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Comments On “A Generic Length-Scale Equation For Geophysical Turbulence Models” By L. Umlauf And H. Burchard, L. Kantha, S. Carniel Jan 2003

Comments On “A Generic Length-Scale Equation For Geophysical Turbulence Models” By L. Umlauf And H. Burchard, L. Kantha, S. Carniel

Journal of Marine Research

Umlauf and Burchard (2003) present a generic length-scale equation... for use in two-equation models of turbulence. However, because of the traditional form used for the diffusion term, it can be used at present for only negative values of n. We show that a simple modification of the diffusion term is sufficient to insure a more universal generic length-scale equation that is valid for all values of m and n, including positive values of n. We also show that an appropriate combination of exponents m and n will enable the generic length-scale equation to simulate any desired length-scale equation...

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Does The Nonlinearity Of The Equation Of State Impose An Upper Bound On The Buoyancy Frequency?, Trevor J. Mcdougall, John A. Church, David R. Jackett Jan 2003

Does The Nonlinearity Of The Equation Of State Impose An Upper Bound On The Buoyancy Frequency?, Trevor J. Mcdougall, John A. Church, David R. Jackett

Journal of Marine Research

Mixing in the ocean is usually accompanied by a net reduction in volume caused by the nonlinear nature of the equation of state. This contraction-on-mixing at a certain depth implies that the whole water column above this depth slumps a little and so suffers a reduction in gravitational potential energy. Under certain circumstances the gravitational potential energy of the entire water column can decrease as a consequence of mixing activity at a certain depth. We examine Fofonoff's hypothesis that in these circumstances the net reduction of gravitational potential energy of the whole water column causes a local increase in the …

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Simultaneous Data-Based Optimization Of A 1d-Ecosystem Model At Three Locations In The North Atlantic: Part Ii—Standing Stocks And Nitrogen Fluxes, Markus Schartau, Andreas Oschlies Jan 2003

Simultaneous Data-Based Optimization Of A 1d-Ecosystem Model At Three Locations In The North Atlantic: Part Ii—Standing Stocks And Nitrogen Fluxes, Markus Schartau, Andreas Oschlies

Journal of Marine Research

This study relates the performance of an optimized one-dimensional ecosystem model to observations at three sites in the North Atlantic Ocean: the Bermuda Atlantic Time Series Study (BATS, 31N 64W), the location of the North Atlantic Bloom Experiment (NABE, 47N 20W), and Ocean Weather Ship INDIA (OWS-INDIA, 59N 19W). The ecosystem model is based on nitrogen and resolves dissolved inorganic nitrogen (N), phytoplankton (P), zooplankton (Z) and detritus (D), therefore called the NPZD-model. Physical forcing, such as temperature and eddy diffusivities are taken from an eddy-permitting general circulation model of the …

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Simultaneous Data-Based Optimization Of A 1d-Ecosystem Model At Three Locations In The North Atlantic: Part I—Method And Parameter Estimates, Markus Schartau, Andreas Oschlies Jan 2003

Simultaneous Data-Based Optimization Of A 1d-Ecosystem Model At Three Locations In The North Atlantic: Part I—Method And Parameter Estimates, Markus Schartau, Andreas Oschlies

Journal of Marine Research

An optimization experiment is performed with a vertically resolved, nitrogen-based ecosystem model, composed of four state variables (NPZD-model): dissolved inorganic nitrogen (N), phytoplankton (P), herbivorous zooplankton (Z) and detritus (D). Parameter values of the NPZD-model are optimized while assimilating observations at three locations in the North Atlantic simultaneously, namely at the sites of the Bermuda Atlantic Time-Series Study (BATS; 31N 64W), of the North Atlantic Bloom Experiment (NABE; 47N 20W), and of Ocean Weather Ship-India (OWS-INDIA; 59N 19W). A method is described for a simultaneous optimization which effectively merges …

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Evaluation Of Excess 234th Activity In Sediments As An Indicator Of Food Quality For Deep-Sea Deposit Feeders, Amanda W. J. Demopoulos, Craig R. Smith, David J. Demaster, William L. Fornes Jan 2003

