安达曼海东部凹陷渐新世以来断裂–构造演化特征及其成因探讨

本文研究内容为印度洋东北部边缘海安达曼海的构造演化。利用安达曼海域东部大范围二维地震数据资料及钻井数据,结合区域地质概况以及前人研究成果,选取8条具有代表性的断层并将其划分为一级和二级断裂,运用生长指数法和古落差法对断层进行定量分析,再通过计算安达曼海东部凹陷4条主测线的构造沉降量,探讨构造演化过程。结果表明：选取的生长断层中3条属于一级断裂,跨度大,几乎切穿整个地层,属于控制安达曼海域地区沉降的大断裂;另外5条属于二级断裂,控制构造带的展布情况,属于构造带的分界线。渐新世时期,印度–澳大利亚板块与欧亚板块之间处于软碰撞阶段,断层发育缓慢,上下盘落差较小,生长指数与构造沉降量也处于低值;中新世时期,板块之间的耦合效应不断增强,断层发育速度加快,此时上下盘厚度最大,是形成多处断裂带以及多种断裂样式的关键时期,各地层生长指数和构造沉降量也达到峰值。上新世至今,安达曼海沟–弧–盆体系逐渐稳定,断层活动减弱,断裂上下盘厚度差基本一致,生长指数差异较小,构造沉降量基本稳定在 1 km 左右。     

A Zonal Pathway for NADW in the South Atlantic

Several large deployments of neutrally buoyant floats took place within the Antarctic Intermediate (AAIW), North Atlantic Deep Water (NADW), and the Antarctic Bottom Water (AABW) of the South Atlantic in the 1990s and a number of hydrographic sections were occupied as well. Here we use the spatially and temporally averaged velocities measured by these floats, combined with the hydrographic section data and various estimates of regional current transports from moored current meter arrays, to determine the circulation of the three major subthermocline water masses in a zonal strip across the South Atlantic between the latitudes of 19°S and 30°S. We concentrate on this region because the historical literature suggests that it is where the Deep Western Boundary Current containing NADW bifurcates. In support of this notion, we find that a net of about 5 Sv. of the 15–20 Sv that crosses 19°S does continue zonally eastward at least as far as the Mid-Atlantic Ridge. Once across the ridge it takes a circuit to the north along the ridge flanks before returning to the south in the eastern half of the Angola Basin. The data suggest that the NADW then continues on into the Indian Ocean. This scheme is discussed in the context of distributions of dissolved oxygen, silicate and salinity. In spite of the many float-years of data that were collected in the region a surprising result is that their impact on the computed solutions is quite modest. Although the focus is on the NADW we also discuss the circulation for the AAIW and AABW layers.     

Species composition and spatial distribution of euphausiids of the yellow sea and relationships with environmental factors

We investigated species composition and spatial distribution of the euphausiid community in the Yellow Sea and identified the relationship with environmental factors (temperature, salinity, chlorophyll a, nitrate, phosphate, and silicate) using bimonthly data from June, 1997 to April, 1998. The environment varied during the sampling period. In warm seasons, thermocline was well developed rendering lower temperature and higher salinity and nutrient concentrations in the bottom layer. During cold seasons the water column was well mixed and no such vertical stratification was noted. Horizontal distribution of temperature, however, differed slightly between near-coast and offshore areas because of the shallow depth of the Yellow Sea, and between southern and northern areas because of the intrusion of water masses such as Yellow Sea Warm Current and Changjiang River Diluted Water. Four euphausiid species were identified:Euphausia pacifica, E. sanzoi, Pseudeuphausia sp. andStylocheron affine. E. sanzoi andS. affine were collected, just one juvenile each, from the southern area in June and December, respectively.Pseudeuphausia sp. were collected in the eastern area all the year round except June.E. pacifica occurred at the whole study area and were the predominant species, representing at least 97.6% of the euphausiid abundance. Further, the distribution pattern of the species was varied in regards to developmental stages (adult, furcilia, calyptopis, egg). From spring to fall,E. pacifica adults were abundant in the central area where the Yellow Sea Bottom Cold Water prevailed. Furcilia and calyptopis extended their distribution into nearly all the study area during the same period. From late fall to winter, adults were found at the near-coastal area with similar pattern for furcilia and calyptopis. The distribution pattern ofE. pacifica was consistent regarding temperature, salinity, and three nutrients during the sampling period, whereas chlorophyll a showed a different pattern according to the developmental stages. The nutrients should indirectly affect via chlorophyll a and phytoplankton concentration. With respect to these results, we presented a scenario about how the environmental factors along with the water current affect the distribution ofE. pacifica in the Yellow Sea.     

Testing taxonomic resolution,data transformation and selection of species for monitoring macroalgae communities

The Water Framework and Habitats Directives require the evaluation of both the conservation and ecological status of macroalgae communities at water body or habitat level. However, assessments of macroalgal communities are highly time-consuming, both in terms of sampling effort and laboratory processing. These constraints have brought about their oversight in many marine monitoring programs, especially in subtidal environments. By using data from intertidal and subtidal macroalgae assemblages of Mouro Island (North coast of Spain) we wanted to identify possible cost-effective methods for monitoring this biological indicator, based on both high taxa levels and use of representative taxa. Multivariate analyses were applied using different data transformations. The results show that macroalgal communities are robust to aggregation to genus or even family level. Moreover, the outcomes show that transformation types introduce higher variation in the multivariate pattern of samples than the taxonomic level to which organisms are identified. Also, the study supports the use of representative taxa as a surrogate to overall community structure. Therefore, we conclude that a rapid-assessment by means of field evaluations, based on coverage of representative taxa, is a reliable alternative for the assessment of macroalgae status. In addition this procedure allows evaluation at a broader spatial scale (water body or habitat level) than traditional quantitative sampling procedure does.     

