A Holistic Approach to Upwelling and Downwelling along the South-West Coast of India     

Phiros Shah  R. Sajeev  K. J. Thara  Grinson George  Muhammad Shafeeque  S. Akash 《Marine Geodesy》2019,42(1):64-84

An attempt has been made to develop a holistic understanding of upwelling and downwelling along the south-west coast of India. The main objective was to elucidate the roles of different forcings involved in the vertical motion along this coast. The south-west coast of India was characterized by upwelling during the south-west monsoon (May to September) and by downwelling during the north-east monsoon and winter (November to February). The average vertical velocity calculated along the south-west coast from the vertical shift of the 26?°C isotherm is 0.57?m/day during upwelling and 0.698?m/day during downwelling. It was concluded that upwelling along the south-west coast of India is driven by offshore Ekman transport due to the alongshore wind, Ekman pumping, horizontal divergence of currents and by the propagation of coastally trapped waves. Whereas downwelling along the coast is driven only by convergence of currents and the propagation of coastally trapped Kelvin waves. Along the west coast of India, the downwelling-favorable Kelvin waves come from the equator and upwelling-favorable waves come from the Gulf of Mannar region.  相似文献   

岬湾海岸中人工岛建设对岬角涡旋及海湾地形冲淤的影响——以海南岛铺前湾为例     

陈亮鸿  林国尧  龚文平 《海洋学报》2019,41(1):41-50

岬湾海岸中一般在岬角的右侧与左侧（面向大海方向）分别发育顺时针与逆时针涡流。这些涡流的存在对泥沙输运、海底地形演变、污染物扩散等都具有重要影响。而在海洋中岛屿的存在将产生局部的岛后尾流。如岛屿与岬角距离较近,岛后尾流可能与岬角涡旋相互作用,反之则相互影响较小。本文以海南岛铺前湾为例,研究在岬湾海岸中湾口处的人工岛建设对湾内涡旋的影响,并进一步分析人工岛建设对整个海湾海底冲淤变化的效应。本项研究主要采用COAWST模型进行研究。结果表明,大潮期在海湾内发育大范围的顺时针涡旋,小潮期涡旋发育不明显,以东向余流为主。人工岛建设并未影响整个海湾的涡旋结构,但人工岛分隔了湾内顺时针涡旋,且在周围产生局部的逆时针与顺时针涡旋。海底冲淤变化的基本格局为湾内以淤积为主,人工岛建设加强了这种趋势,但在人工岛与岸线之间的狭窄通道内,海底出现冲刷。本项研究对岬湾海岸的科学开发管理具有一定意义。  相似文献   

青岛近海物理-生物地球化学过程及其生态响应     

韦钦胜  王保栋  姚庆祯  于志刚  傅明珠  孙俊川  许博超  谢琳萍  辛明 《海洋学报(英文版)》2019,38(2):11-23

近些年来,夏季黄海浒苔大规模暴发,并在青岛近岸海域大面积聚集,引起了广泛的关注。本文基于在夏季和冬季所获得的多学科调查资料,重点研究了青岛近海的水文-生物地球化学过程及其生态影响,阐明了该海域物理-化学-生物等多参数之间的耦合响应。研究显示,夏季黄海冷水团的边界可扩展至青岛近岸海域,并在局部涌升至上层水体,形成沿岸上升流;该上升流可对上层营养盐产生一定的补充,进而促进浮游植物的繁殖,并于底层海域对应形成溶解氧（DO）和pH的低值。夏季青岛近海的上升流可能还有利于随南风漂移至此的浒苔的生长,并在一定程度上引起浒苔的局地旺发;同时,夏季该海域特定的锋面系统对浒苔聚集的影响也不容忽视。冬季黄海暖流在苏北浅滩外侧向山东半岛南部海域延伸,扩展至青岛近海的暖水舌与近岸低温水之间的锋面特征明显,而且在向岸暖水与近岸冷水间还对应形成了明显的营养盐和叶绿素（Chl-a）锋面。该项研究从多学科交叉的视角,增进了对青岛近海物理、化学和生物过程之间耦合关系的认识。  相似文献   

