南印度洋中国中山站至澳大利亚费里曼特尔断面海洋锋位置及其年际变化

根据中国第18次南极科学考察队2002年1～3月在南印度洋从中山站外普里兹湾到澳大利亚费里曼特尔断面的走航XBT/XCTD资料和CTD资料及1998年1月、1999年2月和2000年3月等其他航次的调查资料,分析了该航线上海洋锋的位置及其年际变化:(1)在75°～78°E南极陆坡锋的位置在645°～655°S;在84°～100°E范围极地锋在535°～543°S附近;在96°～103°E亚南极锋在46°S～470°S附近;在110°E附近亚热带锋在372～380°S之间;(2)在南极极锋区存在显著等温线、等盐线的上凸和下凹,不同年份发生位置有变化;(3)在亚南极锋北侧,等温线、等盐线呈垂直排列的状态,温度、盐度垂直方向上分布均匀一致;(4)与1979,1991和1992年该区域同期的资料相比,近4a观测到的极地锋显著偏南1个纬距以上.     

印度洋混合层盐度季节变化机制研究

本文利用Argo盐度、SODA海流量、OAFlux蒸发量和TRMM降水量等数据,采用盐度收支方程定量给出了印度洋混合层盐度的收支,揭示了整个印度洋净淡水通量项、平流项、垂向卷夹项的分布、季节变化特征及其对混合层盐度变化的主要贡献。结果表明,就多年平均而言,平流项负贡献（15.14%）大于正贡献（9.89%）,说明平流输送把低盐水输送到高盐海域,导致印度洋高盐海域混合层的盐度降低。净淡水通量项的分布和季节变化与降水量基本一致,且正贡献（13.70%）大于负贡献（7.81%）,说明净淡水通量项使印度洋的混合层盐度升高（因为多年平均蒸发量大于降水量）。盐度季节变化显著海域的进一步分析表明,6−11月,西南季风漂流把赤道西印度洋的低盐水（相对阿拉伯海高盐水而言）输送到阿拉伯海西部海域,导致该海域的盐度降低。平流输送把孟加拉湾湾口和中部的高盐水带到北部海域,是导致北部海域盐度升高的主要原因。     

印度洋海底压强的季节和长期变化

利用2003—2015年的重力恢复和气候实验(Gravity Recovery and Climate Experiment, GRACE)卫星观测数据, 揭示了印度洋海底压强的变化特征, 并探讨了其变化机制。结果表明, 印度洋海底压强具有显著的季节变化特征, 北半球冬季在40°S以北(南), 海底压强呈负(正)异常, 夏季分布与冬季相反。印度洋区域的海底压强空间分布与Ekman输送空间分布有较好的对应关系。正压涡度方程诊断结果表明, 利用风场重构的海底压强能够较好地解释印度洋海底压强的季节和长期变化。此外, 海平面变化收支分析表明, 海底压强的变化在高纬度区域主导了海平面变化。     

Ferrobasalts from the Central Indian Ocean Basin

We report the occurrence of ferrobasalts recovered from the Central Indian Ocean Basin crust generated at the Southeast Indian Ridge during a phase of moderate to fast spreading accretion (～110–190?mm/yr, full rate).The rocks are rich in plagioclase, FeO* (13–19%), and TiO₂ (2.27–2.76%), poor in olivine and MgO (3.44–6.20%), and associated with topographic highs and increased amplitude magnetic anomalies corresponding to chrons A25 and A24. We suggest that secon dary eruptions from ancient N-MORB magma, which may have been trapped at a shallow depth in a horizon of neutral buoyancy, could have produced the ferrobasalts.     

