Oceanologica Acta最新文献

{"title":"Determining ridge and runnel longshore migration rate using Spot imagery","authors":"Virginie Lafon ,&nbsp;Hélène Dupuis ,&nbsp;Hélène Howa ,&nbsp;Jean-Marie Froidefond","doi":"10.1016/S0399-1784(02)01190-8","DOIUrl":"10.1016/S0399-1784(02)01190-8","url":null,"abstract":"<div><p><span>High-resolution colour satellite imagery is used to map the morphology and to determine the longshore movements of intertidal ridge and runnel systems that characterise the Atlantic southwest coast of France. A couple of Spot images recorded during the summer of 1989 are processed to extract accurate geographical maps of the coastline defined, in this study, as the level corresponding to the lowest astronomical tide. The coastline extraction method is based on a reflectance model, providing depth measurements that were calibrated in the field. This method enables us to map the coastline regardless of the tide level above the lowest astronomical tide at the moment of the image capture. As this model can be extrapolated to a large area when sea water is clear (considering a restricted range of suspended matter concentration) and bottom colour is homogeneous, the variability of both water turbidity and bottom colour have been analysed on the images. From the remotely sensed coastlines, a statistical analysis of ridge and runnel system length and longshore migration has been performed for a 35 km long coastline located to the north of the Arcachon lagoon inlet. It has been observed that, during the summer of 1989 characterised by fair weather conditions, the typical ridge and runnel morphology remains nearly conservative. Whereas the ridge and runnel mean wavelength remains constant during the summer between 435 and 430 m, about 84% of the systems move southward at the mean rate of 2.4 m d</span>^–1. These results derived from Spot image analysis were validated by in situ topographic surveys undertaken during similar hydrodynamical conditions.</p></div>","PeriodicalId":100980,"journal":{"name":"Oceanologica Acta","volume":"25 3","pages":"Pages 149-158"},"PeriodicalIF":0.0,"publicationDate":"2002-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0399-1784(02)01190-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79753742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Croissance de juvéniles de Nereis diversicolor nourris avec des détritus d’halophytes","authors":"Tarik Meziane,&nbsp;Christian Retiere","doi":"10.1016/S0399-1784(02)01187-8","DOIUrl":"10.1016/S0399-1784(02)01187-8","url":null,"abstract":"<div><p>The comparative effect of the uptake of fresh and degraded detritus of halophytic plants, harvested from salt marches of the Mont Saint-Michel Bay (France), on the growth of a juvenile population of the annelid polychaete <em>N</em>. <em>diversicolor</em> (L.) was studied under experimental conditions in summer 1993. Fresh and degraded detritus of <em>Spartina anglica</em>, <em>Halimione portulacoides</em> and <em>Salicornia europeae,</em> as well as the green algae <em>Enteromorpha</em> sp. were distributed separately to homogenous set of juveniles for a 75 d period. The highest growth rate was obtained for worms fed with <em>Enteromorpha</em> sp. Administration of fresh detritus of a given halophyte species to <strong><em>N</em></strong>. <em>diversicolor</em> juveniles always leads to a significantly higher growth rate than did degraded detritus. This is probably due to a great microbial biomass occurring on the fresh detritus, which is moreover, much better assimilated than the detritus they colonize.</p></div>","PeriodicalId":100980,"journal":{"name":"Oceanologica Acta","volume":"25 3","pages":"Pages 119-124"},"PeriodicalIF":0.0,"publicationDate":"2002-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0399-1784(02)01187-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82132736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stable oxygen and hydrogen isotopic tracers in Amazon shelf waters during Amasseds","authors":"Jonathan D Karr,&nbsp;William J Showers","doi":"10.1016/S0399-1784(02)01183-0","DOIUrl":"10.1016/S0399-1784(02)01183-0","url":null,"abstract":"<div><p><span>A detailed hydrographic survey of the water column of the Amazon shelf was performed using stable oxygen and hydrogen isotopes to determine the source and fate of waters on the shelf. </span><em>δ</em>¹⁸O-H₂O and <em>δ</em><span><span>D measurements were made on water column samples from approximately 60 stations (three depths per station) which were each collected during four Amasseds (A Multidisciplinary Amazon Shelf SEDiment Study) cruises: I8909-August 1989, falling river discharge; I9002-March 1990, rising river discharge; I9004-May 1990, </span>peak discharge; I9113-November 1991, minimum discharge. Isotopes were compared with salinity and temperature measurements in order to identify water masses and mixing. The characteristics (salinity, temperature, </span><em>δ</em>¹⁸O, <em>δ</em>D and <em>d</em>) are proposed for the following end-number water masses: river water, open ocean surface water (0–100 m) and open ocean intermediate water (&gt; 300 m). River water: salinity = 0; temperature ≈ 27–29 °C; <em>δ</em>¹⁸O = –4.2 to –6.8 per mil; <em>δ</em>D ≈ –22.1 to –38.9 per mil; <em>d =</em> 9.4 to 17.0 per mil (compare to <em>d</em><span> = 10 for Meteoric Water Line). Open ocean surface water (≈ 0–100 m): salinity ≈ 35 to 37; temperature ≈ 25–29 °C; </span><em>δ</em>¹⁸O ≈ –1 to +2 per mil; <em>δ</em>D ≈ –3.6 to +10.2 per mil. Open ocean intermediate water (≳300 m): salinity = 34.6 to 35.0; temperature = 4.8 to 9.6 °C; <em>δ</em>¹⁸O = –0.2 to +0.3 per mil; <em>δ</em>D = –8.72 to –0.95 per mil. Amazon river water follows a seasonal isotopic cycle in response to basin hydrologic processes. River water mixes with equatorial surface ocean water and intermediate ocean waters originating in mid-to-high southern latitudes. Near-surface waters in the region of North Brazil Current retroflection were identical in isotope–salinity space to waters on the outer shelf during November 1991.</p></div>","PeriodicalId":100980,"journal":{"name":"Oceanologica Acta","volume":"25 2","pages":"Pages 71-78"},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0399-1784(02)01183-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79747567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Contribution of climate variability to occurrences of anoxic crises ‘malaïgues’ in the Thau lagoon (southern France)","authors":"Ali Harzallah ,&nbsp;Annie Chapelle","doi":"10.1016/S0399-1784(02)01184-2","DOIUrl":"10.1016/S0399-1784(02)01184-2","url":null,"abstract":"<div><p>The Thau lagoon, located in southern France, suffers episodically in summer from anoxic crises known as ‘malaïgues’. Such crises mostly occur under warm conditions and low winds. In this paper we investigated effects of local weather conditions (air temperature, wind speed and precipitation over southern France), and two climate oscillations<span> (the North Atlantic Oscillation and the El Niño-Southern Oscillation) on malaïgue occurrences based on 33-year data series and dates when malaïgues appeared. The study shows that the probability of occurrence of malaïgues increases with increasing temperature and decreasing winds in August both mostly associated to the high phase of an index of North Atlantic Oscillation. Malaïgues are found to be frequently preceded by increased precipitation in July which contributes to a larger nutrient input into the lagoon and to its eutrophication. It is also found that malaïgues coincide with the warm phase of an El Niño-Southern Oscillation-like oscillation and are most significantly associated to values of this oscillation during the preceding May. This result is used to propose a simple method for an early warning of appearance of malaïgues with a high degree of confidence.</span></p></div>","PeriodicalId":100980,"journal":{"name":"Oceanologica Acta","volume":"25 2","pages":"Pages 79-86"},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0399-1784(02)01184-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80166037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The influence of quasi resonant internal waves on the radar imaging mechanism of shallow sea bottom topography","authors":"Ingo Hennings ,&nbsp;Margitta Metzner ,&nbsp;G.-P. de Loor","doi":"10.1016/S0399-1784(02)01186-6","DOIUrl":"10.1016/S0399-1784(02)01186-6","url":null,"abstract":"<div><p><span>During previous field experiments in the North Sea it was often assumed that the water column in such shallow coastal tidal waters<span><span> is vertically well mixed and stratification was neglected when discussing the Normalized Radar Cross Section modulation caused by the sea floor. In this paper the influence of quasi resonant internal waves with the sea bed on the </span>radar imaging<span> mechanism of submarine sand waves itself is investigated. In situ data of the tidal current velocity<span> and several water quality parameters such as sea surface temperature<span>, fluorescence, and beam transmittance were measured in the Southern Bight of the North Sea in April 1991. Simulations of the total NRCS modulation caused by sand waves and internal waves as a function of the current gradient or strain rate induced by the internal wave current field at the sea surface have been carried out using the quasi-steady approximation and linear internal wave theory. As a first approximation the strain rate depending on stratification was calculated using the two-layer model. These simulations demonstrate that at least a density difference between the two layers of the order of </span></span></span></span></span><em>Δρ</em> ≈ 1 kg m^–3 is necessary for a sinusoidal thermocline to effect the total NRCS modulation considerably. The NRCS modulation as a function of wind friction velocity has been calculated independently and is discussed with regard to the strain rate of the surface current field caused by the superimposed imaging mechanisms of sand waves and internal waves. It turned out that the existence of a surface roughness-wind stress feedback mechanism cannot be excluded.