Evaluation Of Excess 234th Activity In Sediments As An Indicator Of Food Quality For Deep-Sea Deposit Feeders, Amanda W. J. Demopoulos, Craig R. Smith, David J. Demaster, William L. Fornes

Journal of Marine Research

Deep-sea deposit feeders selectively ingest large volumes of sediment. Knowledge of the nature of this selectivity will help to elucidate the limiting nutritional requirements and geochemical impacts of these abundant animals. Shallow-water and theoretical studies suggest that deep-sea deposit feeders should select particles rich in protein, bacterial biomass, and/or chloropigment concentrations. Recent studies indicate that deep-sea megafaunal deposit feeders exhibit strong gut enrichment of excess (xs) 234Th activity, even though 234Thxs lacks nutritional value. To explore the significance of selective ingestion of 234Thxs activity, we evaluated the correlations between 234Thxs activity and three …

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The Role Of Outflow Geometry In The Formation Of The Recirculating Bulge Region In Coastal Buoyant Outflows, Greg Avicola, Pablo Huq Jan 2003

The Role Of Outflow Geometry In The Formation Of The Recirculating Bulge Region In Coastal Buoyant Outflows, Greg Avicola, Pablo Huq

Journal of Marine Research

Density-driven coastal currents are a common feature in the world's coastal oceans. These currents may separate from the coastline due to variations in geometry. Past studies have shown that this separation may produce two distinctly different flow states: a continuation of the coastal current, or a recirculating gyre downshelf of, and attached to, the separation point. Laboratory experiments of coastal buoyant outflows (rotationally dominated, buoyancy driven) were undertaken to examine the role of bay geometry on the evolution of the outflow. Experiments were conducted on a rotating turntable in relatively deep water (such that the buoyant layer depth was much …

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On The Thermohaline Circulation In Flat Bottom Marginal Seas, Michael A. Spall Jan 2003

On The Thermohaline Circulation In Flat Bottom Marginal Seas, Michael A. Spall

Journal of Marine Research

The thermohaline circulation in an idealized marginal sea is studied using both numerical and analytical models. The circulation is forced by repeating an annual cycle of cooling in the interior of the marginal sea for 2 months and turning off the surface forcing for 10 months. The marginal sea is connected to an open ocean through a narrow strait, thus providing a means to equilibrate the cooling within the marginal sea by exchange with the open ocean. The resulting upper ocean circulation consists of a warm boundary current that flows into the marginal sea through the strait that is gradually …

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The Large-Scale Time-Mean Ocean Circulation In The Nordic Seas And Arctic Ocean Estimated From Simplified Dynamics, Ole Anders Nøst, Pål Erik Isachsen Jan 2003

The Large-Scale Time-Mean Ocean Circulation In The Nordic Seas And Arctic Ocean Estimated From Simplified Dynamics, Ole Anders Nøst, Pål Erik Isachsen

Journal of Marine Research

A simplified diagnostic model of the time-mean, large-scale ocean circulation in the Nordic Seas and Arctic Ocean is presented. Divergences in the surface Ekman layer are extracted from observed climatological wind stress fields. Similarly, divergences caused by the meridional thermal wind transport (relative to the bottom) are calculated from an observed climatological density field. These known quantities are then used to "force" the model's bottom geostrophic velocities. Both scaling arguments and direct observations show that for long time scales the bottom currents are closely aligned with contours of f/H, (where f is the Coriolis parameter and H is the …

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On The Role Of Biological Dynamics In Plankton Patchiness At The Mesoscale: An Example From The Eastern North Atlantic Ocean, M. A. Srokosz, A. P. Martin, M. J. R. Fasham Jan 2003

On The Role Of Biological Dynamics In Plankton Patchiness At The Mesoscale: An Example From The Eastern North Atlantic Ocean, M. A. Srokosz, A. P. Martin, M. J. R. Fasham

