Aliasing due to sampling of the Adriatic temperature, salinity and density in space     

Zoran Pasari&#x;  Mirko Orli&#x;  Craig M. Lee 《Estuarine, Coastal and Shelf Science》2006,69(3-4):636

High-resolution underway temperature and conductivity measurements collected by R/V Knorr during winter and spring 2003 are used to characterize errors associated with spatial aliasing in the northern and central Adriatic Sea. During winter, 99th percentile temperature, salinity and density errors were 0.62 °C, 0.25 and 0.12 kg/m³ (0.25 °C, 0.10 and 0.05 kg/m³) for sampling at 10 km (5 km) horizontal resolution, respectively. The corresponding values in spring were 1.31 °C, 0.50 and 0.40 kg/m³ (0.93 °C, 0.25 and 0.22 kg/m³) for the 10 km (5 km) sample spacing, respectively. The largest errors were associated with energetic regions over the shallow, western Adriatic, in front of the Po River mouth and off the tip of the Istrian peninsula. The deeper eastern basin exhibited smaller errors. The variability of errors in time and space reflected the variability of small-scale density features, characterized by wavelengths as small as 2 km in winter and 1 km in spring and being more pronounced in the western and northern parts of the Adriatic. As these results indicate that errors associated with undersampling can be considerable, they should be taken into account while planning future CTD measurements in the region.  相似文献   

Spatial and Temporal Variations of Sound Speed at the PN Section   总被引：3，自引：0，他引：3  

Lian-Gang Lü  Hong-Xia Chen  Ye-Li Yuan 《Journal of Oceanography》2004,60(4):673-679

Gridded sound speed data were calculated using Del Grosso's formulation from the temperature and salinity data at the PN section in the East China Sea covering 92 cruises between February 1978 and October 2000. The vertical gradients of sound speed are mainly related to the seasonal variations, and the strong horizontal gradients are mainly related to the Kuroshio and the upwelling. The standard deviations show that great variations of sound speed exist in the upper layer and in the slope zone. Empirical orthogonal function analysis shows that contributions of surface heating and the Kuroshio to sound speed variance are almost equivalent. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Contamination of organotin compounds and imposex in molluscs from Vancouver,Canada     

Horiguchi T  Li Z  Uno S  Shimizu M  Shiraishi H  Morita M  Thompson JA  Levings CD 《Marine environmental research》2004,57(1-2):75-88

Gastropods and bivalves were collected at 15 sites at Vancouver and Victoria, Canada between 24 May and 7 June, 1999, to establish tissue concentrations of butyltin and phenyltin compounds, to record imposex symptoms in gastropods, and to assess the present status of organotin contamination around Vancouver. No neogastropods (such as Nucella lima) were found around Vancouver. Neogastropod populations could have been extirpated by severe TBT contamination in Vancouver, as relatively high concentrations of TBT were detected in tissues of Mytilus trossulus from Vancouver, and the neogastropods distributed in Vancouver might be sensitive to TBT. Recovery from imposex, however, was observed in neogastropod populations from three sites at Victoria and Mission Point. TBT contamination has continued around Vancouver, arising from continuous use of TBT in antifouling paints for vessels larger than 25 m in length; however, TBT has decreased around Victoria and Mission Point. Different patterns of TBT accumulation in tissue were observed among the bivalve species from Vancouver. The highest TBT concentration detected in Tresus capax suggested some possible adverse effects. TBT was the most predominant butyltin component in almost all bivalve specimens surveyed, suggesting a low rate of TBT metabolism. Phenyltin compounds were not detected in any molluscan specimens in this study.  相似文献   

Effects of prolonged exposure to 4-tert-octylphenol on toxicity and indices of oestrogenic exposure in the sand goby (Pomatoschistus minutus, Pallas)   总被引：3，自引：0，他引：3  

Robinson CD  Brown E  Craft JA  Davies IM  Moffat CF 《Marine environmental research》2004,58(1):19-38

Alkylphenolic compounds are present in estuarine and marine environments. They are moderately bioaccumulative, and oestrogenic to fish following three week, in vivo, exposures. The effects of prolonged exposure are, as yet, unclear. Sand goby (Pomatoschistus minutus) were exposed to measured concentrations of 4-tert-octylphenol (OP) in a 28-day, dose-ranging study, and a six month temporal response study. Following 28-days exposure to measured 31+/-6 or 101+/-47 microg l(-1) OP (mean+/-SD), immature male sand goby showed elevated vitellogenin (VTG) mRNA expression. Plasma alkali-labile phosphate concentrations were elevated in both sexes and were higher in females than males. Although measured OP concentrations were variable, they were significantly different for each treatment and a range of concentration-dependent effects were observed. The LC(50) for chronic OP exposure (8 weeks) was 29+/-6 microg l(-1), and both sexes demonstrated concentration and duration dependent increases in VTG mRNA expression. Exposure to 28+/-20 microg l(-1) OP (median+/-95% CI) for 6 months inhibited development of male nuptial colouration and sperm duct glands. These findings are discussed in relation to environmental concentrations of alkylphenols and ecological concerns.  相似文献   

Reliability of a model based on a short fishery statistics survey: application to the Northeast Atlantic monkfish fishery     

Rocha  Francisco; Gracia  Joaquin; Gonzalez  Angel F; Jardon  Carlos M; Guerra  Angel 《ICES Journal of Marine Science》2004,61(1):25-34