Ferrobasalts from the Central Indian Ocean Basin

 We report the occurrence of ferrobasalts recovered from the Central Indian Ocean Basin crust generated at the Southeast Indian Ridge during a phase of moderate to fast spreading accretion (∼110–190 mm/yr, full rate).The rocks are rich in plagioclase, FeO^* (13–19%), and TiO₂ (2.27–2.76%), poor in olivine and MgO (3.44–6.20%), and associated with topographic highs and increased amplitude magnetic anomalies corresponding to chrons A25 and A24. We suggest that secon dary eruptions from ancient N-MORB magma, which may have been trapped at a shallow depth in a horizon of neutral buoyancy, could have produced the ferrobasalts. Received: 27 January 1998 / Revision received: 25 May 1998     

近45 年北印度洋海表风、浪特征研究

基于第三代海浪数值模式(WAVEWATCH-Ⅲ),以ERA-40海表风场为驱动场,得到北印度洋1957年9月～2002年8月的海浪场,并分析其特征.研究发现,北印度洋1958～2001年年平均海表风速和有效波高均呈缓慢递增趋势;北印度洋的海表风速、有效波高存在2.36～5.2 a左右的共同周期及26 a的长周期震荡;北印度洋海域年平均海表风速、有效波高的突变形势与冬季相似,突变期在20世纪80年代初.本研究可以为在北印度洋这一重要战略通道上作业的船只提供重要参考.     

东印度洋现生浮游有孔虫

A brief morphometric study of the recent planktonic foraminifera in the eastern Indian Ocean was provided with the taxonomic key to species,synonyms,SEM microphotographs of shells and chamber arrays.By recent classification,currently 20 species representing 13 genera and 6 families(Canderinidae,Heterohelicoidae,Hedbergellidae,Higerigerinoidae,Globigerinoidae,and Globorotaloidae)identified from the planktonic material of the eastern Indian Ocean up to a depth of 200 m.Their distribution in water(0–200 m)also reports on the new range of expansion in the eastern Indian Ocean,with Dentigloborotalia anfracta,Hastigerina pelagica,Streptochilus globigerus,Globigerinella calida,Globigerinella adamsi,Orcadia reidelii,Tenuitella parkerae,Tenuitella compressa,reported for the first time in this study area.In general,only around 50 planktonic species are valid worldwide,more specifically the species,e.g.,H.pelagica,G.calida,G.adamsi,S.globigerus,O.riedeli,T.parkerae,T.compressa,which occur in the eastern Indian Ocean to fill the the paucity of the recent regional taxonomic literature and the problematic identification from the eastern Indian Ocean.This work aims to bridge this gap and help scientists,managers,educators and students to identify plankton foraminifers by using species notes and images.     

The Rossby wave as a key mechanism of Indian Ocean climate variability

We analyze the time-longitude structure of composite cases from model-assimilated ocean data in the period 1958–1998, following on from earlier work by Huang and Kinter (J. Geophys. Res. 107(C11) (2002) 3199) that studied east–west thermocline variability in the Indian Ocean. Our analysis focuses on the Rossby wave signal along the thermocline ridge in the tropical SW Indian Ocean (10°S, 60–80°E), where wind stress curl is important. Anomalous winds in the equatorial east Indian Ocean force successive Rossby waves westward at speeds of 0.1 m s⁻¹±30%. With a wavelength of 7000 km, the period of oscillation is in the range 1.9–5.2 years. The Indian Ocean Rossby wave is partially resonant with the global influence of the El Nino–Southern Oscillation, except during quasi-biennial rhythm. The presence of the Rossby wave offers potential predictability for east–west atmospheric circulation systems and climate that affect resources in countries surrounding the Indian Ocean.     

南印度洋热带气旋快速增强事件气候特征及其年际变率

利用美国联合台风预警中心的热带气旋最佳路径数据集、美国国家海洋和大气管理局的扩展重构海表温度数据、全球海洋数据同化系统的温度、盐度数据及美国国家环境预报中心/国家大气研究中心的再分析资料, 分析了1981—2019年南印度洋热带气旋快速增强事件的气候特征和年际变率。结果表明, 南印度洋热带气旋快速增强事件产生频率呈现单峰分布, 主要产生在每年的12月至次年4月。南印度洋热带气旋增强事件的产生位置呈带状分布, 其中3个高值中心分别位于马达加斯加岛东北海域、南印度洋中部海域和澳大利亚西北海域, 这主要是由于热带气旋热潜和垂直风切变两个大尺度环境变量决定的。年际变率方面, 厄尔尼诺-南方涛动对南印度洋热带气旋增强事件产生频率的调制作用是不对称的, 厄尔尼诺年与拉尼娜年南印度洋热带气旋快速增强事件均减少, 但使其减少的物理机制不同。厄尔尼诺年, 热带气旋快速增强事件减少主要是较高的垂直风切变造成的; 拉尼娜年, 热带气旋快速增强事件减少主要是由于热带气旋热潜的降低, 而海表温度、垂直风切变和相对湿度也存在一定贡献。     

