IMPACTS OF MONTHLY ANOMALIES OF INTRASEASONAL OSCILLATION OVER SOUTH CHINA SEA AND SOUTH ASIA ON THE ACTIVITY OF SUMMER MONSOON AND RAINFALL IN EASTERN CHINA

The impact of strong(weak) intraseasonal oscillation(ISO) over South China Sea(SCS) and South Asia(SA)in summer on the SCS and SA summer monsoon and the summer rainfall in Eastern China are studied by using the NCEP-NCAR analysis data and the rainfall data of 160 stations in China from 1961 to 2010.It is found that the impacts are significantly different in different months of summer.The study shows that in June and July cyclonic(anticyclonic) atmospheric circulation over SCS and SA corresponds to strong(weak) ISO over SCS.In August,however,strong(weak) ISO over SCS still corresponds to cyclonic(anticyclonic) atmospheric circulation over SA.In June and August cyclonic(anticyclonic) atmospheric circulation over South Asia corresponds to strong(weak) ISO over SA while a strong(weak) ISO corresponds to anticyclonic(cyclonic) atmospheric circulation over SA in July.Besides,in June the strong(weak) ISO over SA corresponds to cyclonic(anticyclonic) atmospheric circulation over SCS,while in July and August the atmospheric circulation is in the same phase regardless of whether the ISO over SA is strong or weak.The impacts of the strong(weak)ISO over SCS on the rainfall of eastern China are similar in June and July,which favors less(more) rainfall in Yangtze-Huaihe Rivers basin but sufficient(deficient) rainfall in the south of Yangtze River.However,the impacts are not so apparent in August.In South Asia,the strong(weak) ISO in July results in less(more)rainfall in the south of Yangtze River but sufficient(deficient) rainfall in Yangtze-Huaihe Rivers basin.The influence on the rainfall in eastern China in June and August is not as significant as in July.

Seasonal and annual variations of marine sinking particulate flux during 1993 ~ 1996 in the central South China Sea

A total of 67 samples from the upper and lower sediment traps in the central South China Sea were analyzed, which were collected during 1993 ~ 1996. It is indicated that the distribution of stable isotope values, surface primary productivity, fluxes of total particulate matter, carbonate, biogenic opal, organic carbon, planktonic foraminiferal species and their total amount exhibit obviously seasonal and annual fluctuations. High values of the fluxes occurred in the prevailing periods of the northeastern and southwestern monsoons, and the low values occurred during the periods between the two monsoons. The fluxes of some planktonic foraminiferal species （ Globigerinoides sacculifer , G. ruber , Globigerinita glutinata, Neogloboquadrina dutertrei ） and their percentages also exhibit two prominent peaks during the prevailing periods of the northeastern and southwestern monsoons respectively, while those of Globigerina bulloides, Globorotalia menardii and Pulleniatina obliquiloculata only exhibit one peak in the prevailing periods of the northeastern monsoon. In addition, fluxes and percentages of Globigerinoides sacculifer and Globorotalia menardii as well as the fluxes of carbonate and total amount of planktonic foraminifera decrease gradually from 1993 to 1996, and those of Globigerina bulloides, Globigerinita glutinata and biogenic opal increase gradually from 1993 to 1996. The fluxes of carbonate and organic carbon in the upper trap are higher than those in the lower one. The study indicates that the seasonal and annual variations of the sediment fluxes and planktonic foraminiferal species are mainly controlled by the changes of surface primary productivity and hydrological conditions related to the East Asian monsoon. The lower carbonate and organic carbon fluxes in the lower trap are related to the dissolution.

Characteristics of seismic reflections in central region of the South China Sea and their geological significance

More than 4 000 km 48-channel seismic reflection data from the central region of the South China Sea have been interpreted. Five seismic interfaces have been distinguished, named T1, T2, T4, T6 and Tg respectively Meanwhile, five seismic sequences numbered I - V have been divided with the ages of Quaternary and Pliocene, Later Mocene, Earlier and Middle Miocene, Oligocene and Pre- Oligocene separately. Sequences I-II overlie all parts of the area. In the continental slope and island slope, Sequences III-V are mainly found in the grabens. Sequence III is found at moot profiles of the deep-sea basin, and Sequnce IV is seen not only at the margins of the east subbasin but also at the margins of the southwest subbasin. Strong reflection from Moho is found at most profiles of the deep-sea basin. The depth of Moho varies between 10 and 12 km, with a thickness of 6- 8 km for the crust. Calculated by age-basement depth correlation formula, the age of basaltic basement in the southwest subbasin is 51-39 Ma. It is indicated that the evolution of the southwest subbasin is simultaneous with or earlier than that of the east subbasin.

