The historical geography of the seas around the British Isles

The historical geography of sea uses is outlined as a sequence of stages of developent. The resulting geographical patterns are discussed in terms of the major sea use groups involved, including reference to urban and rural sea use categories. Source materials for the historical geography of the sea are considered, followed by evaluation of major factors involved, including in particular the roles of technological, economic and environmental considerations.     

Variation of the tidal properties around Gran Canaria

Analysis of water level and current meter series from different locations on the island shelf of Gran Canaria reveals strong variations in tidal properties. Semidiurnal sea level amplitudes agree with the results obtained from global tidal models for this region only on the northern coast of the island, while they decrease towards the southwest (10 cm difference for the M₂ constituent). Semidiurnal currents present maxima at the southeastern and northwestern extremities of the island (30–40 cm s⁻¹ for M₂) and minima in the north-northeast and southwest (3–6 cm s⁻¹ for M₂), showing simultaneous strong changes in the phase. Diurnal levels and currents display smaller variations than the semidiurnal band. The behaviour of semidiurnal constituents is studied with the help of analytical and numerical solutions, in which the incident wave is modelled by a barotropic M₂ Kelvin wave. The results show that the insular shelf could be a source of differences in level amplitudes around the island and could be also responsible for the enhancement of currents in the southeast and northwest. They also show that the variation of the current phases is due to the amplification of the standing character of the wave at the northeastern and southwestern parts of the shelf.     

Coastal planning on the Atlantic fringe,north Norway: the power game

The article describes an on-going struggle between local planning authorities, regional fishery authorities and environmental authorities over the management of the Norwegian coastal zone. Particular reference is made to a recent planning project in Nordland County where 18 peripheral communes with weak planning traditions joined forces to produce structure plans for their coastal areas. Concepts of rationality and power are used as points of departure for an interpretation of the actions of the parties involved. The discursively rational nature of the planning project, embodying principles of consensus building, social integration and personal growth, is contrasted to the strictly instrumental behaviour of regional fishery and environmental authorities. The article also relates conflicts between communes and regional sector authorities to the power structure of the field of coastal management and the habitus of the different institutional actors. The actions of the fishery authorities are seen as a defence of their monopoly of the production of ideology in marine management, while the actions of the communes are interpreted as a bid by the periphery for greater control over local resources.     

Numerical study on the flow characteristics of tidal jets induced by a tidal-jet-generator

The flow characteristics of tidal jets induced by a Tidal-Jet Generator (TJG) are investigated using a finite-difference numerical scheme, named Navier–Stokes (NS)–Marker and Cell (MAC)-TIDE, based on the fully 3D NS equations. The TJG is an enclosed rectangular breakwater, which has vertical opening and a large enclosed volume inside. During both phases of tide, strong and uni-directional jets can be obtained locally from the inlet of the TJG, due to the water level difference between the inner and outer sides of TJG.The computed results are extensively compared with three other independently developed numerical models; 3D-ADI, DVM, and CIP-CSF. These models are based on quasi-3D, 2D depth-averaged, and fully 3D NS equations, respectively. It is seen that the present fully 3D numerical model NS–MAC-TIDE can predict the maximum intensity of inlet velocity with higher accuracy than the other numerical models when compared with the empirical function proposed from the experiments. The numerical simulations based on NS–MAC-TIDE can reproduce successfully the processes of generation, development, and dissipation of tidal jets. The effects of gap opening on the main characteristics of the tidal jet flow are assessed. Through numerical assessment, it is also clearly demonstrated that the residual time of a pollutant distributed around the front of the TJG can be decreased by significant amount due to the locally induced tidal jet. The TJG can thus utilize tidal energy for water purification in local marine environment by providing a flushing mechanism.     

Phase distribution of tidal constituents around New Zealand

The phase distributions of the M₂, S₂, K₁, and O₁ tidal constituents around New Zealand are plotted from existing harmonic analyses of tidal heights. Both semidiurnal constituents exhibit a complete 360° range of phase around New Zealand, with complex areas of rapid phase change through or near the strait separating the two main islands. The K₁ amphidrome and that for O₁, which previously were thought to be centred on New Zealand, are shown to be located cast of New Zealand. The distributions plotted highlight areas where tidal observations are lacking.     

