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Potential Vorticity Dynamics In A Domain With Closed Geostrophic Contours. I: Steady Linear Flows, Andrew E. Kiss

Journal of Marine Research

Inertia-less wind-driven barotropic flow with lateral and Ekman friction is investigated in circular basins with various bathymetries. The focus is on the vorticity dynamics of flow in basins encircled by continental shelves, a bathymetry which allows a recirculating flow at lowest order because the geostrophic contours are distorted into closed loops which do not intersect the boundary. In general the wind forcing and friction will not balance everywhere, and the potential vorticity lost to the wind must be recovered elsewhere on each streamline. This recovery takes place in a "western" boundary current if geostrophic contours intersect the boundary, but the …

Physical Forcing Of Phytoplankton Community Structure And Primary Production In Continental Shelf Waters Of The Western Antarctic Peninsula, B. B. Prézelin, E. E. Hofmann, M. Moline, J. M. Klinck

Journal of Marine Research

Analyses of a multidisciplinary data set, collected in continental shelf waters of the Western Antarctic Peninsula (WAP) during austral summer of January 1993, identified a previously unrecognized forcing mechanism that sets up a physical and chemical structure that supports and assures site-specific diatom-dominated communities and enhanced biological production (Prézelin et al., 2000). This forcing is active when the southern boundary of the Antarctic Circumpolar Current (ACC) flows along the shelf edge, thereby facilitating onshelf bottom intrusions of nutrient-rich Upper Circumpolar Deep Water (UCDW), which then is upwelled or mixed into the upper water column. At times or locations where UCDW …

Variability Of The Biological Front South Of Africa From Seawifs And A Coupled Physical-Biological Model, J. Llido, E. Machu, J. Sudre, I. Dadou, V. Garçon

Journal of Marine Research

The spatio-temporal variability of the biological front in the Agulhas Current system is investigated by comparing SeaWiFS chlorophyll a data and modeled chlorophyll fields over the October 1997–October 2001 period. The latter fields are simulated using a regional eddy-permitting (1/3° × 1/3°) coupled physical (AGAPE)-biological model forced by the monthly atmospheric NCEP/NCAR reanalysis. The annual cycle of the observed chlorophyll within the Agulhas Current system biogeochemical provinces is quite well reproduced by the model. The modeled phase of the seasonality in the SWSIG (South Western Subtropical Indian Gyre) is opposite to that of the SCZ (Subtropical Convergence Zone encompassing the …

Oxygen Variability In The Near-Surface Waters Of The Northern North Atlantic: Observations And A Model, Peter Lazarevich, Tom Rossby, Craig Mcneil

Journal of Marine Research

As part of the World Ocean Circulation Experiment a major study was undertaken to determine the absolute circulation of the Subpolar North Atlantic using a large number of acoustically tracked isopycnal floats deployed on the 27.5 σ_ surface. Fifty floats were equipped with sensors to study dissolved oxygen from a Lagrangian perspective. In this paper we comment on very large variations in oxygen along trajectories of fluid parcels that outcrop in winter and resubduct the following spring. We employ a one-dimensional model to interpret these in terms of biophysical processes at and near the surface. In an attempt to …

Linear Instabilities Of A Two-Layer Geostrophic Surface Front Near A Wall, Angelique C. Haza, Nathan Paldor, Arthur J. Mariano

Journal of Marine Research

The development of linear instabilities on a geostrophic surface front in a two-layer primitive equation model on an ƒ-plane is studied analytically and numerically using a highly accurate differential shooting method. The basic state is composed of an upper layer in which the mean flow has a constant potential vorticity, and a quiescent lower layer that outcrops between a vertical wall and the surface front (defined as the line of intersection between the interface that separates the two layers and the ocean's surface). The characteristics of the linear instabilities found in the present work confirm earlier results regarding the …

Observations Of Wind Influence On Exchange Flows In A Strait Of The Chilean Inland Sea, Arnoldo Valle-Levinson, José Luis Blanco

Journal of Marine Research

A > 100-day time series of velocity profiles, sea level and wind velocity at a strait in the Chilean Inland Sea was analyzed to examine the effects of wind forcing on the mean two-layer exchange. Measurements took place in the Meninea Constriction of the Moraleda Channel during a period dominated by northerly winds. The mean flow in the strait, and in general in the Moraleda Channel, showed net surface northward outflow and net bottom southward inflow that likely resulted from the dynamical balance between pressure gradient and friction. The influence of tidal mixing on mean exchange flows was further suggested by …

