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1.
This paper considers wave impacts on baffles, on baffles or decks adjacent to a vertical wall, and on porous seawalls and/or sea beds. For seawalls and vertical baffles, impacts can occur in steep waves, whilst a deck can be struck from below by a rising wave crest either in open sea or in a tank with standing waves (sloshing). A simple analytical model for the pressure impulse, P, due to a wave of idealized geometry and dynamics is developed and applied to the following geometries with impermeable surfaces:
- •horizontal wave impact onto a vertical wall with a deck at the waterline,
- •vertical wave impact under a deck in the same configuration (equivalent to vertical water impact of a horizontal plate),
- •horizontal wave impact onto a surface-piercing vertical baffle in open sea,
- •as for 3. but with the baffle in front of a wall,
- •as for 4. but with a deck extending from the vertical wall to the baffle,
- •bottom-mounted baffle in front of a wall with impact occurring on the wall.
2.
《Oceanologica Acta》1998,21(1):21-31
During the PROGEMA I cruise which took place on the south-western Pacific coast of Mexico (between 14° and 16° N, 92° and 96° W), 3.5 kHz echosounding profiles, surface samples and cores as well as hydrological and oxygen minimum measurements down to 2250 m water depth were made in the Gulf of Tehuantepec. Chemical, sedimentological, mineralogical, X-ray and BEM analyses of waters, core and surface samples provided new data which permit a better knowledge of the Gulf of Tehuantepec margin, where tectonic activity is due to an active subduction.On the shelf of the gulf, the distribution pattern of quaternary deposits is affected by a double tectonic forcing and by eustatic oscillations of the sea level. The first tectonic control is linked to the existence of north-south tectonic troughs in the Tehuantepec Isthmus, in which the atmospheric circulation between the Gulfs of Mexico and Tehuantepec is accelerated by the Venturi effect. The resulting winds, called “Tehuanos”, play an important role in the forcing of surface circulation in the Gulf of Tehuantepec, inducing a deviation of the general circulation and thus forcing the distribution pattern of terrigenous sediment supply according to two physiographically and mineralogically distinct provinces, inherited from the past tectonic evolution, which are separated by the Tehuantepec axis.
- •-|A southeastern province related to the Caribbean Plate and fed by: (1) the rivers draining the Chiapas Massif; and (2) the Costa-Rica Current driving tropical and subtropical waters from Central America.
- •-|A northwestern province part of the North American Plate and fed by: (1) the Rio Tehuantepec which drains the Sierra de Oaxaca; and (2) the Californian Current.
- •-|shallow banks where the products of a present-day phosphatogenesis are concentrated because they are swept by upwellings. The latter are reinforced because the banks are situated south of the wind corridor;
- •-|tectonic depressions acting as sediment traps;
- •-|numerous canyons cutting the slope along brittle accidents, driving weak turbidity currents but which play an important role in the forcing of upwelling currents. Antarctic diatoms are found which are conveyed by the deep circulation from the South-Eastern Pacific and provide evidence that Antarctic Cold Water masses (AABW) rise towards the shelf.
3.
4.
《Ocean & Coastal Management》2000,43(7):537-556
Guidelines for developing and implementing sustainability indicators for marine capture fisheries were drafted during a recent expert consultation jointly organised by Australia and FAO in Sydney (Australia). This paper provides an overview of the guidelines and illustrates their application with an Australian example. As a background to the guidelines, the concept of sustainable development (SD) for marine capture fisheries was discussed and an agreed set of definitions and usage of common terms developed. The guidelines then outline the five sequential steps that need to be addressed in developing a meaningful set of indicators in the context of a Sustainable Development Reference System (SDRS). The five steps are:
- 1.specifying the scope of the SDRS;
- 2.developing a framework to agree on components within the system;
- 3.specifying criteria, objectives, potential indicators and reference values;
- 4.choosing the set of indicators and reference values;
- 5.specifying the method of aggregation and visualisation.
5.
This study aims to constrain the base of the hydrates stability field in structurally complexsites using the case of Woolsey Mound, a fault-controlled, transient, thermogenic hydrates system, in Mississippi Canyon Block 118, northern Gulf of Mexico. We have computed the base of the hydrates stability field integrating results from a recent heat-flow survey, designed to investigate geothermal anomalies along fault zones which exhibit different fluid flux regimes. An advanced “compositional” simulator was used to model hydrate formation and dissociation at Woolsey Mound and addresses the following hypotheses:
- 1.Migrating thermogenic fluids alter thermal conditions of the Hydrate Stability Zone (HSZ), so heat-flow reflects fault activity;
- 2.Gas hydrate formation and dissociation vary temporally at active faults, temporarily sealing conduits for migration of thermogenic fluids;
- 3.High salinity and inclusion of thermogenic gases with higher molecular weight than methane produce opposite effects on the depth to the bottom of the hydrate stability zone.
