2012 Vol. 34, No. 1
Display Method:
2012, 34(1): 1-7.
Abstract:
16 years (1993-2008) of merged sea level anomaly (MSLA) data obtained from Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO) are used to track the trajectories of meso-scale eddies near the Luzon Strait (LS) (18°-23°N ,116°-126°E), and the results indicate that it is difficult to observe meso-scale eddies from the northwestern Pacific propagating into the South China Sea (SCS) through the LS based on the data with the temporal resolution of 7 d. The analysis on one cyclonic eddy observed in the middle of the LS in 1994, suggests that the sea level anomaly from the Northwestern Pacific propagates into the SCS through the LS after coupling with the original signal in the LS. The time-longitude diagram implies that the sea level anomaly signals become discontinuous near the LS (121°-122°E) when they propagate westward. After applying the band-pass filter to the sea level anomaly data in the section 21°N, 116°-140°E with the periods of 1-3 month, 3-6 month and 330-390 d, one can conclude that the signals from the Northwestern Pacific propagating into the SCS through the LS get different blocked, have different westward propagation velocity and have different forcing mechanisms for different period bands.
16 years (1993-2008) of merged sea level anomaly (MSLA) data obtained from Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO) are used to track the trajectories of meso-scale eddies near the Luzon Strait (LS) (18°-23°N ,116°-126°E), and the results indicate that it is difficult to observe meso-scale eddies from the northwestern Pacific propagating into the South China Sea (SCS) through the LS based on the data with the temporal resolution of 7 d. The analysis on one cyclonic eddy observed in the middle of the LS in 1994, suggests that the sea level anomaly from the Northwestern Pacific propagates into the SCS through the LS after coupling with the original signal in the LS. The time-longitude diagram implies that the sea level anomaly signals become discontinuous near the LS (121°-122°E) when they propagate westward. After applying the band-pass filter to the sea level anomaly data in the section 21°N, 116°-140°E with the periods of 1-3 month, 3-6 month and 330-390 d, one can conclude that the signals from the Northwestern Pacific propagating into the SCS through the LS get different blocked, have different westward propagation velocity and have different forcing mechanisms for different period bands.
2012, 34(1): 8-16.
Abstract:
According to the obtained CTD data of northern South China Sea (SCS) shelf and slope area during the winter cruise in 2009-2010, it found that the northwest pacific water intruded into SCS in the upper layer through Luzon Strait, its effect on tempearture and salinity of northeastern SCS upper layer water decreased from east to west and extended up to about 114°E. Due to the effect of anticyclone eddy in the northeastern SCS during intrusion processing, the vertical and horizontal structure of water mass changed remarkably, especially in the center erea of eddy, the depth of mixed layer and salinity maximum layer is evidently deeper than the surrounding area. The warm eddy was confirmed from the geostrophic current, ADCP current and satellite altimeter data. The existence of warm eddy also affacted the spacial diffusion of chemistry elements markedly. Due to the water convergency caused by warm eddy, the upper layer water with higher concentration dissolved oxygen was transported downwards which induced higher concentration dissolved oxygen existing in the center of warm eddy in upper layer.
According to the obtained CTD data of northern South China Sea (SCS) shelf and slope area during the winter cruise in 2009-2010, it found that the northwest pacific water intruded into SCS in the upper layer through Luzon Strait, its effect on tempearture and salinity of northeastern SCS upper layer water decreased from east to west and extended up to about 114°E. Due to the effect of anticyclone eddy in the northeastern SCS during intrusion processing, the vertical and horizontal structure of water mass changed remarkably, especially in the center erea of eddy, the depth of mixed layer and salinity maximum layer is evidently deeper than the surrounding area. The warm eddy was confirmed from the geostrophic current, ADCP current and satellite altimeter data. The existence of warm eddy also affacted the spacial diffusion of chemistry elements markedly. Due to the water convergency caused by warm eddy, the upper layer water with higher concentration dissolved oxygen was transported downwards which induced higher concentration dissolved oxygen existing in the center of warm eddy in upper layer.
2012, 34(1): 17-28.
Abstract:
Based on ADCP data obtained from the northern shelf and slope of the South China Sea from 2006 to 2009, several analysis methods, including FFT Power spectral analysis, harmonic analysis of tidal current, decomposition of residential current and so on, have been applied to calculate the vertical structure, seasonal variation and spacial distribution of the velocity. The study on the sea currents refers to the south china sea warm current and Northern slope current spatiotemporal distribution. The results show the main tidal current pattern is irregular diurnal tide with regular diurnal tide in mid-deep layer of deep water area. Tidal current shows three-layers vertical structure. The ellipticity of current ellipse, such as O1,K1,M2,S2, are clockwise rotation and NW-SE reversing current in the deep sea station. Energy analysis shows that the current of upper and bottom layer are controlled by tidal current except for middle layer.The results based on observation approve western strong current exists and the vertical current structure has seasonal variation. It is not found the south china sea warm current in 200 m depth, however the winter upper layer current above 30 meters flows to NE. In winter the influence of the upper current is caused by the South China Sea warm current, in summer circulation towards southwest is prevailing and has strong current velocity. It is maybe results from the axis of the south china sea warm current is near to shelf in summer and far in winter.
