Temporal and spatial variabilities of sea surface heights in the northeastern South China Sea

Analyses of sea surface height anomalies (SSHA) from Jan. 1993 to Dec. 2001 measured by TOPEX/Poseidon (T/P) satellite altimetry indicate that there are two energy highs of SSHA fluctuations on both sides of the Luzon Strait. The highs centered at (19.5°N, 119.5°E) and (22.0°N, 124.0°E) respectively, are separated by a low energy band in the Strait. Empirical Orthogonal Function (EOF) analysis on the "Far Field" suggests that fluctuations of these two areas are mutually independent. EOF analysis on the "Near Field" shows that SSHA oscillation in the northeastern South China Sea (SCS) is dominated by seasonal variations accompanied with significant intra-seasonal and inter-annual fluctuations. Among which, EOFI and EOF2 reflect 66.7% of the total variance. They are both seasonal but showing three months difference in phase. The basic pattern of EOFI appears to be the seasonal SSHA oscillation centered at (18.0°N, 119.0°E) northwest off Luzon Island, which shows maximums (minimums) in August/Septemb     

Variability of surface circulation in the South China Sea from satellite altimeter data

11-year satellite altimeter sea surface height （SSH） anomaly data from January 1993 to December 2003 are used to present the dominant spatial patterns and temporal variations of the South China Sea （SCS） surface circulation through Empirical Orthogonal Function （EOF） analysis. The first three EOF modes show the obvious seasonal variations of SSH in the SCS. EOF mode one is generally characterized by a basin-wide circulation. Mode two describes the double-cell basin scale circulation structure. The two cells were located off west of the Luzon Island and southeast of Vietnam, respectively. EOF mode three presents the mesoscale eddy structure in the western SCS, which develops into a strong cyclonic eddy rapidly from July to September. EOF mode one and mode three are also embedded with interannual signals, indicating that the SCS surface circulation variation is influenced by El Nino events prominently. The strong El Nino of 1997/98 obviously changed the SCS circulation structure. This study also shows that there existed a series of mesoscale eddies in the western SCS, and their temporal variation indicates intra-seasonal and interannual signals.     

Influences of the surface wave-induced mixing and tidal mixing on the vertical temperature structure of the Yellow and East China Seas in summer

After a classification of the physical processes which affect the vertical mixing, diffusivity induced by the surface wave momentum and tidal currents and its influence on the vertical temperature structure are discussed. Based on three mixing schemes, the vertical temperature structure of the Yellow and East China Seas (YECS) is simulated. Results show that in summer, the surface wave-induced mixing plays a key role in forming the upper mixed layer in the YECS. The tidal mixing controls the lower layers within 30 m above the bottom, which is the main factor in forming the platform-shaped temperature structure in the southern Yellow Sea (YS). Together with the strong surface wave-induced mixing, the tidal mixing makes the thermocline ventilate near the east coast of the southern YS. The double cold cores in the deeper layers of the East China Sea have different causes. The western one is the maintenance of the winter cold water, while the eastern one is configured by circulation. The simulated vertical temperature structure of the YECS with the surface wave-induced mixing and tidal mixing has similar features to the observations, which indicates that these mixing processes are key factors in simulating the thermocline and pycnocline of the coastal oceans.     

Changes in sea surface temperature in western South China Sea over the past 450 ka

Sea surface temperature over the past 450 ka was obtained by the unsaturation of molecular fossil-long chain alkenone with a resolution of about 1 ka from the western South China Sea. This is the longest temperature profile in the South China Sea at such high resolution. The U37^κ-SST results revealed similar glacial-interglacial cycles as the δ^18O profile of planktonic foraminifera, with SST variability of 23-25.5℃ for glacial and 25-28℃ for interglacial periods. The highest SST （28.4℃） was recorded at MIS5.5 and lowest SST （22.6℃） during MIS2. The SST record preceded the planktonic foraminiferal δ^18O on five glacial-interglacial transitions. Comparison of temperature records from the Southern and Northern Hemispheres indicated a more Southern Hemisphere-like pattern for the temperature variation in the SCS. Strong precession and semiprecession signals in the spectra of our SST record manifest the tropical phenomena.     

Pleistocene precession forcing of the upper ocean structure variations of the southern South China Sea

The precession plays a dominant role in driving the tropical monsoon variations. Our high resolution, millennial scale marine isotope records from ODP Site 1143 in the southern South China Sea (SCS) present the detailed history of the upper ocean structure variations over the past 1.56 Ma on glacial/interglacial timescale. The cross spectral analyses between the Earth's orbital variations and the isotopic differences reveal a high coherency between the East-Asian-monsoon-related thermocline and nutricline variations of the SCS and the precession. The variations of monsoon-related isotopic difference between species also demonstrate periodicities of 11-, 12- and 14- thousand years near semi-precession which originates in the tropics, highlighting the importance of the precession in driving the east Asian monsoon changes.     

