2006年冬季粤东沿岸下降流观测分析

根据珠江口及其附近海域2006年冬季(2006年12月至2007年1月)航次的CTD调查资料发现,由于表层水体冷却而产生的对流作用,以及东北季风、浪、流等强动力条件下,冬季陆架水体垂向混合均匀,但粤东近岸海域却存在显著的温跃层及逆盐跃层,其原因在于:东北季风的Ekman效应引起了陆架表层高温、高盐海水向岸输送,东北季风还驱动了西南向沿岸流,其底边界层的Ekman效应引起了沿岸底层低温、低盐海水离岸输送,这样就形成了陆架方向的次生环流,在沿岸海域则为下降流,并表现为沿岸海域的逆盐跃层及温跃层现象。在下降流显著的区域,溶解氧垂向分布均匀且浓度较高,这应归因于下降流将溶解氧浓度较高的表层水带入深层所致。     

A modeling study of the characteristics and mechanism of the westward coastal current during summer in the northwestern South China Sea

The characteristics and dynamical mechanism of summer-time coastal current over the North South China Sea shelf have been investigated based on a high resolution unstructuredgrid finite volume community ocean model (FVCOM). Modeldata comparison demonstrates that the model describes and explains well the coastal dynamics over the North South China Sea shelf. The coastal current on the North South China Sea shelf is greatly influenced by monsoon and the freshwater discharge of the Pearl River. Strong southwesterly wind drives the coastal current northeastward. However, under weak southwest monsoon, the coastal current west of the Pearl River estuary (PRE) advects toward the southwest, and splits into two parts when reaching east of the Qiongzhou Strait, with one branch entering the Gulf of Tonkin through the Qiongzhou Strait, transporting low salinity water into the Gulf of Tonkin, and the other part flows cyclonic and interacts with the northeastward current around southeast of Hainan Island, forming a cyclonic eddy east of the Qiongzhou Strait. A variety of model experiments focused on freshwater discharge, wind forcing, tidal rectification, and stratification are performed to study the physical mechanism of the southwestward coastal current which is usually against the summer wind. Process-oriented experiment results indicate that the southwest monsoon and freshwater discharge are important factors influencing the formation of southwestward coastal current during summer.     

Recruitment dynamics of metamorphosing English sole,Parophorys vetulus,to Yaquina Bay,Oregon

English sole, Parophrys vetulus, spawn in shelf waters off the west coast of North America and early development occurs in coastal waters. Near metamorphosis, however, larvae recruit to nearshore and estuarine nursery areas, an uncommon life-history feature for a species in this region. Recruitment of larval P. vetulus to Yaquina Bay, Oregon, was sampled with moored nets on a weekly basis. Recruitment began during night flood tides in late February and was characterized by three peaks during the season. Planktonic recruitment continued into June, whereas benthic juveniles began to emigrate from the estuary in late May.The data suggest that two developmental stages of recruits immigrated to Yaquina Bay. The first are newly transforming larvae which enter the bay earliest within each peak of recruitment; peaks of abundance are related to onshore Ekman transport. This transport also brings larvae to shallow areas along the open coast where they settle. These transforming stages are still capable of pelagic swimming activity and continue to recruit to the estuary, typically swimming deeper in the water column than the early stages. Estuarine factors, particularly bottom salinity at the end of ebb tide, are most strongly correlated with recruitment of these stages. It seems that tidal stream transport is the primary mechanism used by English sole to recruit to the estuary, but the mechanism of locating the estuary and timing of entry is relatively complex.     

