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Change Of Sea Level Trend In The Mediterranean And Black Seas, I. Vigo, D. Garcia, B. F. Chao Jan 2005

Change Of Sea Level Trend In The Mediterranean And Black Seas, I. Vigo, D. Garcia, B. F. Chao

Journal of Marine Research

Sea level anomaly (SLA) data in the Mediterranean and Black seas obtained by ocean radar altimetry missions (TOPEX/Poseidon, Jason, ERS-1/2 and ENVISAT) are studied in conjunction with corresponding sea-surface temperature (SST) data. The studied time span is 11 years long, 1993-2003. Besides confirming previously published results, we report a significant, but enigmatic, abrupt change in the SLA trend that took place in mid-1999 which has been corroborated by independent tide gauge data. Results obtained from an Empirical Orthogonal Function (EOF) analysis show that the change in 1999 is not uniform in the Mediterranean Sea, which can thus be divided into …

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Energetics Of Wind-Driven Barotropic Variability In The Southern Ocean, Wilbert Weijer, Sarah T. Gille Jan 2005

Energetics Of Wind-Driven Barotropic Variability In The Southern Ocean, Wilbert Weijer, Sarah T. Gille

Journal of Marine Research

This study addresses the energetics of the Southern Ocean, in response to high-frequency wind forcing. A constant-density, multi-layer model is forced with a band of stochastically varying wind stress. The focus is on the interplay between the surface layer and the interior circulation.In line with previous examinations, it is concluded that the interior ocean is not directly energized by the wind work, but rather through the work done by the pressure field. The spatial and temporal characteristics of these terms differ substantially. Although the wind work may be negative in extensive regions of the World Ocean, the pressure work energizes …

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Origin And Fate Of A Bloom Of Skeletonema Costatum During A Winter Upwelling/Downwelling Sequence In The Ría De Vigo (Nw Spain), X. A. Álvarez-Salgado, M. Nieto-Cid, S. Piedracoba, B. G. Crespo, J. Gago, S. Brea, I. G. Teixeira, F. G. Figueiras, J. L. Garrido, G. Rosón, C. G. Castro, M. Gilcoto Jan 2005

Origin And Fate Of A Bloom Of Skeletonema Costatum During A Winter Upwelling/Downwelling Sequence In The Ría De Vigo (Nw Spain), X. A. Álvarez-Salgado, M. Nieto-Cid, S. Piedracoba, B. G. Crespo, J. Gago, S. Brea, I. G. Teixeira, F. G. Figueiras, J. L. Garrido, G. Rosón, C. G. Castro, M. Gilcoto

Journal of Marine Research

The onset, development and decay of a winter bloom of the marine diatom Skeletonema costatum was monitored during a 10 d period in the coastal upwelling system of the Ría de Vigo (NW Spain). The succession of upwelling, relaxation and downwelling-favorable coastal winds with a frequency of 10–20 d is a common feature of the NW Iberian shelf. The onset of the bloom occurred during an upwelling-favorable ½ wk period under winter thermal inversion conditions. The subsequent ½ wk coastal wind relaxation period allowed development of the bloom (gross primary production reached 8g C m−2 d−1) utilizing …

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Interfacial Solitary Wave Run-Up In The St. Lawrence Estuary, Daniel Bourgault, Daniel E. Kelley, Peter S. Galbraith Jan 2005

Interfacial Solitary Wave Run-Up In The St. Lawrence Estuary, Daniel Bourgault, Daniel E. Kelley, Peter S. Galbraith

Journal of Marine Research

Density variations show evidence of interfacial solitary waves (ISW) running up the sloping boundary of an island in the St. Lawrence Estuary, confirming inferences based remote sensing. Further detail is suggested by simulations created with a two-dimensional nonhydrostatic numerical model. The simulations confirm theoretical predictions of the location of wave breaking, something that is difficult to observe in the field. Two other results of the simulations match laboratory findings: the creation of turbulent boluses that propagate upslope of the breaking zone, and the creation of an intermediate layer that transports mixed water away from the mixing site. Although our sampling …