Based on ADCP data obtained from the northern shelf and slope of the South China Sea from 2006 to 2009, several analysis methods, including FFT Power spectral analysis, harmonic analysis of tidal current, decomposition of residential current and so on, have been applied to calculate the vertical structure, seasonal variation and spacial distribution of the velocity. The study on the sea currents refers to the south china sea warm current and Northern slope current spatiotemporal distribution. The results show the main tidal current pattern is irregular diurnal tide with regular diurnal tide in mid-deep layer of deep water area. Tidal current shows three-layers vertical structure. The ellipticity of current ellipse, such as O1,K1,M2,S2, are clockwise rotation and NW-SE reversing current in the deep sea station. Energy analysis shows that the current of upper and bottom layer are controlled by tidal current except for middle layer.The results based on observation approve western strong current exists and the vertical current structure has seasonal variation. It is not found the south china sea warm current in 200 m depth, however the winter upper layer current above 30 meters flows to NE. In winter the influence of the upper current is caused by the South China Sea warm current, in summer circulation towards southwest is prevailing and has strong current velocity. It is maybe results from the axis of the south china sea warm current is near to shelf in summer and far in winter.
2012, 34(1): 29-38.
Abstract:
Based on CCSM3 (Community Climate System Model version 3) model, the long-term sea level trends of global ocean in the 20th and 21st century under IPCC SRES A2 scenario (IPCC, 2001) are analyzed in this paper. The result shows that global sea level rises about 4.0 cm during 20th century through steric expansion, with an acceleration of 0.004 8 mm/a2; eustatic changes are not included in this simulation. CCSM3 simulation also shows that in the 21st century sea level will rise in acceleration; the global sea level will rise 30 cm during the whole century through steric expansion. The vertical distribution of thermosteric and halosteric anomalies that contribute to sea level change is very different between ocean basins. Significant warming of the North Atlantic Ocean can extend to 2 500 m depth, while the salinity change partially counteracts sea level rise due to this warming. The steric anomalies in the Pacific Ocean occur mainly in the upper 700 m. In the Southern Ocean, steric change can extend to the entire water column.
Based on CCSM3 (Community Climate System Model version 3) model, the long-term sea level trends of global ocean in the 20th and 21st century under IPCC SRES A2 scenario (IPCC, 2001) are analyzed in this paper. The result shows that global sea level rises about 4.0 cm during 20th century through steric expansion, with an acceleration of 0.004 8 mm/a2; eustatic changes are not included in this simulation. CCSM3 simulation also shows that in the 21st century sea level will rise in acceleration; the global sea level will rise 30 cm during the whole century through steric expansion. The vertical distribution of thermosteric and halosteric anomalies that contribute to sea level change is very different between ocean basins. Significant warming of the North Atlantic Ocean can extend to 2 500 m depth, while the salinity change partially counteracts sea level rise due to this warming. The steric anomalies in the Pacific Ocean occur mainly in the upper 700 m. In the Southern Ocean, steric change can extend to the entire water column.
2012, 34(1): 39-45.
Abstract:
To improve the tidal prediction accuracy, the error correction of a regional tidal model is carried out using a local model approach based on chaos theory where sufficient tidal measurement data were available. As the examples, for one month (December-2007), the local model correction can remove as much as 74.7% of root mean square error (RMSE) at Chongwu measurement station and 60.5% at Xiamen Station for the prediction horizon T=2 h, and remove around 50% RMSE at above two stations for the prediction horizon T=24 h.
To improve the tidal prediction accuracy, the error correction of a regional tidal model is carried out using a local model approach based on chaos theory where sufficient tidal measurement data were available. As the examples, for one month (December-2007), the local model correction can remove as much as 74.7% of root mean square error (RMSE) at Chongwu measurement station and 60.5% at Xiamen Station for the prediction horizon T=2 h, and remove around 50% RMSE at above two stations for the prediction horizon T=24 h.
2012, 34(1): 46-56.
Abstract:
Based on the measured tide gauge records at 25 stations in the Zhujiang Delta, the periodic oscillations and secular trends of water level series were studied with Power spectra analysis and Fourier transformation analysis. The Power spectra analysis of monthly mean time series reveals that there were several predominant periods of water level change, varying from 0.3 a to 11.7 a. Results from Linear regression of low-passed time series which were the outcome of Fourier transform process suggest that the water level of river network of Zhujiang Delta was rising in general, and the rate of water level change generally ascended as shifting from the top of the delta to the outlets of the Zhujiang River. The rates of water level change of 25 tide gauge stations differ from -3.8 mm/a to 3.7 mm/a, and the secular trend of seven stations among them was descending, which was largely due to large-scale disordered sand excavation in the upper reaches of the Xijiang and Beijiang River network. Analysis on the change in the rates of water level change of different periods indicates that large-scale sand excavation in the river network which led to bed scour and deepening resulted in the significant fluctuation of water level, and even reversed the secular trend of water level change.