大小门岛海域表层潮流和余流特征分析

利用2012年4月份进行水文调查得到的实测海流数据,依据多周日观测的准调和分析原理,对大小门岛海域表层潮流进行调和分析。基于调和分析结果对大小门岛海域潮流和余流特征进行精细化研究。结果表明:大小门岛海域潮流类型为不正规半日浅海潮流,大小门岛西部海域受浅水分潮影响最大。整个海域潮流运动形式以往复流为主,由于受到多股往复流的干涉作用,大门岛西侧旋转流较强;实测落潮流要强于涨潮流,流速在瓯江口外侧达到最大。余流走向存在区域性差异,小门岛西北、瓯江口内部及黄大峡海域余流方向与涨潮流一致,其它区域与落潮流一致,余流流速大小与最大流速分布基本一致。     

Ebb-tidal jets: A model of suspended sediment and mass transport at tidal inlets

Mass transport by turbulent jets issuing from tidal inlets is investigated through a model that includes lateral mixing and entrainment, bottom friction, bathymetric changes, settling rate of particles (size), possible deposition/erosion at the bottom and ambient currents and concentrations. The bottom frictional jet becomes diluted more slowly than a classical jet. A non-vanishing concentration may result offshore and a maximum may occur in the core. The concentration of a jet on a sloping bottom decreases more rapidly due to increased dilution by entraiment. The effects of bottom friction and bottom slope compete in determining the jet concentration. Deposition to the bottom occurs within the jet mainly on both sides of the centre-line, and at lower rates on the centre-line. Erosion or deposition may occur at the jet core depending on the inlet flow conditions. In the case of erosion at the core, the material extracted is deposited on the margins and the offshore areas. Sorting of the sediments is expected, with coarser materials mainly deposited in the marginal areas, while the finer sediments are more uniformly distributed and jetted further off-shore. The main features of the model are verified through a limited set of observations. The qualitative agreement is enhanced for micro- and meso-tidal inlets that are dominated by tidal hydraulics.     

环渤海地区沿海城市的生态效率

环渤海地区是我国最具综合优势和发展潜力的经济增长极之一。为促进环渤海地区的生态文明建设和经济可持续发展,文章采用三阶段DEA模型、Malmquist指数和空间自相关分析法,基于2006—2015年环渤海地区17个沿海城市的面板数据,动静态结合分析其生态效率和空间关联特征。研究结果表明:通过引入环境变量和运用相似SFA模型,剔除外部环境和随机误差的影响,可更加准确地测算区域生态效率;各城市的生态效率均有所提高,主要原因是技术进步;区域生态效率同时存在空间的相关性和差异性,空间格局处于动态变化中。     

Nutrient processing and the development of tidal creek ecosystems

The North Inlet marsh-estuarine system encompasses the spectrum of interaction between the ocean and the uplands typical of the southeastern United States. The system is an ebb-dominated, bar-built estuary with good flow connection to the sea and some freshwater input.The North Inlet basin has evolved from a forested, relic, beach-ridge terrain under a regime of slowly rising sea level (2 mm year⁻¹). This mode of development is supported by historic tide gage data. ²¹⁰Pb dating of sediment cores, the presence of spodic soil horizons and tree roots at shallow depths beneath the marsh surface, and the presence of relic ‘cat eye’ ponds at the edge of the salt marsh. As sea level rises, the boundary between forest and salt marsh recedes upslope and forest spodosols are gradually transformed into marsh soils by salinization, the deposition and mixing of marine mud into the upper horizons of the forest soil and the accumulation of reduced sulfur via sulfate reduction. As a forest watershed is transformed into a salt-marsh basin, the hydraulic geometry of the original, black-water (fresh) stream increases to accommodate the increasing volumes of tidal discharge. Forest sands move seaward while marine muds are transported into the basin.As water moves between the forest and the sea, it passes through creeks in different developmental stages. Large mature creeks interact with the ocean while young, ephemeral creeks drain the uplands and intertidal marsh zones. Intermediate stage creeks connect these two and are characterized by the presence of oyster reefs. Net nutrient fluxes appear to be different in each developmental stage.The ‘Bly Creek’ study of Dame and coworkers addressed the flux of materials between a creek at the intermediate stage of development and the adjacent mature system. Material fluxes from a freshwater stream draining into Bly Creek from the adjacent uplands were also observed. The role of the salt marsh and the oyster reefs in determining material fluxes was examined. The Bly Creek basin imports particulate nutrients and exports dissolved forms.The ‘Outwelling’ study of Dame and coworkers at North Inlet focused on the flux of materials between the mature creeks and the Atlantic Ocean. All constituents were exported seasonally and annually from the estuary, except total sediments (imported during fall and winter) and chlorophyll a (imported in the summer and fall). The export of carbon, nitrogen and phosphorus was high compared with other estuarine systems.On a unit area basis, primary productivity is higher and nutrient fluxes are lower in Bly Creek (intermediate stage of development) as compared with the mature North Inlet system. These observations support the general ecosystem development hypothesis that nutrient storage and retention are higher in younger systems than more mature systems where growth is lower and fewer nutrients are needed.     