舟山外钓山海岸边坡泥沙动力与冲淤演变特征     

刘毅飞  夏小明  贾建军 《海洋通报》2007,26(6):53-60

通过对研究区海域的水文泥沙进行现场测验,对比1960-1962年海图、1995年和2001年水下地形图三期地形数据和分析浅地层探测数据等方法,分析了舟山外钓山岛西海岸边坡的水动力、悬浮泥沙及冲淤特征,探讨了海岸边坡发育演变的模式与机制。研究结果表明,在基岩岬角海岸与潮流深槽的边界控制及往复潮流的作用下,舟山外钓山岛西海岸边坡演变是一个"上淤下冲"的模式,即边坡变陡至边坡土体失稳并在不定期外力触发下滑塌堆积坡脚,然后上部重新淤积、下部滑坡体不断被侵蚀的循环过程。  相似文献   

台风作用下淤泥质海岸动力地貌响应   总被引：6，自引：0，他引：6  

戴志军  张小玲  闫虹  李九发  恽才兴 《海洋工程》2009,27(2):63-69

基于200509号麦莎台风(近似百年一遇)作用前后杭州湾北岸龙泉-南竹港实测的海岸地形和水文资料,利用分形技术、冲刷深度和闭合水深等相关概念分析淤泥质海岸的剖面变化、岸线进退以及地形冲淤,进而探讨海岸响应台风作用的动力地貌行为.结果表明:1)台风作用前后的海岸动力地貌过程表现为水下类似沙坝的堆积体削平、凹处填洼,水下平台发育锯齿或较小的坝--槽,海岸剖面的分维数降低,剖面坡度处于平缓;2)麦莎台风对海床的整体冲淤幅度不大,这可能是由于研究区大潮讯的增水致使波浪对海床的塑造能力减弱以及码头的遮蔽作用造成;3)台风作用对海岸的冲刷深度约为0.8 m,闭合水深为9.5 m,近岸-1 m邻近区成为海岸响应台风作用最敏感的地带;泥沙主要在0 m到闭合水深区间的海床发生纵、横向运移.  相似文献   

苏北废黄河三角洲海岸时空演变遥感分析   总被引：4，自引：0，他引：4  

张旸  陈沈良 《海洋科学进展》2009,27(2)

基于遥感与地理信息系统技术,使用苏北废黄河三角洲海岸地区1978,1987和2000年的Landsat卫星遥感数据,选取岸线指标与波段,提取岸线信息,生成1978-1987年和1987-2000年海岸土地增减时空变化分布图,建立岸线变化距离及增速衡量指标,定量分析了废黄河三角洲海岸面积变化特征,以及灌河口-中山河口、中山河口-扁担港口和扁担港口-双洋河口以南岸段的时空变化格局与分布特征.研究结果表明,废黄河三角洲海岸的自然侵蚀速率呈减小趋势,但侵蚀作用仍在继续.侵蚀强度以废黄河口地区为中心,向南北两侧逐渐减弱.人工保滩护岸措施在一定程度上影响着自然侵蚀格局.其内部各岸段分别呈现缓蚀、侵蚀和基本侵淤平衡的变化格局.  相似文献   

Sun and landscape orientation in adult and juvenile sandhoppers Orchestoidea tuberculata (Amphipoda, Talitridae) from two beaches in south central Chile     

Felicita Scapini  & Jenifer Dugan 《Marine Ecology》2008,29(S1):19-27

The behaviour of a talitrid amphipod, Orchestoidea tuberculata Nicolet 1849, was investigated for populations inhabiting two exposed sandy beaches in south central Chile to evaluate orientation capabilities with respect to sun azimuthal changes and landscape. The study beaches (Calfuco and La Misión) were backed by high cliffs but differed in shoreline orientation. Under test conditions of dry substrate, both populations oriented seawards using celestial cues when landscape vision was screened off and showed a higher concentration seawards when they could see the landscape suggesting additive effects of these cues. The absence of a phototactic response to the sun implies the involvement of an inner circadian clock, as the experiments were conducted at different times of the day. The distribution of juveniles was more concentrated than adults in the trials, a result in accordance with their tendency to occupy a zone located closer to the water than adults. Our results suggest that the Calfuco population was oriented to its shoreline, while animals at La Misión tended to deviate from the expected direction and their distribution was more scattered. This observed difference between the populations may be related to the higher human impact on the latter beach, which was more intensively used for recreation and periodically cleaned, removing the wrack. The comparison of results on orientation of O. tuberculata with those of different sandhopper species contributes new phylogenetic insight concerning this important adaptation. This study not only represents an extension of contemporary knowledge of behavioural adaptations of beach amphipods to coasts differing geographically and ecologically, but also analyses orientation in a southern Pacific species of talitrid amphipod for the first time.  相似文献   

