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Similarity Solutions Of The Thermocline Equations, Rick Salmon, Rainer Hollerbach

Journal of Marine Research

We apply symmetry group methods to find the group of transformations of the dependent and independent variables that leave the thermocline equations unchanged, These transformations lead to an optimal subset of sixteen forms of similarity solution, Each form obeys an equation with one fewer dependent variable than the original thermocline equations. Previously obtained similarity solutions, which are based solely upon scaling symmetries, are special cases of just three of these forms. Two of the sixteen forms lead to linear, two-dimensional, advection-diffusion equations for the temperature, Bernoulli functional or potential vorticity. Simple exact solutions contain "internal boundary layers" that resemble the …

The Effects Of Flow Disturbance By An Oceanic Island, Karen J. Heywood, Eric D. Barton, John H. Simpson

Journal of Marine Research

We present CTD and ADCP surveys around the Indian Ocean coral atolls of Aldabra (46°20′E, 9°25′S) and Cosmoledo (47°30E, 9°45′S) during April–July 1987. These isolated, steep-sided islands situated in deep (4000 m) water in the South Equatorial Current provide examples of flow disturbance which are compared to laboratory studies of eddy generation by a circular cylinder in a channel. For sufficiently strong and steady flows, a doming of the isopycnals is observed in the lee of the islands. The sea-surface temperature decreases and the salinity increases as cool, saline water is mixed from below. Just as in the case of …

Δ14c Balance For The Gulf Of Maine, Long Island Sound And The Northern Middle Atlantic Bight: Evidence For The Extent Of The Antarctic Intermediate Water Contribution, N. Tanaka, M. C. Monaghan, K. K. Turekian

Journal of Marine Research

The radiocarbon signatures of the western Sargasso Sea and the atmosphere as a function of time over the past 200 years are known. These can be combined with seawater dissolved inorganic carbon (DIC) radiocarbon data from the Gulf of Maine and the northern Middle Atlantic Bight (MAB), including Long Island Sound (LIS), for 1983 and pre-1955 shell analyses for radiocarbon, to set the amount of Antarctic Intermediate Water (AAIW) required to balance the ¹⁴C budget in the northern MAB. Approximately 40% of the water entering the Middle Atlantic Bight from the north must be AAIW, the other 60% being …

Barotropic Variability In The Presence Of An Ocean Gyre, Richard J. Greatbatch, Jin Li

Journal of Marine Research

We describe results from some idealized numerical calculations in which we examine the influence of a barotropically stable mean flow on wind-driven variability in a flat-bottomed barotropic vorticity equation model. The mean flow has features in common with the vertically integrated time-mean circulation found in eddy-resolving models with a Sverdrup interior, western boundary current and inertial recirculation region. We integrate the equations of motion linearized about this flow and driven by oscillating wind forcing and compare the results with those obtained when the mean state is one of rest. We find that the presence of a mean flow leads to …

The North Atlantic Current And Subarctic Intermediate Water, Michel Arhan

Journal of Marine Research

The region where the North Atlantic Current crosses the ocean around 50N is studied from a watermass point of view and using the ventilated thermocline model of Luyten et al. (1983). Both approaches focus on the part played by the Subarctic Intermediate Water which, owing to its pronounced thermohaline anomalies stands out as a clue to the complex oceanic circulation in this area. Vertical mixing of this watermass with the overlying North Atlantic Central Water creates a fresher variety of central water found between the two major branches of the North Atlantic Current. Using the ventilated thermocline model several …

Optical Efficiency Factors Of Free-Living Marine Bacteria: Influence Of Bacterioplankton Upon The Optical Properties And Particulate Organic Carbon In Oceanic Waters, André Morel, Yu-Hwan Ahn

Journal of Marine Research

Free-living coccoid bacteria have been repeatedly isolated from the Mediterranean Sea and then cultured in detritus- and predator-free seawater, either unenriched or slightly nutrient-supplemented. The modal diameter of these cultured cells was in the 0.5 to 1 μm range. The spectral values (within the 400–750 nm λ-range) of absorption, total scattering and backscattering have been determined, together with cell enumeration, size distribution and C–N content. Because of their smallness, bacteria are amenable to simplified theoretical expressions providing their optical efficiency factors. Experimental data are in remarkable quantitative agreement with theoretical predictions. As expected, scattering is wavelength (λ⁻²) …