6.
7.
《Oceanologica Acta》1998,21(1):1-20
During the Equanaute survey (June 1992), fourteen submersible dives were performed between 4950 and 2250 m water depths across the southern slope of the Côte d'Ivoire-Ghana Marginal Ridge (CIGMR), in the eastern Equatorial Atlantic. The CIGMR, a high-standing topographic marginal ridge along the Côte d'Ivoire-Ghana transform margin, is believed to result from a complex structural evolution due to the specific wrench-related rifting between Western Equatorial Africa and Northeastern Brazil, in Early Cretaceous times. In this paper we report and discuss geological observations made during dives, and sample analyses to resolve the lithology, paleoenvironmental conditions, age and origin of the CIGMR. The data help in better characterizing the different sedimentary and tectonic regimes which successively prevailed during the CIGMR formation and assessing the thermal regime operative during the fabrication and subsequent evolution of the margin. The thick sedimentary pile exposed along the southern CIGMR slope is made up of a repetitive clastic sequence indicative of a deltaic-to-prodeltaic environment. This sedimentary pile, of Early Cretaceous age, has recorded different stages of the transform margin structural evolution.
- 1.(1)|Syn- to post-lithification deformations first record extensional deformations related to the rifting of the adjacent northern divergent margin segment (the Deep Ivorian Basin).
- 2.(2)|Wrench tectonics has, at a later stage, produced intense fracturing and participated in local folding, chiefly detected upslope. The integrated studies of geological samples and in situ observations obtained during the Equanaute survey support models for transform margin evolution proposed mainly from geophysical data.
8.
A study is made on the surface distribution ofTrichodesmium thiebautii Gomont in the East China Sea during the years 1961–1967.
- This alga is very scarce or absent in the period from January to March, and begins to increase in May and June, reaching the maximum population density from July to September, and again decreases in October and November.
- In summerT. thiebautii is predominantly distributed in the area along the Kuroshio current with high densities of 102–103 filaments/l, occasionally exceeding 103 filaments/l. This alga is estimated to occupy the major part or almost all the parts of chlorophylla in situ contained in the surface water of this season.
- The occurrence ofT. thiebautii off the southern coasts of Central Japan seems to be caused rather by the multiplication in its own habitat than by the transportation by the Kuroshio current from the East China Sea.
9.
《Marine Policy》1998,22(3):229-234
The 1972 United Nations Conference on the Human Environment (Stockholm, UN Conference, 1972) outlined a ‘masterplan’ linking environmental assessment, environmental management and supporting measures as basic and inseparable elements of environmental actions plans. It also indicated the advantages of a regional approach in contributing to the solution of global problems. The Regional Seas Programme of UNEP (United Nations Environment Programme) was subsequently initiated in 1974 (UN General Assembly, 1972). Development of UNEP’s Regional Seas Programme demonstrated that the basic concepts formulated at Stockholm can effectively foster regional cooperation among interested States, and may benefit from the support of the United Nations system as a whole.The present Regional Seas Programme includes fourteen regions, comprising over 140 coastal States. It was conceived as an action-oriented programme encompassing a comprehensive, trans-sectoral approach to marine and coastal areas and to environmental problems, considering not only the consequences, but also the causes of environmental degradation. Each Regional Seas Programme is based on the needs of the region concerned. The Regional Seas Programmes promote the parallel development of regional legal agreements, and of action-oriented programme activities, as embodied in the action plans. The overall strategy to be followed, as defined by UNEP’s Governing Council (UNEP, 1974) is:
- 1. Promotion of international and regional conventions, guidelines and actions for the control of marine pollution and the protection and management of aquatic resources.
- 2. Assessment of the state of marine pollution, pollution sources and trends, and of the impact of pollution on human health, marine ecosystems and amenities.
- 3. Coordination of efforts with regard to environmental aspects of the protection, development and management of marine and coastal resources.
- 4. Support for education and training efforts to facilitate the full participation of developing countries in the protection, development and management of marine and coastal resources.
10.
