东海西部陆架海域水团的季节特征分析

On the basis of the CTD data and the modeling results in the winter and summer of 2009, the seasonal characteristics of the water masses in the western East China Sea shelf area were analyzed using a cluster analysis method. The results show that the distributions and temperature-salinity characteristics of the water masses in the study area are of distinct seasonal difference. In the western East China Sea shelf area, there are three water masses during winter, i.e., continental coastal water（CCW）, Taiwan Warm Current surface water（TWCSW） and Yellow Sea mixing water（YSMW）, but four ones during summer, i.e., the CCW, the TWCSW, Taiwan Warm Current deep water（TWCDW） and the YSMW. Of all, the CCW, the TWCSW and the TWCDW are all dominant water masses. The CCW, primarily characterized by a low salinity, has lower temperature, higher salinity and smaller spatial extent in winter than in summer. The TWCSW is warmer, fresher and smaller in summer than in winter, and it originates mostly from the Kuroshio surface water（KSW） northeast of Taiwan, China and less from the Taiwan Strait water during winter, but it consists of the strait water and the KSW during summer. The TWCDW is characterized by a low temperature and a high salinity, and originates completely in the Kuroshio subsurface water northeast of Taiwan.     

Temporal and spatial distribution of hypoxic/seasonal anoxic zone in Amvrakikos Gulf, Western Greece

Coastal hypoxia and anoxia have become a serious environmental problem in many coastal ecosystems, and recent evidence suggests an increase in the number of systems experiencing hypoxia globally and an increased frequency and duration of hypoxia in many historically hypoxic systems. Eutrophication, low physical energy and large freshwater input are some of the most important factors, which lead to the development of hypoxia in coastal areas. The Amvrakikos Gulf, located in western Greece, is one of the most important protected areas in Greece and in Europe and past studies indicated that some regions of the Gulf experience hypoxia. Despite the importance of the Amvrakikos Gulf ecosystem, little is known about key ecological, chemical, and physical processes in the Gulf and their relationship with oxygen depletion. In the present study, authors try to answer some important questions regarding the distribution and variation of the hypoxic zone. After a year of measurements, it was concluded that according to spatial distribution of DO, the gulf can be divided into two parts, the western and eastern areas, with important differences occurring between them. Within the western area, the water column was well oxygenated during winter and spring and hypoxic conditions occurred only in summer and autumn. The eastern area was hypoxic throughout the year and anoxic conditions occurred only during autumn. In conclusion, taking into account the author’s measurements and previous studies, the seasonally hypoxic eastern area in 1987 converted into a seasonally anoxic area in 2009 and the western part of the gulf, remained seasonally hypoxic, indicating the degradation of the gulf’s environmental state within the last 20 years.     

Changes in the pattern of water masses resulting from a poleward slope current in the Cantabrian Sea (Bay of Biscay)

From September to December 1995, three hydrographic surveys were carried out in the eastern Cantabrian Sea (Bay of Biscay). Changes in the water masses pattern were examined to study the variability and main energetic features in the area. At the beginning of December, an intense Poleward Current (PC), which had come from Portuguese slopes, entered the eastern Cantabrian Sea. This current was the most energetic event in this area in winter. The PC waters increased temperature by about 2 °C (subsurface layers) and salinity by 0.2 (surface layers) in the pattern of water masses in the eastern Cantabrian Sea in winter. The core current was approximately 10 km width and 120 m depth and the water transport, estimated from geostrophic current profiles, was of about 1.3 Sv.A well-defined wavelike front with two significant ridges in the western and eastern sampling area, was observed. The variability and meandering flow of the PC were driven by dominantly baroclinic instabilities, which are due to strong vertical velocity shear. In this synoptic-scale system, the potential vorticity advection, the differential vorticity advection, and the geopotential tendency have shown to be the cause of the ageostrophic motion and the main baroclinic disturbances.One important consequence of the entrance of the PC in the eastern Cantabrian Sea was the profound effect on the pattern of nutrients. The current-induced stratification pattern drives the distribution of nutrients in the different layers and the instabilities and meandering pattern of the PC was an important mechanism of fertilisation offshore.     

