Effects of scattering and resonance on energy dissipation of an internal tide in a narrow shelf     

Yuji Kawamura  Yujiro Kitade 《Journal of Oceanography》2007,63(1):15-25

The effects of scattering and resonance on the energy dissipation of an internal tide were investigated using a two-dimensional model which is a reassembled version of the theoretical generation model devised by Rattray et al. (1969) for internal tide. The basic character of the scattering process at the step bottom was first investigated with a wide shelf model. When the internal wave incited from a deep region (Region II) into the shallow shelf region (Region I), a passing wave into the shallow region, a reflected wave into the deep region, and a beam-like wave, i.e. a scattered wave (SW), emanated at the step bottom. The SW, which consists of the superposition of numerous internal modes, propagated upward/downward into both regions. The general properties of the SW were well expressed around the shelf edge, even in the present model with viscosity effect. The amplitude of the SW decreased dramatically when the depth of the velocity maximum of the incident internal wave in Region II corresponded with the depth of the shelf edge. In the narrow shelf model, where the decay distance of the internal wave in Region I is longer than the shelf width, the incident internal wave reflected at the coast to form a standing wave. When the internal wave in Region I is enhanced by the resonance, the energy of the SW in Region II is also intensified. Furthermore, the energy of the modes in Region II predominated when the velocity maximum is identical to that of the dominant mode in Region I. These results suggest that the spatial scale of shelf region is a very important factor governing the energy dissipation of the internal tide through reflection and scattering in a narrow shelf.  相似文献   

Species, tissue and gender-related organochlorine bioaccumulation in white-sided dolphins, pilot whales and their common prey in the northwest Atlantic   总被引：5，自引：0，他引：5  

Weisbrod AV  Shea D  Moore MJ  Stegeman JJ 《Marine environmental research》2001,51(1):29-50

Organochlorine concentrations were measured in white-sided dolphins, pilot whales, and their prey from the Gulf of Maine and used to identify species, tissue, and gender differences, and trophic transfer trends, in bioaccumulation. Polychlorinated biphenyl concentrations ([PCB]) in dolphin blubber (13 +/- 7.1 micrograms/g fresh wt.) were twice those in pilot whales, but pesticide concentrations (20 +/- 13 micrograms/g fresh) were similar between species. 4,4'-DDE, trans-non-achlor, Cl6(153) and Cl6(138) concentrations were highest. Skin tissues had more recalcitrant organochlorines than the internal organs. Male dolphins bioaccumulated higher concentrations of nonmetabolizable PCBs and hexachlorocyclohexane (HCH) isomers, whereas pilot whales had no gender-related differences in bioaccumulation. Pilot whales, mackerel, and herring had proportionately higher concentrations of DDTs, whereas [PCB] were higher in dolphins and squid. Although these odontocetes feed at the same trophic level and store a similar suite of contaminants, dolphins bioaccumulated higher and potentially hazardous 4,4'-DDE and PCB concentrations from food in their more geographically restricted range.  相似文献   

Analysis of correlations between time series with the use of the phase spectrum     

M. I. Fortus 《Izvestiya Atmospheric and Oceanic Physics》2007,43(5):555-568

In connection with the problem of revealing cause-effect relations among different climatic characteristics, methods for determining the dependence between time series on the basis of selected auto-and cross-covariance functions and periodograms expressed in terms of the Fourier coefficients of the initial series are discussed. Real time series do not always satisfy the conditions of statistical stationarity, so that their analysis requires a combination of statistical and deterministic approaches. The possibility of using the above numerical characteristics in relation to such series is considered. Characteristic features of describing finite segments of time series with the use of their Fourier coefficients is studied in detail. The main emphasis is on the determination of the time shifts (delays) at which the covariance between the series is maximal. The problems that appear during a practical implementation of the periodogram method for shift estimation are discussed. A previously unknown formula that is necessary for further studies and relates the Fourier transform of a selected correlation function to the periodogram of the series is derived.  相似文献   

Relationships between benthic macrofauna and habitat suitability for juvenile common sole (Solea solea, L.) in the Vilaine estuary (Bay of Biscay, France) nursery ground     

D. Nicolas  F. Le Loc'h  Y. Dsaunay  D. Hamon  A. Blanchet  O. Le Pape 《Estuarine, Coastal and Shelf Science》2007,73(3-4):639-650

  相似文献   

Methods of fitting the Fisher-Tippett type 1 extreme value distribution     

D.J.T. Carter  P.G. Challenor 《Ocean Engineering》1983,10(3):191-199

Methods are described for estimating the parameters of the Fisher-Tippet Type 1 extreme value distribution and associated return values from measured extremes, such as maximum wave height. A comparison of these methods, with simulated data, shows that those using Gumbel's plotting position are least satifactory. Maximum likelihood methods give the smallest mean square errors, but the very much simpler method of moments is nearly as good.  相似文献   

Acoustic reflectors in the surface layers of deep sea sediments     

D. M. McCann  F. C. D. Dewes 《Marine Geophysical Researches》1972,1(4):362-380

Using ultrasonic scanning it is possible to display the position of an acoustic discontinuity within a sediment core and the amplitude of the reflected signal which results from it. From these results it has been possible to examine the effect of variations in the geotechnical properties on the reflection of compressional waves at normal incidence within the core at a frequency of 100 kHz. The occurrence of acoustic reflectors in the surface layers of North Atlantic sediments has also been examined.Two ultrasonic scanning systems for the non-destructive testing of marine sediment cores have been developed. The performance of the two systems has been evaluated using the results from measurements made on a suite of marine sediment cores from the North Atlantic in conjunction with X-ray scanning and geological analysis of the same cores.  相似文献   

The power of a contaminant monitoring programme to detect linear trends and incidents     

Fryer  R. J.; Nicholson  M. D. 《ICES Journal of Marine Science》1993,50(2):161-168

  相似文献   

Sediment dynamics of the Huanghe (Yellow River) delta and neighboring gulf of Bohai,People's Republic of China: Project overview   总被引：6，自引：0，他引：6  

G. H. Keller  D. B. Prior 《Geo-Marine Letters》1986,6(2):63-66

  相似文献   

Trace metals and hydrocarbons in sediments from the Southampton water region,with particular reference to the influence of oil refinery effluent     

H. Ármannsson  J.D. Burton  G.B. Jones  A.H. Knap 《Marine environmental research》1985,15(1):31-44

The concentrations of a number of trace metals (Co, Ni, Cu, Zn, Ag, Cd and Hg) have been determined in sediments from cores collected in the Southampton Water region. Measurements of total hydrocarbons were also made on several of the cores. Markedly elevated concentrations of copper, up to 362 μg/g dry wt, were found in sediments which were collected close to the discharge points of oil refinery outfalls and which also showed concentrations of total hydrocarbons considerably greater than the background levels for the estuary. The results of selective chemical extractions showed that much of the copper was present in the non-lattice fraction of the sediment. Although the concentrations of Co, Ni, Zn and Cd were significantly correlated with those of copper in the core showing the highest concentrations of this element, these metals were not enhanced in comparison with the levels found in several other parts of the estuary. Variations in concentrations of metals in sediments throughout the estuary were not correlated with differences in organic carbon content.  相似文献   

The ICES North Sea benthos survey: the sedimentary environment   总被引：2，自引：1，他引：2  

Basford  D. J.; Eleftheriou  A.; Davies  I. M.; Irion  G.; Soltwedel  T. 《ICES Journal of Marine Science》1993,50(1):71-80

  相似文献