Composition of the phytoplankton pigments in the surface waters along a transect from the Northwestern to the southeastern Pacific Ocean

Multidisciplinary oceanic investigation was undertaken in Aug–Sep. 2003 along a transect from Northwestern (Busan, Korea) to Southeastern Pacific (Talcahuano, Chile) to understand the physical, chemical and biological features in the surface water, and to depict their interaction with the atmosphere. Among the twenty parameters measured, we describe the physical, chemical and biological features. Physico-chemical data were analyzed in conjunction with the geographic position and yielded 7 peculiar surface water masses. The first water mass (28.4°N, 130.8°E to 21.5°N, 139.5°E) was warm and low in phosphate and nitrate content, and high in silicate. The concentration of phytoplankton pigment was one of the lowest. The second (20.4°N, 140.7°E to 2.2°S, 162.9°E) was the warmest and the least saline. Nitrate and phosphate concentration were one of the lowest. Chlorophyll a (Chl a) concentration was the lowest among the surface waters. The third (3.4°S, 164.0°E to 14.5°S, 173.3°E) was warm. Nitrate concentration was the lowest. CHL-a, peridinin (Perid), violaxanthin (Viola), zeaxanthin (Zea), chlorophyll-b (Chl b) and β-CAR were abundant. The fourth (18.6°S, 177.5°E to 31.8°S, 123.9°W) was saline and poor in nutrient concentration. The contributions of 19′-butanoyloxyfucoxanthin (But-fuco), 19′-hexanoyloxyfucoxanthin (Hex-fuco), and CHL b to CHL a were non-negligible. The fifth (32.4°S, 122.1°W to 33.8°S, 117.2°W) was relatively cold and well oxygenated. Concentration of Fuco, But-fuco, Hex-fuco and Chl b was high. The sixth (34.2°S, 115.4°W to 37.4°S, 92.1°W) was cold, well oxygenated and enriched with phosphate and nitrate. Concentration of phytoplankton pigment was, however, one of the lowest. The seventh, located off the Chilean coast, from 37.2°S, 87.2°W to 36.1°S, 74.1°W was well oxygenated and highly enriched with nitrate and phosphate. Phytoplankton pigments such as Fuco, Perid, But-fico, and Hex-fuco were rich. The 7 surface water masses are partially attributed to Kuroshio Current, North Equatorial Current and North Equatorial Countercurrent, South Equatorial current, South Pacific Subtropical Gyre, South Pacific Current, Subtropical Front and Chilean coastal water. The differences in physicochemical characteristics and the history of the surface water resulted in difference in quantity and composition of the phytoplankton pigment.     

Simulation of the quasi-biennial oscillations of the zonal wind in the equatorial stratosphere: Part II. Atmospheric general circulation models

The problem of simulating quasi-biennial oscillations (QBOs) of zonal velocity in the equatorial stratosphere in atmospheric general circulation models is considered. In accordance with the results from Part I of this study on the basis of the models developed at the Institute of Numerical Mathematics of the Russian Academy of Sciences (INM RAS), the possibility of implementing (in these models) mechanisms of QBO excitation through both the interaction of planetary waves with the mean flow and breaking of short gravity waves is investigated. A new high-resolution 2° × 2.5° × 80 version of the INM RAS model is designed, a climate simulation with the two 2° × 2.5° × 39 and 2° × 2.5° × 80 versions of the INM RAS model is briefly described, results of spectral analysis of equatorial wave activity are presented, and the QBO formation processes in these models are considered in detail. For the new 2° × 2.5° × 80 model, realistic QBOs of zonal wind are obtained as the result of the action of both mechanisms.     

On the seasonal variation of transport through the Tokara Strait

Results are described from a limited area barotropic model of the North Pacific with 1/3°×1/3° resolution and bounded by latitudes 10°N and 50°N and longitudes 120°E and 160°E. The model employs dynamics linearised about a state of rest and incorporates realistic bottom topography. It is driven by the seasonally varying part of the Hellerman and Rosenstein wind stress field and by inflow along the northern and eastern boundaries specified from a 1°×1° version of the model applied to the whole North Pacific. The model-calculated transport variations through the Tokara Strait are similar to those of the observed seasonal sea level differences across the Strait, although the model appears to underestimate the amplitude of the signal by a factor of at least 2. The inclusion of realistic bottom topography is shown to be crucial in determining the model response.     