东海黄海渤海8个主要分潮的数值模拟

应用球面坐标系下ECOM数值模式,数值模拟了东海黄海渤海的8个主要分潮M₂、S₂、N₂、K₂、K₁、O₁、P₁和Q₁.采用高分辨率网格,计算区域包括东海黄海渤海、东海陆架坡和琉球以东西北太平洋,考虑实际水深和岸线.开边界条件由全球大洋潮汐模式计算的调和常数给出.较成功地模拟出了8个分潮的传播特征,再现了计算区域内半日分潮的5个无潮点和2个蜕化的半个无潮点、全日分潮的3个无潮点.与65个潮位站的观测资料比较,模式计算的M₂、S₂、K1和O₁分潮振幅和位相的均方差分别为7.85 cm和6.81°,5.04cm和8.14°,3.82cm和13.04°,4.34cm和9.33°.与17个潮位站的观测资料比较,N₂、K₂、P₁和Q₁分潮振幅和位相的均方差分别为3.64cm和7.89°,8.47cm和10.51°,1.76cm和7.56°,1.50cm和26.34°.模式模拟的结果可为河口海岸小区域模式提供较为可靠的外海开边界潮汐调和常数资料.     

东亚夏季风系统和南海台风活动的关系

本文用1981,1982年6—9月东亚与澳大利亚部份测站的常规资料作诊断分析,探讨东亚夏季风系统各主要成员与南海台风活动的关系.结果得到,澳大利亚冷高压加强,105°E附近的越赤道气流跟着增强,南海的ITCZ发展,南海台风生成于澳大利亚冷高压高峰后的衰减时段.西南季风气流是南海台风的重要能量输送带。南支高空东风急流的增强与北支东风急流的动量下传,有利于南海台风生成.西太平洋气旋波移入南海促使南海低压生成.     

Observational study of the circulation in the southern South China Sea

CTD data from two oceanographic survey cruises, conducted by “Shiyan No. 3” R/V during two reversing monsoons, were employed to calculate and analyze the distributions of temperature, salinity and geopotential anomaly in the southern South China Sea (SSCS). Based on these distributions, the horizontal structures of the SSCS circulation are described systematically. Study results show that the SSCS circulation structure could be classified as a two-layer (the upper and the lower) pattern, and that the main circulation in the upper layer (0–400 m) is driven by the South China Sea monsoons and is opposite in direction to the reversal of the monsoons. The distributions of principal current systems and their features are presented. Two important local phenomena, local eddy and oceanic front, were observed.     

Sea surface temperature and terrestrial biomarker records of the last 260 ka of core MD05-2904 from the northern South China Sea

This paper reports high-resolution biomarker records of the last 260 ka for core MD05-2904 from the northern South China Sea （SCS）. The sea surface temperature （SST） record using the U37^k＇, index reveals a minimum of 21.5℃（MIS 2） and a maximum of 28.3℃（MIS 5.5）, for a temperature difference of almost 7℃, and provides the longest high-resolution U37^k＇ SST record in northern SCS. The content of odd-number long chain n-alkanes and several n-alkanes indexes such as the CPI, ACL and the C31/C27 ratio, all reveal generally higher values during the glacials and lower values during the interglaclals. Terrestrial input as Indicated by n-alkane content was mostly controlled by sea-level changes： During the glacials, lower sea-level exposed the continental shelf to enable rivers to transport more terrestrial materials to the slope; and the situation reverses during the interglacials. The n-alkane indexes changes reveal more n-alkanes from contemporary vegetation during glacials as a result of the proximity of the core site to the source region, while the increases in ACL and C81/C27 ratio during glaclals indicate a change to more grassy vegetation. However, the highest values for CPI, ACL and the C81/C27 ratio all occurred during late MIS 3, and it was suggested that this period was characterized by a strong summer monsoon-dominated humid climate which resulted in a denser vegetation for the exposed continental shelf region.     