Based on the measured tide gauge records at 25 stations in the Zhujiang Delta, the periodic oscillations and secular trends of water level series were studied with Power spectra analysis and Fourier transformation analysis. The Power spectra analysis of monthly mean time series reveals that there were several predominant periods of water level change, varying from 0.3 a to 11.7 a. Results from Linear regression of low-passed time series which were the outcome of Fourier transform process suggest that the water level of river network of Zhujiang Delta was rising in general, and the rate of water level change generally ascended as shifting from the top of the delta to the outlets of the Zhujiang River. The rates of water level change of 25 tide gauge stations differ from -3.8 mm/a to 3.7 mm/a, and the secular trend of seven stations among them was descending, which was largely due to large-scale disordered sand excavation in the upper reaches of the Xijiang and Beijiang River network. Analysis on the change in the rates of water level change of different periods indicates that large-scale sand excavation in the river network which led to bed scour and deepening resulted in the significant fluctuation of water level, and even reversed the secular trend of water level change.
2012, 34(1): 57-63.
Abstract:
During the third CHINARE Arctic Expedition in summer 2008, 33 days of current profile, near bottom sea water temperature and salinity data in central Chukchi Sea were collected by a mooring system (CN-1). The observed data shows that near bottom water temperature has two rapid and significant changes during the observation. CTD (Conductivity Temperature Depth) data along R-section collected in this expedition, NOAA (National Oceanic and Atmospheric Administration) AVHRR (Advanced Very High Resolution Radiometer) SST (Sea Surface Temperature) and NOAA sea surface wind data are used to analyze the rapid and significant temperature changes. The results showed that water temperature changes rapidly at not only the bottom layer but also the upper layer. The rapid temperature changes are caused by the movement of temperature front. The movement consists of two parts, northward movement and swing in the direction of north-south. The northward movement is related to climate characteristics, and the swing is related to synoptic characteristics.
During the third CHINARE Arctic Expedition in summer 2008, 33 days of current profile, near bottom sea water temperature and salinity data in central Chukchi Sea were collected by a mooring system (CN-1). The observed data shows that near bottom water temperature has two rapid and significant changes during the observation. CTD (Conductivity Temperature Depth) data along R-section collected in this expedition, NOAA (National Oceanic and Atmospheric Administration) AVHRR (Advanced Very High Resolution Radiometer) SST (Sea Surface Temperature) and NOAA sea surface wind data are used to analyze the rapid and significant temperature changes. The results showed that water temperature changes rapidly at not only the bottom layer but also the upper layer. The rapid temperature changes are caused by the movement of temperature front. The movement consists of two parts, northward movement and swing in the direction of north-south. The northward movement is related to climate characteristics, and the swing is related to synoptic characteristics.
2012, 34(1): 64-70.
Abstract:
The impact of variability in the strength of the subtropical circulation in the North Pacific Ocean on the summer precipitation over the eastern China is investigated.The intensity of subtropical circulation in the North Pacific is diagnosed from SODA and ECCO dataset; the atmospheric circulation and the sea surface temperature (SST) are diagnosed from the NCEP/NCAR reanalysis dataset and the Hadley SST; the precipitation data is based on the monthly rainfall observations over 160 stations in China.This study is focused on the interaction between the atmospheric and oceanic circulations over the periods of 1970-2009.The results show that there exists a strong negative correlation between the variability of the sutropical circulatioin and the summer rainfall in the middle and lower reaches of the Changjiang River. When the subtropical gyre is relatively weaker (stronger) than normal, the subtropical high is located further south (north) than normal; an abnormal cyclonic (anticyclonic) circulation prevails over the Changjiang River basin, companied by the vigorous (weak) southwestern moisture transporting here to form a strong moisture convergence (divergence) center.This gives rise to an ascending vertical motion and at the same time the convection is strengthened (weakened).As a result, a very favorable large-scale circulation is established, which can sustain the heavy (weak) rainfalls in the middle and lower reaches of the Changjiang River.Furthermore, the variation in the subtropical wind-driven gyre can generate SST anomaly at middle latitudes, which may be the primarily reason for meridional shifting of the subtropical high in the North Pacific Ocean.