Barotropic Response of the Sea of Okhotsk to Wind Forcing

We have examined wind-induced circulation in the Sea of Okhotsk using a barotropic model that contains realistic topography with a resolution of 9.25 km. The monthly wind stress field calculated from daily European Centre for Medium-Range Weather Forecasting (ECMWF) Re-Analysis data is used as the forcing, and the integration is carried out for 20 days until the circulation attains an almost steady state. In the case of November (a representative for the winter season from October to March), southward currents of velocity 0.1–0.3 m s⁻¹ occur along the bottom contours off the east of Sakhalin Island. The currents are mostly confined to the shelf (shallower than 200 m) and extend as far south as the Hokkaido coast. In the July case (a representative for the summer season from April to September), significant currents do not occur, even in the shallow shelves. The simulated southward current over the east Sakhalin shelf appears to correspond to the near-shore branch of the East Sakhalin Current (ESC), which was observed with the surface drifters. These seasonal variations simulated in our experiments are consistent with the observations of the ESC. Dynamically, the simulated ESC is interpreted as the arrested topographic wave (ATW), which is the coastally trapped flow driven by steady alongshore wind stress. The volume transport of the simulated ESC over the shelf reaches about 1.0 Sv (1 Sv = 10⁶ m³s⁻¹) in the winter season, which is determined by the integrated onshore Ekman transport in the direction from which shelf waves propagate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Community structures of coral reefs around Peninsular Malaysia

Coral community structures at eleven fringing reef sites were investigated along the coast of Peninsular Malaysia. Estimated coverage of coral communities is examined by applying quantitative digital image analysis to the line transect method. Four coral community types were characterized by dominant genera and lifeforms: Acropora branching community, Montipora-Acropora community, Porites massive community, and Heliopora community. Live coral coverage in all study sites ranged from 17.9% to 68.6%. Most reefs were in “fair” condition while some reefs were shown to be in “poor” condition. Coral community structures among the study sites were divided into the west coast of Peninsular Malaysia with a dominant Porites massive lifeform, and the east coast with a variety of lifeform categories of Montipora and Acropora. Physical effects such as the monsoon wind regime and sedimentation are likely to influence the formation of dominant coral communities around Peninsular Malaysia.     

2006年夏季琼东、粤西沿岸上升流研究

利用2006年夏季广东、海南、广西近海的海洋水文调查资料和卫星遥感QuikSCAT风场资料分析琼东、粤西沿岸上升流的空间结构特征, 探讨风场、风应力旋度对上升流的影响以及上升流区水温、海流、海平面对上升流的响应。结果表明:琼东、粤西沿岸上升流区并非相互独立, 从10 m层以下已经连成一片。琼东沿岸上升流主要由夏季西南季风驱动而产生, 风应力旋度也有一定贡献。琼东沿岸上升流的强度比粤西强。琼东沿岸海域的上层海水(18 m以浅)以离岸运动为主, 中下层海水以向岸运动为主。上层的离岸流速大于中下层的向岸流速。琼东沿岸的上升流现象是间歇性的, 与沿岸风速强弱有关。琼东沿岸海域海平面的升降与上升流的强弱有良好的关系, 上升流的强弱滞后于海平面的升降约1～2 d。     

Contrasting local retention and cross-shore transports of the East Australian Current and the Leeuwin Current and their relative influences on the life histories of small pelagic fishes

Transport between shelf and offshore environments supports a significant proportion of ocean primary productivity and is critical to the life cycle of many marine species. While fundamental differences in the underlying dynamics of eastern and western boundary currents have been recognized and studied for more than half a century, the implications for physical dispersal rates have received much less attention. In this study we explore how Australia’s two major boundary current systems, the East Australian Current and the Leeuwin Current, differ in their local retention and cross-shore transports in the upper water column and how these differences favor contrasting life histories of small pelagic fishes. The results suggest that the East Australian Current forms a partial barrier to onshore transport, but is effective in entraining shelf waters and transporting them offshore, particularly in the region where the current separates from the coast. Blue mackerel (Scomber australasicus) spawn on the outer-shelf in this separation region and may thereby maximize the dispersion of eggs and larvae in the mainly oligotrophic waters of the southern Coral Sea. In contrast, the Leeuwin Current system promotes onshore transport through the combined effects of mean onshore flow and eddy-induced mixing. In the Great Australian Bight, sardine (Sardinops sagax) and anchovy (Engraulis australis) may exploit the high coastal retention of the Leeuwin Current system by spawning on the inner-shelf during summer when the current is weakest and winds assist retention and enhance production through local upwelling.     