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Deep Western Boundary Current East Of Abaco: Mean Structure And Transport, Harry L. Bryden, William E. Johns, Peter M. Saunders Jan 2005

Deep Western Boundary Current East Of Abaco: Mean Structure And Transport, Harry L. Bryden, William E. Johns, Peter M. Saunders

Journal of Marine Research

To assess whether the southward deep water flow of the Atlantic meridional overturning circulation can be monitored by measuring the deep western boundary current, the structure and transport of the time-averaged deep western boundary current at 26.5N are estimated from long current meter records deployed in a series of 7 mooring deployments over 11 years from March 1986 to June 1997 east of Abaco Island in the Bahamas. Time-averaged meridional velocities for each current meter record are combined into estimates of mean velocity at 3 to 10 depths at 10 mooring locations extending eastward from the continental slope out to …

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Interannual Variations In Upper-Ocean Transport By The Gulf Stream And Adjacent Waters Between New Jersey And Bermuda, T. Rossby, C. N. Flagg, K. Donohue Jan 2005

Interannual Variations In Upper-Ocean Transport By The Gulf Stream And Adjacent Waters Between New Jersey And Bermuda, T. Rossby, C. N. Flagg, K. Donohue

Journal of Marine Research

Since the fall of 1992, an acoustic Doppler current profiler mounted on a freighter, the CMV Oleander, has been measuring upper-ocean currents between New Jersey and Bermuda on a weekly basis. The extensive database that results from the frequent, systematic, and sustained sampling enables the exploration of a number of questions regarding currents in the northwest Atlantic. This paper reports on interannual variations in transport in the Gulf Stream and adjacent waters. The repeat sampling greatly increases the ability to discern even rather subtle variations in near-surface transport and explore their possible causes. The transect is divided into three subregions: …

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Decadal Changes In The Canary Upwelling System As Revealed By Satellite Observations: Their Impact On Productivity, A. Miguel P. Santos, Alexander S. Kazmin, Álvaro Peliz Jan 2005

Decadal Changes In The Canary Upwelling System As Revealed By Satellite Observations: Their Impact On Productivity, A. Miguel P. Santos, Alexander S. Kazmin, Álvaro Peliz

Journal of Marine Research

Satellite-derived sea-surface temperature (SST) data were used to study the variability of the Canary Upwelling Ecosystem-CUE (12 to 43N) over the last two decades of the 20th century. The analysis reveals well known patterns of climatology and seasonal variability in this upwelling system. In contrast to quasi-regular decadal oscillations of SST anomalies observed in the open ocean, the coastal variability during the 1980s–1990s was better described as a decadal scale shift of the upwelling regime intensity. The analysis of the upwelling index and coastal zonal gradient of SST showed that this shift occurred earlier (∼1992) in the northern part …

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Recruitment Responses Of Benthic Infauna To Manipulated Sediment Geochemical Properties In Natural Flows, Steven J. Engstrom, Roberta L. Marinelli Jan 2005

Recruitment Responses Of Benthic Infauna To Manipulated Sediment Geochemical Properties In Natural Flows, Steven J. Engstrom, Roberta L. Marinelli

Journal of Marine Research

Recent studies have shown that local variation in surface sediment geochemistry can have significant effects on recruitment rates of benthic invertebrates. Experiments presented here tested (1) the utility of manipulating surface porewater concentrations using spiked polyacrylamide gels and (2) the recruitment responses of the polychaete Arenicola cristata and the bivalve Mercenaria mercenaria to manipulated ammonium concentrations in realistic flows provided by a straight flume and an annular flume. Data show that successful manipulation of sediment porewater ammonium concentration is feasible in flowing waters, i.e., overlying waters remained relatively free of ammonium while manipulated concentration levels were maintained within the upper …