Distribution of chlorophyll a, photosynthesis and their relations to the environmental factors in the Central South China Sea

Some studies have been made on the variation of primary productivity in the Central South ChinaSea. This paper studies comprehensively the characteristics of chlorophyll a distributions in time andspace and the primary productivity, as well their relations to the environmental factors.Materals and methods During the comprehensive investigation in the Central South China Sea from September 1983 toDecember 1984, the distributions of chlorophyll a and primary productivity were studied. Figure 1shows the sampling stations and their range of investigation.

Geology and hydrocarbon accumulations in the deepwater of the northwestern South China Sea——with focus on natural gas

The deepwater of the northwestern South China Sea is located in the central to southern parts of the Qiongdongnan Basin （QDN Basin）, which is a key site for hydrocarbon exploration in recent years. In this study, the authors did a comprehensive analysis of gravity-magnetic data, extensive 3D seismic survey, cores and cuttings, paleontology and geochemical indexes, proposed the mechanism of natural gas origin, identified different oil and gas systems, and established the model of hydrocarbon accumulations in the deep-water region. Our basin tectonic simulation indicates that the evolution of QDN Basin was controlled by multiple-phased tectonic movements, such as Indochina-Eurasian Plate collision, Tibetan Uplift, Red River faulting and the expansion of the South China Sea which is characterized by Paleogene rifting, Neogene depression, and Eocene intensive faulting and lacustrine deposits. The drilling results show that this region is dominated by marine- terrestrial transitional and neritic-bathyal facies from the early Oligocene. The Yacheng Formation of the early Oligocene is rich in organic matter and a main gas-source rock. According to the geological-geochemical data from the latest drilling wells, Lingshui, Baodao, Changchang Sags have good hydrocarbon-generating potentials, where two plays from the Paleogene and Neogene reservoirs were developed. Those reservoirs occur in central canyon structural-lithologic trap zone, Changchang marginal trap zone and southern fault terrace of Baodao Sag. Among them, the central canyon trap zone has a great potential for exploration because the various reservoir- forming elements are well developed, i.e., good coal-measure source rocks, sufficient reservoirs from the Neogene turbidity sandstone and submarine fan, faults connecting source rock and reservoirs, effective vertical migration, late stage aggregation and favorable structural-lithological composite trapping. These study results provide an important scientific basis for hydrocarbon exploration in this region, evidenced by the recent discovery of the significant commercial LS-A gas field in the central canyon of the Lingshui Sag.

Evolution of Cenozoic sedimentary architecture in Central and Southern South China Sea basins