用沿岸上升流指数分析中国东南沿岸风生上升流的特征

对1968年1月到2007年12月中国东南沿海(17°N～30°N,109°E～123°E)上升流指数月平均数据进行分析,结论如下:(1)风生沿岸上升流主要在4-8月间发生于海南岛东部、雷州半岛东部、汕头以北至浙江沿岸.(2)风生沿岸上升流的强度具有时空分布变化特征,其中海南岛东部沿岸上升流最强,浙江沿岸其次;整个中国...     

Direct measurements of coastal currents around southern New Zealand

Results are presented from direct measurements of subsurface currents at ten coastal positions around the southern half of New Zealand, and from geomagnetic electrokinetograph measurements of surface currents between these positions. Currents on the continental shelf were predominantly tidal. Strongest mean flows were found on the continental slope adjacent to areas where the continental shelf is narrowest. The flow on the west coast of the South Island was southwards south of 44° S, with a maximum mean speed at a depth of 100 m of 0.64 m.s^‐1. On the east coast of the South Island the flow was generally towards the north, with a maximum speed at a depth of 100 m of 0.21 m.s^‐1 near latitude 42° 30’ S.     

Some hydrological features of Hawke Bay and nearby shelf waters

Temperature and salinity observations were made in Hawke Bay (east coast, North Island) and in the near shore coastal shelf water immediately to’ the south. Water in the bay was cooler and less saline than the shelf water on the open coast to the south. Hydrological analysis confirms that the main inflow is westward along the approximate centre line of the bay.     

海南岛近岸海域夏初浮游动物与环境因子的关系

根据2011年夏初在海南岛近岸海域采集的浮游动物样本,分析了该海域浮游动物的种类组成、优势种类、丰度、生态类群,生物多样性及均匀度,并对浮游动物与环境因子之间的关系进行了探讨。海南岛近岸海域共鉴定出终生性浮游动物164种,阶段性浮游幼体11个类群,其中以桡足类的种类最多,40属82种。优势种主要有棘皮动物幼体Echinodermata larva、鸟喙尖头溞Penilia avirostris、异体住囊虫Oikopleura dioica、长尾类幼体Macrura larva、肥胖软箭虫Ferosagitta enflata、羽长腹剑水蚤Oithona plumifera、小齿海樽Doliolum denticulatum、中型莹虾Lucifer intermedius、泡抱球虫Globigerina bulloides、微驼隆哲水蚤Acrocalanus gracilis等。海南岛近岸海域浮游动物丰度平均值为1 348.68ind/m3,东部海域浮游动物丰度最高,由近岸向远岸呈递减趋势,而北部湾海域和南部海域由近岸向远岸则呈先增后减的趋势。夏初由于受沿岸流和南海暖流的影响,海南岛近岸海域的生态类群以暖水沿岸种和广布暖水外海种为主。浮游动物多样性指数和均匀度平均值为3.03和0.72,东部海域的多样性指数和均匀度较低,主要原因是阶段性浮游幼体的偶然性暴发。相关性分析显示,海南岛近岸海域浮游动物丰度与pH值呈极显著负相关(p0.05,r=-0.360);与浮游植物丰度(PA)呈极显著正相关(p0.01,r=0.395);与盐度、DO、CODMn、NO3-N浓度、NH4-N浓度、PO4-P浓度成正相关,与温度、NO2-N浓度、SiO3-Si浓度呈负相关。     

