter and the abundance and gut contents of juvenile fishes were also made at seep and nonseep stations. …

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Continental-Shelf-Scale Model Of The Leeuwin Current, R. O. R. Y. Thompson Jan 1987

Continental-Shelf-Scale Model Of The Leeuwin Current, R. O. R. Y. Thompson

Journal of Marine Research

A simple model is presented for the poleward eastern boundary current (the Leeuwin Current) off Western Australia. For continental-shelf length-scales and seasonal time-scales, the advective and time-derivative terms are small, and water flows onto the shelf until a sufficient cross-shelf pressure gradient is set up to push the same flux back. In a rotating system, the return flux takes place in a frictional (Ekman) layer at the bottom, and is synonymous with a near-bottom longshore current νB, from−CD|νB|νB = ∫O−H 1/ρ ∂p/∂y dz + u2 …

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Accurately Monitoring The Florida Current With Motionally Induced Voltages, Peter Spain, Thomas B. Sanford Jan 1987

Accurately Monitoring The Florida Current With Motionally Induced Voltages, Peter Spain, Thomas B. Sanford

Journal of Marine Research

A new experimental technique for appraising how accurately submarine-cable (subcable) voltages monitor oceanic volume transport is presented and then used to study voltages induced by the northern Florida Current. Until recently, subcable voltages have been largely dismissed as an oceanographic tool because their interpretation can be ambiguous. They depend upon the transport field, the electrical conductance of the environment, and the mutual spatial distribution of these two quantities. To examine how these three factors affect subcable voltages at a particular site, we combine data from two different velocity profilers: XCP and PEGASUS. These instruments provide vertical profiles of velocity, temperature, …

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Variability Of Diatom Species Populations: From Days To Years, Sargun A. Tont Jan 1987

Variability Of Diatom Species Populations: From Days To Years, Sargun A. Tont

Journal of Marine Research

Based on over 300,000 individual measurements, temporal and spatial variations in diatom abundances and related atmospheric and oceanic variables have been investigated for two locations near the coast of southern California. Time scale of periods investigated ranged from days to 10 years; variability over centuries can be reconstructed from climate records. The results of principal component analysis based on weekly averages indicated that eigenvectors at Scripps and Pt. Hueneme piers, nearly 200 km apart, were similar; removal of seasonal cycles (by calculating anomalies) did not significantly alter these eigenvectors. Principal components derived from matrices based on weekly averages of 20, …

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Components Of The Zooplankton Production Cycle In The Temperate Ocean, Cabell S. Davis Jan 1987

Components Of The Zooplankton Production Cycle In The Temperate Ocean, Cabell S. Davis

Journal of Marine Research

Components of the zooplankton production cycle (assimilation, respiration, and predation) on Georges Bank were analyzed using three models of increasing complexity, i.e., total biomass (Riley, 1947), size-structure (Huntley and Boyd, 1984) and species population (Davis, 1984a). Other temperate marine areas with seasonal cycles in temperature similar to Georges Bank were identified and available data on zooplankton biomass and species cycles were found. For Georges Bank, the species level model, based on well-defined empirical relationships between temperature, development rate, and fecundity, revealed that highest production occurs by small animals during warmest months (e.g., September), when biomass is low. By contrast, the …

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Some Aspects Of The Oxygen-Deficient Conditions And Denitrification In The Arabian Sea, S. W. A. Naqvi Jan 1987

Some Aspects Of The Oxygen-Deficient Conditions And Denitrification In The Arabian Sea, S. W. A. Naqvi

Journal of Marine Research

Utilizing a fairly large amount of recently collected data, some outstanding questions concerning the Arabian Sea denitrification problem are addressed. The true levels of dissolved oxygen, determined colorimetrically, are about an order of magnitude lower than those reported previously from the oxygen minimum zone. Lateral advection of waters from south into the oxygen-deficient layer is suggested by the presence of an intermediate oxygen maximum discernible even at very low oxygen levels. An unusual minimum in nitrate and a corresponding maximum in nitrite are observed occasionally within the depth range 700–1,200 m at several stations, generally located in the northeastern Arabian …

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On The Dynamics Of The California Current System, Julian P. Mccreary Jr., Pijush K. Kundu, Shenn-Yu Chao Jan 1987