Conceptual Models Of Early Diagenetic Processes: The Muddy Seafloor As An Unsteady, Batch Reactor, Robert C. Aller

Journal of Marine Research

Conceptual models of early diagenetic processes in sedimentary deposits guide interpretation and investigation of compositional patterns, elemental fluxes, and biogeochemical interactions. The ideas that sediments are open to exchange, are laterally homogeneous, and often accrete steadily upward underlie most diagenetic theory. Net accumulation rate of a deposit is thus a master variable controlling reactions, net fluxes, and sediment properties. These basic ideas and corresponding models have proved extraordinarily robust and useful. Large regions of the seafloor, however, can deviate significantly from some of the common assumptions of traditional diagenetic models, particularly along continent-ocean boundaries, where most sedimentary debris is processed. …

Passive Tracer Reconstruction As A Least-Squares Problem With A Semi-Lagrangian Constraint: An Application To Fish Eggs And Larvae, G. G. Panteleev, B. De Young, C. S. Reiss, C. T. Taggart

Journal of Marine Research

A variational, data assimilation, algorithm was developed for reconstruction of a two-dimensional, nonstationary, passive tracer field in the ocean with open boundaries and a known velocity field. The observations, spatial smoothing terms and passive tracer conservation equation were included as weak constraints. The algorithm was tested with simulated, nonstationary, pseudo-oceanographic data integrated for a 7-day period. Simulations were run to determine the robustness of the algorithm and the effect of theoretical, simulated 'sampling events,' mimicking the standard oceanographic survey. We explored the sensitivity of the reconstructed tracer fields to the distribution of the pseudo-oceanographic sampling strategy, essentially an antenna problem, …

Diffusivity And Viscosity Dependence In The Linear Thermocline, J. H. Lacasce

Journal of Marine Research

We re-visit the linear model of a thermally-driven ocean in a single hemisphere, to understand dependencies on viscosity and mixing. We focus in particular on the vertical and surface velocities. In all cases, the meridional and vertical flows are intensified near the boundaries; as a result, the overturning depends on viscosity. The two types of viscosity we examine (Rayleigh damping and diffusion with the no-slip condition) yield significantly different boundary transports. This in turn can cause large changes in the surface velocities. We observe a single-gyre surface circulation with a diffusive viscosity but two gyres with the Rayleigh. We also …

Wind-Driven Barotropic Gyre I: Circulation Control By Eddy Vorticity Fluxes To An Enhanced Removal Region, Baylor Fox-Kemper, Joseph Pedlosky

Journal of Marine Research

It is well known that the barotropic, wind-driven, single-gyre ocean model reaches an inertially-dominated equilibrium with unrealistic circulation strength when the explicit viscosity is reduced to realistically low values. It is shown here that the overall circulation strength can be controlled nonlocally by retaining thin regions of enhanced viscosity parameterizing the effects of increased mixing and topographic interaction near the boundaries. The control is possible even when the inertial boundary layer width is larger than the enhanced viscosity region, as eddy fluxes of vorticity from the interior transport vorticity across the mean streamlines of the inertial boundary current to the …

Exchange Processes And Watermass Modifications Along The Subarctic Front In The North Pacific: Oxygen Consumption Rates And Net Carbon Flux, Murat Aydin, Zafer Top, Donald B. Olson

Journal of Marine Research

Exchange processes along the subarctic front and the modification of subpolar water in the North Pacific are investigated using tracer data from World Ocean Circulation Experiment P14N and P17N lines. The North Pacific Current transports water on both sides of the subarctic front from the western to eastern North Pacific. During this transport, subpolar water from the western subpolar gyre becomes warmer and saltier through the main thermocline via isopycnal mixing with subtropical water. It is shown that this modified subpolar water of western origin is the primary source of well-ventilated water to the eastern subpolar gyre. The isopycnal mixing …

Wind-Driven Barotropic Gyre Ii: Effects Of Eddies And Low Interior Viscosity, Baylor Fox-Kemper

Journal of Marine Research

Using boundary-enhanced viscosity to control the mean circulation, a simple model can be created and used for study of strong inertial effects in a western-intensified calculation. The simplicity allows for a greater number of strongly-inertial numerical experiments than computationally feasible in a general circulation model. This paper is an introduction to the behavior of this model, covering its general features. Some of the inertial phenomena, including the primary balances of the boundary current and basin interior, the temporal behavior, and the changes in the mean state across parameter space are presented. The analysis of these phenomena focuses on the effects …

