2014 Vol. 36, No. 7
Display Method:
2014, 36(7): .
Abstract:
2014, 36(7): 1-8.
doi: 10.3969/j.issn.0253-4193.2014.04.001
Abstract:
The Prydz Bay and its adjacent sea area is a key, well-studied area for investigating the southern ocean carried by CHINARE all the time. This work studied on the distribution and characteristics of the main water masses such as the Summer Surface Water, the Antarctic Winter Water, the Shelf Water, the Circumpolar Deep Water (CDW), the Antarctic Bottom Water (ABW) and the Ice Shelf Water, and summarized results of previous studies on water mass which were based on survey data in these areas. The results showed that on the definition of the index characteristic of the Shelf Water, there are still in debate that whether the shelf water is subdivided into High Salinity Shelf Water and Low Salinity Shelf Water, and there exists some overlaps between the defining scopes of High Salinity Shelf Water and the Prydz Bay Bottom Water. Until now, there is no evidence that CDW can be extended to the continental shelf areas of the Prydz Bay, and no direct evidence that ABW can be formed around the Prydz Bay.
The Prydz Bay and its adjacent sea area is a key, well-studied area for investigating the southern ocean carried by CHINARE all the time. This work studied on the distribution and characteristics of the main water masses such as the Summer Surface Water, the Antarctic Winter Water, the Shelf Water, the Circumpolar Deep Water (CDW), the Antarctic Bottom Water (ABW) and the Ice Shelf Water, and summarized results of previous studies on water mass which were based on survey data in these areas. The results showed that on the definition of the index characteristic of the Shelf Water, there are still in debate that whether the shelf water is subdivided into High Salinity Shelf Water and Low Salinity Shelf Water, and there exists some overlaps between the defining scopes of High Salinity Shelf Water and the Prydz Bay Bottom Water. Until now, there is no evidence that CDW can be extended to the continental shelf areas of the Prydz Bay, and no direct evidence that ABW can be formed around the Prydz Bay.
2014, 36(7): 9-16.
doi: 10.3969/j.issn.0253-4193.2014.04.002
Abstract:
Using the multi-model datasets of 20C3M and the SRESA1B scenario projection from Program for Climate Model Diagnosis and Intercomparison for IPCC-AR4,we have investigated the sea surface temperature (SST) changes in the North Pacific and its response to wind stress changes in the North Pacific under different atmospheric greenhouse gases scenarios. The analysis shows that the SST will increase in most parts of the North Pacific as a result of the effect of higher atmospheric CO2 concentration,with the maximum increasing center located along the Kuroshio Extension region. We conclude that the warming in the SRESA1B scenario over the North Pacific especially along the Kuroshio Extension might be attributable to the stronger easterlies prevail in the central Pacific and poleward shift of the zero wind stress curl line. This Ekman response is local and fast. On the other hand,because the zero wind stress curl line displaced to higher latitudes,it generates stronger Kuroshio and its extention. It also generates anomalous Rossby waves at the latitude of zero wind stress curl line which propagate to the west. The Rossby waves change the thermocline in the Kuroshio Extension region and eventually warm the SST. The changes of wind stress in the interior North Pacific eventually generate SST warm anomalies in the Kuroshio Extension region several years later.
Using the multi-model datasets of 20C3M and the SRESA1B scenario projection from Program for Climate Model Diagnosis and Intercomparison for IPCC-AR4,we have investigated the sea surface temperature (SST) changes in the North Pacific and its response to wind stress changes in the North Pacific under different atmospheric greenhouse gases scenarios. The analysis shows that the SST will increase in most parts of the North Pacific as a result of the effect of higher atmospheric CO2 concentration,with the maximum increasing center located along the Kuroshio Extension region. We conclude that the warming in the SRESA1B scenario over the North Pacific especially along the Kuroshio Extension might be attributable to the stronger easterlies prevail in the central Pacific and poleward shift of the zero wind stress curl line. This Ekman response is local and fast. On the other hand,because the zero wind stress curl line displaced to higher latitudes,it generates stronger Kuroshio and its extention. It also generates anomalous Rossby waves at the latitude of zero wind stress curl line which propagate to the west. The Rossby waves change the thermocline in the Kuroshio Extension region and eventually warm the SST. The changes of wind stress in the interior North Pacific eventually generate SST warm anomalies in the Kuroshio Extension region several years later.