Diagnostic analysis on the northern South China Sea winter counter-wind current

The winter counter-wind current （also named the South China Sea Warm Current （SCSWC）） in the northern South China Sea （SCS） has been known well for decades, but its mass and momentum origination have not be quantitatively evaluated before. In this paper, the high resolution three-dimensional ocean circulation model is adopted to reproduce the circulation in the northern SCS. The diagnostic analyses are performed to investigate the momentum budget in the northern SCS continental shelf/slope and the momentum propulsion of the SCSWC. It is indicated that the across-shelf pressure gradient and the across-shelf transport are responsible for the formation of the SCSWC, while the along-shelf pressure gradient is balanced by the surface stress, bottom stress, and Coriolis force. The magnitude of the terms in the along-shelf momentum equation is smaller than that in the across-shelf one. The analysis on the momentum budget in the northem SCS will benefit the marine environmental prediction in the future.     

Higher sea surface temperature in the northern South China Sea during the natural warm periods of late Holocene than recent decades

The large-scale syntheses of global mean temperatures in IPCC fourth report suggested that the Northern Hemisphere temperature in the second half of the 20th century was likely the highest in at least the past 1,300 years and the 1990s was likely the warmest decade. However, this remains debated and the controversy is centered on whether temperatures during the recent half century were higher than those during the Medieval Cli- mate Anomaly （MCA, AD 800-1300） and the Roman Warm Period （RWP, BC 200-AD 400）, the most recent two natural warm periods of the late Holocene. Here the high resolution sea surface temperatures （SSTs） of two time windows around AD 990 （±40） and AD 50 （±40）, which located in the MCA and RWP respectively, were reconstructed by the Sr/Ca ratio and 6180 of Tradacna gigas shells from the northern South China Sea. The resultssuggested that the mean SSTs around AD 990 （±40） and AD 50 （＋40） were 28.1 ℃ and 28.7 ℃, 0.8 ℃ and 1.4 ℃ higher than that during AD 199±2005, respectively. These records, together with the tree ring, lake sediment and literature records from the eastern China and northwest China, imply that the temperatures in recent decades do not seem to exceed the natural changes in MCA, at least in eastern Asia from northwest China to northern SCS.     

土地利用对中国东部地面温度变化的影响

为探索土地利用对气候变化的影响,基于站点观测资料及NCEP/NCAR再分析资料的地面最高、最低温度,采用观测资料减去再分析资料的方法(OMR),研究了1979-2008年我国东部区域地面温度的变化及不同土地利用类型对地面温度变化的影响。研究表明,1979-2008年,研究区域的地面最高、最低温度增加显著,变化趋势分别为0.45和0.47℃/10a;总体上,土地利用状况导致的地面最高温度变化较小,由此导致的地面最低温度变化占最低温度变化总量的25.1%;城镇对地面最高、最低温度的影响最显著,耕地对地面温度日较差的影响最显著;夏、秋季土地利用状况对地面最高、最低温度变化的影响以降低或者增加幅度较小为主,而在春、冬季则主要导致地面温度上升。     

Trends of sea level rise in the South China Sea during the 1990s: An altimetry result

Using 7 years of TOPEX/POSEIDON satellite altimetry data, we have identified a general trend of sea level rising in the South China Sea between January 1993 and December 1999. The estimated bulk rising rate of the entire basin is -1 cm/a. The rise of sea level appears to be spatially non-homogeneous, which shows a highest rate of 2.7 cm/a in the deep basin west of Luzon and generally low (even negative) rates over the shallow continental shelves. It is believed that the observed rapid rising of sea level is a regional phenomenon and is mainly caused by warming of the upper layer of the South China Sea, which showed a bulk warming rate of 0.15℃/a in the same period. It is also suggested that the observed rising trend is mainly a decadal signal, which is possibly associated with decadal variation of the Pacific warm pool region.     

Coupling and propagating of mesoscale sea level variability between the western Pacific and the South China Sea

The coupling and propagating features of mesoscale sea level variability between the western Pacific (WP) and the South China Sea (SCS) were studied based on time series analyses of satellite altimeter measured, along-track sea surface height anomalies (SSHA) along 21°N and the slope of the northern SCS. The analyses show that mesoscale sea level fluctuations in the WP have rather limited coherent effects on the SCS, and no statistically significant propagation of mesoscale variability through the Luzon Strait was observed except in the 45-day band. Evidence suggests that the 45-day fluctuation is very much likely a character of the Kuroshio originating from its low-latitude beginning. It is also sug- gested that the westward propagating Rossby waves will deform when they encounter the dynamical barrier of the Kuroshio. The Kuroshio will then acts on the SCS in its own way. The SCS is a relatively isolated system in the sense of coupling and propagating of oceanic mesoscale waves.     

