2001 Vol. 20, No. 1

Physical Oceanography,Marine Meteorology and Marine Physics
Numerical study on residual current and its impact on mass transport in the Hangzhou Bay and the Changjiang Estuary Ⅰ.A3-D joint model of the Hangzhou Bay and the Changjiang Estuary
Zhu Shouxian, Shi Fengyan, Zhu Jianrong, Ding Pingxing
2001, (1): 1-13.
A 3-D numerical model is set up in a large domain covering the Hang zhou Bay and the Changjiang Estuary based on the ECOM model in orthogonal curvilinear coordinates.The numerical schemes for baroclinic pressure gradient (BPG) terms and convective terms are improved in the paper according to the characteristics of velocity field and mass transport in the area.The model is validated by the simulations of residual current and salinity transport in the Hangzhou Bay and the Changjiang Estuary.
Three dimensional diagnostic, semidiagnostic and prognostic calculations of current in the East China Sea in April of 1994
Wang Huiqun, Yuan Yaochu
2001, (1): 15-28.
Three dimensional diagnostic, semidiagnostic and prognostic models in the a-coordinate are used to compute the current in the Fast China Sea with wind and hydrographic data obtained from the investigation of ocean fluxes in the East China Sea during the cruise of April 1994.The computed results show that:the density and velocity fields and so on have been adjusted when time t≈23 d, i.e., the solution of semidiagnostic calculation has been obtained.The quasi-steady state solution also has been reached after about 60 d.Comparing the results of diagnostic calculation with those of semidiagnostic and prognostic calculations, it is found that they agree qualitatively For example, they all show that:(1) The Kuroshio flows along the shelf break of 200~1 000m isobaths; (2) In the southeastern part of the computational region there is a stronger counter-current with an anticyclonic eddy; (3) The volume transport through Section lPN is about 30×106m3/s and so on.However there are some quantitative differences between them.For example, (1) For the semidiagnostic results the Kuroshio current is stronger and clearer than that for diagnostic results and the Kuroshio width is more narrow than that for diagnostic results.This shows that the semidiagnostic calculation can better reflect the topography effect; (2) In most computed region the vertical component of velocity intensifies for semidiagnostic result, especially on the shelf break.Comparing the results of semidiagnostic calculation with those of prognostic calculation, they agree qualitatively, and also agree quantitatively in the middle of computed region.
Three-dimensional numerical simulation for tide and tidal current in the Beibu Gulf
Sun Hongliang, Huang Weimin
2001, (1): 29-38.
By means of three-dimensional POM model, which computes the eddy viscosity coefficient based on two-order turbulent closed model, the tide and tidal current in the Beibu Gulf are simulated with fine grid.In the computed region, six islands are considered and the bottom friction coefficients are taken to be various values from the difference of sea region.Acquired tidal harmonic constants are compared with that of 81 tidal observatories.The absolute mean error of K1 constituent amplitude is 4.6cm and of the lag is 9°.The absolute mean error of O1 constituent amplitude is 5.6 cm and of the lag is 7°.The absolute mean error of M2 constituent amplitude is 6.2 cm and of the lag is 15°.The tide, tidalcurrent, residual water level and tide-induced residual current, as well as the vertial distribution of horizontal velocity in this sea region are analysed by the simulated results.
Marine Meteorology
Responses of CO2 in surface water in subtropical West Pacific to El Niño event
Xing Runan, Ma Liming, Qiao Ran, Wang Zhanggui
2001, (1): 39-50.
In order to investigate the relationships between the change of TCO2, △PCO2 and SST, current, upwelling and biological activities during El Niño event in the subtropical Pacific, the responses of TCO2 and △PCO2 in surface water in the subtropical Pacific during El Niño and La Nina have been simulated using a three-dimension carbon cycle model with biota pump.The results of numerical simulations show that TCO2 in sea water increases with reducing of SST during mature phase of El Niño in the subtropical West Pacific.At the same period, the Kuroshio in this region was weakened, the zonal currents were divergence, the upwelling carried the water with high concentrations of CO2 to the sea surface, so both of TCO2 and △PCO2 in surface water were increased.But TCO2 and △pCO2 were decreased during La Nina period.These simulated results confirmed the observations in 1982/1983, 1986/1987, 1991/1995 and 1997/1998 El Niño events.