琼州海峡东部水进入北部湾对广西沿海环流的影响

本文通过对琼州海峡东部水域温盐资料和沿岸海洋站同步观测资料的对比发现：夏季,广西涠洲岛盐度变化规律和琼州海峡东部、中部变化规律一致,广西北海略受影响,而远离琼州海峡的龙门和白龙尾两站,则更多反映夏季陆地水文规律。同时,采用琼州海峡多年海流资料和涠洲岛定点站及近期测流站的海流观测资料对比看出,琼州海峡冬夏季余流方向仍然是自东向西。结合数值模拟计算结果,同样得出琼州海峡东部水自东向西进入北部湾的事实。这些温盐分布特征和余流观测结果进一步证实：粤西沿岸流是琼州海峡水向西输运的主要来源,形成粤西沿岸流这种现象的根源在于珠江冲淡水的西向流,它们通过琼州海峡进入北部湾,加强了北部湾北部气旋式环流的形成。夏季,在强的西南风作用下,产生较强北部湾西岸北向沿岸流,促使低盐冲淡水向外海输运,然后在东部涠洲岛附近形成更大范围内气旋式环流。琼州海峡东部水进入北部湾对广西沿海环流影响的研究,直接向琼州海峡冬夏季水体输运方向的传统结论提出了新的挑战。     

Seasonal changes in the distribution and exchange of inorganic nitrogen between sediment and water in the Northern Baltic (Gulf of Bothnia)

The concentration profiles of nitrate plus nitrite, ammonium, and redox potential in sediment and water column were determined in late winter and summer at a sampling site off Norrbyn, northern Sweden, in the Gulf of Bothnia. The sediment had an oxidized surface layer during winter and spring, and nitrification occurred. Nitrate but not ammonium was present in the water column at this time. During summer a layer of planktonic detritus was deposited onto the sediment and led to its deoxygenation and reduction. Ammonium was then the predominant form of inorganic nitrogen in the water column.Laboratory experiments confirmed that nitrification in the surface layer of sediment prevented ammonium export during winter. Enhanced temperature or organic detritus deoxygenated the surface sediment and inhibited nitrification, and export of ammonium from the sediment increased. Although nitrification was important in determining the flow of nitrogen in the sediment it accounted for at most only 5% of the total oxygen uptake by the sediment.     

The role of atmospheric circulation in spatial and temporal variations in the structure of currents in the western South China Sea

Based on numerical simulations, we calculate the integral water circulation of the South China Sea on the eastern Vietnam shelf in the Vietnam coastal current area. The main objective of simulations was to study the hydrodynamic structures of this current in the winter–summer interseasonal period. The calculations were performed for the period from April to June 1999, which had the necessary primary field data. Two types of atmospheric processes were considered: the first is characterized by a small pressure gradient over the South China Sea and the second includes tropical cyclones in the southern part of the sea. The simulation results showed that there are three hydrodynamic gyres in the study area during the given time period: two anticyclonic gyres and a cyclonic gyre that separates them, which together form a complex pattern of the Vietnam current. These gyres persist for the given types of atmospheric processes and are quasi-stationary structures. The Vietnam current carries coastal water masses from south to north within the anticyclonic gyres in summer and from north to south within the cyclonic gyres in winter.     

Hydrographic conditions in the Tsushima Strait revisited

Long-term averaged temperature and salinity distributions in the Tsushima Strait are investigated on the basis of a concurrent dataset of the eastern and western channels during 1971–2000. Both temperature and salinity show a clear seasonal variation with weak and strong stratifications in December–April and June–October, respectively. The largest standard deviations occur in summer around the thermocline for temperature and in the surface layer for salinity. This indicates large interannual variability in the development of a thermocline and low salinity water advection from the East China Sea. The water masses in both channels are distinctly different from each other; the water in the western channel is generally colder and fresher than that in the eastern channel throughout the year. Baroclinic transport based on the density distributions shows a seasonal variation with a single peak in August for the eastern channel and double peaks in April and August for the western channel. However, this cannot explain the seasonal variation in the total volume transport estimated from the sea level differences across the channels. The spatial distribution of baroclinic transport shows a year-round negative transport towards the East China Sea behind the Iki Island in the eastern part of the eastern channel. This negative transport reflects the baroclinic structure between the offshore Tsushima Current Water and cold coastal water. The corresponding southwestward currents are found in both Acoustic Doppler Current Profiler (ADCP) and high frequency (HF) radars observations.     