The impact of variability in the strength of the subtropical circulation in the North Pacific Ocean on the summer precipitation over the eastern China is investigated.The intensity of subtropical circulation in the North Pacific is diagnosed from SODA and ECCO dataset; the atmospheric circulation and the sea surface temperature (SST) are diagnosed from the NCEP/NCAR reanalysis dataset and the Hadley SST; the precipitation data is based on the monthly rainfall observations over 160 stations in China.This study is focused on the interaction between the atmospheric and oceanic circulations over the periods of 1970-2009.The results show that there exists a strong negative correlation between the variability of the sutropical circulatioin and the summer rainfall in the middle and lower reaches of the Changjiang River. When the subtropical gyre is relatively weaker (stronger) than normal, the subtropical high is located further south (north) than normal; an abnormal cyclonic (anticyclonic) circulation prevails over the Changjiang River basin, companied by the vigorous (weak) southwestern moisture transporting here to form a strong moisture convergence (divergence) center.This gives rise to an ascending vertical motion and at the same time the convection is strengthened (weakened).As a result, a very favorable large-scale circulation is established, which can sustain the heavy (weak) rainfalls in the middle and lower reaches of the Changjiang River.Furthermore, the variation in the subtropical wind-driven gyre can generate SST anomaly at middle latitudes, which may be the primarily reason for meridional shifting of the subtropical high in the North Pacific Ocean.
2012, 34(1): 71-78.
Abstract:
The spatio-temporal variations of sea surface temperature (SST) and sea surface height anomaly (SSHA) induced by three sequential typhoons in September 2008 were investigated by using multi-satellite data.Possible factors influence SST and SSHA variations were discussed.The typhoon-induced strong upwelling (1×10-5-150×10-5m/s) caused extreme sea surface cooling (1-6 ℃) and significant SSHA decrease(10-50 cm).Besides, the typhoon-induced maximum SST cooling centers were closely associated with negative sea surface height (or mesoscale eddy) area.Furthermore, the results provide convincible evidences that the typhoon translation speed (or forcing time), typhoon intensity and pre-existing cold eddy may play important roles in this process.A cyclonic eddy emerged in the pre-existing positive SSHA area due to the three sequential typhoons forced jointly.This study implies that some typhoons, e.g., sequential typhoons passing over the same area, may play a notable role in ocean mesoscale eddies generating processes.
The spatio-temporal variations of sea surface temperature (SST) and sea surface height anomaly (SSHA) induced by three sequential typhoons in September 2008 were investigated by using multi-satellite data.Possible factors influence SST and SSHA variations were discussed.The typhoon-induced strong upwelling (1×10-5-150×10-5m/s) caused extreme sea surface cooling (1-6 ℃) and significant SSHA decrease(10-50 cm).Besides, the typhoon-induced maximum SST cooling centers were closely associated with negative sea surface height (or mesoscale eddy) area.Furthermore, the results provide convincible evidences that the typhoon translation speed (or forcing time), typhoon intensity and pre-existing cold eddy may play important roles in this process.A cyclonic eddy emerged in the pre-existing positive SSHA area due to the three sequential typhoons forced jointly.This study implies that some typhoons, e.g., sequential typhoons passing over the same area, may play a notable role in ocean mesoscale eddies generating processes.
2012, 34(1): 79-89.
Abstract:
Based on WOA05 climatological database and the measured hydrologic data in the northern Huanghai Sea, the effect of typical mixed-layer structures on the acoustic propagation in a surface duct environment in adjacent sea areas of China is discussed using the BELLHOP Gaussian beam model. The mixed-layer structures show distinct variations between different areas and seasons. In the deep sea, the mixed-layer depth is a main variable factor, which defines the vertical space of the surface duct. A obvious difference of acoustic energe level appears when the propagation occurs in a surface channel inside the mixed-layer compared with that in a shadow zone outside the mixed-layer. In the shallow water, the mixed-layer depth and the sound speed grads are both streaky. More reversal rays are involved when the sound speed grads enhancing or the mixed-layer depth deepening, which make the energe level in the surface duct increased. Two groups of measured data show that the mixed-layer depth may yield or fade suddenly with time and distribute asymmetrically with range. Under a thermocline enviroment in the shallow water, the acoustic energy level near the surface can be evidently raising when the surface duct comes into being in condition of some specific oceanographic phenomena in the air-sea boundary layer.
Based on WOA05 climatological database and the measured hydrologic data in the northern Huanghai Sea, the effect of typical mixed-layer structures on the acoustic propagation in a surface duct environment in adjacent sea areas of China is discussed using the BELLHOP Gaussian beam model. The mixed-layer structures show distinct variations between different areas and seasons. In the deep sea, the mixed-layer depth is a main variable factor, which defines the vertical space of the surface duct. A obvious difference of acoustic energe level appears when the propagation occurs in a surface channel inside the mixed-layer compared with that in a shadow zone outside the mixed-layer. In the shallow water, the mixed-layer depth and the sound speed grads are both streaky. More reversal rays are involved when the sound speed grads enhancing or the mixed-layer depth deepening, which make the energe level in the surface duct increased. Two groups of measured data show that the mixed-layer depth may yield or fade suddenly with time and distribute asymmetrically with range. Under a thermocline enviroment in the shallow water, the acoustic energy level near the surface can be evidently raising when the surface duct comes into being in condition of some specific oceanographic phenomena in the air-sea boundary layer.