Marine Physics
Study on detection of coastal water environment of China by ocean color remote sensing
Pan Delu, Mao Tianming, Li Shujing, Huang Haiqing
2001, (1): 51-63.
Coastal water environment is essentially enhanced by ocean color which is basically decided by substances concentration in water such as chlorophyll, suspended material and yellow substance.It is very difficult, even not possible, to detect water color by expensive ship routing, because of its temporal and spatial variety of feature and scales in the very complicated dynamical system of coastal water.With the development of satellite technique in the last 20 a, space sensors can be applied to detect ocean color by measuring the spectra of water-leaving radiance.It is proven that ocean color remote sensing is a powerful tool for understanding the process of oceanic biology and physics.
Since the 1980s, great attention has been paid to the advanced remote sensing technique in China, especially to development of satellite programs for the coastal water environment.On 7 September 1988, China launched her first polar orbit satellite FY-1A for meteorological and oceanographic application (water color and temperature) and the second satellite FY-1B two years later.In May 1999, China launched her second generation environment satellite FY-1C with higher sensitivies, more channels and stable operation.The special ocean color satellite HY-1 is planned to be in the orbit in 2001, whose main purpose is to detect the coastal water environment of China seas.China is also developing a very advantageous sensor termed as Chinese moderate imaging spectra radiometer (CMODIS) with 91 channels, which will be a good candidate of the third generation satellite FY-3 in 2003.
The technical system of ocean color rermote sensing was developed by the Second Institute of Oceanography (SIO), State Oceanic Administration (SOA) in 1997.The system included data receiving, processing, distribution, calibration, validation and application units.The Hangzhou Station of SIO, SOA has the capability to receive FY-1 and AVHRR data since 1989.It was also a SeaWiFS scientific research station authorized by NASA, USA to free receive SeaWiFS data from 16 September 1997.
In the recent years, the local algorithms of atmospheric correction and inversion of ocean color have been developed for FY-1C and SeaWiFS, to improve the accuracy of the measurement from satellites efficiently.The satellite data are being applied to monitor coastal water environment, such as the spatial distribution of chlorophyll, suspended material and yellow substance, red tide detection and coastal current study.The results sbow that the ocean color remote sensing has latent capacity in the detection of coastal water environment.In consideration of the update technique progress of ocean color remote sensing and its more important role in the detection of coastal water in the 2000s, some suggestions are set forth, which would be beneficial to the design of a cheaper but practical coastal water detection system for marine environment preservation.
Marine Chemistry
Nutrients concentration and changes in decade-scale in the central Bohai Sea
Yu Zhigang, Mi Tiezhu, Yao Qingzhen, Xie Baodong, Zhang Jing
2001, (1): 65-75.
The nutrients contents and distributions are discussed briefly, based on the data obtained in 1998~1999.Besides explanation of the results, a 20-a time series data of nutrients and biological parameters for central Bohai Sea are reviewed.It is found that both concentration and relative content of nutrients have been changed dramatically.The increase of nitrogen and decrease of phosphate and silicate led to the dramatically increase of N/P ratio and the decrease of Si/N ratio.The situation of nitrogen limiting in central Bohai Sea is gradually changing to that of relative lack of phosphate and silicate The decrease of the Huanghe River input to the Bohai Sea may be responsible for this change.These in turn may limit the growth of diatom and thus promote the development of pyrrophyta if other conditions (e.g.temperature and hydrodynamics) are suitable.We conclude that this may be the major inducement factor of pyrrophyta red tide in the Bohai Sea.