Predictability Of Lagrangian Particle Trajectories: Effects Of Smoothing Of The Underlying Eulerian Flow, Annalisa Griffa, Leonid I. Piterbarg, Tamay Özgökmen

Journal of Marine Research

The increasing realism of ocean circulation models is leading to an increasing use of Eulerian models as a basis to compute transport properties and to predict the fate of Lagrangian quantities. There exists, however, a significant gap between the spatial scales of model resolution and that of forces acting on Lagrangian particles. These scales may contain high vorticity coherent structures that are not resolved due to computational issues and/or missing dynamics and are typically suppressed by smoothing operators. In this study, the impact of smoothing of the Eulerian fields on the predictability of Lagrangian particles is first investigated by conducting …

The Vertical Structure And Subtidal Dynamics Of The Inner Shelf Off New Jersey, Richard W. Garvine

Journal of Marine Research

This paper seeks to exploit a recent data set obtained off the coast of New Jersey, USA in the summer of 1996. The two major objectives are to gain insight into mechanisms controlling the vertical structure, particularly the temperature and density, and into the subtidal frequency dynamics. The setting was strongly affected by three conditions: stratification was high, the bottom slope was comparable to the isopycnal slope, and buoyancy forcing from an upshelf freshwater source was, on average, of the same strength as wind forcing. Bottom mixed layer (bml) and surface mixed layer (sml) thicknesses increased offshore, opposite the sense …

Interaction Of Transient Shelf Currents With A Buoyancy-Driven Coastal Current, Alexander E. Yankovsky

Journal of Marine Research

Observations on the inner New Jersey shelf (1996) showed that transient wind-driven currents of 3–4-day periods strongly interacted with a buoyancy-driven coastal current (or buoyant plume) originating from the Hudson estuary. In particular, the depth-averaged current fluctuations were amplified in the buoyant water. This phenomenon is studied here using a primitive equation numerical model (SPEM5). Transient (periodic) shelf currents are introduced in the form of incident barotropic shelf waves (BSW). The model domain is an idealized channel with open upstream/downstream boundaries and the depth exponentially increasing offshore, which allows the BSW propagation through the model domain. In most cases, the …

Using Jgofs In Situ And Ocean Color Data To Compare Biogeochemical Models And Estimate Their Parameters In The Subtropical North Atlantic Ocean, I. Dadou, G. Evans, V. Garçon

Journal of Marine Research

How well do biogeochemical data sets serve to decide among models and model parameter values? Data at 21N, 31W from the French JGOFS EUMELI cruises and the SeaWiFS ocean color sensor were used to estimate parameters for three very different models of biological nitrogen flux in a water column. The three models are (1) an NPZD (Nutrients, Phytoplankton, Zooplankton and Detritus) model (Oschlies et al., 2000), (2) a seven-component model with two pools of dissolved organic matter and detritus with different remineralization and sinking rates (Dadou et al., 2001) and (3) a model of nutrients and phytoplankton including aggregates (Kriest …

Regimes Of Low-Frequency Variability In A Three-Layer Quasi-Geostrophic Ocean Model, Janine J. Nauw, Henk A. Dijkstra, Eric Simonnet

Journal of Marine Research

The temporal variability of the midlatitude double-gyre wind-driven ocean circulation is studied in a three-layer quasi-geostrophic model over a broad range in parameter space. Four different types of flow regimes are found, each characterized by a specific time-mean state and spatio-temporal variability. As the lateral friction is decreased, these regimes are encountered in the following order: the viscous antisymmetric regime, the asymmetric regime, the quasi-homoclinic regime and the inertial antisymmetric regime. The variability in the viscous and the inertial antisymmetric regimes (at high and low lateral friction, respectively) is mainly caused by Rossby basin modes. Low-frequency variability, i.e.on interannual to …

Observed Mechanisms Of El Nino Sst Evolution In The Pacific, P. Niiler, D. K. Lee, J. Moisan

Journal of Marine Research

Tropical Pacific Ocean SST and velocity observations are used to construct NINO3 and NINO4 area average, 20-year long interannual time series of local and advective convergences of thermal energy. The variability of the sum of these observed convergences in each region is balanced by the vertical convergence of thermal energy due to the latent surface flux (86% in NINO3; 84% in NINO4). The latitude scale of the El Nino SST anomalies is shown to be equal to the ratio of the poleward mean speed of water parcels to the time scale at which thermal energy is given back to the …