Variability of the Southern Hemisphere Subtropical Jet Stream in the Second Half of the 20th Century and Early 21st Century

Latitudinal position and wind speed of the Southern Hemisphere subtropical jet stream have been investigated on the basis of ERA-Interim, JRA-55, and NCEP–NCAR reanalysis data for 1948–2013. The analysis covers different time intervals in summer and winter seasons, as well as different spatial domains. It has been shown that the variability of the southern jet stream parameters in both winter and summer seasons is predominantly characterized by wind-speed weakening on the jet-stream axis and its poleward shift. The winter seasons of 2000–2013 identified a shift in the jet-stream axis toward the equator in the Atlantic (60°–0° W) and African (0°–60° E) sectors; the wind-speed increase in the Atlantic sector was statistically significant. The wind speed on the jet-stream axis in both winter and summer is closely related to the temperature difference in the upper tropospheric layer of 200–400 hPa between the latitudinal zones of 0°–30° S and 30°–60° S. A significant negative correlation (r = ?0.78) between wind speed and temperature difference has been revealed for the winter season in the upper tropospheric layer between the latitudinal zones of 30°–60° S and 60°–90° S, which can be explained by the Southern Annular Mode variability in this season. No such relationship has been found for the summer season.     

Statistical features of eddies approaching the Kuroshio east of Taiwan Island and Luzon Island

This study examined the statistical features of eddies approaching the Kuroshio east of Taiwan Island and Luzon Island. In total, 315 eddies (138 anticyclonic and 177 cyclonic eddies) were detected from 19.5 years of satellite altimeter sea-level data, with more than 95% of these eddies being generated in the ocean west of the Mariana Islands. Eddy trajectory statistics indicated that eddies frequently intrude into the Kuroshio regime at two latitude bands, namely 18°N–19°N and 22°N–23°N, with periods of 146 ± 62 and 165 ± 46 days, respectively. The interaction time is longer within the two active bands (33 ± 10 days at 18°N–19°N and 45 ± 17 days at 22°N–23°N) than at other latitudes. These two eddy-intrusion bands are associated with the northern and southern Subtropical Countercurrents (STCCs). These STCCs have a vertically reversed sign of the meridional potential vorticity gradient, thus providing a key energy source for eddy generation. In addition, when westward-propagating eddies approach the Ryukyu Islands, the southwestward recirculation flow east of the island chain as well as topographic effects cause some eddies to head southwestward to the east of Taiwan and intrude into the Kuroshio at 22°N–23°N, rather than to dissipate directly. Therefore, we suggest that the STCCs play a key role in inducing the eddies to frequently intrude into the Kuroshio at 18°N–19°N and 22°N–23°N. In addition, the Ryukyu Islands are responsible for concentrating the eddies within 22°N–23°N.     

Evaluation of GODAS Using RAMA Mooring Observations from the Indian Ocean

We present a comparison of the Global Ocean Data Assimilation System (GODAS) five-day ocean analyses against in situ daily data from Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) moorings at locations 90°E, 12°N; 90°E, 8°N; 90°E, 0°N and 90°E, 1.5°S in the equatorial Indian Ocean and the Bay of Bengal during 2002–2008. We find that the GODAS temperature analysis does not adequately capture a prominent signal of Indian Ocean dipole mode of 2006 seen in the mooring data, particularly at 90°E 0°N and 90°E 1.5°S in the eastern India Ocean. The analysis, using simple statistics such as bias and root-mean-square deviation, indicates that standard GODAS temperature has definite biases and significant differences with observations on both subseasonal and seasonal scales. Subsurface salinity has serious deficiencies as well, but this may not be surprising considering the poorly constrained fresh water forcing, and possible model deficiencies in subsurface vertical mixing. GODAS reanalysis needs improvement to make it more useful for study of climate variability and for creating ocean initial conditions for prediction.     