Narrow and broad senses on salinity scale
Bao Wanyou, Liu Ximin, Zhang Hao
2001, (1): 76-83.
The narrow sense and applicable limit of Practical Salinity Scale 1978 (PSS78) and volumetric titration using silver nitrate to measure the salinity of non-conservative oceanwater are discussed.The salinity obtained by electrical conductivity method and chlorinity salinity method obviously deviates from the absolute salinity (SA).The Density Salinity Scale (DSS98) proposed by the writers can be extensively used in conservative and non-conservative water samples.The merits of the density salinity scale are as follows, (1) The Density Salinity Scale is only related to seawater mass and its buoyant effect, and is not influenced by the variation in seawater composition, and therefore, has high reliability, and repeatability for salinity determination. (2) The salinity values measured by the DSS98 have a conservative property.For oceanwater samples the salinity values are the same as those determined by the PSS78; for non-conservative water samples (e.g.samples from industrial sources), the salinity values are close to the absolute salinity values in comparison with those measured by the PSS78 and the Knudsen method. (3)For a solution with given solute mass, the solution concentration can be converted into the corresponding salinity by the Density Salinity Scale using the expansion coefficient of the solution and the calibration coefficient of the partial molar volume of the solute.
On sedimentation of phosphorus in specified area outside of the Changjiang Estuary
Zhou Huaiyang, Pan Jianming, Chen Jianfang, Wang Huaizhao, Y. Saito, Y. Kanai
2001, (1): 85-93.
Phosphorus content of surface sediments (0~1cm) sampled by multicorer in specified area (31°00'~32°00'N, 122°30'~124°00'E) outside of the Changjiang Estuary in October 1997 and May 1998 respectively is analyzed.Combined with the data of phosphorus concentration in seawaters, grain size and chemical composition as well as the isotopic sedimentary rate of surface sediment and etc., it is recognized that seasonal variability of different water massea could be sensitively recorded in sediments.Distribution pattern of phosphorous in surface sediment in the area is probably both controlled by the Changjiang River diluted water mass and the Huanghai Sea and the East China Sea mixed water mass.Retransportation and resedimentation perhaps do actively happen in the study region that could make resuspended sediments release pollutants as phosphorus into seawater and have significant impacts on marine ecosystem, although it is indicated that at least some of phosphorus in sediments exists in immobile or inorganic forms.
Marine Geology and Geomorphology
Geochemistry of trace elements and Sr-Nd isotopes of foraminifera shell from the Okinawa Trough
Meng Xianwei, Du Dewen, Cheng Zhenbo
2001, (1): 95-103.
Trace elemental associations and Sr-Nd isotopic compositions are of important to recognition of biogenic material from mixed marine sediments.The foraminifera shell from the Okinawa Trough strongly enrichesSr, P, Mn andBa, enriches Li, U, Th, Sc, Co, Cu, Pb, Zn, Cr, Rb, Y, Sb and light rare earth elements, slightly enriches V, Ga, Zr, Nb, Cd and middle rare earth elements, is short of Mo, In, Sn, Cs, Hf, Ta, W, Ti, Bi and heavy rare earth elements.The mechanism of elemental enrichment in forminifera is the concentrations of trace elements in sea water and selective absorption of trace elements during foraminifera living, as well as the geochemical affinity between major elements and trace elements.The REE (rare earth elements) partition pattern of foraminifera shell of the Okinawa Trough shows enrichment of middle rare earth elements with slightly negative Ce anomaly, which are different from those of foraminifera of the Pacific Ocean.The Sr, Nd isotopic ratios of the Okinawa Trough foraminifera are 0.709 769 and 0.512 162, respectively, which are different not only from those of oceanic water, but also from those of river water of China's Mainland, the former is slightly higher than those of oceanic water, but much lower than those of river water; the latter is slightly lower than those of oceanic water, but higher than those of river water, demonstrating that the Okinawa Trough sea water has been influenced by river water of China's Mainland.