东中国海拉格朗日环流数值模拟Ⅱ.环流模拟

依据自适应数值模型，模拟了东中国海冬、夏季三维斜压Lagrange环流。模拟发现：台湾暖流的上层水来自台湾海峡入流和台湾东北黑潮的表层水；50m以下的深底层水主要由台湾东北黑潮的次表层水入侵陆架生成。冬季对马暖流外海一侧主要由黑潮水构成，而其近陆一侧由台湾暖流和陆架混合水构成，西朝鲜沿岸流在济州海峡汇入对马暖流；夏季它还包含转向后的长江冲淡水。冬季黄海暖流并非对马暖流的直接分支，黄海暖流水是对马暖流水和陆架水混合而成，这与传统观点相悖，而与中韩黄海水循环动力学合作调查结果一致。黄海暖流东西两侧分别为2支向南流动的滑岸流。夏季黄海环流构成基本封闭的逆时针环流。冬季渤海环流主要有一逆时针大环流，但辽东湾的环流是顺时针向的。渤海环流冬强夏弱，水流在渤海海峡北进南出。     

Diel Changes in Vertical Distribution and Feeding Conditions of the Chaetognath Parasagitta elegans (Verill) in the Subarctic Pacific in Summer

Diel changes in vertical distribution and feeding conditions of the chaetognath Parasagitta elegans (Verill) were observed in three regions of the subarctic North Pacific in the summer of 1997. Samples were collected by repeated vertical hauls with a Vertical Multiple Plankton Sampler (VMPS) for 15–45 hours by demarcating the 0–500 m water column into four sampling layers. Integrated abundance through the entire water column and the proportion of juveniles were higher in the Bering Sea than the western and eastern subarctic Pacific. Juveniles always inhabited the surface layer in the western subarctic Pacific and Bering Sea, but they inhabited the underlying layer in the eastern subarctic Pacific. Stages I–III concentrated into the upper 150 m in the western subarctic Pacific but were distributed widely from 20–300 m in the Bering Sea. Among them, Stages II and III migrated rather synchronously over a wide vertical range in the eastern subarctic Pacific. The feeding rate of P. elegans was calculated to be 0.18 prey/chaetognath/day in the western subarctic Pacific, 0.27 prey/chaetognath/day in the Bering Sea and 0.07 prey/chaetognath/day in the eastern subarctic Pacific.     

Processes influencing iron distribution in the coastal waters of the Tsugaru Strait,Japan

We report measurements of iron, nutrients, dissolved oxygen, humic-type fluorescence intensity and chlorophyll a concentrations in the coastal waters at the inflow (western) and outflow (eastern) ends of Tsugaru Strait (Japan) in June 2003 and 2004. Two different water masses (intensive eastward flow “subtropical Tsugaru Warm Current Water (TWCw)” and weak westward flow “subarctic Oyashio Water (OW)”) were observed at the eastern end of the strait. TWCw at the southern part of the eastern strait was vertically homogeneous with a uniform concentrations of iron (0.7–1.1 nM for labile dissolved Fe and 14–20 nM for total dissolvable Fe in 2003) as well as other chemical, biological and physical components throughout the water column of 200 m due to strong vertical mixing in the strait. The degree of mixing in the Tsugaru Warm Current (TWC) is predominantly affected by diurnal tidal current, which is strong during the period of tropical tides and weak during the period of equinoctial ones. The especially strong vertical water mixing in 2003 is caused by large dissipation energy input due to the bottom friction of passage-flow through the strait and tidal current. At the northern part of the eastern strait, the fresh surface layer overlying the OW and the deep-bottom waters in 2003 contained large concentrations of dissolved iron, resulting from iron supplied from river runoff and shelf sediments, respectively. These results suggest that the most important mechanism for transporting iron in the strait is the strong vertical water mixing due to the tidal current, and that the iron sources in the coastal waters are the organic-associated, iron-rich freshwater input into the surface water.     