Nannoplankton of the Atlantic Ocean from sediment trap samples

Calcareous nannoplankton from sediment trap samples collected at six sites in the Atlantic Ocean from 23° S to 73° N (cruise 20 of R/V Vityaz’ and cruise 33 and 34 of R/V Akademik Mstislav Keldysh). Those samples were studied with a scanning electron microscope. In the coastal and open-sea regions of the North and South Atlantic and in the subarctic region of the Norwegian Sea, the conditions are significantly different. In the shelf area of the Benguela upwelling, 11 species were recognized; some of them were agglutinated by diatoms and tintinnides or covered the surface of pellets. The Broken Spur and TAG pelagic areas of the North Atlantic contained up to 43 coccolith species. They included holococcoliths, large pelagic, and delicate easily soluble species distributed over the entire water column. The presence of coccoliths in the high-latitude area of the Norwegian Sea is related to their supply with the warmer North Atlantic waters. These assemblages are distinguished by a low species diversity and an enhancement of the coccolith solubility with the depth increase.     

台湾海峡西部上升流的生成和长消原因分析

台湾海峡西部海域是上升流多发区,近年来已引起众多海洋学家的重视。我国海洋学家通过对台湾海峡区水团、海流和营养盐等的分析研究,不仅得出了台湾海峡西部海域上升流的分布范围和特征,并对其成因也作了探讨,取得了一些有价值的研究结果。由于这些研究都是采用间接方法,因此对上升流的主要成因尚存在不同的看法。本文通过对引起台湾海峡西部海域上升流的各驱动力因子量级的分析,进而判断出上升流的主要成因。     

Seasonal and spatial distributions of phytoplankton biomass associated with monsoon and oceanic environments in the South China Sea

Seasonal variations of phytoplankton/chlorophyll-a （Chl-a） distribution, sea surface wind, sea height anomaly, sea surface temperature and other oceanic environments for long periods are analyzed in the South China Sea （SCS）, especially in the two typical regions off the east coast of Vietnam and off the northwest coast of Luzon, using remote sensing data and other oceanographic data. The results show that seasonal and spatial distributions of phytoplankton biomass in the SCS are primarily influenced by the monsoon winds and oceanic environments. Off the east coast of Vietnam, Chl-a concentration is a peak in August, a jet shape extending into the interior SCS, which is associated with strong southwesterly monsoon winds, the coastal upwetling induced by offshore Ekman transport and the strong offshore current in the western SCS. In December, high Chl-a concentration appears in the upwelling region off the northwest coast of Luzon and spreads southwestward. Strong mixing by the strong northeasterly monsoon winds, the cyclonic circulation, southwestward coastal currents and river discharge have impacts on distribution of phytoplankton, so that the high phytoplankton biomass extends from the coastal areas over the northern SCS to the entire SCS in winter. These research activities could be important for revealing spatial and temporal patterns of phytoplankton and their interactions with physical environments in the SCS.     

Coastal upwelling in the California current system

Coastal upwelling in the California Current system has been the subject of large scale studies off California and Baja California, and of small scale studies off Oregon. Recent studies of the winds along the entire coast from 25°N to 50°N indicate that there are significant along-shore variations in the strength of coastal upwelling, which are reflected in the observed temperature distribution. Active upwelling appears to be restricted to a narrow coastal band (about 10–25 km wide) along the entire coast, but the region influenced by coastal upwelling may be much wider. Intensive observations of the upwelling zone during summer off Oregon show the presence of a southward coastal jet at the surface, a mean vertical shear, a poleward undercurrent along the bottom, and persistently sloping isopycnals over the continental shelf; most of the upwelling there occurs during relatively short periods (several days long) of upwelling-favorable winds. During the upwelling season off Oregon, the offshore Ekman transport is carried by the surface Ekman layer, and the onshore return flow occurs through a quasi-geostrophic interior. It is not known whether the structure and dynamics observed off Oregon are typical of the upwelling zone along the entire coast, though some of the same features have been observed off Baja California. Current and future research will eventually show whether the Oregon results are also applicable in the region of persistently strong upwelling-favorable winds off northern California, and in the region of complex bathymetry off central and southern California.     

