Fish wars: Conflict and collaboration in fisheries management in Southeast Asia     

《Marine Policy》2007,31(6):645-656

As a result of declining and overfished small-scale nearshore fisheries in Southeast Asia, there are increasing conflicts and social tensions between and among different user groups, leading to coastal “fish wars”. A challenge facing fishers, resource managers and national decision makers in the region is to identify more appropriate governance and public policy mechanisms to manage conflicts over fishery resources and to resolve them productively in the interests of both long-term sustainability and short-term economic feasibility. A quantitative analysis undertaken in selected coastal communities in Indonesia, the Philippines, Thailand and Vietnam with and without co-management indicate that co-management does lead to reduced resource conflict levels. The analysis has also shown that when resource conflicts are reduced, food security improves.  相似文献   

Near real-time ocean circulation assimilation and prediction in the Intra-Americas Sea with ROMS     

《Dynamics of Atmospheres and Oceans》2010,49(1-3):46-68

We present the feasibility of a prototype, near real-time assimilation and ensemble prediction system for the Intra-Americas Sea run autonomously aboard a ship of opportunity based on the Regional Ocean Modeling System (ROMS). Predicting an ocean state depends upon numerical models that contain uncertainties in their modeled physics, initial conditions, and model state. An advanced model, four-dimensional variational assimilation, and ensemble forecasting techniques are used to account for each of these uncertainties. Every 3 days, data from the previous 7 days period were assimilated to generate an estimate of the circulation and to create an ensemble of 2 weeks forecasts of the ocean state. This paper presents the methods and results for a multi-resolution assimilation system and ensemble forecasts of surface fields and dominant surface circulation features. When compared to post-processed science quality observations, the state estimates suffer from our reliance on real-time, quick-look satellite observations of the ocean surface. Despite a number of issues, the ensemble forecast estimate is often superior to observational persistence. This proof-of-concept prototype performed well enough to reveal deficiencies, provide useful insights, valuable lessons, and guidance for future improvements in real-time ocean forecasting.  相似文献   

A magnetic fluid laboratory model of the global buoyancy and wind-driven ocean circulation: Analysis     

《Dynamics of Atmospheres and Oceans》2006,41(2):121-138

A magnetic fluid laboratory model of the global buoyancy and wind-driven ocean circulation is analyzed. Magnetic fluid is attached to a horizontal cylinder rotating about a vertical axis through its center. The magnetic gravity is radially inwards and is much larger than the normal terrestrial gravitational acceleration g. Motion is driven by imposed meridional heating gradients and/or a surface wind stress. Since the fluid occupies the region from equator to pole, or perhaps some other range of latitude spanning at least 90°, such a facility allows the laboratory simulation of large scale ocean flows. The method of forming the magnetic gravity involves the use of a stack of cylindrical disk magnets, separated by spacers. Although the dominant component of the magnetic gravity is radial and axially invariant, there is a residual “anomalous gravity” that is periodic with a wavelength equal to the magnet spacing along the direction of the magnet stack. The nature of secondary circulations induced by this spatial variation of magnetic gravity will interfere with the proposed experiments on ocean circulations. In this paper we determine the size of such circulations, and compute the expected changes in stability properties of the system due to these anomalies. The spatially-periodic secondary circulations and gravity modulations can be either stabilizing or destabilizing. The physical mechanisms affecting the stability in the limits of small and large values of the Rayleigh number are extracted from the analysis.  相似文献   

Sedimentary features of the Yangtze River-derived along-shelf clinoform deposit in the East China Sea     