2014, 36(7): 17-26.
doi: 10.3969/j.issn.0253-4193.2014.04.003
Abstract:
There is a controversy about the role of Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO) in the Kuroshio intrusion into the South China Sea. In this study, we firstly analyzed the correlation of the subsurface high salinity water in the 120°E section and the North Equatorial Current Bifurcation(NEC-Y). Secondly, we analyzed the relation of Kuroshio intrusion index(KI index), North Equatorial Current index(NEC index)and the North Equatorial Current Bifurcation. Finally, we analyzed the pertinence of PDO index, Niño 3.4 index and the North Equatorial Current bifurcation by methods of EMD and correlation coefficient and analyzed the mechanism by NECP wind data. The result shows: (1) the NEC-Y has a well correlation with subsurface high salinity water in the 120°E section, the KI index and the NEC index. So the NEC-Y can been a good index of the strength of Kuroshio intrusion into the South China Sea; (2) there is a well 0.5 level of correlation coefficients between NEC-Y and the PDO index, the Niño 3.4 index. These well correlated coefficients show that both PDO and ENSO have important effect on the strength of Kuroshio intrusion into the South China Sea; (3) in El Niño (La Niña) year, a western (eastern) anomalous wind of the tropical Pacific causes a northward (southward) shift of the North Equatorial Current Bifurcation Latitude. This results in a weakened (enhanced) Kuroshio off Luzon, favoring Kuroshio intrusion into the South China Sea..While PDO is in the warm (cold) phase, the western (easern) anomalous wind will be strenghened in tropical Pacific and this will cause a northward(southward) shift of the North Equatorial Current Bifurcation Latitude too. So, the strength of Kuroshio intrusion into the South China Sea will be enhanced (weakened).
There is a controversy about the role of Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO) in the Kuroshio intrusion into the South China Sea. In this study, we firstly analyzed the correlation of the subsurface high salinity water in the 120°E section and the North Equatorial Current Bifurcation(NEC-Y). Secondly, we analyzed the relation of Kuroshio intrusion index(KI index), North Equatorial Current index(NEC index)and the North Equatorial Current Bifurcation. Finally, we analyzed the pertinence of PDO index, Niño 3.4 index and the North Equatorial Current bifurcation by methods of EMD and correlation coefficient and analyzed the mechanism by NECP wind data. The result shows: (1) the NEC-Y has a well correlation with subsurface high salinity water in the 120°E section, the KI index and the NEC index. So the NEC-Y can been a good index of the strength of Kuroshio intrusion into the South China Sea; (2) there is a well 0.5 level of correlation coefficients between NEC-Y and the PDO index, the Niño 3.4 index. These well correlated coefficients show that both PDO and ENSO have important effect on the strength of Kuroshio intrusion into the South China Sea; (3) in El Niño (La Niña) year, a western (eastern) anomalous wind of the tropical Pacific causes a northward (southward) shift of the North Equatorial Current Bifurcation Latitude. This results in a weakened (enhanced) Kuroshio off Luzon, favoring Kuroshio intrusion into the South China Sea..While PDO is in the warm (cold) phase, the western (easern) anomalous wind will be strenghened in tropical Pacific and this will cause a northward(southward) shift of the North Equatorial Current Bifurcation Latitude too. So, the strength of Kuroshio intrusion into the South China Sea will be enhanced (weakened).
2014, 36(7): 27-33.
doi: 10.3969/j.issn.0253-4193.2014.04.004
Abstract:
Statistical results indicate the relationships between the SST along the Kuroshio in previous winter and the summer precipitation in northeastern China have experienced a remarkable interdecadal variation. In the 1950s and 1960s,the correlation is positive but weak,while in recent two decades the counterpart is significantly negative. In the flood or drought events in northeastern China,the SST along the Kuroshio shows quite different features and can be used as a precursory signal in climate prediction operation. The possible influencing mechanism is also analyzed in this paper. It is found the lower SST along the Kuroshio will cause an abnormal anticyclone in the lower troposphere in summer owing to the persistence of the thermal conditions of the ocean. This abnormal anticyclone will lead to an abnormal northeastly in the northwest side of the western Pacific subtropical high (WPSTH) and an abnormal southwestly in the southeast part of the northeastern cold vortex (NECV),and result in an abnormal cyclone over the WPSTH and the NECV respectively. Thus the WPSTH is weakened while the NECV is strengthened. Under this circulation pattern,more summer precipitation will be found in northeastern China. On the contrary,the warmer SST along the Kuroshio will trigger an abnormal cyclone in the lower troposphere,and strengthen the WPSTH while weaken the NECV,and finally lead to less precipitation.