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The Physics Of Blue Crab Larval Recruitment In Delaware Bay: A Model Study, Charles E. Tillburg, John T. Reager, Michael M. Whitney Jan 2005

The Physics Of Blue Crab Larval Recruitment In Delaware Bay: A Model Study, Charles E. Tillburg, John T. Reager, Michael M. Whitney

Journal of Marine Research

Recent studies have shown that the tidal-, wind- and buoyancy-driven surface currents govern the transport of blue crab (Callinectes sapidus) larvae within the coastal ocean and estuaries. Here, we develop a model of larval transport within Delaware Bay and the adjoining coastal ocean using a particle advection scheme coupled to a previously validated physical circulation model which includes realistic tidal forcing, bottom bathymetry, wind stress and river discharge. The coupled model is then used to quantify the effects of several mechanisms on larval transport and recruitment in this region and hindcast actual larval settlement for a four-year period.The …

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Mixing Within The Interior Of The Faeroe-Shetland Channel, Phil Hosegood, Hans Van Haren, Cornelis Veth Jan 2005

Mixing Within The Interior Of The Faeroe-Shetland Channel, Phil Hosegood, Hans Van Haren, Cornelis Veth

Journal of Marine Research

Observations of the distribution of the density field, the dissipation rate of turbulent kinetic energy, ε, the vertical diffusivity, Kz, and optical backscatter over a repeated cross-section of the Faeroe-Shetland Channel (FSC) are presented within the context of ocean mixing. Turbulence in the permanent pycnocline occurs in discrete vertical patches of thickness 20–50 m coincident with layers of elevated vertical current shear magnitude, |S| > 10−2 s−1. The layers of elevated shear result from high-wavenumber internal waves which may break through shear instabilities as indicated by critical Richardson numbers, Ri < 1. The internal waves are ubiquitous features of strong boundary currents flowing along continental shelves and are likely generated here by geostrophic adjustment of the pycnocline in response to lateral excursions of the boundary current over the Shetland slope or by the scattering of internal tide energy. The pycnocline as a whole exhibits Kz > 10−4.5 m2 …

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Statistical Inversion Of South Atlantic Circulation In An Abyssal Neutral Density Layer, Ian W. Mckeague, Geoff Nicholls, Kevin Speer, Radu Herbei Jan 2005

Statistical Inversion Of South Atlantic Circulation In An Abyssal Neutral Density Layer, Ian W. Mckeague, Geoff Nicholls, Kevin Speer, Radu Herbei

Journal of Marine Research

This paper introduces a Bayesian inversion approach to estimating steady state ocean circulation and tracer fields. It is based on a quasi-horizontal flow model and a PDE solver for the forward problem of computing solutions to the tracer field advection-diffusion equations. A typical feature of existing ocean circulation inverse methods is a preprocessing stage in which the tracer data are interpolated over a regular grid and the interpolation error is ignored in the subsequent inversion. Our approach only uses interpolated data at those grid points that have neighboring hydrographic stations. By exploiting physically-based models in an integrated fashion, the method …

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Buoyancy-Forced Circulations In Shallow Marginal Seas, Michael A. Spall Jan 2005

Buoyancy-Forced Circulations In Shallow Marginal Seas, Michael A. Spall

Journal of Marine Research

The properties of water mass transformation and the thermohaline circulation in shallow marginal seas with topography and subject to surface cooling are discussed in the context of an eddy-resolving primitive equation model and an analytic planetary geostrophic model. A unique and important aspect of the model configuration is that the geostrophic contours, or characteristics of the system, extend from a region where temperature is restored toward a uniform value, providing a source of heat, through the cooling region. This removes a degree of symmetry that has often been imposed in previous studies of deep convection. The heat loss within the …

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Lagrangian Spin Parameter And Coherent Structures From Trajectories Released In A High-Resolution Ocean Model, Milena Veneziani, Annalisa Griffa, Zulema D. Garraffo, Eric P. Chassignet Jan 2005

