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31.
32.
Oleg Zaytsev Rafael Cervantes-Duarte Orzo Montante Artemio Gallegos-Garcia 《Journal of Oceanography》2003,59(4):489-502
High primary productivity on the Pacific coast of the Baja California Peninsula is usually related to coastal upwelling activity
that injects nutrients into the euphotic zone in response to prevailing longshore winds (from the northwest to north). The
upwelling process has maximum intensity from April to June, with the coastal upwelling index varying from 50 to 300 m3/s per 100 m of coastline. Along the entire coast of the peninsula, the upwelling intensity changes in accordance with local
wind conditions and bottom topography. Spatial variability can also be modulated by the influence of mesoscale meanders of
the California Current. We have identified the seasonal and synoptic variability of upwelling signatures on the Baja California
shelf, using averaged monthly and weekly sea surface temperature (SST) distributions obtained from remote sensing imagery
from the Advanced Very High Resolution Radiometer in the period from 1996 to 2001. Analysis of SST distribution and direct
experimental data on temperature and nutrient concentration shows that the areas with the coldest SST anomalies were closely
related to the bottom slope, shelf width, and coastline orientation relating to wind direction. We also assume that the nutrient
transport into the coastal lagoons may be forced by the coupling of coastal upwelling and tidal pumping of surface waters
into the lagoon system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
33.
Modeling bed-load transport of coarse sediments in the Great Bay Estuary, New Hampshire 总被引:1,自引:0,他引:1
A. Bilgili M. R. Swift D. R. Lynch J. T. C. Ip 《Estuarine, Coastal and Shelf Science》2003,58(4):937-950
Current, sea level and bed-load transport are investigated in the Lower Piscataqua River section of the Great Bay Estuary, New Hampshire, USA—a well-mixed and geometrically complex system with low freshwater input, having main channel tidal currents ranging between 0.5 and 2 m s−1. Current and sea level forced by the M2M4M6 tides at the estuarine mouth are simulated by a vertically averaged, non-linear, time-stepping finite element model. The hydrodynamic model uses a fixed boundary computational domain and accounts for flooding–drying of tidal flats by making use of a groundwater component. Inertia terms are neglected in comparison with pressure gradient and bottom friction terms, which is consistent with the observed principal dynamic balance for this section of the system. The accuracy of hydrodynamic predictions in the study area is demonstrated by comparison with four tidal elevation stations and two cross-section averaged current measurements. Simulated current is then used to model bed-load transport in the vicinity of a rapidly growing shoal located in the main channel of the lower system. Consisting of coarse sand and gravel, the shoal must be dredged every five to eight years. Two approaches are taken—an Eulerian parametric method in which nodal bed-load flux vectors are averaged over the tidal cycle and a Lagrangian particle tracking approach in which a finite number of sediment particles are released and tracked. Both methods yield pathways and accumulations in agreement with the observed shoal formation and the long-term rate of sediment accumulation in the shoal area. 相似文献
34.
A Computational Model for Velocity Separation in Shallow Sea 总被引:1,自引:0,他引:1
Based on the hydrodynamical feature and the theoretical velocity profiles of tidal flow and vvind-induced flow in shal-low sea, a computational model is established for the first time, which can separate observed velocity into tidal velocity and wind-induced velocity by use of the least square method. With the model, not only the surface velocities of tidal flow and vvind-induced flow are obtained, but also the bed roughness height is determined and the wind velocity above the wa-ter surface is estimated. For verification of the model, the observed velocity in the Yellow River Estuary and the laborato-ry test is separated, then it is applied to the Yangtze River Estuary. All the results are satisfactory. The research results show that the model is simple in method, feasible in process and reasonable in result. The model is a valid approach to analysis and computation of field dala, and can be applied to separate the observed velocity in shallow sea; at the same time, reasonable boundary conditions of th 相似文献
35.
36.
本文用能谱方法分析了黄海的海表面水温(SST)场的准周期变化。由分析结果清楚地看出,SST具有高频准周期变化:黄海北部以2.6—3.2,1.4—1.7,3.6—3.8和6.7个月的准周期为主;3.3—3.6,5,1.3—2.3及6.7个月在黄海南部占优势。同时,两个海域都有6.7和3.3年的明显的准周期变化。 相似文献
37.
本文对北部湾三维潮波进行了数值研究,并将所得结果与现有观测资料作了比较。通过比较发现两者相当一致。文中还绘制了M_2和K_1分潮的同潮图,并对其作了讨论。可以断定,北部湾的日潮优势是由日潮共振所引起的。M_2和K_1分潮流的水平分布表明,强流区位于它们各自的蜕化无潮点附近。还讨论了分潮流的铅直结构,可以看出这种结构十分接近实际分潮流场的特征。 相似文献
38.
对含多资料的分潮波模型的超定问题进行探讨,建立一种有限差分—最小二乘方法,该方法使得岸边资料直接进入了计算方程,并保证岸界法向流速为零条件。通过对渤海的四大分潮的试算,证实本方法可行。 相似文献
39.
Xavier De Montaudouin 《Journal of Sea Research》1996,36(3-4)
In Arcachon Bay, a macrotidal coastal lagoon in southwest France, growth rates of cockles Cerastoderma edule (L.) differ greatly between locations. Sampling of populations at different tidal levels showed that the mean shell length was significantly and positively correlated with immersion time, whereas no correlation was found with population density and microphytobenthos biomass. Transplants of cockles between two intertidal sites were used to examine the relative importance of habitat and site of origin for growth rate and condition index. Artifacts due to manipulation were assessed, i.e. the impact of enclosures on growth, conditon index and mortality. During a 5-mo reciprocal transplant experiment, growth rates of the transplanted cockles and the cockles already present were similar, whereas the sites of origin did not affect growth rate. Condition index, however, displayed significant differences in relation to both transplant and origin sites. During a further 6-mo experiment in which cockles were transplanted from one site to four new sites, growth was mainly influenced by tidal level. These results indicate that net growth started when cockles were immersed 30% of the time. It is concluded that, on the scale of Arcachon Bay (156 km2), differences in growth and condition between cockle populations are largely phenotypic. Tidal level (i.e. food supply and emersion stress) accounts for most of these differences, but the existence of genetically or physiologically different populations cannot be excluded. 相似文献
40.
潮汐沉积率与沉积间断 总被引:16,自引:3,他引:16
在浙北奥陶系文昌组和长江三角洲开敞型淤泥质海岸非潮道潮汐纹层研究的基础上,得出与国外同类研究相近的沉积率。现代海岸进积速度和潮坪沉积的观察及测试证明,上述沉积率是难以置信的。现代潮坪观测表明,潮汐纹层在形成过程中即包含着改造,所保留的纹层占应形成数的不到10%,其余90%以上被侵蚀。小型层序是风暴和平静天气的产物,为风暴层序,与大小潮周期无关。其地层中保留的数量不到应生成数的10%,其余90%被改造。小型层序被侵蚀,其中的纹层随之消失。致使潮坪层序中保存的纹层数仅为应形成数的0.2%。被改造的纹层和单层留下的仅是侵蚀面,即小间断。在进行潮汐沉积高分辨率的研究时应充分重视沉积间断的作用 相似文献