The Indian Ocean HydroBase: A high-quality climatological dataset for the Indian Ocean

The present study developed a high-quality climatological dataset for the Indian Ocean - the Indian Ocean HydroBase (IOHB) - from a combined dataset including the World Ocean Database 1998 version 2 (WOD98v2). Methods are similar to those used by previous studies for other oceans. Japanese data for the IOHB originated from the Japanese datasets MIRC (Marine Information Research Center) Ocean Dataset 2001 and Far Seas Collection; these datasets contain more Japanese observations than WOD98v2. Water mass properties in the IOHB climatology are consistent with previous studies. Seasonal patterns of properties near the sea surface are well reproduced, and deep-layer properties are consistent with the Reid-Mantyla climatology that is derived from high-quality observations. The isopycnal climatology of the IOHB differs from the World Ocean Atlas 2001 (WOA01) along the fronts associated with the Antarctic Circumpolar Current (ACC). The WOA01 shows a warm and saline intermediate water intrusion from South Africa to the east along the northern edge of the front. Such an intrusion is absent in IOHB where less saline intermediate water extends continuously northward from the southern ocean. The WOA01 shows a continuous belt of low potential vorticity along the ACC. This feature is less distinct in the IOHB climatology and in the Reid-Mantyla climatology. The IOHB consists of a 1° × 1° gridded climatology and the datasets of raw and quality-controlled hydrographic stations. The latter is valuable for quality control of the Argo float salinity data as climatological reference. These datasets are available freely via the Internet.     

印尼贯穿流对印度洋的热量贡献

本文基于海洋环流模式模拟的高分辨率欧拉场,利用拉格朗日追踪方法,评估了印尼贯穿流（ITF）对印度洋的热量贡献。通过计算ITF水体在印度洋的传输路径及伴随的温度变化来获取ITF水体在印度洋的热量传输过程。模拟结果表明ITF进入印度洋后主要向西流动并在到达马达加斯加后分叉,进入南、北印度洋。热收支分析表明ITF在北印度洋吸收0.41 PW热量,在南印度洋释放0.56 PW热量;这两个过程相互补偿,导致ITF对整个印度洋的净加热贡献并不显著,只有0.15 PW。进一步的检查ITF离开印度洋的出口（跨过34°S）,结果表明ITF主要随着位于西边界的奥古拉斯流和位于东边界的利文流离开印度洋。约89%的ITF水体沿着西边界离开印度洋,其余的11%主要沿着东边界离开印度洋;前者对整个印度洋的净加热贡献为0.10 PW,后者的净加热贡献为0.05 PW。     

季风转换期印度洋经向热输运的年际变异及其机理

本文采用SODA3.4.2再分析数据和POP2海洋模式研究了季风转换期间（春季和秋季）热带印度洋经向热输运异常（Meridional Heat Transport Anomaly, MHTA）的年际变异特征。春季MHTA存在两个主要模态,即一致模态和辐合辐散模态：一致模态表现为热带印度洋上层一致的向北输运,受热带印度洋海温一致模相关的赤道反对称风场（赤道以北/南为东北风/西北风异常）调控;辐合辐散模态则呈现关于赤道对称的表层辐散次表层辐合特征,受控于赤道以南的热带西南印度洋和副热带东南印度洋海温偶极子。然而,秋季MHTA仅表现为辐合辐散模态,受到印度洋偶极子期间赤道东风和赤道外反气旋式风应力异常影响。此外,POP2敏感性试验也验证了印度洋海温模态影响下异常风场对MHTA的调控作用,即反对称的风引起一致向北的MHTA,赤道东风异常引起MHTA表层辐散、次表层辐合现象。因此,热带印度洋海气耦合模态年际变化对印度洋上层热量再分配有着重要的意义。     