2012, 34(1): 90-94.
Abstract:
Island is a relative independent ecosystem. Just because of its independence, once happening natural deserters, the landscape patterns of island ecosystem would change, which makes the landscape not be stable. Landscape stability shows fastness and resilience. So the resilience that island recovers to its original stable situation once it was destroyed is correlation with island risk degree. The more stable landscape is, the smaller risk degree is, and vice versa. The relation between landscape stability and landscape diversity, landscape fragile degree, landscape mosaic's spatial diversity and human disturbance degree is analyzed. The correlation of island landscape pattern with island risk degree is pointed. A risk assessment method of natural hazard for island based on landscapes patterns was presented. Based on landscape diversity index, landscape fragile index, landscape mosaic's spatial diversity index, and the proportion of manmade landscapes, a risk assessment model of natural disasters for islands is proposed. Daheishan Island, Beichangshan Island and Nanchangshan Island of Nanwu Island in China are chose for study areas, and the proposed risk assessment method in this paper is applied in the study areas. It shows that the assessment results using the proposed method were coincided with the traditional methods.
Island is a relative independent ecosystem. Just because of its independence, once happening natural deserters, the landscape patterns of island ecosystem would change, which makes the landscape not be stable. Landscape stability shows fastness and resilience. So the resilience that island recovers to its original stable situation once it was destroyed is correlation with island risk degree. The more stable landscape is, the smaller risk degree is, and vice versa. The relation between landscape stability and landscape diversity, landscape fragile degree, landscape mosaic's spatial diversity and human disturbance degree is analyzed. The correlation of island landscape pattern with island risk degree is pointed. A risk assessment method of natural hazard for island based on landscapes patterns was presented. Based on landscape diversity index, landscape fragile index, landscape mosaic's spatial diversity index, and the proportion of manmade landscapes, a risk assessment model of natural disasters for islands is proposed. Daheishan Island, Beichangshan Island and Nanchangshan Island of Nanwu Island in China are chose for study areas, and the proposed risk assessment method in this paper is applied in the study areas. It shows that the assessment results using the proposed method were coincided with the traditional methods.
2012, 34(1): 95-100.
Abstract:
Bounded by the Taiwan Strait, the north part of coastal zone in China is long and narrow in north-south direction, the south part is also long and narrow but in west-east direction. The imagery database of marine cadaster should adapt to this particular long and narrow spatial form. The paper carried out a composite block model of Binary Tree and Quadtree model, and according to this model, presented an improved Morton code—"CMorton code".We used multi-resolution remote sensing data of the Changjiang Estuary,Hangzhou Bay in north-south and coastal image in Fujian Province in west-east direction to test the coding method.The result showed that, compared with the usual row-column number coding, the CMorton code can significantly shorten the construction time cost of data block, it can satisfy the real-time visualization of marine cadaster data and efficiently adapt to the spatial form of Chinese marine cadaster imagery data.
Bounded by the Taiwan Strait, the north part of coastal zone in China is long and narrow in north-south direction, the south part is also long and narrow but in west-east direction. The imagery database of marine cadaster should adapt to this particular long and narrow spatial form. The paper carried out a composite block model of Binary Tree and Quadtree model, and according to this model, presented an improved Morton code—"CMorton code".We used multi-resolution remote sensing data of the Changjiang Estuary,Hangzhou Bay in north-south and coastal image in Fujian Province in west-east direction to test the coding method.The result showed that, compared with the usual row-column number coding, the CMorton code can significantly shorten the construction time cost of data block, it can satisfy the real-time visualization of marine cadaster data and efficiently adapt to the spatial form of Chinese marine cadaster imagery data.
2012, 34(1): 101-108.
Abstract:
Temporal and spatial variations of landscape changes and their driving forces are analyzed in Yancheng coastal wetlands based on topography data in 1976 and remote sensing data in 1987, 1992, 1997, 2002 and 2007.The results show that the area of Yancheng natural coastal wetlands decreased gradually with the massive loss of Aeluropus sinensis, Suaeda glauca communities and great increase of fish ponds and agricultural lands.A landscape index shows Yancheng coastal wetlands are rapidly deteriorating and experiencing landscape fragmentation.Their driving forces are pushed by both human disturbance and physical conditions with policy-oriented activities of all kinds of wetlands development, alien species introduction and coastal erosion/accretion conditions.The existing development model on Yancheng coastal wetlands might be substituted by wise use and scientific management as soon as possible for the aim of biodiversity conservation and ecosystem health.