长江口渔场、舟山渔场硅酸盐浓度分布与生物量关系的研究

根据1998年和2000年东海北部的营养盐调查资料和相应的历史资料,以及同期开展的虾类资源调查资料,研究了冬、夏季长江冲淡水的流向以及它对长江口渔场、舟山渔场硅酸盐分布规律和虾类生物量分布规律的影响。结果表明,长江冲淡水转向的原因可以归纳为4类,夏季长江冲淡水的流动界限由123°E,30．3°N到127．3°E,33°N的直线和由123°E,31．8°N到127．3°E,34．5°N的直线所围的区域。长江冲淡水给长江口渔场、舟山渔场提供了大量的硅酸盐,对提高该海区的初级生产力起到了积极的作用,有利于生物的繁衍生息,提高了生物量。最后,用该海区虾类的分布密度证实了由该水团所做出的对生物量的推论。     

Spatial variations in the air turbidity factor above the European part of Russia under conditions of abnormal summer of 2010

We analyze spatial variations in the air turbidity factor T obtained from the interpolation of ground-based solar radiometry data within the territory (40°–70° N, 30°–60° E) in summer 2010. The abnormal heat and connected fires of summer 2010 changed the mean values of air turbidity and the character of its spatial variations. As a result, a “tongue” of increased values of the turbidity factor was observed in the south-to-north direction in July, and a closed region of anomalous high T was formed over the territory (48°–55° N, 37°–42° E) to the south of Moscow and partly covered the Moscow region in August. Such a pattern resulted from blockage preventing from ingress of air masses from the west and producing closed air circulation over the European Part of Russia (EPR).     

吕宋海峡附近中尺度涡特征的统计分析

采用1993年1月到2008年12月16a融合海面高度距平数据,追踪吕宋海峡附近海域(18°～23°N,116°～126°E)中尺度涡的移动轨迹,结果表明:时间分辨率为7d的卫星高度计资料难以观测到中尺度涡从西北太平洋通过吕宋海峡传进南海的过程,但对1994年吕宋海峡中部观测到的一个气旋涡及其附近中尺度涡的运动轨迹进行分析可见,西北太平洋海面高度变化会与吕宋海峡内部海面高度耦合后向南海传播。海面高度距平数据的时间-经度图表明,西北太平洋海面高度变化信号在西传至吕宋海峡附近(121°～122°E)时出现信号不连续。对21°N,116°～140°E断面的海面高度距平数据按周期分别为1～3月、3～6月、330～390d(年信号)进行分段带通滤波,发现不同周期的西北太平洋信号穿过吕宋海峡传入南海受到的阻隔作用、向西传播的速度以及它们所受的强迫机制均不同。     

Influence of ridges on hydrographic parameters in the Southwest Indian Ocean

The objective of the paper is to use the data collected along two meridional sections (45° E and 57°30′ E) during the austral summer (January–March) 2004 to understand the influence of seabed topography across the Madagascar and Southwest Indian Ridges on hydrographic parameters. The study was supplemented by World Ocean Circulation Experiment (WOCE) Conductivity-Temperature-Depth data collected during February–March 1996 along 30° E, as well as Levitus climatology. A southward shift of 2° latitude (between 45° E and 57°30′ E) was recorded for the two predominant frontal structures, i.e., the Agulhas Return Front and Southern Subtropical Front, which is attributed to the influence of seabed topography on hydrographic parameters. No significant spatial variation of these fronts was noted between the 30° E and 45° E meridional sections. Between latitudes 31° S and 42° S, the temperature and salinity structures show deepening over the ridges. The Antarctic Circumpolar Current core was detected between 40°15′ S and 43° S.     