A Mechanistic View Of The Particulate Biodiffusion Coefficient: Step Lengths, Rest Periods And Transport Directions, R. A. Wheatcroft, P. A. Jumars, C. R. Smith, A. R. M. Nowell

Journal of Marine Research

We link specific mechanisms of biogenous sediment mixing with the commonly used bioturbation coefficient (D_b) that describes their bulk effects. Using an isotropic, stationary, unbiased random walk model we mechanistically decompose the particulate bioturbation coefficient into the fundamental dimensions of length and time. The result shows that D_b depends directly on the square of the distance particles are moved (step length) and inversely on the elapsed time between movements (rest period). This new decomposition in terms of explicit mechanisms (i.e., animal activities), leads to scaling arguments that large, deposit feeding animals will in nearly all cases …

On The Influence Of The Continental Slope On The Western Boundary Layer: The Enhanced Transport And Recirculation, Zhengyu Liu

Journal of Marine Research

Quasi-geostrophic theory is used to study the effect of a continental slope on the Western Boundary Layer. The compression of the vortex tubes by the slope results in a strong northward boundary current called the Continental Slope Boundary Current (hereafter CSBC). On the β-plane, for a reasonably high slope, we find a strong barotropic recirculation which enhances the total transport of the Western Boundary Current significantly. The two-layer model further shows that the CSBC is trapped in the lower layer. In oceans with very deep lower layers, the CSBC transport increases dramatically. Consequently, even for a very weak lower layer …

Hydrography And Circulation Off The West Coast Of India During The Southwest Monsoon 1987, S. R. Shetye, A. D. Gouveia, S. S. C. Shenoi, D. Sundar, G. S. Michael, A. M. Almeida, K. Santanam

Journal of Marine Research

During June–August 1987 thirteen hydrographic sections, each approximately perpendicular to the coast, covered the coastal region off western India. The southernmost section showed occurrence of upwelling, the nearshore surface temperature being about 2.5°C lower than farther offshore. There was a shallow (approximately 75 to 100 m deep) equatorward surface current, below which there were signatures of downwelling indicative of a poleward undercurrent hugging the continental slope. T-S characteristics showed that the undercurrent carried low salinity water found in the southwestern Bay of Bengal. Conditions similar to those found at this section existed up to around 15N but the intensity of …

Early Diagenesis And Recycling Of Biogenic Debris At The Seafloor, Santa Monica Basin, California, Richard A. Jahnke

Journal of Marine Research

Seafloor recycling of organic materials in Santa Monica Basin, California was examined through in situ benthic chamber experiments, shipboard whole-core incubations and pore water studies. Mass balance calculations indicate that the data are internally consistent and that the estimated benthic exchange rates compare well with those derived from deep, moored conical sediment traps and hydrographic modeling. Pore water and benthic flux observations indicate that the metabolizable organic matter at the seafloor must be composed of at least two fractions of very different reactivities. While the majority of reactive organic compounds degrade quickly, with a half-life of <6.5 years, ¼ of the total metabolizable organic matter appears to react more slowly, with a half-life on the order of 1700 years. Down-core changes in pore water sulfate and titration alkalinity are not explained by stoichiometric models of organic matter diagenesis and suggest that reactions not considered previously must be influencing the pore water concentrations. Measured recycling and burial rates indicate that 43% of the organic carbon reaching the basin seafloor is permanently buried. The results for Santa Monica Basin are compared to those reported for other California Borderland Basins that differ in sedimentation rate and bottom water oxygen content. Organic carbon burial rates for the Borderland Basins are strongly correlated with total organic carbon deposition rate and bulk sedimentation rate. No significant correlation is observed between carbon burial and bottom water oxygen, extent of oxic mineralization and sediment mixing. Thus, for the California Borderlands, it appears that carbon burial rates are primarily controlled by input rates and not by variations in preservation.