海南岛沿岸海域砗磲资源调查及保护前景展望

砗磲是珊瑚礁海域的重要贝类之一,对维护珊瑚礁生态系统平衡起着重要作用。然而,近年来海洋的大力开发和利用给我国沿海砗磲资源造成严重威胁。本研究通过截线样带法对海南岛沿岸海域砗磲的种类和分布进行实地调查,结果表明,海南岛沿岸海域砗磲覆盖度呈现南北差异,东南沿岸海域砗磲覆盖度明显高于西北沿岸海域,这种差异可能是由自然因素和人为因素共同造成。调查海域共发现3种砗磲:诺亚砗磲(Tridacna noae)最多,占砗磲样品总数的58.6%;其次是番红砗磲(T. crocea),占34.3%;鳞砗磲(T. squamosa)最少,仅占7.1%。海洋管理部门应该加强对砗磲多样性的保护力度,合理开发和可持续利用并重,从而有效保护砗磲、珊瑚礁乃至海洋生态系统。     

南海上升流研究概述

本文对近40a来南海上升流研究结果进行了概述，重点介绍了南海北部陆架区上升流的时空分布特征，及其消长和形成机制等研究成果．这些研究成果揭示上升沈是整个南海北部陆架区夏季的普遍现象，具有南海海盆的空间尺度．引起南海北部陆架区夏季上升流存在的动力因素是盛行的西南季风．该上升流在空间和时间上的分布是不均一的，海南岛东北和闽、粤边界海域是上升流中心区；台湾浅滩周围的上升流呈多元结构，各上升流区海水的理化性质存在看明显差异；在粤东，上升流的影响可达沿海港湾内部，并支配看这些港湾的夏季水文条件．南海除了在其北部陆架区存在看夏季上升流外，夏季在越南东部沿岸和冬季在吕宋岛沿岸均存在看上升流。     

Input of river-derived sediment to the New Zealand continental shelf: I. Mass

The input of river-borne sediments to the New Zealand continental shelf has been calculated for all the major rivers and basins in New Zealand. South Island yields 284 ± 40 × 10⁶ tonnes per year of sediment from a land area of 152 977 km² and North Island yields 105 ± 9·4 × 10⁶ tonnes per year from a land area of 114 621 km². Particularly high discharges are noted off the west coast of South Island and east coast of North Island and result in higher offshore sedimentation there. The data are compatible with measured sedimentation rates on the New Zealand continental shelf. The specific sediment yield from South Island is amongst the highest previously recorded.     

The nearshore current along a high-rainfall,trade-wind coast-Nicaragua

Runoff from abundant rainfall on the watersheds along the east coast of Nicaragua results in a well-defined nearshore current, extending 20–40 km out from the coast. Important terms in the controlling dynamical balance are the Coriolis forces, and eddy frictional forces. Calculations of the diabathic surface slope 0(10^?5) show a smooth setup of 4–5 cm from the outer edge of the current to the shoreline. A longshore surface slope of 0(10^?8) appears to be set up by the longshore wind stress, and further computations allow an estimate of ～ 6 gr cm^?1 s^?1 for the dynamic eddy viscosity. An analytical expression including diabathic surface slope and density gradient, parabathic surface slope, wind stress, and quadratic bottom friction reproduces the salient observed features of the nearshore current. These include the pronounced maximum in the parabathic (along-shelf) current about 10 km off the coast, a complex diabathic velocity structure, and a shelf countercurrent just seaward of the outer edge. Further calculations suggest that the dominant driving arises from the freshwater-induced density gradients, accounting for upward of 80% of the flow velocity. As suggested by Royer (1982), the prevailing trade wind exerts an onshore wind stress that serves the important role of maintaining the integrity of the density gradients via the convergence of a surface Ekman layer toward the coast.