The Central and Southern South China Sea(CSSCS) has a complex tectonic dynamic background and abundant oil and gas resources, which has always been a hot topic of academic and industrial attention.However, systematic analyses are still lacking regarding its sediment filling structure and evolution, mostly due to limited borehole penetration and poor quality of seismic reflection data for deeply buried sequences. No consensus has been reached yet on the sedimentary infilling processes, which impeded the reconstruction of the palaeogeography of Southeast Asia and the oil-and-gas exploration undertakings. Here, we illustrate the Cenozoic sedimentary evolution of the CSSCS region by synthesizing relevant data from previous literature and our own observations and displaying the evolution of depositional systems in sequential reconstructions. Besides, the controlling factors of preferred sedimentary scenarios in the CSSCS incorporate the latest interpretations of the spreading of South China Sea(SCS) as well as the demise of the hypothetical Proto-South China Sea(PSCS). The results show that there are three types of sedimentary basins in the CSSCS(foreland,strike-slip, and rift basins) with different sedimentary filling structures. The foreland basins formed a depositional pattern of ‘transition from deep water to shallow water environments', dominated by deep-water depositional systems which were formed before the Early Oligocene with submarine fans developed. Later,the foreland basins were gradually dominated by shallow-water depositional systems with deltas and shallow marine facies. The strike-slip basins showed the depositional architecture of ‘transition from lake to marine environments', i.e. the basins were dominated by lacustrine deposits during the Eocene and evolved into the marine depositional environment since Oligocene with delta developed in the western part of the basin. The depositional evolution of rift basins illustrated the characteristics of 'transition from clastic to carbonate deposits', i.e., the rift basins were dominated by Eocene-Oligocene shallow marine clastic depositional systems, while carbonate platforms started to develop since the Early Oligocene from east to west. The above-mentioned differences of depositional architecture in the CSSCS were controlled by the scissor-style closure of the PSCS and the progressive-style expansion of the SCS. Specifically, the early-period deep-water sedimentary environment of CSSCS basins was controlled by the distribution of PSCS in the Eocene. As the scissor-style closure of PSCS progressed from west to east during the Oligocene to Early Miocene, the northwest of Borneo continued to rise, providing a great number of clastic materials to the basins and gradually developing large-scale deltas from west to east. The distribution of early-period lacustrine sedimentation of strike-slip basins was affected by paleo uplift, and the basins transgressed from the northeast and gradually evolved into marine sedimentary environment due to the expansion of SCS. The expansion of SCS also controlled the sedimentary filling evolution of the rift basins, which broke away from the South China continent and drifted southward. Thus, the rift basins lacked the supply of terrigenous clastic sediments which hindered the development of large-scale deltas and formed a clear water environment conducive to the development of carbonate platforms from east to west.

An Inquiry into the Approach to Asian Regional Trade Integration Under the Belt and Road Initiative——The Case of the Alignment of a China-Japan-South Korea Free Trade Area

It has been five years since the Belt and Road Initiative (BRI) was first introduced. Though there has been a growing body of literature on regional cooperation between covered countries, Japan and South Korea have been barely discussed. This paper starts with the consensus-based mechanism of a China-Japan-South Korea Free Trade Area (FTA) to probe the approach of its alignment with the BRI in terms of the sequence of “master plans,”“viability of cooperation,” and “embedding of rules.” This inquiry found that the three countries have a shared interest in cooperation in Central Asia to which China prefers a pragmatic approach, while Japan and South Korea an approach combining idealism with pragmatism. Given the huge potential of cooperation between the trio, it is suggested that a “Central Asia chapter” be incorporated in the negotiation framework of this trilateral FTA, and that the design feature three aspects;fundamental principles, specific rules, and an executive body with a view to functionally contributing to regional trade integration in Asia. This approach may also be applied to the alignment of other Asian areas with the BRI.

Dynamic Controls on the Formation of Mantle Plume Beneath the South China Sea Region

The South China Sea(SCS)has attracted intensive structural and geophysical research over the past decades,with a focus on its extensional history and relevant dynamic tectonic models.Seismic tomographic images obtained

The Turn of the Tide:Explaining China’s Growing Assertiveness in the South China Sea

Before the late 2000s,China employed a diplomatic“next generation”approach to its territorial disputes in the South China Sea(SCS).Beginning in the late 2000s,however,China has assumed threatening attitudes,and taken a strong stand against other disputants.Why has China recently shown its assertiveness when dealing with the South China Sea issue?This study argues that two factors-China’s growing naval capabilities and the growing presence of China’s strategic rivals around the South China Sea-led China to adopt a more assertive policy regarding the South China Sea issue.

The Effects of the Thermal Anomalies over the Tibetan Plateau and Its Vicinities on Climate Variability in China

The evident effects of the thermal anomalies over the Tibetan Plateau (TP) and its vicinities are summarized and discussed in this paper. By the singular value decomposition (SVD) technique and numerical simulations of the effect of the snow depth anomaly over the TP, it is shown that the snow depth anomaly, especially in winter, is one of the factors innuencing precipitation in China, and the winter snow anomaly is more important than the spring one. The relations between the sensible heat anomaly over the TP and the intensity of the South China Sea summer monsoon (SCSSM) are studied, too, and two key areas of the sensible heat anomaly over the TP are found. The relationships between the South Asia High (SAH) and the precipitation in the years with typical droughts or floods in the mid to lower valleys of the Yangtze River (MLVYR) and North China are investigated in some detail. It is found that not only the intensity of the SAH over the TP, but also the 100-hPa height in a large area influences the precipitation in the above two regions. The effects of the SAH on the onsets of the tropical Asian summer monsoon (TASM) including the SCSSM and the tropical Indian summer monsoon (TISM) are studied as well. It is found that the onset times of both the SCSSM and the TISM are highly dependent upon the latitudinal position of the SAH center.