Invertebrate Larval Availability During Summer Upwelling And Downwelling On The Inner Continental Shelf Off New Jersey, Hongguang Ma, Judith P. Grassle

Journal of Marine Research

This study examined the effects of wind-driven, cross-shelf circulation on invertebrate larval supply to benthic habitats on the inner continental shelf off Tuckerton, New Jersey, USA. Study sites were located along an inshore/offshore transect in the LEO-15 research area at Beach Haven Ridge, a 12–20 m deep, shore-oblique sand ridge. Meroplankton was sampled using Moored, Automated, Serial Zooplankton Pumps which were programmed to take 250-l samples, ~1 m above the bottom, every 4 h. Upwelling and downwelling conditions were characterized using wind data from the nearby meteorological tower at the Rutgers University Marine Field Station, and bottom temperatures from LEO-15 …

Lessons From The Protracted Mox Plant Dispute: A Proposed Protocal On Marine Environmental Impact Assessment To The United Nations Convention On The Law Of The Sea, Maki Tanaka

Michigan Journal of International Law

Although the ITLOS order attempted to facilitate dialogue between the parties, the Tribunal was incapable of addressing the root cause of the MOX plant controversy, namely the lack of an adequate mechanism for transboundary environmental impact assessment at the onset of the conflict under UNCLOS. Similarly, the OSPAR and Annex VII tribunals have failed to bring about the efficient resolution of this procedural environmental dispute. This Article addresses the prevention of similar incidents by proposing the creation of a marine environmental impact assessment protocol to UNCLOS to make assessment procedures operational from the initial stage of controversial projects.

Baroclinic Boundary Currents With Downstream Decreasing Buoyancy: A Study Of An Idealized Nordic Seas System, Gösta Walin, Göran Brostrom, Johan Nilsson, Olof Dahl

Journal of Marine Research

The dynamics of a baroclinic boundary current losing buoyancy along its path is analyzed both theoretically and using a numerical ocean-circulation model. A fundamental ingredient in our analysis is that the side boundaries of the ocean basin are sloping gently down to the deep ocean. Theoretically we find that the coastal boundary current develops two branches: one seaward baroclinic jetstream and one barotropic current, which is confined to the continental slope. The baroclinic jetstream decreases its transport as the buoyancy is lost from the surface layer. This decrease in transport is compensated by an increase in the barotropic flow on …

An Experimental Study Of A Mesoscale Vortex Colliding With Topography Of Varying Geometry In A Rotating Fluid, Claudia Adduce, Claudia Cenedese

Journal of Marine Research

The interaction of a self-propagating barotropic cyclonic vortex with an obstacle has been investigated and the conditions for a vortex to bifurcate into two vortices determined. As in a previous study, after a self-propagating cyclonic vortex came into contact with the obstacle, fluid peeled off the outer edge of the vortex and a so-called "streamer" went around the obstacle in a counterclockwise direction. Under certain conditions, this fluid formed a new cyclonic vortex in the wake of the obstacle, causing bifurcation of the original vortex into two vortices. In the present study we performed three sets of idealized laboratory experiments …

Factors Influencing Organic Carbon Recycling And Burial In Skagerrak Sediments, H. Ståhl, A. Tengberg, J. Brunnegård, E. Bjørnbom, T. L. Forbes, A. B. Josefson, H. G. Kaberi, I. M. Karle Hassellöv, F. Olsgard, P. Roos, P. O. J. Hall

Journal of Marine Research

Different factors influencing recycling and burial rates of organic carbon (OC) were investigated in the continental margin sediments of the Skagerrak (NE North Sea). Two different areas, one in the southern and one in the northeastern part of the Skagerrak were visited shortly after a spring bloom (March 1999) and in late summer (August 2000). Results suggested that: (1) Organic carbon oxidation rates (C_ox) (2.2–18 mmol C m^-2d^-11) were generally larger than the O₂ uptake rates (1.9 –25 mmol m^-2d^-1). Both rates were measured in situ using a benthic …

The U.S. National Climate Change Assessment: Do The Climate Models Project A Useful Picture Of Regional Climate?, Roger A. Pielke, Sr.

Water, Climate and Uncertainty: Implications for Western Water Law, Policy, and Management (Summer Conference, June 11-13)

9 pages.