Intraseasonal variability of the surface zonal current in the equatorial Indian Ocean: Seasonal differences and causes

Using observations and numerical simulations, this study examines the intraseasonal variability of the surface zonal current(u ISV) over the equatorial Indian Ocean, highlighting the seasonal and spatial differences, and the causes of the differences. Large-amplitude u ISV occurs in the eastern basin at around 80°–90°E and near the western boundary at 45°–55°E. In the eastern basin, the u ISV is mainly caused by the atmospheric intraseasonal oscillations(ISOs), which explains 91% of the standard...     

Paleomonsoon precipitation deduced from a sediment core from the equatorial Indian Ocean

Rapid shifts in past climate recorded in polar ice sheets have elicited various explanations relating to either thermohaline circulation changes by ice-rafting or natural greenhouse gas concentrations modulated by climatic conditions in the tropics. To compare the tropical paleoclimate record with the polar record, one must choose sediment cores from highly productive ocean regions. Necessarily, such regions reflect the wind records in the tropics, because high productivity is associated with upwelling driven by winds. Comparing tropical precipitation records with high-latitude records is, however, a more difficult task because sediments recording paleoprecipitation usually have low sedimentation rates, and offer coarser resolution relative to polar ice cores. Here, we present δ ¹⁸O data of three planktonic species of Foraminifera (a proxy for precipitation) from such a sediment core, spanning the past 35 ka for the equatorial Indian Ocean, which falls under the southwest monsoon (SWM) realm. Results show that minimum SWM precipitation occurred at the Last Glacial Maximum, with a subsequent increase at Termination IA. During the Holocene, SWM precipitation intensified uniformly up to the core top (∼2.2 ka b.p.), as revealed by generally decreasing δ ¹⁸O values. Variations in precipitation are consistent with climate changes recorded in polar ice sheets. Although the different resolutions of the two records preclude a rigorous comparison, abrupt cooling/warming events appear to be accompanied by sudden reduction/enhancement in (SWM) rainfall. Thus, mechanisms with time scales much shorter than a millennium, such as natural greenhouse warming (e.g., CH₄ concentration), controlled by emissions from the tropics, could have played a major role in high-latitude climate change.     

应用波浪数值模式对北印度洋海浪场进行计算和统计分析

以11年QSCAT/NCEP混合风场数据为输入,采用WAVEWATCH-Ⅲ波浪模式,对北印度洋海域1999-2009年的海浪场进行了数值计算。与Janson-1高度计波浪资料进行对比验证后发现,波浪计算结果较好。将计算结果进行统计分析,得出北印度洋风浪有如下特点:(1)冬季盛行东北向浪,夏季盛行西南向浪;(2)北印度洋中部波高较大,北部和南部较小。夏季波高全年最大,较冬季强盛得多;冬季次之,春季最小。     

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.     

The Arctic Ocean halocline and its interannual variability from 1997 to 2008

As a key structure to understand the role of the ocean on the sea ice mass balance, the Arctic Ocean halocline and its spatiotemporal variability require serious attention. In this paper, we are proposing a new definition of the halocline, which is based on the salinity gradient structure, taking into account both the salinity amplitude and the thickness of the halocline. The Brunt Vaisala frequency is used as the halocline stratification index. CTD data collected from 1997 to 2008 and coming from various sources (icebreaker cruises, drifting buoys, etc.) are used to determine the halocline, and its time and space variability during three time periods, with a special focus on three main regions of the Arctic Ocean: the Canada basin, the Makarov basin and the Amundsen basin. Observations reveal that the halocline in the Amundsen basin was always present and rather stable over the three time periods. In contrast, the Canada and Makarov basins' halocline became more stratified during the IPY than before, mainly because of surface water freshening. In addition, observations also confirmed the importance of the halocline thickness for controlling the stratification variability. Observations suggest that both large scale and small scale processes affect the halocline. Changes in surface salinity observed in the Makarov basin are more likely due to atmospheric variability (AO, Dipole Anomaly), as previously observed. More locally, some observations point out that salt/heat diffusion from the Atlantic water underneath and brine rejection during sea ice formation from above could be responsible for salt content variability within the halocline and, as a consequence, being influential for the variability of the halocline. In spite of the existence of interannual variability, the Arctic Ocean main stratification, characterized by a stable and robust halocline until now, suggested that the deep ocean had a limited impact on the mixed layer and on sea ice in actual conditions. The drastic changes observed in Arctic sea ice during this period (1997-2008) cannot be attributed to a weakening of the halocline that could trigger an enhanced vertical heat flux from the deep ocean.     