We have studied the relation between the hydrography, the composition and horizontal structure of the larval fish community, and the horizontal distribution patterns of larval fish abundances in an area characterised by strong mesoscale oceanographic activity, located between the Canary Islands and the African coast (the Canaries Coastal Transition Zone), during August 1999. Upwelling, upwelling filaments, cyclonic and anticyclonic eddies and island wakes are typical mesoscale features of the northwest African coast in summer. A single upwelling filament off Cabo Juby was joined in mid-August by a second that originated about 100 km to the north. The two filaments flowed together and merged 100 km offshore. The merged filament was partially entrained around a cyclonic eddy, trapped between the Canary Islands and the African coast, and interacted with cyclonic and anticyclonic eddies shed from Gran Canaria. Mesoscale oceanographic features strongly influenced the horizontal distributions of fish larvae. Eddies acted as a mechanism of concentration, while upwelling filaments were dispersive, transporting larvae from the African neritic zone into oceanic areas and towards the Canary archipelago. This transport was the major cause of the predominance of neritic larvae in the composition of the larval fish community of the area. The results also suggest: (1) that anchovy larvae are good indicators of the offshore displacement of upwelled water; (2) that the alternation between anchovy and sardine as species dominant in the larval fish community of the area during summer depends upon the water temperature in the African upwelling region, anchovy dominating at higher temperature; (3) that a coupling of anchovy and sardine spawning with the mesoscale oceanographic structure formed by the upwelling filaments and trapped eddy overcomes the negative effect that Ekman transport has on their populations. 相似文献
11.
High quality CTD data were collected in the north of the Shikoku Basin where an abyssal boundary current has been observed through direct current measurements. Analyses of hydrographic data showed:
- Colder and saltier water (heavier water) compared to surrounding waters is found above the continental shelf-toe and the eastern flank of the Kyushu-Palau Ridge where the existence of the abyssal boundary current has been expected. The heavier water has a horizontal extent of about 50 km.
- The heavier water has the vertical scale of 2000 m from the sea bottom, and is associated with a thermal wind shear which enhances a component of the flow toward a direction looking the Nankai Trough (a trough located along the northern end of the Shikoku Basin) to the left in the abyss. The assumed “level of no motion” at about 2500 m depth gives the geostrophically estimated current in a good agreement with the directly measured current.
12.
Deep currents measured by moored current meters over the shelf-slope off Cape Shiono-misaki, Kii Peninsula during the period from 28 April, 1981 to 4 May, 1982 are analyzed to determine characteristics of the deep current before and after the large meander of the Kuroshio formed. The observed deep currents show some different characteristics between the periods before and after the formation of the large meander of the Kuroshio,i.e.:
- The mean current direction over the shelf slope changed to westward after the meander was formed, though it was eastward at two offshore stations before the meander was formed.
- The eddy kinetic energy, \(ke((\overline {u'^2 } + \overline {\upsilon '^2 } )/2)\) became large at all stations after the meander formed.
- It appears that there were current variations in the period band shorter than 10 days which propagated offshore before the meander formed but inshore after the meander formed.
- After the meander formed, the current variations with a period of O(25 days) were amplified at two of the three stations. The current variations in this period band showed high coherence among the three stations.
13.
The distribution of pelagic blue-green algae, especially ofTrichodesmium thiebautii, was investigated on the basis of the collection of theHakuhō Maru Cruise KH-69-4 along 155°W (50°N-15°S) in the North Pacific Ocean from September to November 1969.
- Five species were identified:Trichodesmium thiebautii (most predominant),T. erythraeum, Oscillatoria sp.,Katagnymene spiralis andRichelia intracellularis.
- T. thiebautii was most abundant in the western North Pacific central water and abundant next to it in the equatorial water, but it did not occur in the subarctic water.
- T. thiebautii was ubiquitously distributed in the lower layer of 100–200 m in the equatorial water, though not in a large quantity.
- T. thiebautii inhabited only the water warmer than 20°C. In its main habitat, nitrate and nitrite were almost zero, but ammonia and phosphate were present. There was not found any correlation between its occurrence and the salinity.
- Blue-green algae were generally thinly populated in the water rich in diatoms.
14.
Eric D. Barton Javier Arístegui Paul Tett Eleuteria Navarro-Prez 《Progress in Oceanography》2004,62(2-4):71
The physical background to a suite of biological studies carried out in the Canary Islands upwelling region is presented. The area is unique in that the coastal transition zone is spanned by an archipelago of islands that shed mesoscale eddies of diameter 50–100 km into the alongshore flow. A recurrent filament and eddy system was sampled intensively to study the changing properties of waters as they are advected towards the open ocean in the filament and to investigate the exchanges between filament and eddies. The system was more complex than previously revealed. In early August, a single filament extended offshore from near Cape Juby. Two weeks later, a second filament had developed slightly farther north and extended offshore to merge with the first at 100 km offshore. The merged filament was entrained around a recurrent, topographically trapped cyclonic eddy and interacted with transient cyclonic and anticyclonic eddies shed from the island of Gran Canaria. Between the two filaments and the coast, a pair of counter-rotating eddies re-circulated water parcels for several weeks. Surface layer drifters cycled around this near-shore re-circulation several times before following convoluted paths that demonstrate significant exchange between continental shelf and open ocean waters. 相似文献
15.