环北部湾海岸带的生态环境建设

本文在对环北部湾海岸带生态环境进行综合评价的基础上，综合该地区在海岸带资源开发利用过程中引发的一系列环境问题，对海岸带生态环境的建设对策进行了探讨。     

The role of tidal vortices in material transport around straits

The strong tidal current (tidal jet) in straits generates tidal vortices with a scale of several kilometers. The role of the vortices in material transport was investigated in the Neko Seto Sea, located in the western part of the Seto Inland Sea of Japan. A clockwise vortex with a diameter of about 0.8 km was observed in Nigata Bay (lying between two straits, the Neko Seto Strait and the Meneko Seto Strait). It was concluded that the clockwise vortex was the tidal vortex which was generated by the tidal jet in the Meneko Seto Strait. The vortex moved into the bay with the tide, but tended to stay on the sand bank in the bay. It was confirmed by current measurement with an ADCP and turbidity measurement that the secondary convergent flow was generated in the bottom layer of the vortex. This secondary flow seemed to contribute to the formation of the sand bank. It was suggested that tidal vortices may play an important role in the sediment transport and formation of topography in and around straits.     

Formation of sand banks due to tidal vortices around straits

Sand banks around straits are used as a commercial fishing ground. In order to clarify the mechanism of sand bank formation, the Lagrangian method was used to measure currents and turbidity around the banks in the Neko Seto Sea in the Seto Inland Sea of Japan. A neutrally buoyant float released in the Neko Seto Strait at the maximum tidal flow stage was engulfed in a pair of tidal vortices and moved around one of the sand banks. The vertical distribution of turbidity, which was measured by the vessel moving with the neutral float, showed an extremely high turbidity in the bottom layer of this bank area. According to the analysis of these observational data, the process of sand bank formation around straits is as follows. The tidal vortex transports water mass with suspended materials (including sand) which are whirled up at the bottom by the tidal jet. In the decaying stage of the vortex, the materials in the bottom layer are gathered in the central part of the vortex by the secondary convergent flow in the vortex. Among these materials, a large-size sand particle with a high critical erosion velocity accumulates at the bottom and forms banks. The distribution of bottom sediment and the thickness of alluvium support this result.     

岙山监测浮标周边海域水质分析与评价

文章根据岙山监测浮标周边海域2015年9-12月水质调查资料,采用水质有机污染指数(A)、富营养化指数(E)和营养状态质量指数(NQI)等进行评价。结果表明:岙山监测浮标周边海域水质化学需氧量(COD)、溶解氧(DO)、油类(oils)符合二类海水水质标准,无机磷(DIP)和无机氮(DIN)含量均超过二类海水水质标准,DIP最高为0.048mg/L,DIN最高为0.753mg/L,总磷(TP)各月平均含量范围0.098~0.185mg/L,总氮(TN)各月平均含量范围0.650~0.818mg/L,叶绿素a(Chl a)含量基本稳定,DIN是主要的超标污染因子;富营养化评价结果显示,岙山监测浮标周边海域水质富营养程度严重,E值最高达9.10,NQI值最高为4.58;有机污染评价结果表明,岙山监测浮标周边海域水质总体处于轻度污染状态,A值最小为10月的1.90,最大为12月的2.73;使用A值、E值和NQI值方法同时对岙山监测浮标周边海域进行评价,其结果变化的一致性较好。     

Residual and tidal circulation revealed by VHF radar surface current measurements in the southern Channel Isles region (English Channel)

Two very high-frequency radars (VHFRs), operating in the southern Channel Isles region (English Channel) in February–March 2003, provided a continuous 27-day long dataset of surface currents at 2 km resolution over an area extending approximately 20 km offshore. The tidal range in the region of study is one of the highest in the world and the coastal circulation is completely dominated by tides. The radar data resolve two modes which account for 97% of the variability of the surface current velocities, with the major contribution of the first mode. This mode accounts for oscillating tidal currents whereas the second mode represents motions emerging from the interaction of tidal currents with capes and islands (eddy in the vicinity of the Point of Grouin and jet south of Chausey). A fortnightly modulation of the modal amplitudes causes the exceptional (more than 600%) variability of currents which is well captured by the VHFR observations. The radar data revealed that tidal circulation in the region is flood-dominated with a strong asymmetry of current velocity curve. Wind events and fortnightly variability affect the course of tidal cycle by modifying the magnitude and duration of ebb and flood. In addition to expected features of coastal circulation (tidally dominated flow, eddies) and high wind-current coupling, the residual currents revealed a strong cross-shore structure in the mean and a significant variability which has the same order of magnitude.     