Carbon isotopic record of foraminifers in surface sediments from the South China Sea and its significance

Since the 1990s, the papers and data involved withthe South China Sea (SCS) have been emerging in largenumbers in the world as people pay more attention to thepaleoceanography of the SCS. There have been more than100 cores mentioned in papers containing p…     

热带海温异常与南海夏季风建立迟早的初步研究

利用NCEP再分析的海表温度场、风场、高度场的格点资料,应用合成和相关分析等方法,初步探讨了热带印度洋和热带太平洋海温异常与南海夏季风建立的关系.研究结果表明,热带印度洋和热带太平洋海温异常在有些年份并不同号,从而对南海夏季风建立迟早的影响并不完全一致.进一步分析表明,热带印度洋和热带太平洋海温异常可能是通过影响热带地区Walker环流建立和加强,进而南海夏季风建立的迟早.     

Coastal seafloor observatory at Xiaoqushan in the East China Sea

The seafloor observation system is becoming an important infrastructure for marine research because it is transforming oceanic research from temporal investigation to long term observation.The East China Sea coastal seafloor observatory,located between 30°31′44″N,122°15′12″E and 30°31′34″N,122°14′40″E,is constructed near the Xiaoqushan Island outside the Hangzhou Bay on the inner continental shelf of the East China Sea.The observatory is connected by a submarine optical fiber composite power cable that is more than one kilometer long and consists of a special junction box that transmits power and communication signals to different instruments.The special junction box has a variety of waterproof plugs and connects to three different instruments installed in a trawl preventer.The submarine optical fiber composite power cable is landed on the platform by The East China Sea Branch,State Oceanic Administration and the power is continuously supplied by the solar panels and solar battery on the top of the platform.The real time data are directly sent through the cable to the platform and are transmitted by CDMA wireless to the receiver at the State Key Laboratory of Marine Geology of Tongji University.Measurements at the observatory have been taken since April 20,2009 after installation and the results have been interpreted.The characteristics of the near bottom boundary are constrained by a sediment suspension model using portion of the observed data.In particular,discussion is provided on the sea surface height anomaly at Xiaoqushan Island influenced by the tsunami driven by the 2010 Earthquake in Chile.The successful establishment of the coastal seafloor observatory is the first step toward future development of seafloor observation systems in China.It not only accumulates experiences in technology and engineering,but also paves the way for performing important oceanic research using the long term continuous observation platform.     

Sea surface temperature records of core ZY2 from the central mud area in the South Yellow Sea during last 6200 years and related effect of the Yellow Sea Warm Current

Sea surface temperature (SST) records in the South Yellow Sea during the last 6200 years are reconstructed by the unsaturation index of long-chain alkenones (K 37 U ’) in sediment core ZY2 from the central mud area.The SST records varied between 14.1 and 16.5°C (15.6°C on average),with 3 phases:(1) A high SST phase at 6.2-5.9 cal ka BP;(2) A low and intensely fluctuating SST phase at 5.9-2.3 cal ka BP;and (3) A high and stable SST phase since 2.3 cal ka BP.Variation of the SST records is similar to intensity of the Kuroshio Current (KC),and corresponds well in time to global cold climate events.However,the amplitude of the SST response to cooling events was significantly different in different phases.The SST response to global cooling event was weak while the KC was strong;and the SST response was strong while the KC was weak.The difference in amplitude of the SST response is possibly caused by the modulation effect of the Yellow Sea Warm Current which acts as a shelf branch of the KC and a compensating current induced by the East Asia winter monsoon.The warm waters brought by the Yellow Sea Warm Current cushion the SST decrease induced by climate cooling,and both the Kuroshio and East Asian winter monsoon play important roles in the modulation mechanism.The SST records display a periodicity of 1482 years.The same period was found in the KC records,indicating that variation of the SST records in the central South Yellow Sea is strongly affected by KC intensity.The same period was also found in Greenland ice cores and North Atlantic and Arabian Sea sediment cores,showing a regional response of marine environmental variability in the East China Seas to that in the global oceans.     

渤海典型余环流及其影响因素研究

以大阪大学海湾模型（ODEM）,三维斜压水动力模型研究了渤海夏、冬季节典型余环流结构及其控制园子的影响．浅析了不同计算工况下余流结构对海域不同部分水交换能力的影响．通过分析渤海中部流速的垂向分布,探讨了潮汐、季风和表面热交换对杂环流的贡献．从表面和底层的潮余流结构可以看出渤海的余环流由多个而不是一个旋涡构成,海域的地形和海岸线形状是控制沿岸潮余流结构的主要因素．渤海典型风向下的夏季风和冬季风对余环流的影响差异较大;区域性热盐效应导致的密度流不管是否引起层化现象都会对凤生流和潮余流产生较大的影响．