《Continental Shelf Research》2006,26(17-18):2141-2156

A predominant sigmoidal clinoform deposit extends from the Yangtze River mouth southwards 800 km along the Chinese coast. This clinoform is thickest (∼40 m) between the 20 and 30 m isobaths and progressively thins offshore, reaching water depths of 60 and 90 m and distances up to 100 km offshore. Clay mineral, heavy metal, geochemical and grain-size analyses indicate that the Yangtze River is the primary source for this longshore-transported clinoform deposit. ²¹⁰Pb chronologies show the highest accumulation rates (>3 cm/yr) occur immediately adjacent to the Yangtze subaqueous delta (north of 30 °N), decreasing southward alongshore and eastward offshore. The interaction of strong tides, waves, the China Coastal Current, winter storms, and offshore upwelling appear to have played important roles in trapping most Yangtze-derived sediment on the inner shelf and transporting it to the south.  相似文献   

Effect of the mesoscale hydrographic features on larval fish distribution across the shelf break of East China Sea     

《Continental Shelf Research》2007,27(10-11):1616-1628

Surveys of fish larvae and oceanographic conditions were conducted along transects across the shelf break region in the East China Sea (ECS) in May 2001. The objective of this study was to investigate the distribution and assemblages of fish larvae across the shelf break region and their relationships to mesoscale hydrographic features. There was a warm surface streamer from the Kuroshio which extended toward the shelf region of the ECS; concurrently, we observed the intrusion of the less saline shelf water into the subsurface layer towards the offshore. In all 66 taxa (65 families and 1 order) of larvae were collected by oblique net tows using a bongo net, the larval fish density and number of families sampled were lower in the low-temperature area. Based on cluster analysis and environmental factor, two larval fish assemblages were identified: off-shelf/Kuroshio and shelf break. In shelf break assemblage, Auxis spp. and Diaphus spp. were abundant in the warm surface streamer. In contrast, Maurolicus japonicus, Synagrops spp., Bregmaceros sp. and Champsodon spp. were found in the off-shelf region where the offshore intrusion of less-saline water occurred. This different pattern of the horizontal distribution would reflect vertical distribution of the larvae in the water column. Moreover, copepod nauplii density was higher in the upper layer of the shelf region. Thus, dynamic interactions between the Kuroshio and shelf waters at the frontal boundary are concluded to potentially affect larval fish transport and prey availability.  相似文献   

Abrupt resumption of the African Monsoon at the Younger Dryas—Holocene climatic transition     

《Quaternary Science Reviews》2007,26(5-6):690-704

A high-resolution sedimentary record from Lake Masoko (Tanzania), based on pollen assemblages and magnetic susceptibility, shows that the most prominent environmental change of the last 45 000 years occurred ca 11.7 cal. ka BP, near the end of the Younger Dryas event. During this climatic transition, the Masoko catchment vegetation changed from being intolerant to a long/severe dry season to being tolerant, while the inferred lake-dynamics indicates strengthened seasonal fluctuations and/or lower levels than before. Comparison of the Masoko record with other regional palaeoclimatic data shows that evidence of this climatic transition is widespread in tropical Africa. The proposed failure of the African Monsoon during the Younger Dryas, associated with a southward position/migration of the meteorological equator in East Africa, was followed by an abrupt and lasting resumption of monsoon activity, and more pronounced migration of the Intertropical Convergence Zone (ITCZ) over the African continent. Such a reorganisation of the atmospheric circulation, equally observed across the whole tropical region (South America, East and West Asia, and Africa), could have been a strong amplifier of northern high latitude changes in temperature and precipitation across this major climatic transition.  相似文献   

Numerical models for evolution of extreme wave groups     

《Applied Ocean Research》2019

The paper considers the application of two numerical models to simulate the evolution of steep breaking waves. The first one is a Lagrangian wave model based on equations of motion of an inviscid fluid in Lagrangian coordinates. A method for treating spilling breaking is introduced and includes dissipative suppression of the breaker and correction of crest shape to improve the post breaking behaviour. The model is used to create a Lagrangian numerical wave tank, to reproduce experimental results of wave group evolution. The same set of experiments is modelled using a novel VoF numerical wave tank created using OpenFOAM. Lagrangian numerical results are validated against experiments and VoF computations and good agreement is demonstrated. Differences are observed only for a small region around the breaking crest.  相似文献   