</p></div>","PeriodicalId":100980,"journal":{"name":"Oceanologica Acta","volume":"25 2","pages":"Pages 87-99"},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0399-1784(02)01186-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"56208794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seasonal variations of downward particle fluxes in front of a reef pass (Moorea Island, French Polynesia)","authors":"Muriel Schrimm ,&nbsp;Serge Heussner ,&nbsp;Roselyne Buscail","doi":"10.1016/S0399-1784(02)01182-9","DOIUrl":"10.1016/S0399-1784(02)01182-9","url":null,"abstract":"<div><p><span>Downward particle fluxes<span> off the Taotoi Pass, a typical Polynesian lagoon pass, have been measured over an annual cycle by means of an array of three mooring lines deployed at 40 m depth on the external sandy plain seawards of the Tiahura reef. Each line was equipped with two hand-operated sediment traps located 1.5 and 10 m above the bottom. During the 1-year survey, the traps were deployed for seven periods of 2–3 weeks. One line equipped with an automated trap was further deployed at 400 m depth on the deep fore-reef slope to collect deep settling particles over two consecutive 6-month periods. For all periods investigated, fluxes on the external plain were highest in front of the pass, and decreased by half on either side (up- and downstream with respect to general circulation), indicating a net export through the pass. At all three locations, the highest downward fluxes recorded (60–100 g m</span></span>^–2 d^–1) corresponded to coarse particles mostly carbonate, whereas the lower fluxes (a few g m^–2 d^–1<span>) corresponded to smaller and lighter material mostly organic carbon. Fluxes on the deep slope were much lower than on the sandy plain (1.5–7.3 g m</span>^–2 d^–1<span><span>), but followed a broadly similar seasonal trend. Comparison of our trap data with published production values for the Tiahura reef system suggests that inorganic and organic carbon export through the pass is limited. The minimum estimates represent around 6% of total calcification but only 1% of the net production of the reef system. The qualitative and quantitative temporal evolution of downward fluxes showed a seasonally-contrasted trend, related to local hydrodynamic conditions. Fluxes were always higher during the southern summer season, and lower during winter. Carbon export appears to be ultimately controlled by </span>climatic factors, i.e. seasonal changes in the orientation and heights of swells and waves that modulate the amount of water flowing into the lagoon, before being flushed out into the open ocean, entraining particles.</span></p></div>","PeriodicalId":100980,"journal":{"name":"Oceanologica Acta","volume":"25 2","pages":"Pages 61-70"},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0399-1784(02)01182-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"56208768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modelling subsurface dynamics in the Black Sea","authors":"Gökay Karakaş,&nbsp;Alec James,&nbsp;Alaa Al-Barakati","doi":"10.1016/S0399-1784(02)01185-4","DOIUrl":"10.1016/S0399-1784(02)01185-4","url":null,"abstract":"<div><p>Dependency of major hydrophysical/chemical features of highly stratified basins on density surfaces in the vertical makes isopycnic models an attractive tool for simulating the dynamics of marginal marine environments such as the Black Sea because of the ability of these models to restrict vertical transport to some desirable degree. In the present work the seasonal variations of the subsurface dynamics of the Black Sea are investigated using an isopycnic model. Particular attention is given to the interfaces of the Cold intermediate layer and Suboxic layer and finally, the deep layer circulation in the basin is studied. It appears that although the depth range of the base of the Cold intermediate layer and the lower Soboxic layer interface do not change seasonally, their horizontal distribution is defined by the upper layer dynamics of the basin. Cyclonic surface circulation diminishes with increasing depth and the deep layer circulation is characterised by an anti-cyclonic rim current driven by density gradients created from river runoff and the influx of Mediterranean water.</p></div>","PeriodicalId":100980,"journal":{"name":"Oceanologica Acta","volume":"25 2","pages":"Pages 101-116"},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0399-1784(02)01185-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"56208776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A numerical study of the generation and propagation of internal solitary waves in the Luzon Strait","authors":"Shuqun Cai,&nbsp;Xiaomin Long,&nbsp;Zijun Gan","doi":"10.1016/S0399-1784(02)01181-7","DOIUrl":"10.1016/S0399-1784(02)01181-7","url":null,"abstract":"<div><p><span>A new composite model, which consists of a generation model of the internal tides and a regularized long wave propagation model, is presented to study the generation and evolution of internal </span>solitary waves in the sill strait. Internal bores in the sill strait are first simulated by the generation model, and then the internal tidal field outside of the sill region is given as input for the propagation model. Numerical experiments are carried out to study the imposing tide, depth profile, channel width and