Difference in full-filled time and its controlling factors in the Central Canyon of the Qiongdongnan Basin

Based on the interpretation of high resolution 2D/3D seismic data, sedimentary filling characteristics and full- filled time of the Central Canyon in different segments in the Qiongdongnan Basin of northwestern South China Sea have been studied. The research results indicate that the initial formation age of the Central Canyon is traced back to 11.6 Ma （T40）, at which the canyon began to develop due to the scouring of turbidity currents from west to east. During the period of 11.6-8.2 Ma （T40-T31）, strong downcutting by gravity flow occurred, which led to the formation of the canyon. The canyon fillings began to form since 8.2 Ma （T31） and were dominated by turbidite deposits, which constituted of lateral migration and vertical superposition of turbidity channels during the time of 8.2-5.5 Ma. The interbeds of turbidity currents deposits and mass transport deposits （MTDs） were developed in the period of 5.5-3.8 Ma （T30-T28）. After then, the canyon fillings were primarily made up of large scale MTDs, interrupted by small scale turbidity channels and thin pelagic mudstones. The Central Canyon can be divided into three types according to the main controlling factors, geomorphology-controlled, fault-controlled and intrusion- modified canyons. Among them, the geomorphology-controlled canyon is developed at the Ledong, Lingshui, Songnan and western Baodao Depressions, situated in a confined basin center between the northern slope and the South Uplift Belt along the Central Depression Belt. The fault-controlled canyon is developed mainly along the deep-seated faults in the Changchang Depression and eastern Baodao Depression. Intrusion-modified canyon is only occurred in the Songnan Low Uplift, which is still mainly controlled by geomorphology, the intrusion just modified seabed morphology. The full-filled time of the Central Canyon differs from west to east, displaying a tendency of being successively late eastward. The geomorphology-controlled canyon was completely filled before 3.8 Ma （T28）, but that in intrusion-modified canyon was delayed to 2.4 Ma （T27） because of the uplifted southern canyon wall. To the Changchang Depression, the complete filling time was successively late eastward, and the canyon in eastern Changchang Depression is still not fully filled up to today. Difference in full-filled time in the Central Canyon is mainly governed by multiple sediment supplies and regional tectonic activities. Due to sufficient supply of turbidity currents and MTDs from west and north respectively, western segment of the Central Canyon is entirely filled up earlier. Owing to slower sediment supply rate, together with differential subsidence by deep-seated faults, the full-filled time of the canyon is put off eastwards gradually.

Siliceous microplankton fluxes and seasonal variations in the central South China Sea during 1993-1995: monsoon climate and ? Nino responses

Seasonal variations of radiolarian and diatom fluxes in the central South China Sea during 1993-1995 were overwhelmingly controlled by monsoon climate. Radiolarian and diatom increased obviously during the Northeast (from November to February) and Southwest (from June to September) monsoons and decreased during the periods between the monsoons. The change of circulation driven by the monsoons improved water exchange in the different areas that brought rich nutrient materials for the surface microplankton, thereby enhancing radiolarian and diatom fluxes. Variation of radiolarian flux coincided with organic carbon flux, surface primary and export productivities. High radiolarian flux corresponded to high surface primary productivity. Radiolarian and diatom fluxes raised abnormally during 1994-1995 could be attributed to the El Nino event during the period.

中美博弈:近昔和当今及对中国战略的意涵

过去15年里,中美关系的首要特征是博弈而非协调。两国博弈先在战略阵线开启,继而在战略、经贸、高技术和意识形态四条主要阵线展开。就中美博弈总体而言,美国处于“防守型”战略态势,美国认为它长时期拥有的重大优势地位一个又一个地丧失或被侵蚀,首要动能在中国一边。中共十八大以来,中国逐渐成为一个急剧腾升的强国。大为增强的国力,使中国更加坚定了自信和抱负。中国内外发力,争取在世界政治经济和全球治理的某些问题领域参与引领甚或单独引领,实现在亚洲大陆以及发展中世界的经济和外交优势,大致取得在西太平洋的对美战略和军事优势,进一步地,对第一至第二岛链之间的战略空间的控扼能力愈益被视为必要。回顾奥巴马、特朗普和拜登三届美国政府的对华态势和政策,对未来中美关系应做好准备应对可能的疾风暴雨。