The Mixed-Layer Climatology In The Northwestern Part Of The North Pacific Subtropical Gyre And The Formation Area Of Subtropical Mode Wate, Toshio Suga, Kimio Hanawa

Journal of Marine Research

Climatological character of the mixed layer in the northwestern part of the subtropical North Pacific and the formation area of Subtropical Mode Water (STMW) are investigated using all available hydrographic data compiled by the Japan Oceanographic Data Center. Various monthly mean properties of the mixed layer averaged over 2° × 5° (lat. × lon.) rectangles are presented. In the heating season, the mixed layer is less thick throughout the region, while in the cooling season, a prominent thick mixed layer whose properties correspond with those of STMW evolves just off the Kuroshio both south and east of Japan. This probable …

The Evolution Of Salt Fingers In Inertial Wave Shear, Eric Kunze

Journal of Marine Research

Shadowgraph profiles collected in the thermohaline staircase east of Barbados reveal nearly-horizontal banding—unlike the vertical banding that has been observed in other fingering-favorable parts of the ocean. A plausible interpretation of this optical microstructure is that vertical shear is tilting over fingers. This paper presents a model for shear-tilting of salt fingers. The Ri = 6 inertial wave shears observed in C-SALT would tilt over and damp out square planform (k_x = k_y) fingers so rapidly that they could not produce significant fluxes. Vertical sheets aligned with the shear (k_y = 0) would behave …

A Nitrogen-Based Model Of Plankton Dynamics In The Oceanic Mixed Layer, M. J. R. Fasham, H. W. Ducklow, S. M. Mckelvie

Journal of Marine Research

As a first step toward the development of coupled, basin scale models of ocean circulation and biogeochemical cycling, we present a model of the annual cycles of plankton dynamics and nitrogen cycling in the oceanic mixed layer. The model is easily modified and runs in FORTRAN on a personal computer. In our initial development and exploration of the model's behavior we have concentrated on modeling the annual cycle at Station "S" near Bermuda using seven compartments (Phytoplankton, Zooplankton, Bacteria, Nitrate, Ammonium, Dissolved organic nitrogen and Detritus). This choice of compartments and the attendant flows (fluxes or intercompartmental exchanges) permits a …

The Mesoscale Variability Of The Sea Surface Temperature: An Analytical And Numerical Mode, Patrice Klein, Bach Lien Hua

Journal of Marine Research

This study examines the emergence and evolution of a mesoscale sea surface temperature (SST) variability induced by a uniform and impulsive wind stress when an embedding quasigeostrophic (QG) flow is present. The SST variability which is triggered by the mixed-layer deepening closely resembles some characteristic properties of the QG flow, namely either the subsurface temperature or relative vorticity, depending on the amplitude of the deepening. The SST variance can have the same order of magnitude as the subsurface temperature variance. Within 10 days, the SST field, which is stirred only by the horizontal QG flow, displays a rapid spectral evolution …

Deep Western Boundary Current Variability At Cape Hatteras, Robert S. Pickart, D. Randolph Watts

Journal of Marine Research

Data from an array of inverted echo sounders and bottom current meters off Cape Hatteras, where the Gulf Stream and Deep Western Boundary Current (DWBC) cross each other, are analyzed to investigate the deep components of flow. While the mean flow is to the southwest with the DWBC, the observed temporal variability is dominated by energetic 40 day topographic Rossby waves. By optimally weighting the individual deep current meter measurements, the deep flow is averaged across the wavelength of the 40 day wave, thereby reducing the wave signal and revealing variations of the spatially averaged DWBC. The DWBC fluctuations are …

Physical, Chemical And Biological Structure Of A Coastal Eddy Near Cape Mendocino, Thomas L. Hayward, Arnold W. Mantyla

Journal of Marine Research

We sampled mesoscale physical, chemical and biological structure in the coastal region of northern California in May, 1987. The circulation was dominated by an equatorward-flowing coastal jet and by a set of mesoscale eddies. High-velocity flow in the core of the coastal jet was composed of low-salinity, low-nutrient water, Cyclonic coastal eddies were observed near Cape Mendocino and Pt. Arena. The Cape Mendocino eddy is examined in detail. This eddy is a common feature which was present both before and after the spring transition, suggesting a relatively weak coupling between the eddy and the local wind field.The coastal circulation strongly …

Near-Inertial And Diurnal Motions In The Trajectories Of Mixed Layer Drifters, Pierre-Marie Poulain

Journal of Marine Research

We analyze the near-inertial/diurnal motions in the trajectories of surface mixed layer drifters in the California Current System between 19N and 36N. The observed near-inertial or diurnal oscillations are very intermittent in time and have a time scale of about 10 inertial periods. Using a simple slab model of wind-driven inertial currents, we show that their temporal variations are related to the fluctuations in the local wind stress field. Three events of strong (20 cm s⁻¹) near-inertial/diurnal motions are studied in detail. Two events at the diurnal frequency occur on the continental shelf. For the first, the observed …