Lagrangian Spin Parameter And Coherent Structures From Trajectories Released In A High-Resolution Ocean Model, Milena Veneziani, Annalisa Griffa, Zulema D. Garraffo, Eric P. Chassignet

Journal of Marine Research

A study of the mesoscale eddy field in the presence of coherent vortices, by means of Lagrangian trajectories released in a high-resolution ocean model, is presented in this paper. The investigation confirms previous results drawn from real float data statistics (Veneziani et al., 2004) that the eddy field characteristics are due to the superposition of two distinct regimes associated with strong coherent vortices and with a typically more quiescent background eddy flow. The former gives rise to looping trajectories characterized by subdiffusivity properties due to the trapping effect of the vortices, while the latter produces nonlooping floats characterized by simple …

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Two Coastal Upwelling Domains In The Northern California Current System, Adriana Huyer, Jane H. Fleischbein, Julie Keister, P. Michael Kosro, Natalie Perlin, Robert L. Smith, Patricia A. Wheeler Jan 2005

Two Coastal Upwelling Domains In The Northern California Current System, Adriana Huyer, Jane H. Fleischbein, Julie Keister, P. Michael Kosro, Natalie Perlin, Robert L. Smith, Patricia A. Wheeler

Journal of Marine Research

A pair of hydrographic sections, one north and one south of Cape Blanco at 42.9N, was sampled in five summers (1998–2000 and 2002–2003). The NH line at 44.6N lies about 130 km south of the Columbia River, and spans a relatively wide shelf off Newport, Oregon. The CR line at 41.9N off Crescent City, California, lies 300 km farther south and spans a narrower shelf. Summer winds are predominantly southward in both locations but the southward winds are stronger on the CR line. Sampling included CTD/rosette casts (to measure temperature, salinity, dissolved oxygen, nutrients, chlorophyll), zooplankton net tows and continuous …

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Growth Rates Of Interface-Feeding Spionid Polychaetes In Simulated Tidal Currents, Brian T. Hentschel, Brenda S. Herrick Jan 2005

Growth Rates Of Interface-Feeding Spionid Polychaetes In Simulated Tidal Currents, Brian T. Hentschel, Brenda S. Herrick

Journal of Marine Research

Most spionid polychaetes switch from surface deposit feeding to suspension feeding as current speed and the flux of suspended food increase. Previous experiments testing the effects of flow on the growth of facultative, interface feeders have been limited to very simplified flow regimes such as constant, unidirectional currents. To measure the growth of interface-feeding spionids in more realistic currents, we programmed two identical counter-rotating annular flumes to simulate two different semidiurnal tidal currents. Each regime included four speeds that varied in hourly steps. At 5 mm above bottom, speeds in the slower flow regime were 0, 2.5, 5, and 7.5 …

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Analytical Solutions For The Acc And Its Overturning Circulation, Timour Radko Jan 2005

Analytical Solutions For The Acc And Its Overturning Circulation, Timour Radko

Journal of Marine Research

An explicit analytical model of the Antarctic Circumpolar Current (ACC) is presented in which the key feature is the balance between the Eulerian circulation acting to overturn the isopycnals and geostrophic eddies which tend to flatten them. Solutions for the stratification and overturning circulation are obtained by expanding the governing residual mean equations of motion in a small parameter (ε) which measures the relative strength of the surface buoyancy flux and mechanical forcing by winds. Our balanced asymptotic model extends and reconciles the earlier views on the dynamics of the (streamwise-averaged) ACC by demonstrating that the zero order balance between …

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Parameterizations Of Lagrangian Spin Statistics And Particle Dispersion In The Presence Of Coherent Vortices, Milena Veneziani, Annalisa Griffa, Andy M. Reynolds, Zulema D. Garraffo, Eric P. Chassignet Jan 2005

Parameterizations Of Lagrangian Spin Statistics And Particle Dispersion In The Presence Of Coherent Vortices, Milena Veneziani, Annalisa Griffa, Andy M. Reynolds, Zulema D. Garraffo, Eric P. Chassignet