Journal of Marine Research

In situations where the direct physical forcing of biological processes, through nutrient supply or light limitation of phytoplankton, does not show significant spatial variability, it is demonstrated that the effects of the mesoscale circulation and population dynamics on plankton patchiness are in principle, separable. In this case, the physical stirring and mixing control the size and shape of structures seen in plankton distributions, whilst the biological dynamics controls the size of the populations within those structures. This is demonstrated using field observations and a simple process model. The field data, which come from mesoscale surveys of a region (16 -20W, …

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Modes Of Internal Thermohaline Variability In A Single-Hemispheric Ocean Basin, Lianke A. Te Raa, Henk A. Dijkstra Jan 2003

Modes Of Internal Thermohaline Variability In A Single-Hemispheric Ocean Basin, Lianke A. Te Raa, Henk A. Dijkstra

Journal of Marine Research

In this study, the internal modes of variability of the thermohaline ocean circulation in an idealized single-hemispheric basin are investigated. The modes are determined systematically by performing linear stability analyses of fully three-dimensional thermohaline flows. Relevant for the large-scale low-frequency variability of the flows are two kinds of oscillatory modes. The modes in one of these classes, which have an interdecadal time scale, are truly three-dimensional phenomena and are characterized by westward propagating temperature anomalies, while modes in the other class have a centennial time scale. The latter modes are shown to persist as internal modes of variability of two-dimensional …

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A Model Of Fluff Layer Erosion And Subsequent Bed Erosion In The Presence Of The Bioturbator, Hydrobia Ulvae, Francis Orvain, Pierre Le Hir, Pierre-Guy Sauriau Jan 2003

A Model Of Fluff Layer Erosion And Subsequent Bed Erosion In The Presence Of The Bioturbator, Hydrobia Ulvae, Francis Orvain, Pierre Le Hir, Pierre-Guy Sauriau

Journal of Marine Research

Previous studies have shown that the gastropod Hydrobia ulvae destabilizes the top layers of fine-grained sediments. This process is mediated by the formation of a "biogenic" fluff layer that includes tracks, faecal pellets and mucus. This fluff layer has been shown to be easily resuspended before general bed erosion. In order to examine how fluff layer and bed erosion interact, flume experiments were performed with fluid sediments of varying water contents. Ten thousand snails were placed and allowed to crawl for 5 h on the sediment surface, and then the resuspended sediment mass was measured in response to step-wise shear …

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Adaptive Model Of Dom Dynamics In The Surface Ocean, Markus Pahlow, Alain F. Vézina Jan 2003

Adaptive Model Of Dom Dynamics In The Surface Ocean, Markus Pahlow, Alain F. Vézina

Journal of Marine Research

The bulk of marine dissolved organic matter (DOM) forms a large, old, refractory carbon pool in the deep ocean, yet a small fraction in the surface ocean is actively involved in the global carbon cycle and may contribute significantly to the biological pump. We argue that present models of plankton and DOM in the surface ocean are incompatible with current knowledge of marine DOM dynamics. We present a plankton model with an adaptive formulation of bacteria-DOM interactions which is more consistent with observations. Our model reproduces net accumulation of DOM and is the first to reconcile the prevailing reports of …

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The Seasonal And Spatial Variability Of Small-Scale Turbulence At The Iberian Margin, Toby J. Sherwin, Mark E. Inall, Ricardo Torres Jan 2002

The Seasonal And Spatial Variability Of Small-Scale Turbulence At The Iberian Margin, Toby J. Sherwin, Mark E. Inall, Ricardo Torres

Journal of Marine Research

Turbulence measurements were made off the northwest coast of Spain in January and August 1998. In winter the water column was vertically mixed to about 100 to 150 m, due to the combined effects of the vertical convection of warm northward-moving water and wind stress. A highly dissipative surface boundary layer was present at all times to a depth (of about 20 m) that correlated well with the local wind and wave amplitude. Below this layer dissipation levels decreased from about 10-7 m2 s-3 at a rate that was commensurate with 'law of the wall' boundary theory. …

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Effects Of Gut Chemistry In Marine Bivalves On The Assimilation Of Metals From Ingested Sediment Particles, Sarah B. Griscom, Nicholas S. Fisher, Robert C. Aller, Byeong-Gweon Lee Jan 2002