基于产卵场环境因子的阿根廷滑柔鱼资源补充量预报模型研究

西南大西洋阿根廷滑柔鱼Illex argentinus是短生命周期种类,其资源量极易受到海洋环境变化的影响。根据2003—2011年我国鱿钓船队在西南大西洋的生产统计数据,以及产卵场海洋表面温度(SST)、海表温度距平值(SSTA),计算分析了阿根廷滑柔鱼在产卵期产卵场各月最适表层水温范围占总面积的比例(用PS表示)以及表征海流强度的SST、SSTA等多种环境变量因子与单位捕捞量渔获量(CPUE)的相关性,建立多种基于主要环境因子的资源补充量预报模型,同时分析比较预报模型的优劣。相关性分析表明:6月份有3片连续区域的SST与CPUE之间存在强相关性,分别为38°~39°S、54°~55°W,40.5°~41.5°S、51°~52°W,39.9°~40.4°S、42.6°~43.1°W。利用6月份此3片连续区域SST与次年CPUE建立的三元线性模型,模型符合统计检验,偏差解释率为82.4%。在此基础上加入7月份PS影响因子建立3种方案下的误差反向传播(EBP)神经网络模型。结果认为,包含了福克兰寒流与巴西暖流表温信息的方案3模型优于其他两种模型,其准确率可以达到90%以上。     

Hydrography and circulation of the bay of Bengal during withdrawal phase of the southwest Monsoon

Hydrographic data were collected from 3 to 10 September 1996 along two transects; one at 18° N and the other at 90° E. The data were used to examine the thermohaline, circulation and chemical properties of the Bay of Bengal during the withdrawal phase of the southwest monsoon. The surface salinity exhibited wide spatial variability with values as low as 25.78 at 18° N / 87° E and as high as 34.79 at 8° N / 90° E. Two high salinity cells (S > 35.2) were noticed around 100 m depth along the 90° E transect. The wide scatter in T-S values between 100 and 200 m depth was attributed to the presence of the Arabian Sea High Salinity (ASHS) water mass. Though the warm and low salinity conditions at the sea surface were conducive to a rise in the sea surface topography at 18° N / 87° E, the dynamic height showed a reduction of 0.2 dyn.m. This fall was attributed to thermocline upwelling at this location. The geostrophic currents showed alternating flows across both the transects. Relatively stronger and mutually opposite currents were noticed around 25 m depth across the 18° N transect with velocity slightly in excess of 30 cm s⁻¹. Similar high velocity (> 40 cm s⁻¹) pockets were also noticed to extend up to 30 m depths in the southern region of the 90° E transect. However, the currents below 250 m were weak and in general < 5 cm s⁻¹. The net geostrophic volume transports were found to be of the order of 1.5 × 10⁶ m³ s⁻¹ towards the north and of 6 × 10⁶ m³ s⁻¹ towards west across the 18° N and 90° E transects respectively. The surface circulation patterns were also investigated using the trajectories of drifting buoys deployed in the eastern Indian Ocean around the same observation period. Poleward movement of the drifting buoy with the arrival of the Indian Monsoon Current (IMC) at about 12° N along the eastern rim of the Bay of Bengal has been noticed to occur around the beginning of October. The presence of an eddy off the southeast coast of India and the IMC along the southern periphery of the Bay of Bengal were also evident in the drifting buoy data.     

Simulation of the spatiotemporal variability of the World Ocean sea surface hight by the INM climate models

The results of simulations of the World Ocean sea surface hight (SSH) in by various versions of the Climate Model of the Institute of Numerical Mathematics, Russian Academy of Sciences, are compared with the CNES-CLS09 fields of the mean dynamic topography (deviation of the ocean level from the geoid). Three models with different ocean blocks are considered which slightly differ in numerical schemes and have various horizontal spatial resolution, i.e., the INMCM4 model, which participated in the Climate Model Intercomparison Project (CMIP Phase 5, resolution of 1° × 1/2°); the INMCM5 model, which participates in the next project, CMIP6 (resolution of 1/2° × 1/4°); and the advanced INMCM-ER eddy-resolving model (resolution of 1/6° × 1/8°). It is shown that an increase in the spatial resolution improves the reproduction of ocean currents (with Agulhas and Kuroshio currents as examples) and their variability. A probable cause of relatively high errors in the reproduction of the SSH of Southern and Indian oceans is discussed.     