Observation of bottom water renewal and export production in the japan basin, east sea using tritium and helium isotopes

Tritium (₃H or T) has been produced mostly by atmospheric nuclear weapon tests, and entered the ocean in the form of water (HTO). As tritium exists as water itself, it has been regarded as an ideal tool to study the transport of water masses. In April 2001 we collected water samples in the western Japan Basin (WJB) for tritium and helium measurement. The timely sampling provided direct evidence of the bottom water formation, resulting in the drastic increase in tritium concentration from 0.3 TU in 2000 to 0.67 TU in 2001. Considering that the new bottom waters were found mostly in the WJB, it implies that maximum 1% of the whole bottom layer below 2600 m should be replaced with the surface water during the severely cold winter 2000—2001.₃H-₃He age, showing the elapsed time since the water left from the surface, can be used to calculate oxygen utilization rate by dividing AOU by the age. Under the condition of 90% oxygen saturation in the surface water, the integration of OUR in the water column below 200 m yields net oxygen consumption of 12 mol (O₂) m^-2 yr^-1, which corresponds to the export production of 99 g C m^-2 yr^-1 . This estimate is comparable to a previous estimate based on satellite data and implies that the ratio of export to primary production (f -ratio) is as high as 0.5 in the WJB.     

Variations in the Atlantic inflow to the Nordic Seas, 1955–1996

Hydrographic observations on the Svinøy section, which runs NW from about 62°N on the Norwegian coast to 64°40′N on the prime meridian, have been used to investigate variations in the Atlantic inflow to the Nordic Seas. The data are from the winter 1955 to 1973 and from the spring and the summer 1978 to 1996. The observations show that in the summer there exist two cores of water with salinity above 35.25 at about 100 m depth, but in the spring and the winter the core furthest offshore is less distinct. Geostrophic calculations show that, for all data sets, there are two kernels with northward currents in the Svinøy section: one over the inner part of the continental slope (over 600–800 m depths) and one further offshore (over 1400–2500 m depth). The mean volume transports of Atlantic water in the section are 4.5, 5.0 and 5.6 Sv in spring, summer and winter, respectively. Results from an Empirical Orthogonal Function analysis of the summer data indicate that there is a dual structure in the section when interannual variations are considered. In the western part of the section the temperature and salinity are negatively correlated with the winter North Atlantic Oscillation index, but in the eastern part of the section they are weakly positively correlated. This is not found in the winter data from 1955 to 1973. The geostrophic volume transport in the summer through the Svinøy section is positively correlated with the NAO indices for winter and spring, where the March NAO index gave the best correlation. Also, the summer volume transports west and east in the section seem to be in opposite phase. From the summer data 1978 to 1996 there is a positive linear trend for the eastern transport (+2.4 Sv), but there is a negative linear trend for the western transport (−2.0 Sv). The transport through the whole section has increased by 1.1 Sv during the same similar period. The atmospheric conditions were different in years with relatively low temperatures and salinities in the western part of the section compared to those years with relatively high temperatures and salinities. It is proposed that interannual variations of temperature, salinity and volume transport in the Svinøy section are controlled mostly by a large-scale variable pressure system (i.e. the North Atlantic Oscillation index).     

Effects of the Wind and Ice Conditions on the Upwelling along the Western Kamchatka Coast (Sea of Okhotsk) Based on the Satellite Data

The variability of the upwelling along the western coast of the Kamchatka Peninsula (northeastern part of the Sea of Okhotsk) has been studied based on an analysis of the multisensor satellite data. The intensity of upwelling is estimated on the basis of wind-forced offshore Ekman transport (upwelling index). The wind data for studying the seasonal variation of upwelling were collected in 1999–2009 using a Quik-SCAT/SeaWinds scatterometer. The upwelling events along the western Kamchatka coast were observed in December at the beginning of the winter monsoon period. During the period of strong winter monsoon northern winds from January to the middle of March, the drifting ice prevents the upwelling of the deep water at the western Kamchatka shelf edge under the mean conditions. The oceanographic data show that upwelling in the western coastal zone of Kamchatka was also observed during the transitional periods from winter to the summer monsoon (April). In summer, upwelling events are rarely observed in this region. The main cause of the summer upwelling is the propagation of the atmospheric cyclones over the Kamchatka Peninsula.     