Statistical results indicate the relationships between the SST along the Kuroshio in previous winter and the summer precipitation in northeastern China have experienced a remarkable interdecadal variation. In the 1950s and 1960s,the correlation is positive but weak,while in recent two decades the counterpart is significantly negative. In the flood or drought events in northeastern China,the SST along the Kuroshio shows quite different features and can be used as a precursory signal in climate prediction operation. The possible influencing mechanism is also analyzed in this paper. It is found the lower SST along the Kuroshio will cause an abnormal anticyclone in the lower troposphere in summer owing to the persistence of the thermal conditions of the ocean. This abnormal anticyclone will lead to an abnormal northeastly in the northwest side of the western Pacific subtropical high (WPSTH) and an abnormal southwestly in the southeast part of the northeastern cold vortex (NECV),and result in an abnormal cyclone over the WPSTH and the NECV respectively. Thus the WPSTH is weakened while the NECV is strengthened. Under this circulation pattern,more summer precipitation will be found in northeastern China. On the contrary,the warmer SST along the Kuroshio will trigger an abnormal cyclone in the lower troposphere,and strengthen the WPSTH while weaken the NECV,and finally lead to less precipitation.
2014, 36(7): 34-44.
doi: 10.3969/j.issn.0253-4193.2014.04.005
Abstract:
The purpose of this paper was to investigate the method of retrieving ocean wave spectrum from GPS buoy sea surface height time series. GPS buoy,an innovative instrument on ocean topography measurement,played an important role in in-situ sea level measurements and satellite altimetry calibration during past years. This paper demonstrated the method and procedure of wave spectrum retrieval by simulation experiments. Firstly,the wave surface elevation time series were generated based on the Longuest model,and the statistical characteristics were constrained by the Pierson-Moscowitz wind wave spectrum,and the randomicities were introduced from the wave phase. Along with the simulated tide height and GPS buoy instrument noise time series,the 1 Hz (one point per second) random sea surface time series of 1 hour length were synthesized. Afterward,the simulated wave power spectrum was acquired by the auto-correlation function method,containing high-pass filter and compression. The simulated spectrum was pretty close to the theoretic one,and could fulfill the requirements of ocean wave spectrum retrieval. Finally,the retrieving method presented in this paper was validated by the in-situ GPS buoy campaign in the offshore of Shidao,Shandong Province. The study in this paper solved the key issues of the new technology,enriched the approaches of ocean wave spectrum retrieval,explored the application of GPS buoy,and could be served for China's forthcoming satellite radar wavimeter.
The purpose of this paper was to investigate the method of retrieving ocean wave spectrum from GPS buoy sea surface height time series. GPS buoy,an innovative instrument on ocean topography measurement,played an important role in in-situ sea level measurements and satellite altimetry calibration during past years. This paper demonstrated the method and procedure of wave spectrum retrieval by simulation experiments. Firstly,the wave surface elevation time series were generated based on the Longuest model,and the statistical characteristics were constrained by the Pierson-Moscowitz wind wave spectrum,and the randomicities were introduced from the wave phase. Along with the simulated tide height and GPS buoy instrument noise time series,the 1 Hz (one point per second) random sea surface time series of 1 hour length were synthesized. Afterward,the simulated wave power spectrum was acquired by the auto-correlation function method,containing high-pass filter and compression. The simulated spectrum was pretty close to the theoretic one,and could fulfill the requirements of ocean wave spectrum retrieval. Finally,the retrieving method presented in this paper was validated by the in-situ GPS buoy campaign in the offshore of Shidao,Shandong Province. The study in this paper solved the key issues of the new technology,enriched the approaches of ocean wave spectrum retrieval,explored the application of GPS buoy,and could be served for China's forthcoming satellite radar wavimeter.
2014, 36(7): 45-56.
doi: 10.3969/j.issn.0253-4193.2014.04.006
Abstract:
Adding skewness, a new second order echo model was derived according to the one of Amarouche. With respect to characteristics of HY-2A altimeter waveforms, six retracking schemes were derived with singular value decomposition filtering and different parameters wanted based on maximum likelihood estimation; After processing the data with five-parameter scheme, the proper skewness of elevation probability distribution function of scattering points was 0.15. According to comparisons between significant wave height from the six schemes and that from buoy, Jason-1 and HY-2A IDR, the accuracy of the schemes were analyzed, and the scheme MLE4_SVD (singular value decomposition filtering is conducted before retracking) was the better one for retrieving significant wave height from HY-2A altimeter retracking.