On The Dynamics Of The California Current System, Julian P. Mccreary Jr., Pijush K. Kundu, Shenn-Yu Chao

Journal of Marine Research

The dynamics of the California Current system are studied using two ocean models, one with a shelf and one without. Both models are viscid and linearized about a background density field Pb(Z), Solutions are forced by steady and annually periodic winds with and without curl, and by an idealization of the observed wind field off California. Solutions forced by a steady, equatorward, curl-free wind τy all have an equatorward surface coastal jet and a poleward undercurrent. Due to the β-effect and horizontal mixing, the circulation is not necessarily confined within a Rossby radius of …

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On The Energetics Of The Gulf Stream At 73w, T. Rossby Jan 1987

On The Energetics Of The Gulf Stream At 73w, T. Rossby

Journal of Marine Research

From September 1980 through May 1983 a series of nineteen sections of velocity profiles were obtained across the Gulf Stream 200 km northeast of Cape Hatteras. By decomposing the velocity and temperature observations into mean and fluctuating fields in two coordinate systems, geographic (or Eulerian) and 'stream' coordinates, it is shown that at least ⅔ of the eddy kinetic and potential energy is caused by the meandering of a well defined baroclinic front with a structure that is nearly independent of space and time. It is also shown that more than 95% of the kinetic energy of the front can …

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Single-Particle Dispersion, Lagrangian Structure Function And Lagrangian Energy Spectrum In Two-Dimensional Incompressible Turbulence, Armando Babiano, Claude Basdevant, Pascal Le Roy, Robert Sadourny Jan 1987

Single-Particle Dispersion, Lagrangian Structure Function And Lagrangian Energy Spectrum In Two-Dimensional Incompressible Turbulence, Armando Babiano, Claude Basdevant, Pascal Le Roy, Robert Sadourny

Journal of Marine Research

The single-particle dispersion, Lagrangian structure functions and Lagrangian energy spectra characteristic of two-dimensional incompressible turbulent flows are investigated theoretically and numerically. The domain of validity of the classical asymptotic estimates is extended; it is shown in particular that the asymptotic behavior of the single-particle dispersion at small times remains valid throughout the whole self-similar range when the Lagrangian energy spectrum is steeper than ω−1. Straightforward estimates of the Lagrangian integral time scale TL and the diffusion coefficient at large times K, based on energy and enstrophy, are proposed; to some extent, they remain valid locally, which …

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Lagrangian Properties Of Eddy Fields In The Northern North Atlantic As Deduced From Satellite-Tracked Buoys, W. Krauss, C. W. Böning Jan 1987

Lagrangian Properties Of Eddy Fields In The Northern North Atlantic As Deduced From Satellite-Tracked Buoys, W. Krauss, C. W. Böning

Journal of Marine Research

One hundred and thirteen satellite-tracked buoys have been used during their first 5 months after deployment in order to calculate Lagrangian statistics of the eddy field in the northern North Atlantic between Newfoundland and the Canary basin. r.m.s. velocities are isotropic and increase from southeast to northwest. Lagrangian integral time scales, derived both from correlation function and from dispersion, are slightly anisotropic and decrease from the subtropics toward the North Atlantic Current. Time scale is inversely proportional to the r.m.s. velocity of the eddies. Eddy length scale is approximately constant in the North Atlantic. Dispersion is in good agreement with …

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A Least-Squares Fit Of The Advective-Diffusive Equations To Levitus Atlas Data, Nelson G. Hogg Jan 1987

A Least-Squares Fit Of The Advective-Diffusive Equations To Levitus Atlas Data, Nelson G. Hogg

Journal of Marine Research

The distributions of temperature, oxygen and potential vorticity on two isopycnals and the geostrophic shear between them are used to obtain the flow fields and diffusivities through a least-squares inversion of the steady state, advective-diffusive equations. The source of the data is the Levitus Atlas, and the two isopycnals are located in a 24° square centered on the Mediterranean Water tongue in the eastern North Atlantic. One isopycnal is in the thermocline and the other beneath so chosen to be near the level of maximum salinity and temperature anomaly.Although tracer distributions on the two levels are similar, the inversion suggests …

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