THE ESTABLISHMENT OF THE SOUTH CHINA SEA SUMMER MONSOON IN 1998:THE NORTHWARD JUMP OF SOUTH ASIA ANTICYCLONE AND ITS EFFECT ON THE ONSET OF SOUTH CHINA SEA SUMMER MONSOON

By using the NCEP/NCAR reanalysis data,the activities of the 200 hPa South Asia Anticyclone (SAA) and its effect on the onset of South China Sea (SCS) summer monsoon in May 1998 are studied.The results show that:(1)During the pre-onset period the reversal of the mid- upper troposphere meridional horizontal temperature gradient over South Asia to the east of 90°E was caused mainly by warm horizonal thermal advections over this area.About 36 h after the reversal,the SCS summer monsoon bursts.(2)The variation of thermal wind circulation caused by the reversal of temperature gradient gave rise to the 200 hPa center of the SAA to jump from 15°N to 21°N within 12 hours.(3)The northward jump of the SAA and the intrusion eastward of the SAA under the effect of the warm horizonal thermal advections resulted in the rapid development of a trough over the South China coast.This induced the West Pacific Subtropical Anticyclone ridge,which originally controlled the South China Sea,to weaken rapidly and retreat eastward.Subsequently,the SCS summer monsoon built.(4)The superimposition in phase of the anticyclone ridge moving eastward over the middle-latitudes of China with the SAA has a rather important influence on the development of the trough over the South China coast.

FEATURES OF GRAVITY AND MAGNETIC ANOMALIES IN CENTRAL AND NORTHERN PARTS OF THE SOUTH CHINA SEA AND THEIR GEOLOGICAL INTERPRETATION

The gravity and magnetic survey lines of about 13,500 km were carried out in the centraland northern parts of the South China Sea from 1977 to 1978. The results obtained showthat the Bouguer gravity and magnetic anomalies have a tendency to increase gradually theirvalues from the northern continental shelf, through the slope, to the central abyssal basin of theSouth China Sea. The change in free-air gravity anomaly values coincides to a certain degreewith the undulation of the sea-bottom topography. The primary factor determining regionalvariation of the Bouguer gravity anomayl values is the Moho depth. The main factor deter-mining the magnetic anomly values is the nature of the basement rock. The high magnetieand Bouguer gravity anomaly values observed in some fault basin areas are inferred to becaused by draping the basic and ultrabasic magma extruding along the faults on the basementof the metamorphic rock,or by intrusion of the same magma into the basement.

深水中大型气田滚动勘探技术体系与成效——以琼东南盆地中央峡谷A边际气田为例

为了促进琼东南盆地中央峡谷深水A边际气田开发,引入目标搜索研究、目标评价研究、目标钻探研究等完整气田滚动勘探技术体系。A边际气田目标搜索除利用传统的区带油气潜力目标搜索技术外,提出评价过程目标搜索技术,共搜索了5个油气潜力区块,并优选A4构造进行油气目标评价。从圈闭解释与落实、圈闭烃类检测两方面对A4构造油气成藏主控因素开展研究。A4构造中部预测优势含气区具有强振幅属性、低密度、低速度、低纵波阻抗、低纵横波速度比等有利含气信息特征,总体为Ⅲ类AVO异常,且能够升级HL_0气组控制天然气地质储量,部署滚动探井A4-1井实施钻探,在黄流组钻遇气层超20 m,莺歌海组二段钻遇可疑气层近10 m,获得天然气探明地质储量近30亿立方米,钻探效果好。滚动勘探研究在深水A边际气田的应用,不仅有效地促进了A边际气田后续滚动勘探活动,而且证实了滚动勘探同样适用于深水油气勘探。