Effects Of Gut Chemistry In Marine Bivalves On The Assimilation Of Metals From Ingested Sediment Particles, Sarah B. Griscom, Nicholas S. Fisher, Robert C. Aller, Byeong-Gweon Lee

Journal of Marine Research

Bioavailability and uptake of trace metals by benthic animals are often assumed to be limited by authigenic sulfide minerals because of their low metal solubilities and reactivities under sedimentary conditions. However, digestive processes and gut conditions such as Eh, pH, and enzyme or surfactant activity, can affect the release of ingested metals in the gut and control uptake. In a series of laboratory experiments with the deposit-feeding clam, Macoma balthica and the suspension-feeding mussel, Mytilus edulis, we assessed assimilation efficiencies (AE) of radioisotopes of Ag, Cd and Co associated with acid-volatile sulfide (AVS), iron oxide (re-oxidized AVS), and reduced …

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Modeling Of Advective Solute Transport In Sandy Sediments Inhabited By The Lugworm Arenicola Marina, Karen Timmermann, Jan H. Christensen, Gary T. Banta Jan 2002

Modeling Of Advective Solute Transport In Sandy Sediments Inhabited By The Lugworm Arenicola Marina, Karen Timmermann, Jan H. Christensen, Gary T. Banta

Journal of Marine Research

Irrigation by the lugworm Arenicola marina has a major impact on solute transport and distributions in nearshore environments due to the subsurface injection of overlying water at depth (typically 15-20 cm) and the resulting advective water flow within the sediment back toward the sediment surface. A mechanistic one-dimensional diffusion and advection model which emphasizes the injection and advective transport of solutes within the sediment not described in previous irrigation models was developed to describe irrigation by A. marina. The model was verified by comparing its results to measured pore-water tracer (Br) profiles and it is concluded that the model …

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Structure Of The Internal Boundary Layer Over A Patch Of Pinnid Bivalves (Atrina Zelandica) In An Estuary, Vladimir Nikora, Malcolm O. Green, Simon F. Thrush, Terry M. Hume, Derek Goring Jan 2002

Structure Of The Internal Boundary Layer Over A Patch Of Pinnid Bivalves (Atrina Zelandica) In An Estuary, Vladimir Nikora, Malcolm O. Green, Simon F. Thrush, Terry M. Hume, Derek Goring

Journal of Marine Research

Measurements of tidal-current boundary-layer flow over an experimental 2-m by 2-m patch of pinnid bivalves (Atrina zelandica) in a northern New Zealand estuary are presented. Previous work demonstrated a link between "mesoscale" (order 100 m) patchiness of the benthic biota and time-averaged boundary-layer dynamics. The aim in this new experiment was to describe the three-dimensional structure of turbulence at the patch scale (order 1 m). Flow over three densities of Atrina was investigated: 340 individuals per 4 m2, 50 individuals per 4 m2 and zero individuals. An internal boundary layer (IBL) grows downstream from the …

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Physical And Biogeochemical Fluxes And Net Budgets In The Subpolar And Temperate North Atlantic, Marta Álvarez, Harry L. Bryden, Fiz F. Pérez, Aida F. Ríos, Gabriel Rosón Jan 2002

Physical And Biogeochemical Fluxes And Net Budgets In The Subpolar And Temperate North Atlantic, Marta Álvarez, Harry L. Bryden, Fiz F. Pérez, Aida F. Ríos, Gabriel Rosón

Journal of Marine Research

A transoceanic hydrographic section across the North Atlantic Subpolar gyre from Vigo (northwestern Iberian Peninsula) to Cape Farewell (south of Greenland) was sampled in summer 1997 as part of the World Ocean Circulation Experiment program (WOCE A25, 4x cruise). The circulation pattern across the 4x section is diagnosed using inverse methods. The flow is constrained with measured mass transports at specific sites, while conserving mass and salt for the region north of the section and forcing the silicate flux to a reasonable value. The fluxes of physical (heat and freshwater) and chemical (nutrients and oxygen) properties are estimated and decomposed …