Surface circulation of the Levantine Basin: Comparison of model results with observations

The eastern Mediterranean (Levantine Basin) hydrography and circulation are investigated by comparing the results of a high-resolution primitive equation model with observations. After a 10-year integration, the model is able to reproduce the major water masses and the circulation patterns of the eastern Mediterranean. Comparisons with the POEM hydrographical observations show good agreement. The vertical distribution of the water masses matches that of the observations quite well in terms of monthly mean. The model surface circulation is in agreement with circulation schemes derived from recent observations. Some well-known mesoscale features of the upper thermocline circulation are also realistically reproduced. In agreement with satellite observations, the model shows that high-energy mesoscale eddies dominate the upper thermocline circulation in the southern and the central parts of the Levantine Basin. Most of the Atlantic Water follows the north African coast and forms a strong coastal jet near the Libyan coast rather than forming the Mid-Mediterranean Jet described by several authors. The sub-basin circulation shows a strong seasonal signal. A strong and stable current flows along the isobaths in winter, becoming weaker and with more meanders in summer. The mesoscale eddies throughout the whole basin are more energetic in summer than in winter.     

北黄海夏、冬季叶绿素和初级生产力的空间分布和季节变化特征

依据2006～2007年夏、冬两季的北黄海海洋综合调查资料,分析了叶绿素和初级生产力的空间分布和季节变化特征,并浅析了其主要影响因素.夏季北黄海Chl a的平均含量为30.75 mg·m-2(7.64～92.57 mg·m-2),冬季平均含量为18.72 mg·m-2(3.04～50.55 mg·m-2),与夏季相比显著偏低(P<0.05).夏季Chl a浓度的垂直分布呈现较为明显的分层现象,最大值基本出现在次表层;冬季大部分海域垂直分布均匀.夏季水柱初级生产力含量的平均值为471.2 mg·m-2·d-1(70.1～1 308.2 mg·m-2·d-1),其分布大致呈现近岸海域高、东部开阔海域较低的格局;冬季平均值为125.4 mg·m-2·d-1(72.6～245.5 mg·m-2·d-1),约为夏季的1/4,且分布较均匀.北黄海夏季磷酸盐可能成为限制浮游植物生长的因素,而冬季无机氮和磷酸盐可能同时成为限制因子.夏季和冬季的海表温度与表层Chl a浓度之间均呈负相关关系,R2分别为0.44(P=0.01,n=73)和0.41(P=0.01,n=71).     

舟山渔场及其邻近海域水团的季节特征

根据2001年夏季和2002年冬季两次现场调查所收集的CTD和营养盐资料,利用模糊聚类分析法,对舟山渔场及其邻近海域水团的季节特征进行了分析.结果表明,舟山渔场及其邻近海域水团的配置、分布范围、温盐特性和营养盐含量都有明显的季节特征.其中,冬季在全海域共有3个水团(江浙沿岸水、台湾暖流表层水和黄海混合水),而夏季则存在4个水团(江浙沿岸水、台湾暖流表层水、台湾暖流深层水和黄海混合水);冬季,江浙沿岸水的分布范围较小,温度偏低,盐度略高,营养盐偏高,而夏季,其分布范围较大,温度偏高,盐度偏低,营养盐偏低;冬季,台湾暖流表层水北伸最强,厚度最厚,温度最低,盐度最高,硅酸盐和硝酸盐偏高,而夏季,则北伸最弱,厚度最薄,温度最高,盐度最低,硅酸盐和硝酸盐偏低;台湾暖流深层水是一个季节性水团,它含有较丰富的营养盐;黄海混合水的分布范围和营养盐含量也都呈现出明显的季节特征.     