Temporal and spatial variations of landscape changes and their driving forces are analyzed in Yancheng coastal wetlands based on topography data in 1976 and remote sensing data in 1987, 1992, 1997, 2002 and 2007.The results show that the area of Yancheng natural coastal wetlands decreased gradually with the massive loss of Aeluropus sinensis, Suaeda glauca communities and great increase of fish ponds and agricultural lands.A landscape index shows Yancheng coastal wetlands are rapidly deteriorating and experiencing landscape fragmentation.Their driving forces are pushed by both human disturbance and physical conditions with policy-oriented activities of all kinds of wetlands development, alien species introduction and coastal erosion/accretion conditions.The existing development model on Yancheng coastal wetlands might be substituted by wise use and scientific management as soon as possible for the aim of biodiversity conservation and ecosystem health.
2012, 34(1): 109-119.
Abstract:
The contents of main and trace elements, total organic carbon (TOC) and carbonate are reported in sediments recovered from the offshore areas of the Shandong Peninsula.The aims are to understand the provenance and diffusion pattern of the sediments by the element composition characteristics.The results indicate that the content of some elements, such as Al, K, Na, Mg, Fe, Ca, Cu and Zn is higher in the offshore areas than in the upper continental shelf (UCC), and the content of Mn, Co, Ni, Cr as well as rare earth element (REE) is lower.Si and Ti in the offshore areas are same as UCC.HREE fractionates obviously in sand and the value of cn(La)/cn(Yb) is close to that of Korean rivers.The normalized curve of other sediments is same as that in the Huanghe River and different from that in the Changjiang River.The element composition mainly is controlled by source rocks and influenced by granularity.Furthermore, Fe-Mn oxides and biogenous carbonate also exert some influence on the element composition.The result of provenance discrimination exhibits that the sediments offshore and in the southeastern area are mainly derived from Huanghe River.Where the transportation pattern of sediment is controlled by Shandong Peninsula coastal current and tide.The coarse sediments in the northeast mainly are the relict sands and their element component is same as that of the Korean Peninsula and the Yalu River.This means that the coarse sediments in the northeast may be supplied by the Korean peninsula or the Yalu River in the last glacial when the sea level was low.
The contents of main and trace elements, total organic carbon (TOC) and carbonate are reported in sediments recovered from the offshore areas of the Shandong Peninsula.The aims are to understand the provenance and diffusion pattern of the sediments by the element composition characteristics.The results indicate that the content of some elements, such as Al, K, Na, Mg, Fe, Ca, Cu and Zn is higher in the offshore areas than in the upper continental shelf (UCC), and the content of Mn, Co, Ni, Cr as well as rare earth element (REE) is lower.Si and Ti in the offshore areas are same as UCC.HREE fractionates obviously in sand and the value of cn(La)/cn(Yb) is close to that of Korean rivers.The normalized curve of other sediments is same as that in the Huanghe River and different from that in the Changjiang River.The element composition mainly is controlled by source rocks and influenced by granularity.Furthermore, Fe-Mn oxides and biogenous carbonate also exert some influence on the element composition.The result of provenance discrimination exhibits that the sediments offshore and in the southeastern area are mainly derived from Huanghe River.Where the transportation pattern of sediment is controlled by Shandong Peninsula coastal current and tide.The coarse sediments in the northeast mainly are the relict sands and their element component is same as that of the Korean Peninsula and the Yalu River.This means that the coarse sediments in the northeast may be supplied by the Korean peninsula or the Yalu River in the last glacial when the sea level was low.
2012, 34(1): 120-126.
Abstract:
Magnetic and multibeam data were collected from DAYANG No.1 first world cruise at Mid Atlantic Ridge.The interpretation of magnetic anomalies and bathymetric data shows the geophysical characteristics of hydrothermal plumes at the Logatchev vent field. Logatchev vent site is situated on the eastern inner flank of the rift valley and between the high value of positive and negative anomalies. NWW-SEE and NS trending fault not only control basement depth and upwelling-sag,but also dose the distribution of ultramafic rock and heat source. It is suggest that the Logatchev hydrothermal field is associated with ultramafic-hosted, off-axis location with detachment faulting, oceanic core complex, abundant gravitational landslides.
Magnetic and multibeam data were collected from DAYANG No.1 first world cruise at Mid Atlantic Ridge.The interpretation of magnetic anomalies and bathymetric data shows the geophysical characteristics of hydrothermal plumes at the Logatchev vent field. Logatchev vent site is situated on the eastern inner flank of the rift valley and between the high value of positive and negative anomalies. NWW-SEE and NS trending fault not only control basement depth and upwelling-sag,but also dose the distribution of ultramafic rock and heat source. It is suggest that the Logatchev hydrothermal field is associated with ultramafic-hosted, off-axis location with detachment faulting, oceanic core complex, abundant gravitational landslides.