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Mixing In The Surface Waters Of The Western Bay Of Bengal Using 228ra And 226ra, R. Rengarajan, M. M. Sarin, B. L. K. Somayajulu, R. Suhasini Jan 2002

Mixing In The Surface Waters Of The Western Bay Of Bengal Using 228ra And 226ra, R. Rengarajan, M. M. Sarin, B. L. K. Somayajulu, R. Suhasini

Journal of Marine Research

228Ra and 226Ra have been measured in the surface waters of the western Bay of Bengal during five cruises conducted between 1988 and 1999. The ranges and mean (given in brackets) concentrations for 228Ra and 226Ra are 6.8-42.1 (17.8 ± 7.9) dpm/100 kg and 6.0-16.7 (9.2 ± 2.2) dpm/ 100 kg, respectively. (228Ra/226Ra) Activity Ratio (henceforth denoted as [228/226]) ranges from 0.8 to 3.4 with a mean of 1.9 ± 0.5. Both 228Ra and 226Ra show inverse correlation with salinity, the former much stronger. A surface 2-D diffusion-advection model is …

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Renewal Time And Transport Of Unventilated Central Intermediate Water Of The Weddell Sea Derived From Biogeochemical Properties, Mario Hoppema, Hein J. W. De Baar, Eberhard Fahrbach, Richard G. J. Bellerby Jan 2002

Renewal Time And Transport Of Unventilated Central Intermediate Water Of The Weddell Sea Derived From Biogeochemical Properties, Mario Hoppema, Hein J. W. De Baar, Eberhard Fahrbach, Richard G. J. Bellerby

Journal of Marine Research

We have investigated the intermediate water mass of the central Weddell Gyre using TCO2 and oxygen data of FS Polarstern cruises in 1992, 1996 and 1998. This water mass, designated as Central Intermediate Water (CIW), is enriched in CO2 and depleted in O2 relative to its source water due to biological degradation. CO2 enrichment and O2 depletion were quantified by calculating the difference between the concentrations in the CIW and those in the more southern source water, the Circumpolar Deep Water, which derives from the Antarctic Circumpolar Current. Inventories of enrichment and depletion were determined …

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Transport And Digestive Alteration Of Uniformly 13c-Labeled Diatoms In Mudflat Sediments, Carrie J. Thomas, Neal E. Blair Jan 2002

Transport And Digestive Alteration Of Uniformly 13c-Labeled Diatoms In Mudflat Sediments, Carrie J. Thomas, Neal E. Blair

Journal of Marine Research

Uniformly 13C-labeled diatoms were used to elucidate the effect deposit feeders have on the distribution and composition of phytodetritus within the seabed. Mudflat infauna contained in microcosms reacted quickly to the emplacement of labeled diatoms onto the sediment-water interface by moving the phytodetritus nonlocally during feeding and hoeing activities. Although redistribution of tracer was rapid, not all infauna exposed to the tracer ingested it. Using four species of deposit-feeding annelids that had ingested the 13C-labeled phytodetritus during the microcosm experiment, molecular-level, digestive alterations of 13C-labeled diatoms were documented. Fecal material produced by the deposit feeders had 13 …

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Tracing Amazon River Water Into The Caribbean Sea, Ferdi L. Hellweger, Arnoldo L. Gordon Jan 2002

Tracing Amazon River Water Into The Caribbean Sea, Ferdi L. Hellweger, Arnoldo L. Gordon

Journal of Marine Research

Monthly Amazon River discharge is correlated to historical monthly sea surface salinity (SSS) in the western tropical Atlantic Ocean and the Caribbean Sea. At Barbados a very high inverse correlation (R2 = 0.92) exists if the discharge is lagged by two months, which corresponds to the travel time from the Amazon mouth to Barbados. Due to its proximity to Barbados, a small amount of the correlation can also be attributed to the Orinoco River. Between Barbados and the central Caribbean Sea (75W) the peak correlation of Amazon River discharge and SSS occurs at progressively longer lag times, representing …

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Meridional Transport In The Indian Ocean Traced By Coral Radiocarbon, Nancy S. Grumet, Thomas P. Guilderson, Robert B. Dunbar Jan 2002