Review on current and seawater volume transport through the Taiwan Strait

Patterns and features of currents and seawater volume transports in the Taiwan Strait have been reviewed by examining the results from more than 150 research papers in recent decades. It is noted that there are diverse or even conflicting viewpoints on these subjects. Here both common and different opinions are summarized. This review paper covers the studies involving in situ measurements and numerical modeling of current velocity, analyses of hydrographic data, and classification of water masses. Generally speaking, there are three currents in the Taiwan Strait: the China Coastal Current along the Fujian coast in the western Taiwan Strait, the extension of the South China Sea Warm Current in the western and central Taiwan Strait, and the Kuroshio’s branch or loop current intruding through the eastern Taiwan Strait. The current pattern in winter is quite different from that in summer, and the currents also exhibit differences between the upper and lower layers. The seawater volume transport through the Taiwan Strait is about 2.3 Sv northward in summer but about 0.8 Sv northward in winter. Both the current pattern and the seawater transport vary with local winds in the Taiwan Strait. This is particularly true in winter when the currents and the transport in the upper layer are significantly affected by strong northeasterly winds.     

Meridional asymmetric distribution of the primary production in the Atlantic Sector of the Southern Ocean in the austral spring and summer

The spatial distribution of the phytoplankton productivity was investigated in the Atlantic Sector of the Southern Ocean in the austral summer of 2009?C2010 and the spring of 2010 on the basis of field measurements. In October?CNovember, the average integrated primary production and the concentration of surface and integrated (photosynthetic layer) chlorophyll ??a?? in the Subantarctic waters of the Drake Passage exceeded the similar values along the Greenwich meridian by 3, 2, and 1.5 times, respectively. Similar primary production was observed in December?CJanuary for the water column in the eastern and western sectors of the studied area. The chlorophyll ??a?? concentration in the surface water layer was higher by 1.7 times for the Greenwich meridian area compared to the deep layers, but the concentrations of this pigment in the deeper layers did not differ. During the spring, the average primary production in the water column (the chlorophyll ??a?? concentration in the surface and in the photosynthetic layer) differed in the Drake Passage and along the Greenwich meridian by 2.3, 1.6, and 1.7 times, respectively. The opposite pattern was observed during the summer period, when the parameters listed above were higher for the Greenwich meridian area by 1.9, 2.5, and 1.7 times, respectively. Therefore, the western Antarctic areas in the spring are characterized by higher production than the eastern ones, and an opposite pattern is observed in the summer. The possible reasons for the meridional zonation of the chlorophyll ??a?? and the primary production are discussed in regard to different seasons.     

阿拉伯海高盐水入侵孟加拉湾的季节形态及动力机制

本研究利用Argo温盐、Aquarius遥感盐度等资料,研究了阿拉伯海高盐水入侵孟加拉湾的主要路径及季节变化机制.分析显示阿拉伯海高盐水入侵孟加拉湾存在3种类型,即夏季型、冬季型和春季型.夏季型入侵发生在湾口西部,入侵时间为7—10月,净体积输送达1.53 Sv.冬季型(12月至次年1月)和春季型(3—5月)阿拉伯海高...     

2008/2009年冬季南海冷涌天气过程的海-气热通量交换及热量收支

冬季风期(11月—翌年3月)南海显著的气候特点是盛行东北季风并频繁地发生冷涌天气过程。使用2008年10月到2009年4月在西沙群岛永兴岛近海进行的海-气通量观测试验资料,分析了西沙海域冬季风期,尤其是冷涌时段的海-气通量交换和热量收支特征。结果表明:冬季风前期由于海-气温差增大,感热通量比西南季风期稍增加;潜热通量平均值与西南季风期接近;太阳总辐射明显降低,大气长波辐射减小,海洋热量净收入成为负值,使得秋季之后海面温度不断降低。冷涌期间海-气之间的感热通量高于冬季风期平均值,潜热通量大部分(1月份之前)也高于冬季风期平均值;由于潜热通量增大和太阳短波辐射减小,1月份之前的冷涌过程海洋热量净收支普遍出现较大负值,海洋失热量强于冬季风期,甚至强于2008年台风过程平均值。到了冬季后期太阳总辐射增强,海洋热量净收入转为正值,海水温度又逐渐升高。季节之间比较,观测区感热通量以冬季风期间最大,秋季次之,春季最小;而潜热通量夏季风期出现最大值,冬季次之,秋季最小。