从敌人到战略伙伴:越美关系发展的原因与限度

2023年9月,越南与美国领导人在河内宣布建立全面战略伙伴关系,越美关系进入历史最好时期。为何越南与美国能从曾经的生死敌手演变为如今的战略伙伴?在越美关系的演变历程中,两国关系的发展受到多重因素的综合影响。首先,越美两国对解决越战遗留问题的积极态度有助于消解双方对彼此负面的历史记忆,为两国关系改善提供了前提条件。其次,大国关系变化也催化了越美关系发展。冷战后期越南跟随苏联主动改善与美国关系,实现了关系正常化并开展初步合作。自2009年起,随着美国发起对华竞争并拉拢越南,越美关系进入战略合作阶段。最后,越南对美国的发展需求、安全需求与美国对越南的经济战略需求和安全战略需求相交织,共同推动了越美合作水平的不断提升。然而,越美战略合作进一步发展仍存在制约因素,包括两国意识形态分歧、美国可靠性不足及越南避免“选边站队”的政策倾向。对此,中国在大国竞争的变局下应未雨绸缪,通过理性审慎的对越政策,管控分歧、推进合作,妥善处理好中越关系。

Sedimentary evolution of the Central Canyon System in the Qiongdongnan Basin, northern South China Sea

This study elucidates sedimentary evolution history of the Central Canyon System(CCS),a large axial submarine canyon in the Qiongdongnan Basin(QDNB),northern South China Sea.Thegeomorphological characteristics and infill architectures of the CCS are summarized based on theanalysis of two-and three-dimensional seismic data.Based on a comparative analysis of the CCS indifferent segments and evolutionary stages and in consideration of the tectono-sedimentary conditionsof the QDNB four stages of the sedimentary evolution of the CCS can be divided,i.e.initialdevelopment stage in the Late Miocene(11.6-5.7Ma),erosion-infilling stage in the Early Pliocene(5.7-3.7 Ma),tranquil infilling stage in the Late Pliocene(3.7-1.81 Ma),and rejuvenation stage sincethe Pleistocene(1.81 Ma to present).In the 1ate Middle Miocene(~11.6 Ma),the rudiment of CCswas developed by a regional tectonic transformation in the eastern part of the basin.In the EarlyPliocene,the CCS was further developed from west to east and restrained in the central depressionbelt of the basin due to abundant sediment supplies from the northwestern and northem provenances,the blocking effect of the southern uplift belt,and the restrictive geomorphological features of theeastern part of the basin.In the Late Pliocene,changes in the sedimentary environment resulted in thedevelopment of the CCS in the eastern part of the basin only.Since the Pleistocene,the joint action ofclimatic factors and geomorphological features of the eastern part of the basin led to the rejuvenationof the CCS.

美国“一体化威慑”战略下的南海政策及影响

拜登政府执政后,基于威胁认知推出“一体化威慑”战略,即推进跨领域、跨区域、跨冲突频谱、跨政府部门,以及与盟国和合作伙伴的“一体化”,并以拒止性威慑、韧性威慑、直接和集体成本强加进行威慑3种不同的逻辑加强威慑行动,针对特定的竞争对手量身定制,塑造对手关于针对美国核心利益行动的风险和成本的认识。在该战略下,美国以南海作为“塑造中国周边战略环境”的重要抓手,在南海对中国采取成本强加政策,除了开展“航行自由行动”、抵近侦察、多边联合军事演习,更加重视借重盟友和合作伙伴联手对华施压,增加前沿军事基地存在,并加大对法律、外交、准军事等方向的投入,以一种类似于混合战争的方式增加中国在南海的行动成本,从而使南海成为美国实施对华“一体化威慑”的战略前沿。这使中国和南海沿岸国管控分歧,稳定复杂南海局势的决心和努力面临更多新的困难和不确定性因素。

海南自由贸易港建设推动南海区域经济合作的策略研究

海南自由贸易港建设是推进高水平对外开放、推动经济全球化的国家战略。在党的二十大精神引领下,文章运用系统分析、政策分析等方法,主要分析了海南自贸港建设推动南海区域经济合作的新机遇、挑战与对策。研究结论表明,党的二十大关于高水平对外开放的方针为海南自贸港建设推动南海区域经济合作提供了新机遇,但自贸港建设与区域合作也面临一系列问题和挑战。对此,文章提出海南自贸港建设要面向东南亚推动以制度型开放为核心的高水平对外开放,依托博鳌亚洲论坛加强区域交流,构建“南海经济合作圈”,以特色产业加强与“一带一路”沿线南海国家和地区的合作,打造海南自贸港—东盟互联互通,推进建设“两个总部基地”。