中国东南沿海和平水母科二新种   总被引：1，自引：1，他引：0  

郭东晖  许振祖  黄加祺 《海洋学报》2008,30(2):124-129

报道中国东南沿海和平水母科2新种,即八辐和平水母Eireneoctonemalis sp.nov.和黑疣真瘤水母Eutimakrampi sp.nov.。  相似文献   

Coastal and estuarine habitat mapping, using LIDAR height and intensity and multi-spectral imagery   总被引：3，自引：1，他引：2  

Guillem Chust  Ibon Galparsoro  ngel Borja  Javier Franco  Adolfo Uriarte 《Estuarine, Coastal and Shelf Science》2008,78(4):633-643

The airborne laser scanning LIDAR (LIght Detection And Ranging) provides high-resolution Digital Terrain Models (DTM) that have been applied recently to the characterization, quantification and monitoring of coastal environments. This study assesses the contribution of LIDAR altimetry and intensity data, topographically-derived features (slope and aspect), and multi-spectral imagery (three visible and a near-infrared band), to map coastal habitats in the Bidasoa estuary and its adjacent coastal area (Basque Country, northern Spain). The performance of high-resolution data sources was individually and jointly tested, with the maximum likelihood algorithm classifier in a rocky shore and a wetland zone; thus, including some of the most extended Cantabrian Sea littoral habitats, within the Bay of Biscay. The results show that reliability of coastal habitat classification was more enhanced with LIDAR-based DTM, compared with the other data sources: slope, aspect, intensity or near-infrared band. The addition of the DTM, to the three visible bands, produced gains of between 10% and 27% in the agreement measures, between the mapped and validation data (i.e. mean producer's and user's accuracy) for the two test sites. Raw LIDAR intensity images are only of limited value here, since they appeared heterogeneous and speckled. However, the enhanced Lee smoothing filter, applied to the LIDAR intensity, improved the overall accuracy measurements of the habitat classification, especially in the wetland zone; here, there were gains up to 7.9% in mean producer's and 11.6% in mean user's accuracy. This suggests that LIDAR can be useful for habitat mapping, when few data sources are available. The synergy between the LIDAR data, with multi-spectral bands, produced high accurate classifications (mean producer's accuracy: 92% for the 16 rocky habitats and 88% for the 11 wetland habitats). Fusion of the data enabled discrimination of intertidal communities, such as Corallina elongata, barnacles (Chthamalus spp.), and stands of Spartina alterniflora and Phragmites australis, which presented misclassification when conventional visible bands were used alone. All of these results were corroborated by the kappa coefficient of agreement. The high classification accuracy found here, selecting data sources, highlights the value of integrating LIDAR data with multi-spectral imagery for habitat mapping in the intertidal complex fringe.  相似文献   

莱州湾南岸第三陆相层年龄的铀系等时线法（TSD）测定     

许博超  于志刚  江雪艳  陈洪涛  姚庆祯  米铁柱 《海洋科学》2008,32(5):51-56

于莱州湾南岸ZK32-1钻孔第三陆相层上下边界处选取自生钙质结核,采用样品全溶铀系等时线法(TSD法)测定钙质结核的年龄。测试结果表明,所有等时线上的数据都有很好的线性关系,表明所获得的年龄数据是合理的。通过对样品代表性的讨论,说明所选取的钙质结核的年龄确可代表其所在地层的年龄,从而得出莱州湾南岸第三陆相层的沉积起止时间为72.16ka B.P.±7.41ka B.P.到45.34ka B.P.±5.35ka B.P.的结论。本研究首次获得莱州湾南岸地层的铀系TSD年龄,为全面认识该地区晚更新世地层年代学提供了一个新视角。  相似文献