Distribution and Origin of Seamounts in the Central Indian Ocean Basin

Approximately 200 seamounts of different dimensions have been identified, from multibeam bathymetry maps of the Central Indian Ocean Basin (CIOB) (9°S to 16°S and 72°E to 80°E), of which 61% form eight chains that trend N-S. The seamounts are clustered above and below 12°S latitude. Area II (9°–12°S) shows a concentration of smaller seamounts (≤400 m height), and area I (12°–15°S) has a mixed population (including both less and more than 400 m height). Inspite of the differences in their height, the seamounts of these eight chains are morphologically (slope angle, flatness, basal width) corelatable. Furthermore, we suggest that height-width ratio could be useful in identifying the style of seamount eruption. The seamount chains in the CIOB probably originated from propagative fractures and were produced between 61 and 52 Ma (chrons A26 to A23) as a result of the interaction between the conjugate crusts of the Central Indian and Southeast Indian Ridges during the Indo-Eurasian collision event.     

南海与西太平洋海水的交换:氧、氦同位素证据

研究了西太平洋海域(7°～26°N,122°～130°E)不同深度海水的氧、氦同位素组成和分布特征.结果表明,巴士海峡附近海域几个深度上δ18O等值线均向东弯曲,δ3He等值线也出现了类似的分布特征,可能反映了南海海水与黑潮水的混合作用.氧、氦同位素的研究结果为南海海水通过巴士海峡侵入了西太平洋提供了地球化学证据.     

2016年秋季热带西太平洋网采浮游植物群落结构

作者于2016年9月27日～10月25日对热带西太平洋(0°～20°N, 120°～130°E)10个站位的网采浮游植物群落结构进行了采样调查。应用Uterm?hl方法对调查海域浮游植物的物种组成、细胞丰度、优势物种以及群落多样性等相关生态特征进行了分析。希望为热带西太平洋提供一些基础的背景资料,为以后的研究奠定基础。结果表明, 鉴定出浮游植物共计4门、66属、243种(包括变种、变型), 含硅藻门(Bacillariophyta)34属、103种, 甲藻门(Pyrrophyta)28属、133种, 金藻门(Chrysophyta)2属、4种,蓝藻门(Cyanophyta)2属、3种。浮游植物细胞丰度1 965.573×10³ 细胞/m³ , 其中蓝藻的细胞丰度为1 945.169×10³ 细胞/m³ , 决定了浮游植物的分布格局, 占总细胞丰度的98.96%, 高值区分布在0°N130°E-10°N130°E的4个站位(E130-13、E130-15、E130-17、E130-19); 硅藻丰度在20°N断面N20-4站位存在高值区; 甲藻丰度在130°E断面的3个站位(E130-10、E130-13、E130-15)存在高值区。本次调查的优势种依次为铁氏束毛藻(Trichodesmium thiebaultii)、扁形原甲藻(Prorocentrum compressum)、扁豆原甲藻(Prorocentrum leniculatum)、胞内植生藻(Richelia intracellularis)、菱形海线藻(Thalassionema nitzschioides)、细弱海链藻(Thalassiosira subtilis)、具边线形圆筛藻(Coscinodiscus marginato-lineatus)、科氏角藻(Ceratium kofoidii)、鲁比膝沟藻(Gonyaulax lurbynaii)、中华半管藻(Hemiaulus sinensis)、霍氏半管藻(Hemiaulus hauckii)、小等刺硅鞭藻(Dictyocha fibula)。Shannon-Weiner多样性指数的均值为2.440,Pielou 均匀度指数的均值为0.163。相关分析结果显示浮游植物空间分布主要受PO₄-P、NH₄-N的影响,且由蓝藻的相关性决定的。聚类分析得出群落结构分为大洋群聚和近岸群聚两种类型(其中大洋群聚的站位又划分为0°～10°N纬度范围聚集和10°～20°N纬度范围聚集)。     