A wave-flume study of scour at a pile breakwater: Solitary waves     

《Applied Ocean Research》2019

Understanding the sediment transport and the resulting scour around coastal structures such as pile breakwaters under local extreme wave conditions is important for the foundation safety of various coastal structures. This study reports a wave-flume experiment investigating the scour induced by solitary waves at a pile breakwater, which consists of a row of closely spaced large piles. A wave blacking gate with a simple operation procedure in the experiment was designed to eliminate possible multiple reflections of the solitary wave inside the flume. An underwater laser scanner and a point probe were used in combination to provide high-resolution data of the bed profile around the pile breakwater. Effects of incident wave height and local water depth on the maximum scour depth, the maximum deposition height and the total scour and deposition volumes were examined. An existing empirical formula describing the evolution of the scour at a single pile in current or waves was extended to describe the scour at the pile breakwater under the action of multiple solitary waves, and new empirical coefficients were obtained by fitting the formula to the new experimental data to estimate the equilibrium scour depth. It appears that the maximum scour depth and the total scour volume are two reliable quantities for validation of numerical models developed for the scour around pile breakwaters under highly nonlinear wave conditions.  相似文献   

Effects of reef morphology variations on wave processes over fringing reefs     

《Applied Ocean Research》2019

Many low-lying tropical and sub-tropical atolls fringed by coral reefs are susceptible to coastal inundation during extreme wave events. Previous studies have shown that the infragravity (IG) wave is the dominant component of shoreline run-up compared to the sea and swell (SS) wave and the wave-induced setup. To better understand both the SS and IG wave dynamics over a fringing reef with various morphologies, a series of laboratory experiments were conducted in a wave flume based on an idealized fringing reef profile. The shoreline responses of waves to different reef morphologies with/without the reef crest, the lagoon and the reef surface roughness were examined. IG wave resonance on the reef flat was identified by a spectral analysis of the shoreline wave records. Subsequently, a numerical model based on the Boussinesq equations was validated by the experimental data. The model was then applied to investigate the impacts of varying reef morphologic features (fore-reef slope, reef-crest width, lagoon width, and reef roughness coefficient) on the shoreline wave motions.  相似文献   

Response based design metocean conditions for a permanently moored FPSO during tropical cyclones: Estimation of greenwater risk     

《Applied Ocean Research》2019

Response based analysis (RBA) is used to establish the design metocean conditions (DMCs) of a generic weather-vaning FPSO off the North West Shelf (NWS) of Australia for determining greenwater severity. A vessel heading prediction tool, an essential component of the RBA analysis for weather-vaning vessels, is developed and evaluated by comparing with full-scale measurements from an operating FPSO. Locations at the bow, amidships and the stern of the vessel are found to be susceptible to greenwater risks and the vessel is often exposed to oblique waves during tropical cyclones. Long-term extrapolation is performed to estimate 1 in. N-year return relative wave-vessel motions represented by both the most probable maximum relative wave-vessel motion within a storm r_mp, and the maximum individual relative wave-vessel motion r_Max. It is observed that r_Max ˜ (1.1–1.2) r_mp. The use of r_Max allows for the variability of the short term maxima per storm and also the fact that the peak in response might not come in the most severe sea-state. Given the focus on greenwater rather than wave severity, the slightly larger value of r_Max at a given return period is used for assessment of greenwater risk. The sea-states that lead to r_Max at a 1 in 100 year level are identified and subsequently used for characterising the wave groups causing maximum relative wave-vessel motion at various locations around the vessel. For a given location, the shapes of the wave time histories which give rise to extreme relative wave-vessel motions in a set of design metocean conditions are similar, indicating that a ‘design wave’, derived within the framework of linear wave theory, may be a useful approach to tackle highly nonlinear and complex greenwater overtopping problems.  相似文献