Journal of Marine Research

Coherent vortices are known to play an important role in transport processes of ideal flows such as two-dimensional and quasi-geostrophic turbulent flows. In this paper, their effect on eddy dispersion and diffusivity is studied in a realistic oceanic flow, using synthetic Lagrangian data simulated within a high-resolution ocean general circulation model in the Gulf Stream recirculation region. The possibility of using a Lagrangian Stochastic Model (LSM) with nonzero mean spin statistic, Ω, to parameterize the observed characteristics is considered. The probability distribution of the Ω parameter (which is representative of the looping behavior of trajectories embedded inside the coherent vortices) …

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The All-Atlantic Temperature-Salinity-Pressure Relation And Patched Potential Density, Roland A. De Szoeke, Scott R. Springer Jan 2005

The All-Atlantic Temperature-Salinity-Pressure Relation And Patched Potential Density, Roland A. De Szoeke, Scott R. Springer

Journal of Marine Research

The relation between temperature, salinity, and pressure in the Atlantic Ocean is examined. Most of the Atlantic resolves itself into three two-dimensional manifolds of three-dimensional thermodynamic space: a northern, more saline, branch, and a southern, fresher, branch, each quite independent of pressure, and between them a bridge, on which density is uniform at constant pressure. The properties of the branches are crucial to the construction of joint potential density surfaces, patched together at 1000 db intervals. By resolving more finely in pressure (illustrated with 200 db spacing), a finer system of patched potential density surfaces can be obtained, and indeed …

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Diffusion Scale Dependent Change In Anaerobic Carbon And Nitrogen Mineralization: True Effector Experimental Artifact?, Thomas Valdemarsen, Erik Kristensen Jan 2005

Diffusion Scale Dependent Change In Anaerobic Carbon And Nitrogen Mineralization: True Effector Experimental Artifact?, Thomas Valdemarsen, Erik Kristensen

Journal of Marine Research

Burrowing macrofauna is known to influence the diffusion properties and solute transport within sediments as well as promoting aerobic microbial processes. It has recently been argued that changes in diffusion scales also affect anaerobic microbial processes in sediments. We tested this contention on coastal sandy sediment using a widely employed sediment plug flux-incubation technique. Our results confirm that volume specific microbial carbon and nitrogen mineralization apparently are enhanced (6–15 and 3–9 times, respectively) in thin (1 mm) compared with thick (10 cm) sediment plugs incubated in anoxic seawater. However, differential accumulation of inhibiting substances among plug sizes cannot explain this …

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The Life And Work Of Nick Fofonoff, T. J. Mcdougall, R. W. Schmitt, G. Veronis, F. Webster Jan 2005

The Life And Work Of Nick Fofonoff, T. J. Mcdougall, R. W. Schmitt, G. Veronis, F. Webster

Journal of Marine Research

Nicholas Paul Fofonoff was born August 18, 1929, and raised on a small farm near Queenstown in Alberta, Canada. His parents spoke only Russian at home, so Nick did not learn English until he attended the two-room school that served the first six grades for the town of 200. He was the second born of four, the prince among three sisters. The small school meant he was exposed to several grades at a time and could advance quickly. He also learned many practical skills on the farm from a clever father and the necessity to be self-sufficient. It was a …

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The Material Derivative Of Neutral Density, Trevor J. Mcdougall, David R. Jackett Jan 2005

The Material Derivative Of Neutral Density, Trevor J. Mcdougall, David R. Jackett

Journal of Marine Research

An expression for the rate of change of neutral density following a fluid parcel (the material derivative) is derived and checked numerically. This expression can be used to quantify the degree to which neutral density varies even under purely adiabatic and isohaline motions. We also present an approximate form of neutral density, namely a rational function of only two variables, either salinity and conservative temperature or salinity and potential temperature.