Effects Of Large-Scale Topography On Abyssal Circulation, David N. Straub, Peter B. Rhines

Journal of Marine Research

Two models are employed to study the effect of topographically induced planetary islands (i.e. closed contours of potential vorticity) on the abyssal circulation of an ocean basin. The first is a steady state calculation using a 1½ layer model of the abyssal ocean forced by a uniform upwelling. Planetary geostrophic dynamics yield a characteristic equation in which the inverse potential vorticity serves as a streamfunction for the characteristic velocity field. Aside from warping the classic Stommel-Arons flow in the immediate vicinity of the planetary island, the topography introduces two new elements to the zonal flow west of the topography. The …

Some Features Of The Upwelling Off Oman, Alan J. Elliott, Graham Savidge

Journal of Marine Research

Hydrographic and ADCP data were collected in the coastal waters of Oman during the 1987 summer monsoon. The minimum surface temperatures, up to 5°C below ambient offshore values, were found close to the coast and in the vicinity of the Kuria Muria Islands. Strong surface gradients were observed near Ras al Hadd at the entrance to the Gulf of Oman where the geostrophic surface flow exceeded 1.0 m/s. The alongshore flux in the top 300 m of a region extending 100 km from the coast was estimated to be 10 × 10⁶ m³/s. Evidence for an offshore …

Meridional Variations Of The Springtime Phytoplankton Community In The Sargasso Sea, D. A. Siegel, R. Iturriaga, R. R. Bidigare, R. C. Smith, H. Pak, T. D. Dickey, J. Marra, K. S. Baker

Journal of Marine Research

Meridional distributions of particle, pigment, optical, chemical and physical in situ oceanographic properties, as well as satellite-sensed sea-surface temperature and color imagery, are used to investigate phytoplankton community distributions and their relation to the near-surface water masses of the S bnargasso Sea. 0-H3059 Measurements were made during April of 1985 along a 1200 km transect on 70W (from 24N to 35N). The seasonal evolution of subtropical Mode water (18° water) is shown to be the primary factor controlling the spatial distribution and evolution of the phytoplankton community in the northern Sargasso Sea (31 to 35N). The springtime near-surface restratification of …

Dissipative Dynamics Of Western Boundary Currents, Paola Cessi, R. Vance Condie, W. R. Young

Journal of Marine Research

We investigate the steady barotropic circulation patterns driven by inflow-outflow boundary conditions on a rectangular β-plane domain. An inertial jet enters the domain in the southwest corner and a broad eastward outflow is prescribed at the eastern boundary. On the western wall there is no mass flux and no slip.With weak viscosity, ν the western boundary jet ?overshoots? northward, beyond the latitude band of the eastern outflow. As the viscosity is reduced the length of this overshoot increases as ν^−2/3, before the jet gradually peels away from the western wall, plunges southward and eventually turns eastward. Away …

Covariability Of Dissolved Oxygen With Physical Processes In The Summertime Chesapeake Bay, Lawrence P. Sanford, Kevin G. Sellner, Denise L. Breitburg

Journal of Marine Research

Long, rapidly sampled time series measurements of dissolved oxygen, temperature, salinity, currents, winds, tides, and insolation were collected during the summer of 1987 across the mesohaline Chesapeake Bay. Analyses of the data show that short term variability of dissolved oxygen was both large and spatially heterogeneous. Time scales of variability ranged from the longest period fluctuations resolved (several days) to the sampling interval (several minutes). The largest variability was associated with large amplitude, wind and tide forced lateral internal oscillations of the pycnocline in the mainstem of the Bay. These resulted in advection of saline, hypoxic water from below the …

Inversions Of Observations Near The Azores Front, Grant R. Bigg

Journal of Marine Research

CTD data from Discovery Cruise 138 of late June, 1983 in the Madeira Abyssal Plain show a strong, but isolated, Mediterranean Water (MW) signal around 35N, 25W. This water mass gives rise to an anticyclonic eddy at its southward tip and, through double diffusive processes, to modification of the density field a few hundred meters below. Current estimates have been calculated from the cruise data using the Bernoulli inverse technique. Extensions of this inverse method, which take into account the depth dependence of dynamically informative density and potential vorticity functions, are developed to investigate the flow field and the consistency …

Estuarine Studies : An Activities Text For Maine Schools, Education Division - Department Of Marine Resources

Maine Collection

Estuarine Studies : An Activities Text for Maine Schools

Fisheries Education Unit #16 - Produced by The Education Division, Department of Marine Resources, State House Station 21, Augusta, Maine 04333-0021.