Includes illustrations

"Dr. Roger A. Pielke, Sr., President of the American Association of State Climatologists, Colorado State Climatologist and Professor, Department of Atmospheric Science, Colorado State University"

"From testimony presented to the House Subcommittee on Oversight and Investigations, July 25, 2002, and published in Colorado Water, April 2003, 15-19."

Interpreting Wind-Driven Southern Ocean Variability In A Stochastic Framework, Philip Sura, Sarah T. Gille

Journal of Marine Research

A stochastic model is derived from wind stress and bottom pressure gauge data to examine the response of the Antarctic Circumpolar Current (ACC) transport to wind stress forcing. A general method is used to estimate the drift and diffusion coefficients of a continuous stationary Markovian system. As a first approximation, the response of the ACC to wind stress forcing can be described by a multivariate Ornstein-Uhlenbeck process: Gaussian red noise wind stress drives the evolution of the ACC transport, which is damped by a linear drag term. The model indicates that about 30(±10)% of ACC variability is directly driven by …

A Generic Length-Scale Equation For Geophysical Turbulence Models, L. Umlauf, H. Burchard

Journal of Marine Research

A generalization of a class of differential length-scale equations typically used in second-order turbulence models for oceanic flows is suggested. Commonly used models, like the k-ε model and the Mellor-Yamada model, can be recovered as special cases of this generic model, and thus can be rationally compared. In addition, a method is proposed that yields a generalized framework for the calibration of the most frequently used class of differential length-scale equations. The generic model, calibrated with this method, exhibits a greater range of applicability than any of the traditional models. Stratified flows, plane mixing layers, and turbulence introduced by …

Relative Dispersion At The Surface Of The Gulf Of Mexico, J. H. Lacasce, Carter Ohlmann

Journal of Marine Research

We examine the relative motion of pairs and triplets of surface drifters in the Gulf of Mexico. The mean square pair separations grow exponentially in time from the smallest resolved scale (1 km) to 40-50 km, with an e-folding time of 2-3 days. Thereafter, the dispersion exhibits a power law dependence on time with an exponent of between 2 and 3 (depending on the measure used) up to scales of several hundred kilometers. The straining is for the most part isotropic, with only weak regional variations. But there are suggestions of anisotropy in the western basin, probably due to boundary …

Control Of Black Sea Intermediate Water Mass Formation By Dynamics And Topography: Comparison Of Numerical Simulations, Surveys And Satellite Data, Emil V. Stanev, Malcolm J. Bowman, Elissaveta L. Peneva, Joanna V. Staneva

Journal of Marine Research

The processes of cold intermediate water (CIW) formation in the Black Sea are quantified by analyzing the results of numerical simulations using the Modular Ocean Model (MOM) plus observations obtained from both hydrographic surveys and the TOPEX/POSEIDON altimeter. In the first phase of integration the model is forced with seasonally-variable atmospheric data. After reaching a quasi-periodic state, the integration is continued using forcing data for the period 1991-1994 provided by the United Kingdom Meteorological Office. The performance of the model is assessed in reproducing the dominant physical mechanisms that control the process and rate of CIW formation, viz., circulation, vertical …

On The Generation Of North Brazil Current Rings, Markus Jochum, Paola Malanotte-Rizzoli

Journal of Marine Research

A high resolution general circulation model (OGCM) is used to investigate the life cycle of North Brazil Current (NBC) rings. The focus of the study is on explaining the generation mechanisms of the rings and their vertical structure. The OGCM is used in a configuration simplified as much as possible but capable of reproducing a realistic mean circulation of the tropical Atlantic. Three numerical experiments are analyzed: no wind; steady wind; seasonally varying winds. With wind forcing, a consistent scenario emerges for the generation of NBC rings. It is shown first that the NECC is barotropically unstable, radiating Rossby waves …

Relations Between Local, Nonlocal, Discrete And Continuous Models Of Bioturbation, Filip J. R. Meysman, Bernard P. Boudreau, Jack J. Middelburg

Journal of Marine Research

A general framework is proposed that classifies existing bioturbation models according to two dividing lines: discrete/semi-discrete/continuous and local/nonlocal. Based on a common stochastic approach, which models biological reworking of particles as a position jump process, the relationships among the different model classes are exposed and the assumptions underlying each model are explicitly derived. We find that discrete/semi-discrete/continuous formulations are principally equivalent, leaving two basic modeling formalisms: (1) the more inclusive nonlocal exchange formalism and (2) the local biodiffusion model, which is obtained as a special case of the former. Three fundamental criteria determine the applicability of these formalisms, termed the …