shoaling effect, etc., on the generation and evolution of internal solitary waves. It is shown that only when the amplitude of internal tide at the forcing boundary of the propagation model is large enough that a train of internal solitary waves would be induced. The amplitude of the imposing tide in the generation model, shoaling effect, asymmetry of the depth profile and channel width have some effects on the amplitude of the induced internal solitary wave. The imposing tidal flow superimposed on a constant mean background flow has a great damping effect on the induced internal waves, especially on those propagate against the background flow direction. The generation and propagation of internal solitary waves in three possible straits among the Luzon Strait are simulated, and the reasons for the asymmetry of their propagation are also explained.</p></div>","PeriodicalId":100980,"journal":{"name":"Oceanologica Acta","volume":"25 2","pages":"Pages 51-60"},"PeriodicalIF":0.0,"publicationDate":"2002-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0399-1784(02)01181-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73931613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Penetration of coastal waters into the Eastern Mediterranean Sea using the SeaWiFS data","authors":"Guenrik Karabashev,&nbsp;Marina Evdoshenko,&nbsp;Sergei Sheberstov","doi":"10.1016/S0399-1784(02)01180-5","DOIUrl":"10.1016/S0399-1784(02)01180-5","url":null,"abstract":"<div><p>Offward transport of surface coastal waters was studied in the Eastern Mediterranean from 31° to 37° N between 31° to 36° E using cluster analysis of water-leaving radiance spectra from SeaWiFS<span> color scanner imagery for spring-summer period of 1998. Some types of spectra were found to be characteristic of products of mixing of coastal and offshore waters and served as a quasiconservative tracer of water transport. Three sectors of the eastern coastal zone supplied colored and suspended matter into the open sea areas as occasional pulse discharges of 3-5 week periodicity. The Haifa sector was the most powerful source of such matter producing traceable separate radiance inhomogeneities as far as 200 km west of Haifa. It appears that the discharges were triggered when a set of specific conditions took place and that evolution and life time of discharged waters depended on currents and horizontal mixing. Advantages of cluster approach to imagery analysis are briefly discussed.</span></p></div>","PeriodicalId":100980,"journal":{"name":"Oceanologica Acta","volume":"25 1","pages":"Pages 31-38"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0399-1784(02)01180-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89324003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Examples of spatial and temporal variations of some fine-grained suspended particle characteristics in two Danish coastal water bodies","authors":"Ole Aarup Mikkelsen","doi":"10.1016/S0399-1784(01)01175-6","DOIUrl":"10.1016/S0399-1784(01)01175-6","url":null,"abstract":"<div><p><span>In June and September of 1999, a LISST-100 in situ laser diffraction particle sizer was used to analyse the temporal and spatial variation of the beam attenuation coefficient<span>, the in situ median particle (aggregate) diameter and the median volume concentration of suspended matter in two Danish coastal water bodies. One of the study sites was generally exposed to wind, while the other was quite sheltered. Measurements of the mass concentration of total suspended matter and chl a were made simultaneously. The in situ median effective density, settling velocity and vertical flux of the suspended matter are computed. Results demonstrate that in September, the in situ median aggregate diameter, settling velocity and vertical flux was smaller (by a factor of up to 16) and the concentration higher (by a factor of up to almost two) than in June. This is attributed to varying degrees of turbulence in the water in the weeks preceding the </span></span>field work<span>, causing aggregates to break up (lowering in situ aggregate diameter and settling velocity) and sediment to be resuspended (increasing concentration) in September. The fractal dimension of the suspended aggregates is estimated. The fractal dimension is found to increase from June to September at both study sites, supporting the notion of aggregate break-up in September due to turbulence in the upper part of the water column. An algae bloom occurred at the sheltered study site in September. In situ particle size spectra from this site demonstrated increasing aggregate sizes towards the bottom. It is suggested, that the increase in size is due to biologically induced aggregation, causing large aggregates to settle out of the upper part of the water column, leaving finer particles and aggregates behind.</span></p></div>","PeriodicalId":100980,"journal":{"name":"Oceanologica Acta","volume":"25 1","pages":"Pages 39-49"},"PeriodicalIF":0.0,"publicationDate":"2002-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0399-1784(01)01175-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"97879682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}