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Estimation of Sea Ice Thickness from SARAL/AltiKa in Drifting Orbit Phase     

Purvee Joshi  Sandip R. Oza  Ujjwal K. Gupta  Shailendra Saini  D. Ram Rajak  I. M. Bahuguna 《Marine Geodesy》2020,43(3):302-323

Abstract

Intra and inter-annual variations in the sea ice thickness are highly sensitive indicators of climatic variations undergoing in the earth’s atmosphere and oceans. This paper describes the method of estimating sea ice thickness using radar waveforms data acquired by SARAL/Altika mission during its drifting orbit phase from July 2016 onwards yielding spatially dense data coverage. Based on statistical analysis of return echoes, classification of the surface has been carried out in three different types, viz. floe, lead and mixed. Time delay correction methods were suitably selected and implemented to make corrections in altimetric range measurements and thereby freeboard. By assuming hydrostatic equilibrium, freeboard data were converted into sea ice thickness. Results show that sea ice thickness varies from 4 to 5?m near ice shelves and 1 to 2.5?m in the marginal sea ice regions. Freeboard and sea ice thickness estimates were also validated using NASA’s Operation Ice Bridge (OIB) datasets. Freeboard measurements show very high correlation (0.97) having RMSE of 0.13. Overestimation of approximately 1–2?m observed in the sea ice thickness, which could be attributed to distance between AltiKa footprint and OIB locations. Moreover, sensitivity analysis shows that snow depth and snow density over sea ice play crucial role in the estimation of sea ice thickness.  相似文献   

Occurrence of Nummulitic coralline limestone from offshore Palar Basin,Bay of Bengal,India     

S. Ramesh  K. Nvv Murthy  S. M. Hussain  S. Ramasamy  G. A. Ramadass 《Marine Georesources & Geotechnology》2020,38(1):57-63

Abstract

Palar basin is located between Pennar and Cauvery sedimentary basins of East coast of India in Bay of Bengal, northeast Indian Ocean. Sea floor drill (Wire-line Autonomous Coring System – WACS) with operational capability of up to 3000?m water depth was developed to collect long cores from deep sea floor for geotechnical and ocean resource assessment studies. During the drilling operation it encountered Nummulitic coralline limestone of Lower Eocene age at 18 meters below the seafloor (mbsf) at 850?m water depth indicating carbonated platform presence for the first time at the study region. Bathymetry contour from Naval Hydrography Chart and General Bathymetric Chart of the Oceans (GEBCO) has revealed the presence of shallow mounds from 50 to 200?m depth closure contour near the sampling site at 850?m water depth which might be a submerged carbonated structure. Since, Nummulites are shallow water dwelling fauna (<20?m depth) but its occurrence at 18 mbsf in 850?m water depth is recorded because of the advancement in technology tool for long core sampling by means of sea floor drill.  相似文献   

Growth and primary productivity of marine macrophytes exposed to domestic sewage effluents     

Andrew C. Kindig  Mark M. Littler 《Marine environmental research》1980,3(2):81-100

This study provides the first response data for ten Southern California macrophytes exposed to untreated, primary, secondary and secondary chlorinated sewage effluent during long-term culture studies in the laboratory as well as short-term metabolic studies in the field and in the laboratory. Bossiella orbigniana, Lithothrix aspergillum and Corallina officinalis var, chilensis had relatively broad homeostatic capabilities and enhanced net production rates when exposed to primary treated sewage. In the long-term cultures, Amphiroa zonata, B. orbigniana and C. officinalis var. chilensis all demonstrated enhanced growth in the presence of primary sewage. Chlorination of effluent had only a short-term negative effect; i.e. species' responses to secondary and secondary chlorinated sewage were virtually identical beyond the second week in culture. Three populations of C. officinalis var. chilensis with differing pollution histories showed a tolerance to sewage corresponding to the extent of previous exposure, indicating that this species may be able to acclimate physiologically to sewage stress. The more sewage-tolerant macrophytes displayed lower photosynthetic quotient values during exposure to effluent than those possessing little tolerance to sewage.  相似文献   

Estimation of winds over the sea from land-based measurements     

Jen-Men Lo  N. Al-Madani  M. A. Tayfun  D. Al-Ajmi 《Ocean Engineering》1994,21(7)

Simultaneous measurements of wind velocities at two different sites, one over the sea and the other over land, can differ substantially and therefore cannot be interchanged. In situations where the wind data at an offshore site are missing while simultaneous measurements from a land-based station exist, a linear mean-square estimation (LMSE) technique can be used to estimate the missing data. This technique relies on past wind data gathered simultaneously at the two locations, and it generates from the associated correlation a set of four transfer functions capable of predicting one data set from the other. In the present case, the LMSE technique is outlined briefly, and is then applied to construct seasonal transfer functions between a land-based station and two coastal/offshore sites in Kuwait. Comparisons between the actually observed wind characteristics and those predicted by the LMSE technique are favorable, and thus tend to confirm the applicability of the technique under appropriate conditions.  相似文献   

Threshold condition of sand particles under codirectional combined wave and current flow     

M. S. Kapdaşli 《Geo-Marine Letters》1990,10(1):45-49

Flume experiments were carried out to determine the threshold of movement of sand on rippled surface and flat beds under the codirectional combined flows due to waves and currents. The results indicate that Shields's curve can be used to determine the threshold condition under combined flows, provided that the maximum bed shear stress is used.  相似文献