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Diffusively-Driven Overturning Of A Stable Density Gradient, Andrew F. Thompson, George Veronis Jan 2005

Diffusively-Driven Overturning Of A Stable Density Gradient, Andrew F. Thompson, George Veronis

Journal of Marine Research

We present the results of an experimental study on the formation and propagation of thermohaline intrusions from an initial state that is stably stratified in two diffusing components. The intrusions form in a layer that contains compensating horizontal gradients of the two components and that lies above a denser reservoir layer that is homogeneous. In the initial state, a vertical barrier separates the upper layer into two half layers each with a different concentration but with the same density. Differential diffusion of solute from the reservoir into the upper layer initiates intrusions that are separated by an interface and that …

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Preformed Phosphate, Soft Tissue Pump And Atmospheric Co2, Takamitsu Ito, Michael J. Follows Jan 2005

Preformed Phosphate, Soft Tissue Pump And Atmospheric Co2, Takamitsu Ito, Michael J. Follows

Journal of Marine Research

We develop a new theory relating atmospheric pCO2 and the efficiency of the soft tissue pump of CO2 in the ocean, measured by P*, a quasi-conservative tracer. P* is inversely correlated with preformed phosphate, and its global average represents the fraction of nutrients transported by the export and remineralization of organic material. This view is combined with global conservation constraints for carbon and nutrients leading to a theoretical prediction for the sensitivity of atmospheric pCO2 to changes in globally averaged P*. The theory is supported by sensitivity studies with a more complex, …

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Homoclinic Bifurcations In The Quasi-Geostrophic Double-Gyre Circulation, Eric Simonnet, Michael Ghil, Henk Dijkstra Jan 2005

Homoclinic Bifurcations In The Quasi-Geostrophic Double-Gyre Circulation, Eric Simonnet, Michael Ghil, Henk Dijkstra

Journal of Marine Research

The wind-driven double-gyre circulation in a rectangular basin goes through several dynamical regimes as the amount of lateral friction is decreased. This paper studies the transition to irregular flow in the double-gyre circulation by applying dynamical systems methodology to a quasi-geostrophic, equivalent-barotropic model with a 10-km resolution.The origin of the irregularities, in space and time, is the occurrence of homoclinic bifurcations that involve phase-space behavior far from stationary solutions. The connection between these homoclinic bifurcations and earlier transitions, which occur at larger lateral friction, is explained. The earlier transitions, such as pitchfork and asymmetric Hopf bifurcation, only involve the nonlinear …

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The Variability Of The East Sakhalin Current Induced By Winds Over The Continental Shelf And Slope, Genta Mizuta, Kay I. Ohshima, Yasushi Fukamachi, Masaaki Wakatsuchi Jan 2005

The Variability Of The East Sakhalin Current Induced By Winds Over The Continental Shelf And Slope, Genta Mizuta, Kay I. Ohshima, Yasushi Fukamachi, Masaaki Wakatsuchi

Journal of Marine Research

Long-term current measurements of the East Sakhalin Current (ESC) in the Sea of Okhotsk are analyzed using the technique of empirical orthogonal functions (EOFs) in the frequency domain. The first and second EOFs at subtidal frequencies represent motions over the continental shelf and slope, respectively, corresponding to the variability of the two cores of the intense ESC. The first EOF can be explained by the first-mode coastal trapped wave (CTW). The structure of the second EOF is similar to that of the second-mode CTW to the first approximation. According to the distribution of the cross-spectra between EOFs and the wind …

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Effects Of Habitat Complexity And Hydrodynamics On The Abundance And Diversity Of Small Invertebrates Colonizing Artificial Substrates, Nazan Atilla, John W. Fleeger, Christopher M. Finelli Jan 2005

Effects Of Habitat Complexity And Hydrodynamics On The Abundance And Diversity Of Small Invertebrates Colonizing Artificial Substrates, Nazan Atilla, John W. Fleeger, Christopher M. Finelli