2012, 34(1): 127-135.
Abstract:
The research on deep-water tractive deposition is extremely valuable for the palaeooceanographical and palaeoclimatic reconstruction, slope deposition studies and mineral and energy exploration.The abundance of tractive structures developed in Zhujiang formation,Baiyun sag,Zhujiang Basin.They included parallel-bedding fine sandstone and doubling mud layers, bidirectional cross-bedding silty-fine sandstone,wavy-bedding and flaser-bedding globigerina limestone, wavy-bedding and flaser-bedding siltstone and silty-fine sandstone, lenticular-bedding silty-fine sandstones. They were totally different from pelagic turbidite and hemipelagite-pelagite. Combining with the depositional setting, the rich tractive structures were believed as deep-water deposition. The discovery of the deep-water tractive deposition in Miocene Zhujiang formation would be of great importance. It could be inferred that a deep-water current had existed since the formation of the shelf-break during late Oligocene(23.8 Ma) in Baiyun sag, which influenced and controlled the resources and depositional processes in Zhujiang formation. The tractive current may influence and change the composition and its distribution. And this would have a great enlightenment to the reconstruction of the palaeo-ocean circulation in the south china sea. Further studies will be needed.
The research on deep-water tractive deposition is extremely valuable for the palaeooceanographical and palaeoclimatic reconstruction, slope deposition studies and mineral and energy exploration.The abundance of tractive structures developed in Zhujiang formation,Baiyun sag,Zhujiang Basin.They included parallel-bedding fine sandstone and doubling mud layers, bidirectional cross-bedding silty-fine sandstone,wavy-bedding and flaser-bedding globigerina limestone, wavy-bedding and flaser-bedding siltstone and silty-fine sandstone, lenticular-bedding silty-fine sandstones. They were totally different from pelagic turbidite and hemipelagite-pelagite. Combining with the depositional setting, the rich tractive structures were believed as deep-water deposition. The discovery of the deep-water tractive deposition in Miocene Zhujiang formation would be of great importance. It could be inferred that a deep-water current had existed since the formation of the shelf-break during late Oligocene(23.8 Ma) in Baiyun sag, which influenced and controlled the resources and depositional processes in Zhujiang formation. The tractive current may influence and change the composition and its distribution. And this would have a great enlightenment to the reconstruction of the palaeo-ocean circulation in the south china sea. Further studies will be needed.
2012, 34(1): 136-144.
Abstract:
The suspended sediment transport processes were analyzed on the basis of hydrodynamics and suspended sediment survey in the Tianjin subtidal waters of the Bohai Sea. The flow in the study area was characterized by the irregular semidiurnal tide and reciprocating flow. The current speed of flood was stronger than ebb.There is a significant linear relationship between the depth-averaged velocity and the suspended sediment concentration at the bottom layer during the flood period but not during the ebb, which indicates a strong resuspension event during the flood. The suspended sediment transported with strong asymmetric characteristics during tidal cycles, which results in the net sediment transportation onshore. The calculation of flux decomposition shows that the tidal pumping effect, especially the tidal trapping, is the main contribution in terms of the suspended sediment transport in the study area. It is followed by the Lagrangian advection transport, which as one order lower than the tidal pumping; the vertical shear contribution is minimum. In conclusion, the strong asymmetry of both the current velocity and suspended sediment concentration during the flood and ebb, were the main factor resulting in a strong tidal trapping. In addition, the suspended sediment transport patterns in the subtidal area may be related to the fine-grained sediment trapping over the intertidal area.
The suspended sediment transport processes were analyzed on the basis of hydrodynamics and suspended sediment survey in the Tianjin subtidal waters of the Bohai Sea. The flow in the study area was characterized by the irregular semidiurnal tide and reciprocating flow. The current speed of flood was stronger than ebb.There is a significant linear relationship between the depth-averaged velocity and the suspended sediment concentration at the bottom layer during the flood period but not during the ebb, which indicates a strong resuspension event during the flood. The suspended sediment transported with strong asymmetric characteristics during tidal cycles, which results in the net sediment transportation onshore. The calculation of flux decomposition shows that the tidal pumping effect, especially the tidal trapping, is the main contribution in terms of the suspended sediment transport in the study area. It is followed by the Lagrangian advection transport, which as one order lower than the tidal pumping; the vertical shear contribution is minimum. In conclusion, the strong asymmetry of both the current velocity and suspended sediment concentration during the flood and ebb, were the main factor resulting in a strong tidal trapping. In addition, the suspended sediment transport patterns in the subtidal area may be related to the fine-grained sediment trapping over the intertidal area.
2012, 34(1): 145-152.