西风爆发、次表层暖水东移与厄尔尼诺现象

利用最近20 a的大气海洋资料,分析了厄尔尼诺事件与赤道太平洋西风异常以及赤道太平洋次表层海温之间的关系.结果表明,赤道西太平洋(5°S～5°N,120°～160°E)和赤道中东太平洋(5°S～5°N,160°E～160°W)西风异常都存在着与厄尔尼诺周期一致的年际变化,但前者还包含有显著的2～3个月季节内振荡.赤道西太平洋次表层冷暖水东移也呈现年和年际时间尺度的振荡周期.在厄尔尼诺发生前,赤道西太平洋次表层海水出现持续性增暖,赤道西太平洋西风异常频率加快,强度增强.随后赤道中太平洋(160°E～160°W)出现持续性(3个月以上)强西风异常(即西风爆发),并进一步向东扩展,同时次表层暖水沿着赤道波导东移到赤道东太平洋混合层,导致赤道东太平洋海表大面积异常增暖,形成一次厄尔尼诺现象.最后,模式模拟了1980～1984年赤道太平洋海温的变化,进一步证实了赤道纬向西风异常对暖水东移起着重要的作用.     

The potential hydrothermal systems unexplored in the Southwest Indian Ocean

Deep-sea hydrothermal vents possess complex ecosystems and abundant metallic mineral deposits valuable to human being. On-axial vents along tectonic plate boundaries have achieved prominent results and obtained huge resources, while nearly 90% of the global mid-ocean ridge and the majority of the off-axial vents buried by thick oceanic sediments within plates remain as relatively undiscovered domains. Based on previous detailed investigations, hydrothermal vents have been mapped along five sections along the Southwest Indian Ridge (SWIR) with different bathymetry, spreading rates, and gravity features, two at the western end (10°–16°E Section B and 16°–25°E Section C) and three at the eastern end (49°–52°E Section D, 52°–61°E Section E and 61°–70°E Section F). Hydrothermal vents along the Sections B, C, E and F with thin oceanic crust are hosted by ultramafic rocks under tectonic-controlled magmatic-starved settings, and hydrothermal vents along the Section D are associated with exceed magmatism. Limited coverage of investigations is provided along the 35°–47°E SWIR (between Marion and Indomed fracture zones) and a lot of research has been done around the Bouvet Island, while no hydrothermal vents has been reported. Analyzing bathymetry, gravity and geochemical data, magmatism settings are favourable for the occurrence of hydrothermal systems along these two sections. An off-axial hydrothermal system in the southern flank of the SWIR that exhibits ultra-thin oceanic crust associated with an oceanic continental transition is postulated to exist along the 100-Ma slow-spreading isochron in the Enderby Basin. A discrete, denser enriched or less depleted mantle beneath the Antarctic Plate is an alternative explanation for the large scale thin oceanic crust concentrated on the southern flank of the SWIR.     

Determining the weights of two types of artificial reefs required to resist wave action in different water depths and bottom slopes

The interaction between waves and artificial reefs (ARs; a hollow cube weighing 8.24 kN (0.84 t) and a water pipe weighing 1.27 kN (0.13 t)) in shallow waters was investigated with respect to variations in design weight, orientation (for cube; 45° and 90° angles, for pipe; 0°, 90°, and 180° angles to flow), depth (1–20 m), and bottom slope (10^?1, 30^?1, and 50^?1). Physics equations and FLUENT software were used to estimate resisting and mobilising forces, and drag coefficients. Drag coefficients for the hollow cube were 0.76 and 0.85 at 45° and 90° angles to the current, respectively, and 0.97, 0.38, and 1.42 for the water pipe at 0°, 90°, and 180° angles to the current, respectively. Deepwater offshore wave conditions at six stations were transformed into shallow nearshore waters representative of the artificial reef site. Waters deeper than 12 and 16 m are safe to deploy blocks with angles of 45° and 90°, respectively. However, water pipes constructed at angles of 90° and 180° to the current were estimated as being unstable for 365 out of 720 cases at all stations (only one station was stable for all cases). Water pipes angled at 0° were found to be stable in all 360 cases. Slope had a significant effect on weight and depth. Results from this study provide an important reference for engineers performing projects aiming to increase the performance and service life of ARs.