Adding skewness, a new second order echo model was derived according to the one of Amarouche. With respect to characteristics of HY-2A altimeter waveforms, six retracking schemes were derived with singular value decomposition filtering and different parameters wanted based on maximum likelihood estimation; After processing the data with five-parameter scheme, the proper skewness of elevation probability distribution function of scattering points was 0.15. According to comparisons between significant wave height from the six schemes and that from buoy, Jason-1 and HY-2A IDR, the accuracy of the schemes were analyzed, and the scheme MLE4_SVD (singular value decomposition filtering is conducted before retracking) was the better one for retrieving significant wave height from HY-2A altimeter retracking.
2014, 36(7): 57-69.
doi: 10.3969/j.issn.0253-4193.2014.04.007
Abstract:
Instrumented tripod observations of bottom boundary layer flows and sediment transport were conducted in the 2012 flood season in the Pearl River Estuary,South China. An inversion of high-frequency sediment concentration was performed based on the signal-to-noise ratio of the acoustical Doppler velocimeter with a sampling frequency of 64 Hz. Sediment concentration,upward flux of sediment diffusion,eddy viscosity and sediment diffusivity are highly tide-affected,with large values occurring during peak tides,and small ones during slack tides. Settling velocity of sediment particles is dependent on the power of sediment concentration,rather than linearly on sediment concentration. The analyses of turbulence bursting events demonstrated that ejection and sweep are the major momentum source of sediment diffusion. The sediment diffusion is predominately controlled by the amplitude of bursting events,irrespectively of the occurrence number and duration of turbulence events. The large-amplitude bursting events were found to be responsible for upward sediment diffusion.
Instrumented tripod observations of bottom boundary layer flows and sediment transport were conducted in the 2012 flood season in the Pearl River Estuary,South China. An inversion of high-frequency sediment concentration was performed based on the signal-to-noise ratio of the acoustical Doppler velocimeter with a sampling frequency of 64 Hz. Sediment concentration,upward flux of sediment diffusion,eddy viscosity and sediment diffusivity are highly tide-affected,with large values occurring during peak tides,and small ones during slack tides. Settling velocity of sediment particles is dependent on the power of sediment concentration,rather than linearly on sediment concentration. The analyses of turbulence bursting events demonstrated that ejection and sweep are the major momentum source of sediment diffusion. The sediment diffusion is predominately controlled by the amplitude of bursting events,irrespectively of the occurrence number and duration of turbulence events. The large-amplitude bursting events were found to be responsible for upward sediment diffusion.
2014, 36(7): 70-76.
doi: 10.3969/j.issn.0253-4193.2014.04.008
Abstract:
Gulf of Thailand experienced pre-rift, rift and post rift tectonic evolution stages. In sequence, there developed several rift basins. However, the northeast part was influenced by a reversion event, and stronger than other area. The wells in reversion structure and adjacent area and the seismic facies in this area were analyzed in this paper. Furthermore, we analyzed the sediment facies and tectonic evolution stages. It can be concluded that the tectonic style and sediment facies have great difference with adjacent area. Thus, there developed newpetroleum play innew exploration formation that has not been discovered: Eocene lacustrine shale acts as efficient source rock; Eocene-Oligocene deltaic sandstone acts as reservoir; Lower Miocene delta front shale and Upper Miocene Marine shale act as seals in this play. Eocene petroleum play has been drilled by exploration well in study area, which is proved as effective play in Gulf of Thailand area.
Gulf of Thailand experienced pre-rift, rift and post rift tectonic evolution stages. In sequence, there developed several rift basins. However, the northeast part was influenced by a reversion event, and stronger than other area. The wells in reversion structure and adjacent area and the seismic facies in this area were analyzed in this paper. Furthermore, we analyzed the sediment facies and tectonic evolution stages. It can be concluded that the tectonic style and sediment facies have great difference with adjacent area. Thus, there developed newpetroleum play innew exploration formation that has not been discovered: Eocene lacustrine shale acts as efficient source rock; Eocene-Oligocene deltaic sandstone acts as reservoir; Lower Miocene delta front shale and Upper Miocene Marine shale act as seals in this play. Eocene petroleum play has been drilled by exploration well in study area, which is proved as effective play in Gulf of Thailand area.