Meridional Transport In The Indian Ocean Traced By Coral Radiocarbon, Nancy S. Grumet, Thomas P. Guilderson, Robert B. Dunbar

Journal of Marine Research

Ocean circulation in the Indian Ocean is predominantly driven by the monsoon and is responsible for convergence along the equator. As a result, upwelling is primarily restricted to the western boundary where surface waters are anomalously depleted in 14C. Here, we describe aspects of western boundary upwelling based on insights derived from the first coral radiocarbon time-series in the Indian Ocean. The absence of a distinct subannual pre-bomb Δ14C signal suggests that open and coastal upwelling are negligible off the coast of Kenya. Instead, our results suggest that upwelling from the coast of Somalia and possibly Oman …

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Flume Experiments On Post-Settlement Movement In Polychaetes, Karen I. Stocks Jan 2002

Flume Experiments On Post-Settlement Movement In Polychaetes, Karen I. Stocks

Journal of Marine Research

The ability of benthic polychaetes to move as adults and juveniles was examined using flume experiments. The main question asked was whether post-settlement movement is a passive process predictable from the hydrodynamic characteristics of the environment and the individual, or whether active behavior is involved. In one set of experiments, the percent of individuals moving during a six-hour period in low-food conditions was compared among five species of intertidal polychaetes. Flow speed was set at a velocity that did not cause sediment erosion but did cause bedload transport of anesthetized individuals. Species varied significantly in percent of movement, with Laeonereis …

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Cross-Frontal Entrainment Of Plankton Into A Buoyant Plume: The Frog Tongue Mechanism, Robert D. Hetland, Dennis J. Mcgillicuddy Jr., Richard P. Signell Jan 2002

Cross-Frontal Entrainment Of Plankton Into A Buoyant Plume: The Frog Tongue Mechanism, Robert D. Hetland, Dennis J. Mcgillicuddy Jr., Richard P. Signell

Journal of Marine Research

A mechanism for the cross-frontal entrainment of plankton by a buoyant plume influenced by wind stress is described and tested using an idealized numerical model. Under the right circumstances, plankton may enter a buoyant plume during an upwelling wind stress, then be transported shoreward during a subsequent downwelling wind stress. In order for the plankton to enter the plume, they must swim upward at a velocity (wp) bounded by Hplume/T < wp < κ/ Hmix where Hplume is the thickness of the buoyant plume, Hmix is the thickness of the upper oceanic mixed layer …

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Internal Gravity Wave Frequencies And Wavenumbers From Single Point Measurements Over A Slope, S. A. Thorpe, L. Umlauf Jan 2002

Internal Gravity Wave Frequencies And Wavenumbers From Single Point Measurements Over A Slope, S. A. Thorpe, L. Umlauf

Journal of Marine Research

It is shown that information about the intrinsic frequency of internal inertial gravity waves, together with their vector wavenumber and their steepness spectrum, may be derived using data from a meter recording current and temperature just above a uniform sloping boundary. The analysis assumes that, over the periods of time in which estimates are made, the local mean buoyancy frequency, N, and temperature gradient are uniform, and the bottom slope, α, is constant over the scale of the observed waves and is known. It is further assumed that, during short periods of analysis, the internal wave field is dominated …

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Water Masses And Baroclinic Transports In The South Atlantic And Southern Oceans, Karen J. Heywood, Brian A. King Jan 2002

Water Masses And Baroclinic Transports In The South Atlantic And Southern Oceans, Karen J. Heywood, Brian A. King

Journal of Marine Research

We describe the World Ocean Circulation Experiment (WOCE) A23 hydrographic section from Antarctica to Brazil, nominally along 35W. The section crossed the center of the Weddell Gyre, the Antarctic Circumpolar Current (ACC) and the Subtropical Gyre in the Argentine Basin. We precisely define the locations of fronts, the changes in water mass properties across them, and their transports. The Antarctic Slope Front was crossed above the continental slope of Antarctica, with a baroclinic transport of 4 Sv, part of the cyclonic Weddell Gyre circulation of 19 Sv. We repeated a section in the Weddell Sea occupied in 1973, and saw …