Environmental evaluation and development problems of the Mexican Coastal Zone

The coastal zone is the main source of foreign currency for Mexico so that federal policies are adjusting to try to improve its conditions. To that end, a large and comprehensive study was financed by the government to assess the state of knowledge of the water quality of coastal waters and the environmental status of the whole coastal area in Mexico. Based on the existing literature found in the most important research institutions of the country, as well as on field visits to 42 coastal cities from 1996 to 1998, and complemented with interviews of more than 80 persons (“key informants”) involved in the different key activities of the sites visited, the main environmental parameters useful to assess water and environmental quality were selected. All the sites where data existed and in particular the 42 main coastal cities were then analyzed according to the different categories of stress to which they are subjected and the degree of damage observed and reported. As a result, an environmental diagnosis of the Mexican coastal zone is outlined, divided by type of activity. The oil and related petrochemical industries as well as the big tourist resorts were identified as the largest contributors to the degradation of the natural ecosystems in the Mexican Coastal Zone.     

山东沿海台风浪数值模拟与统计分析

为了得到山东沿海台风浪的重现期波高分布场,以Jelesnianski-Ⅱ模型构建的风场作为模式驱动,利用SWAN模式建立了山东及其附近海域的台风浪数值模型。通过对典型台风过程"麦莎"和"梅花"的数值计算,将模拟的有效波高与观测数据作了对比分析,验证了模型在计算海域的适用性;基于建立的模型,对1960-2012年期间发生于山东沿海的50场台风进行模拟。选取计算海域10个点的模拟所得波高序列,寻求复合极值分布拟合最优的分布型式,根据所得分布进行重现期波高的统计分析;最终绘制计算海域50年一遇和100年一遇的台风浪波高分布图,为山东沿海的防灾减灾和海洋结构设计提供参考依据。     

Numerical simulation of characteristics of semidiurnal tidal waves in sea region around Taiwan

INTRODUCTIONNumerica comutation and simu1ation of tidal waves in the closed ocean of China havebo greatly imProved in recent years. As far as the method Of numerica comPU8tion are con-cemed, we can divide them into two classes: beundary va1ue methed and initial value methed.The fOrmer needs the tidal level value of coast beund8ry and the side beundary of water shOuldbe given, and its calculative result dePends on the reliability of boundary value. The rnan-madeermr, caed by getting the…     

环台湾岛海域半日潮波特征的三维模拟

用1997版POM海洋模式,首次应用于环台湾岛海域的潮波数值研究.得到该海域的半日潮波主要为23°N以南西太平洋传来的胁振潮.影响台湾海峡的半日潮波分别由海峡南北口传入的两支潮波,且北支强于南支.福建沿岸湄州湾-兴化湾为最强潮区,其M₂分潮最大振幅可达240cm.最强潮流区位于澎湖水道,M₂分潮最大潮流达196cm/s.环台湾岛海域潮波潮流水平结构上除海峡北部原有一个圆流点外,还发现另外存在4个新的圆流点.潮流垂直结构上主要为右偏,接近底层处为左偏.     

Accurate ocean tide modeling in southeast Alaska and large tidal dissipation around Glacier Bay

An accurate prediction of ocean tides in southeast Alaska is developed using a regional, barotropic ocean model with a finite difference scheme. The model skill is verified by the observational tidal harmonics in southeast Alaska including Glacier Bay. The result is particularly improved in Glacier Bay compared to the previous model described by Foreman et al. (2000). The model bathymetry dominates the model skill. We re-estimate tidal energy dissipation in the Alaska Panhandle and suggest a value for tidal energy dissipation of 3.4 GW associated with the M₂ constituent which is 1.5 times the estimation of Foreman et al. (2000). A large portion of the M₂ energy budget entering through Chatham Strait is dissipated in the vicinity of Glacier Bay. Moreover, it is shown that the developed model has the potential to correct the ocean tide loading effect in geodetic data more efficiently than the model of Foreman et al. (2000), especially around Glacier Bay.