Journal of Marine Research

Invertebrate colonization in a shallow estuarine embayment was studied with the use of artificial substrates (bottle brushes) to create and mimic complex habitats. Substrates were manipulated to obtain varying levels of habitat density and surface area by shortening and/or removing bristles from the brushes. Complexity was quantified as the total surface area of bristles and bristle surface area within the geometric volume of the substrate (i.e., bristle density). Short-bristled brushes provided greater habitat density while long-bristled brushes provided larger surface area within the same removal treatment. Abundance of invertebrates that recruited from the water column (mostly from the meiobenthos) averaged …

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Intense Short-Period Internal Waves In The Ocean, Konstantin Sabinin, Andrey Serebryany Jan 2005

Intense Short-Period Internal Waves In The Ocean, Konstantin Sabinin, Andrey Serebryany

Journal of Marine Research

Trains of quasi-periodic high-frequency internal waves (IWs) of large amplitude are common in the upper thermocline of the ocean. Sources for these waves may be different ones but it is not always possible to experimentally establish them for certain. We analyzed results of many IW experiments carried out in different representative regions of the World Ocean, including continental margins in the Mid-Atlantic Bight, in the northwestern Pacific at Kamchatka, the Seyshelles-Mascarene bottom rise, and some regions of the open ocean where the intense short-period IWs occur. Comparative analysis of the intense IWs observed in the Mid-Atlantic Bight and at Kamchatka …

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Speculations On A Schematic Theory Of The Younger Dryas, Carl Wunsch Jan 2005

Speculations On A Schematic Theory Of The Younger Dryas, Carl Wunsch

Journal of Marine Research

The possible implications of a change in deep ocean mixing generated by the abrupt coverage of continental shelves during deglaciation is explored schematically. A simple Cartesian continental shelf/deep ocean tidal model is used to mimic the behavior of tidal dissipation at a variety of frequencies relative to a basin-near-resonance. The actual estimated sea level curve is then used to calculate a representative deep water tidal dissipation through time, which is then translated by means of a one-dimensional loop flow to explore the implications of a change in deep ocean mixing. It is possible to pick parameters for the loop model, …

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High Cyanobacterial Abundance In Three Northeastern Gulf Of Mexico Estuaries, Michael C. Murrell, Jane M. Caffrey Jan 2005

High Cyanobacterial Abundance In Three Northeastern Gulf Of Mexico Estuaries, Michael C. Murrell, Jane M. Caffrey

Gulf and Caribbean Research

Aquatic phytoplankton comprise a wide variety of taxa spanning more than 2 orders of magnitude in size, yet studies of estuarine phytoplankton often overlook the picoplankton, particularly chroococcoid cyanobacteria (cf. Synechococcus). Three Gulf of Mexico estuaries (Apalachicola Bay, FL; Pensacola Bay, FL; Weeks Bay, AL) were sampled during summer and fall 2001 to quantify cyanobacterial abundance, to examine how cyanobacterial abundance varied with hydrographic and nutrient distributions, and to estimate the contribution of cyanobacteria to the bulk phytoplankton community. Cyanobacterial abundances in all 3 estuaries were high, averaging 0.59 ± 0.76 X 109 L–1 in Apalachicola Bay, …

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Nonlinear Double-Diffusive Intrusions At The Equator, Neil R. Edwards, Kelvin J. Richards Jan 2004

Nonlinear Double-Diffusive Intrusions At The Equator, Neil R. Edwards, Kelvin J. Richards

Journal of Marine Research

Previous, linear analysis has suggested that observations of interleaving, quasi-horizontal layers in the equatorial oceans may be explained by double-diffusive or inertial instability. Here we describe an idealized, two-dimensional, numerical investigation of the nonlinear development of these instabilities, focusing almost exclusively on the double-diffusive case. We consider the mechanisms for equilibration and maintenance of the interleaving intrusions and perform a thorough sensitivity analysis. Nonlinearity arising from changes in diffusive regime is found to be more important than advective nonlinearity in promoting global equilibration. When variations in effective flux ratio are weak, local constraints prevent equilibration until large amplitudes are reached. …

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