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Recent Turbidite Deposition In The Eastern Atlantic: Early Diagenesis And Biotic Recovery, P. Anschutz, F. J. Jorissen, G. Chaillou, R. Abu-Zied, C. Fontanier Jan 2002

Recent Turbidite Deposition In The Eastern Atlantic: Early Diagenesis And Biotic Recovery, P. Anschutz, F. J. Jorissen, G. Chaillou, R. Abu-Zied, C. Fontanier

Journal of Marine Research

An interface core taken in Capbreton canyon shows a succession of sedimentary facies interpreted as classical Bouma turbiditic sequences. Activities of 234Th and 210Pb suggest that the deposition of the most recent turbidite was triggered by the violent storm that affected the Atlantic coast of southern France on the 27th of December 1999, about four months before the sampling of the core. This turbidite allows us to study the ongoing diagenesis of the new sediment layer and of the previous sediment-water interface, which has been buried and only slightly eroded. A study of benthic foraminiferal populations informs …

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Fe Redox Cycling In Iberian Continental Margin Sediments (Ne Atlantic), Claar Van Der Zee, Wim Van Raaphorst, Willem Helder Jan 2002

Fe Redox Cycling In Iberian Continental Margin Sediments (Ne Atlantic), Claar Van Der Zee, Wim Van Raaphorst, Willem Helder

Journal of Marine Research

In this paper, data are presented on the vertical distribution of pore water Fe2+, ferrozine-extractable Fe2+ and solid phase Fe in sediments along four across-slope transects including the Nazarécanyon at the Iberian margin. Sorbed Fe2+ cannot be measured directly and is operationally defined as the fraction that can be extracted with ferrozine. Our objectives were (1) to investigate the potential role of Fe2+ sorption in the Fe redox cycle, (2) to quantify Fe redox cycling and (3) to determine its rate limiting factors, with emphasis on differences between stations across the slope and in the …

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A Four-Year Eddy-Permitting Assimilation Of Sea-Surface Temperature And Altimetric Data In The South Atlantic Ocean, Thierry Penduff, Pierre Brasseur, Charles-Emmanuel Testut, Bernard Barnier, Jacques Verron Jan 2002

A Four-Year Eddy-Permitting Assimilation Of Sea-Surface Temperature And Altimetric Data In The South Atlantic Ocean, Thierry Penduff, Pierre Brasseur, Charles-Emmanuel Testut, Bernard Barnier, Jacques Verron

Journal of Marine Research

Sea-surface temperature (SST) and sea-surface height (SSH) data are assimilated with a reduced-order sequential filter every 10 days over four years (1993-1996) in a 1/3-degree resolution South Atlantic primitive equation model. At every assimilation step, the misfit between observations and their model counterparts is evaluated and projected onto the dominant 10 multivariate, full-depth local modes of variability diagnosed from a free model run (without assimilation). Satellite observations are used to perform a sequential update of all model variables according to their "natural" correlations with the surface variables. In this paper, we perform a validation of both the mean state and …

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Physical And Numerical Modeling Of The Role Of Hydrodynamic Processes On Adult-Larval Interactions Of A Suspension-Feeding Bivalve, Mats Lindegarth, Per R. Jonsson, Carl André Jan 2002

Physical And Numerical Modeling Of The Role Of Hydrodynamic Processes On Adult-Larval Interactions Of A Suspension-Feeding Bivalve, Mats Lindegarth, Per R. Jonsson, Carl André

Journal of Marine Research

The importance of hydrodynamic processes for adult-larval interactions in the cockle, Cerastoderma edule, was examined through physical and numerical modeling. A set of physical experiments in a flow-tank using adult cockles and larval mimics showed that the settlement of particles was affected by adult cockles. Settlement was reduced by 20% in an area of 2.5 cm2 surrounding the siphons, and the most marked decrease occurred near the inhalant siphon. On a larger spatial scale downstream of the siphons, settlement was more heterogeneous compared to surfaces without cockles. The experimental results near individual cockles were compared with numerical models …

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