Revised 1990. Printed Under Appropriation No. 3140.3260.

On The Generation And Propagation Of Rossby Waves In An Ocean With A Zonally Shoaling Mixed Layer, M. S. Darby, A. J. Willmott

Journal of Marine Research

This paper presents the theory for freely propagating and forced Rossby waves in a continuously stratified ocean where the bouyancy frequency, N, varies with longitude and depth. In this study zonal variations in N occur because the climatological mixed layer depth, h, varies with longitude.With the assumption that changes in h occur on a length scale which is large compared to a horizontal wavelength the free modes on a β-plane are examined. It is found that realistic mixed layer depth changes can cause amplitude modulations, the largest amplitudes occurring where the mixed layer is shallowest. The requirement …

Recirculation And Separation Of Boundary Currents, Paola Cessi

Journal of Marine Research

An inertial multi-layer model of the recirculation gyres surrounding a separated boundary current is presented. The boundary current is defined to be separated when the upper layer thickness vanishes. The strong eastward flow found at the outcrop causes the circulation to extend to the bottom through baroclinic instability. In order to decrease the vertical shear responsible for the instability, the deep flow must also have maximum eastward velocity at the outcrop latitude. Thus the deep flow to the north of the outcrop (where no upper fluid is present) must move so as to keep velocity continuous. The eastward flowing deep …

Double-Diffusive Convection With Imposed Vertical Mass Flux, R. Krishnamurti, Y. Zhu

Journal of Marine Research

Vertical advection and double-diffusive convection are both processes affecting the stratification of the oceans. The effect of vertical advection on double-diffusive convection is investigated by considering the situation in which a horizontal layer of fluid has imposed upon it a destabilizing vertical temperature gradient, a stabilizing vertical salinity gradient and a uniform vertical mass flux. The effect of the imposed vertical mass flux is to remove the stabilizing salt gradient, but not the destabilizing temperature gradient over most of the depth of the layer. This arises from the fact that heat diffuses much more quickly than does salt. The Peelet …

Shell Growth Rates Of Pteropod And Heteropod Molluscs And Aragonite Production In The Open Ocean: Implications For The Marine Carbonate System, Victoria J. Fabry

Journal of Marine Research

Shell calcification rates of four species of euthecosomatous pteropods and two species of shelled heteropods were measured in short-term ⁴⁵Ca uptake experiments. In subtropical, temperate, and subarctic waters of the North Pacific Ocean and Atlantic Ocean, animals were hand-collected by Scuba divers, captured with the use of a submersible and caught in plankton nets. Shell growth rates of pteropods ranged from 1.1 to 7.8 μg Ca deposited (mg Ca shell)⁻¹ h⁻¹. Heteropod growth rates ranged from 4.6 to 4.9 μg Ca deposited (mg Ca shell)⁻¹ h⁻¹. Aragonite production of shelled pteropods …

Simulating The Time-Variable Coastal Upwelling During Code 2, Dake Chen, Dong-Ping Wang

Journal of Marine Research

The time-variable coastal upwelling during CODE 2 is simulated using a mixing-advection coupled model. The agreement between model results and observations is generally good. During periods of strong equatorward wind stress, shelf water is cold and weakly stratified, and a front moves offshore; during periods of wind relaxation, surface temperature rises markedly, but the subsurface front usually does not go back toward the coast. At the onset of each wind event, a quick cooling of the surface layer is first caused by wind mixing followed closely by offshore advection of upwelled cold water. Due to the combined effect of mixing …

The Thermocline As An "Internal Boundary Layer", Rick Salmon

Journal of Marine Research

In this paper, we analyze one-, two- and three-dimensional numerical solutions of a simple, inertia-less ocean circulation model. The solutions, which all approach a steady state, demonstrate that, in the limit of vanishing thermal diffusivity κ, a front of thickness κ^1/2, identifiable with the thermocline, spontaneously appears at a location anticipated by simple arguments that treat the front as an "internal boundary layer." The temperature and velocity are generally discontinuous across the front, but the velocity component normal to the front is zero. In the asymptotic limit of vanishing diffusivity, the temperature has no vertical variation within …