Response of BITS (a benthic index based on taxonomic sufficiency) to water and sedimentary variables and comparison with other indices in three Adriatic lagoons

The European Water Framework Directive (WFD, 2000/60/EC) recommends the development of biotic indices for assessing the ecological quality status of water bodies. The Benthic Index based on Taxonomic Sufficiency (BITS) was specifically developed for lagoonal systems, according to the tolerant/opportunistic approach. Macrobenthic data, variables indicative of eutrophication and variables indicative of sedimentary organic matter quality were collected during 18 surveys carried out between 2004 and 2005 in three Adriatic coastal lagoons (Venice Lagoon, Sacca di Goro, Lesina Lagoon). The relationship between environmental variables and biotic indices (AMBI, BENTIX, BITS, BOPA and FINE) was tested using multivariate analyses. Indices based on species classification level appeared to relate better with the variables describing organic matter quality, whereas BITS, which is based on family classification level, seemed related to eutrophication indicative variables, such as sulphide, ammonium, dissolved oxygen and orthophosphate concentrations. The BITS approach reduces the costs associated with sorting and identification of organisms. Providing a rapid assessment of ecological quality, and producing an ecologically relevant classification, BITS seems a promising tool for monitoring programs of Adriatic lagoonal ecosystems. Its sensitivity in reflecting the field conditions elsewhere, however, remains to be assessed.     

Soft computing approach for real-time estimation of missing wave heights

This paper presents soft computing approach for estimation of missing wave heights at a particular location on a real-time basis using wave heights at other locations. Six such buoy networks are developed in Eastern Gulf of Mexico using soft computing techniques of Artificial Neural Networks (ANN) and Genetic Programming (GP). Wave heights at five stations are used to estimate wave height at the sixth station. Though ANN is now an established tool in time series analysis, use of GP in the field of time series forecasting/analysis particularly in the area of Ocean Engineering is relatively new and needs to be explored further. Both ANN and GP approach perform well in terms of accuracy of estimation as evident from values of various statistical parameters employed. The GP models work better in case of extreme events. Results of both approaches are also compared with the performance of large-scale continuous wave modeling/forecasting system WAVEWATCH III. The models are also applied on real time basis for 3 months in the year 2007. A software is developed using evolved GP codes (C++) as back end with Visual Basic as the Front End tool for real-time application of wave estimation model.     

The mid-depth circulation of the northwestern tropical Atlantic observed by floats

A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600–1050 dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200–2050 dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e.g. shipborne or mooring observations. Mean transports in each of five zonal equatorial current bands is found to be between 2.7 and 4.5 Sv. Pathways carrying AAIW northward beyond the North Brazil Undercurrent are clearly visible in the mean velocity field, in particular a northward transport of 3.7 Sv across 16°N between the Antilles islands and the Mid-Atlantic Ridge. New maps of Lagrangian eddy kinetic energy and integral time scales are presented to quantify mesoscale activity. For the uNADW, mean flow and mesoscale properties are discussed as data availability allows. Trajectories in the uNADW east of the Lesser Antilles reveal interactions between the Deep Western Boundary Current (DWBC) and the basin interior, which can explain recent hydrographic observations of changes in composition of DWBC water along its southward flow.     

象山港水交换数值研究──Ⅰ.对流-扩散型的水交换模式

以溶解态的保守性物质作为湾内水的示踪剂,建立了对流－扩散型的海湾水交换数值模型。数值模型使用参数化的方法把重力环流和潮振荡的垂向剪切作用的水平混合效应包纳在水平二维的示踪剂对流－扩散方程中。在空间网距较小时,模型的稳定性和守恒性均可满足海湾水交换研究的需要。     

Long-Term Variations of Potential Temperature and Dissolved Oxygen of the Japan Sea Proper Water

Observed potential temperatures and concentrations of dissolved oxygen are analyzed to elucidate their variations during the period from 1958 to 1996 at Stn. P (37°43′ N, 134°43′ E) and from 1965 to 1996 at Stn. H (40°30′ N, 137°40′ E) in the Japan Sea. At Stn. P, increases of the potential temperature for the period are found below 800 m depth with the largest value of 0.16 ± 0.09°C per century at 800 m depth. At Stn. H, the potential temperature increased below 500 m depth. The increase rate has the largest value of 0.50 ± 0.18°C per century at 500 m depth and it is 0.30 ± 0.09°C per century at 800 m depth. The concentrations of dissolved oxygen increased around 800 m depth at Stn. P. At Stn. H, they increased above 800 m depth. On the other hand, they decreased below 1200 m depth at both stations. The layer of the dissolved oxygen minimum has deepened in these decades. These features appearing in the distributions of temperature and dissolved oxygen are successively simulated by a vertical one-dimensional advection-diffusion model including consumption of dissolved oxygen and termination of the deep water supply. These results suggest that the supply of the Japan Sea Proper Water into the deep layer, which is cold and rich in dissolved oxygen, has been decreasing for the last four decades. This revised version was published online in August 2006 with corrections to the Cover Date.