Abstract:
Fifteen suspended sediment concentrations(SSC) resulting images are retrieved from Landsat images using Gordon formulation in the Changjiang Estuary in China.Base upon these results, a spatial and temporal analysis has been conducted with the findings as following: the SSC in the Changjiang Estuary decrease significantly by nearly 40% over the past 40 a; their variation curves show high similarity with curve of decrease in riverine sediment supply, which is deduced by a geological environment change and big hydraulic engineering projects, that is to say, to some extent, the SSC maps retrieved from remote sensing images can suggest the geological environment change in the long time scale, as well as the dramatical variation caused by human being engineering activities in short time scale.Although the retrieve work ignores the influentical factors such as topography and tide, it represents high sensibility in response to the decrease of sediment supply.
Fifteen suspended sediment concentrations(SSC) resulting images are retrieved from Landsat images using Gordon formulation in the Changjiang Estuary in China.Base upon these results, a spatial and temporal analysis has been conducted with the findings as following: the SSC in the Changjiang Estuary decrease significantly by nearly 40% over the past 40 a; their variation curves show high similarity with curve of decrease in riverine sediment supply, which is deduced by a geological environment change and big hydraulic engineering projects, that is to say, to some extent, the SSC maps retrieved from remote sensing images can suggest the geological environment change in the long time scale, as well as the dramatical variation caused by human being engineering activities in short time scale.Although the retrieve work ignores the influentical factors such as topography and tide, it represents high sensibility in response to the decrease of sediment supply.
2012, 34(1): 153-162.
Abstract:
Investigation was carried out in July 2009 in Huanghe Estuary in China and its adjacent area after the ninth water regulation in order to study the influence of the event on phytoplankton community structure in this area. The species composition, abundance, dominant species and community diversity of net-phytoplankton were studied.A total of 53 phytoplankton species were identified. The Bacillariophyta accounted for 81.1% with 44 species and the Pyrrophyta accounted for 11.3% with 6 species. Besides, there were also Cyanophyta, Chrysophyta and Chlorophyta. The total abundance of phytoplankton was 0.96×104—76.32×104 cells/m3 and the mean value was 21.23×104 cells/m3. The main dominant species were Nostocaceae, Actinocyclus octonarius, Thalassionema frauenfeldii and Chaetoceros castracanei.The increased runoff of the Huanghe River caused by the water regulation had significant impacts on the phytoplankton community structure.The phytoplankton community structure of specific period is revealed, the basic information of phytoplankton community is enriched and important references are provided for further research about the influences of environmental changes on the phytoplankton community in the Huanghe Estuary and its adjacent area.
Investigation was carried out in July 2009 in Huanghe Estuary in China and its adjacent area after the ninth water regulation in order to study the influence of the event on phytoplankton community structure in this area. The species composition, abundance, dominant species and community diversity of net-phytoplankton were studied.A total of 53 phytoplankton species were identified. The Bacillariophyta accounted for 81.1% with 44 species and the Pyrrophyta accounted for 11.3% with 6 species. Besides, there were also Cyanophyta, Chrysophyta and Chlorophyta. The total abundance of phytoplankton was 0.96×104—76.32×104 cells/m3 and the mean value was 21.23×104 cells/m3. The main dominant species were Nostocaceae, Actinocyclus octonarius, Thalassionema frauenfeldii and Chaetoceros castracanei.The increased runoff of the Huanghe River caused by the water regulation had significant impacts on the phytoplankton community structure.The phytoplankton community structure of specific period is revealed, the basic information of phytoplankton community is enriched and important references are provided for further research about the influences of environmental changes on the phytoplankton community in the Huanghe Estuary and its adjacent area.
2012, 34(1): 163-177.
Abstract:
A two-dimensional numerical flume is presented to investigate the regular wave slamming on an open-piled structure using the corrected SPH method. The model employs CSPM and Riemann solution to discretize the Navier-Stokes equations. Solid boundaries are simulated by wall particles. The pressures of these dummy particles are determined by a coupling approach, which can keep the pressure field more stable near the boundaries. A new impacting boundary condition is proposed to track the hydrodynamic characteristics around the structure. The improved SPH model is employed to simulate the regular wave impacting the open-piled structure in the splash zone. The main features of the velocity and pressure fields near the structure are presented. And the model is validated against the experimental data and a good agreement is observed.
A two-dimensional numerical flume is presented to investigate the regular wave slamming on an open-piled structure using the corrected SPH method. The model employs CSPM and Riemann solution to discretize the Navier-Stokes equations. Solid boundaries are simulated by wall particles. The pressures of these dummy particles are determined by a coupling approach, which can keep the pressure field more stable near the boundaries. A new impacting boundary condition is proposed to track the hydrodynamic characteristics around the structure. The improved SPH model is employed to simulate the regular wave impacting the open-piled structure in the splash zone. The main features of the velocity and pressure fields near the structure are presented. And the model is validated against the experimental data and a good agreement is observed.
2012, 34(1): 178-182.
Abstract:
2012, 34(1): 183-188.
Abstract:
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