We study the energy exchange between jets of the Antarctic Circumpolar Current (ACC) and synoptic eddies generated by them in the surface layer of the ocean in the Drake Passage and Scotia Sea based on 22-year-long satellite altimetry time series from the French CLS Agency (DT Global–MADT–Upd product, http://www.aviso.altimetry.fr) under the assumption, based on observations, that each of the jets is confined between two fixed contour lines of the absolute dynamic topography of the ocean. We calculate and analyze the 22-year evolution of the kinetic energy of each ACC jet and cyclonic and anticyclonic eddies generated by it. We demonstrate the fundamental dependence of fluctuations in jet energy on the phase of their meander and eddy formation, as well as their back absorption by jets. We calculate the mean and extreme energetic characteristics of jets and eddies and compare the jets in terms of the intensity of the generated eddies. 相似文献
16.
《Marine Policy》1999,23(1):11-24
By 1 August 1998 Regulation I/7 of the 1995 amendments to the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (1978) requires a comprehensive submission of information to the International Maritime Organization supporting an Administration’s claim that it complies fully with, or is in the process of implementing, STCW ’95 via policy and legislative processes. Once the complete information is received by the International Maritime Organization, the Secretary-General must submit a report to this effect to the Maritime Safety Committee. Three questions emerging from this controversial provision in STCW ’95 are:
- •When, if ever, is the information from an Administration complete?
- •What is the time frame allocated for confirmation by the IMO Secretariat?
- •How does IMO assess whether the claim by an Administration is valid?
17.
The vorticity generation around a coastal promontory is examined using a transport vorticity equation. The complete vorticity balance analysis is made for the transient and residual vorticity generations around an idealized, symmetric promontory. The topographic vorticity tendency is found to be the dominant forcing term in the production of transient tidal vorticities. This result is different from the previous works which emphasized the effects of lateral and bottom frictions. The residual vorticity balance is between advection and topographic vorticity tendency. The model results are consistent with the observations off Gay Head, Massachusetts. Also, the stability of a promontory as well as the offshore sand bank formation are studied by examining the sand transport pattern around the promontory. Strong deposition occurs off the tip of the promontory while erosion occurs along the upstream slope of the promontory suggesting that an originally symmetric promontory tends to incline cyclonically from the axis normal to the tidal stream. Such tendency is indeed found among coastal promontories. 相似文献
18.
Effects of the longshore variation of the coastline geometry and the bottom topography on coastal upwelling are discussed. Longshore variations of the topography cause local enhancing or weakening of upwelling in the process of the generation and propagation of internal Kelvin and the shelf waves. 相似文献
19.
Shinsuke Tanabe 《Journal of Oceanography》1985,41(5):358-370
I am extremely grateful and honored for being awarded the Okada Prize (1985) for my study. The present article reviews my research on the distribution, behavior and fate of PCBs in the marine environment. The outline of this study is summarized as follows:
- Polychlorinated biphenyls (PCBs) were detectable in the wide range of environmental media and biota of the Seto-Inland Sea, Japan, in which much high concentrations were found in sediment and biological samples due to their hydrophobic, lipophilic and less biodegradable properties as well as their extensive production and use in estuarine and coastal regions.
- PCBs extend the boundaries of their distribution all over the global environment, being evidenced by their occurrence in open ocean atmosphere, hydrosphere and biosphere, even in Antarctica. The global contamination of PCBs is much more prominent in northern hemisphere than in southern hemisphere.
- The sinking rate of PCBs from surface to deeper layers in open ocean water column is relatively slower in tropical waters than in high latitude ones. This implies the possible prolonged contamination of persistent synthetic organic chemicals in the tropical marine environment.
- The bioaccumulation processes in marine ecosystems can be explained by the physicochemical and biochemical properties of PCBs and the metabolic capacity of organisms. In higher animals, additional factors such as parturition and lactation are also related to this process.
- Total PCB load in global environment was estimated to be about 370 thousand tons. Of this, most amounts were in coastal sediment and open ocean water. Presently, about 780 thousand tons of PCBs are still in use mainly in electrical equipments. In order to reduce the PCB levels in marine environment, pertinent measures to prevent the further discharge and safe disposal of PCBs are required.
20.
The oil pollution in the Izu Islands waters are observed as follows:
- Globules and lumps of oil were collected 2.56 g on the average in wet weight by each taw(174 m3) of a larval net at 389 stations, up to the maximum collection of more than 500 g.
- On the investigation of the Oshima—Torishima line (J1–J10), globules and lumps of oil were collected more at the south of the Kuroshio Current than at the north.
- In the coastal region (T1–T19) of Japan, many globules and lumps of oil were collected when a cold water mass was located at the west side of the Izu Islands, from south to east side of where the Kuroshio Current took a roundabout and closed near to the Bōsō peninsula (Aug. 1971, Jun. 1972, Aug. 1972), or when the Kuroshio Current took a roundabout the cold water mass which extended as far as Oshima from the coast of the Bōsō peninsula (Sept. 1971).