Linear magnetic anomalies and tectonic development of the middle Okinawa Trough
Liang Ruicai, Wu Jinlong, Liu Baohua, Wang Yong, Wang Shugong
2001, (1): 105-116.
By analyzing the magnetic anomalies, the linear magnetic anomalies in the middle Okinawa Trough are identified.It means that the crust along the spreading axis is broken, and new oceanic crust is formed.Geophysical data have revealed that a model of three extensive episodes occurs in the Okinawa Trough, which can be named as "doming episode" from the Middle to Late Miocene (Phase Ⅰ), the episode from the Pliocence to Early Pleistocene (Phase Ⅱ), and the recent "spreading episode" (Phase Ⅲ).The magnetic anomalies in the middle Okinawa Trough are very similar to those found in the middle Red Sea, indicating that the Okinawa Trough is developing towards the "Red Sea stage".Similar to the Red Sea, there are a "main trough" and a "axial trough" in the Okinawa Trough.
Marine Biology and Fishery
Primary productivity in the western tropical Pacific and equatorial warm waters
Chen Xingqun, Zhang Ming, Chen Qihuan
2001, (1): 117-129.
Primary productivity in the western tropical Pacific and equatorial warm waters was studied in the WOCE cruise in November of 1991 and the TOGA-COARE cruise from November of 1992 to February of 1993.It is shown that the total amount of integrated chlorophyll a (chloro.a) was 19.79mg/m2 in depth of 0~150 m and the average daily primary productivity was 171 mg/(m2·d) (C)appeared in the western tropical Pacific while a higher chloro, a (21.68 mg/m2) and primary productiv ity[228 mg/(m2·d) (C)] were observed in the equatorial warm waters.The highest chloro.a was found at the coastal stations of Philippines and Irian while the lowest chloro, a was at the offshore areas bounded by 2°~4°N.The distribution pattern of chloro, a biomass was related to different physical processes.Upwelling, which may have led to a high biomass, was a critical factor changing the distributions of temperature, salinity and nutrient in these areas.
Bacterioplankton production in dilution zone of the Changjiang(Yangtze) Estuary
Liu Zilin, Koshikawa Hiroshi, Ning Xiuren, Shi Junxian, Cai Yuming
2001, (1): 131-139.
The hacterioplankton production and bacterioplankton abundance were surveyed in dilution zone of the Changjiang Estuary and a mesocosm experimental device for enriched phosphate experiment and oil contaminated experiment was placed in the waters nearby Luhua Island during October 1997 and May 1998.The results showed that the average bacterioplankton production in spring was higher than that in autumn, the production at the surface water was higher than that at the bottom in the surveyed area; the higher values appeared in the middle of the area.The results from mesocosm experiment with adding phosphate and oil contaminated showed that the bacterioplankton production increased rising trend day by day during the experiment period.
Response of Arctic marine microalgae to changes of salinity
Zhang Qing, Rolf Gradinger, Zhou Qingsong, Zeng Jiangning
2001, (1): 141-151.
An algal assemblage collected from the bottom of floe in the Greenland Sea was batchcultured at 1±1℃ and 10 salinity gradients varied from 4.0 to 90.8 for 19 d.The growth for both the algal community and individual populations was characterized by an initial lag phase of six days followed by positive growth.Maximum growth rates were obtained as 0.19/d for the algal community and 0.32 to 0.39 d-1 for individual populations for the whole experiment period, which mostly occurred at the lower salinities.The competition between the algal species and the evolution of the algal assemblages under the salinity changes was checked.After 14-d culture, the dominating algae in the lower salinities were centric diatoms, pennate diatoms and phytoflagellates, while ones in the higher salinities almost belonged to pennate diatoms.It is suggested that the sea ice algal community from the Greenland Sea prefer lower salinities to higher ones, and the decrease in salinity in small ranges could stimulate the growth of sea ice algae.