On the origin of phosphorites from Christmas Island in the Indian Ocean

A detailed investigation of microstructures of the phosphorites from Christmas Island under a scanning electron microscope coupled with an analysis of their chemical composition revealed that both their structure and composition are quite similar to those of the granular and microgranular phosphorites on present-day continents, as well as those of the phosphorites on some of the Pacific guyots. Their composition, together with their geological position and interrelationships with the surrounding rocks, proves that the ornitogenic hypothesis based on the presumed guano accumulation followed by its transformation into phosphatic rock is not compatible with the field observations. Meanwhile, the problem of the source of the Fe and Mn impregnation in the phosphorites remains unresolved and needs further investigations.     

Interannual variability of the heat content of the upper layer in the equatorial Indian Ocean and the Indian-Ocean dipole

The aim of the present work is to study the characteristics of interannual variability of the heat content of the upper layer in the Equatorial Indian Ocean according the XBT-data accumulated in 1983–2003 for the evaluation the role of various physical factors specifying the space and time structure of the Indian-Ocean dipole in the subsurface layer. The existence of the significant influence of intense events of El Niño on the Indian-Ocean dipole is confirmed. These events generate the maximum disturbances of the thermal structure in the upper layer of the east part of the Indian Ocean propagating then in the westward direction with velocities varying from 3–4 to 8 cm/sec.     

Fronts, baroclinic transport, and mesoscale variability of the Antarctic Circumpolar Current in the southeast Indian Ocean

Fronts,baroclinic transport,and mesoscale variability of the Antarctic Circumpolar Current(ACC) along 115°E are examined on the basis of CTD data from two hydrographic cruises occupied in 1995 as a part of the World Ocean Circulation Experiment(WOCE cruise I9S) and in 2004 as a part of CLIVAR/CO2 repeat hydrography program.The integrated baroclinic transport across I9S section is(97.2×106±2.2×106) m3/s relative to the deepest common level(DCL).The net transport at the north end of I9S,determined by the south Australian circulation system,is about 16.5×106m3/s westward.Relying on a consistent set of water mass criteria and transport maxima,the ACC baroclinic transport,(117×106 ±6.7×10 6)m3/s to the east,is carried along three fronts:the Subantarctic Front(SAF) at a mean latitude of 44°-49°S carries(50.6×10 6 ±13.4×106)m3/s;the Polar Front(PF),with the northern branch(PF-N) at 50.5°S and the southern branch(PFS) at 58°S,carries(51.3×106 ±8.7×106)m3/s;finally,the southern ACC front(SACCF) and the southern boundary of the ACC(SB) consist of three cores between 59°S and 65°S that combined carry(15.2×106 ±1.8×106)m3/s.Mesoscale eddy features are identifiable in the CTD sections and tracked in concurrent maps of altimetric sea level anomalies(SLA) between 44°-48°S and 53°-57°S.Because of the remarkable mesoscale eddy features within the SAF observed in both the tracks of the cruises,the eastward transport of the SAF occurs at two latitude bands separating by 1°.Both the CTD and the altimetric data suggest that the mesoscale variability is concentrated around the Antarctic Polar Frontal Zone(APFZ) and causes the ACC fronts to merge,diverge,and to fluctuate in intensity and position along their paths.