2014, 36(7): 77-89.
doi: 10.3969/j.issn.0253-4193.2014.04.009
Abstract:
Seamounts in the ocean are the main base of cobalt-rich ferromanganese crusts (hereinafter called crusts) mineralization. The distribution of crusts is not only influenced by large-scale macroscopic factors, for example the oxygen minimum zone, the carbonate compensation depth, biological productivity, ore-forming material sources and oxygen content of the seawater etc, but also controlled by small-scale factors of seamount topography, marine sedimentation and bottom current scouring. Based on in-depth study of ore formation and distribution of cobalt-rich crusts on the Seamount R, central Pacific mainly, those are discovered that crusts enrich in the shallower water on seamount, elevation of the summit, translation zone between summit and slope, saddle, ridge and upper slope are all favorable topography for crust mineralization with better quality and coverage, whereas the down slope, valley, flat region of the summit and subdued platform of the slope are pauvre of crusts, with smaller thickness and coverage, the mineralization of crusts is better in area with gradient less than 15°, optimal in 3° to 7°, and where with gradient larger than 15° will degressive, and become worst in cliff area, seamount topography have a fundamental influence on distribution and mineralization of the crusts, sedimentation and bottom current scouring play a part of obstruction and promotion individually, bottom current is the key factor to ensure long-term growth of crusts on lower gradient, the essence of controlling on crusts mineralization by seamount topography is a process to countermine sedimentation by cooperation between bottom current and topography.
Seamounts in the ocean are the main base of cobalt-rich ferromanganese crusts (hereinafter called crusts) mineralization. The distribution of crusts is not only influenced by large-scale macroscopic factors, for example the oxygen minimum zone, the carbonate compensation depth, biological productivity, ore-forming material sources and oxygen content of the seawater etc, but also controlled by small-scale factors of seamount topography, marine sedimentation and bottom current scouring. Based on in-depth study of ore formation and distribution of cobalt-rich crusts on the Seamount R, central Pacific mainly, those are discovered that crusts enrich in the shallower water on seamount, elevation of the summit, translation zone between summit and slope, saddle, ridge and upper slope are all favorable topography for crust mineralization with better quality and coverage, whereas the down slope, valley, flat region of the summit and subdued platform of the slope are pauvre of crusts, with smaller thickness and coverage, the mineralization of crusts is better in area with gradient less than 15°, optimal in 3° to 7°, and where with gradient larger than 15° will degressive, and become worst in cliff area, seamount topography have a fundamental influence on distribution and mineralization of the crusts, sedimentation and bottom current scouring play a part of obstruction and promotion individually, bottom current is the key factor to ensure long-term growth of crusts on lower gradient, the essence of controlling on crusts mineralization by seamount topography is a process to countermine sedimentation by cooperation between bottom current and topography.
2014, 36(7): 90-98.
doi: 10.3969/j.issn.0253-4193.2014.04.010
Abstract:
Based on the geological and geophysical data,including shallow stratigraphic profiles,multibeam and single-beam bathymetric data,and sidescan sonar photographs,the potential geohazards in the sea area near Nanpu-Caofeidian,Hebei Province were analysed and classified,the geohazard map and geomorphologic map of the study area are compiled,and studied the spatial distribution characteristics of the geohazards which are closely related to marine engineering,such as shallow gas,active sand waves,seafloor erosion,active fault,buried cross-bedded sand layers,steep slopes,steep scarps and grooves,are examined. The shallow gas,steep slopes and scarps are usually developed near the boundary between the gentle erosive-accumulative nearshore slope and steep erosive nearshore slope. Large-scales grooves and seafloor erosion are usually distributed in erosive shelf depression. In the other parts of the study area,geohazard types are less discovered,while active sand waves and buried cross-bedded sand layers are local found in the shelf area.
Based on the geological and geophysical data,including shallow stratigraphic profiles,multibeam and single-beam bathymetric data,and sidescan sonar photographs,the potential geohazards in the sea area near Nanpu-Caofeidian,Hebei Province were analysed and classified,the geohazard map and geomorphologic map of the study area are compiled,and studied the spatial distribution characteristics of the geohazards which are closely related to marine engineering,such as shallow gas,active sand waves,seafloor erosion,active fault,buried cross-bedded sand layers,steep slopes,steep scarps and grooves,are examined. The shallow gas,steep slopes and scarps are usually developed near the boundary between the gentle erosive-accumulative nearshore slope and steep erosive nearshore slope. Large-scales grooves and seafloor erosion are usually distributed in erosive shelf depression. In the other parts of the study area,geohazard types are less discovered,while active sand waves and buried cross-bedded sand layers are local found in the shelf area.
2014, 36(7): 99-110.
doi: 10.3969/j.issn.0253-4193.2014.04.011
Abstract:
The large estuarine sediment dynamic process has been the core content of the land ocean interactions in the coastal zone research. The vertical exchange for sediments in the different water depth of the estuary is a key in the analysis of estuarine dynamics and deposition mechanism. Here,a large-scale and dense sediment samples cruise of the Changjiang (Yangtze) Estuary was carried out in December 2011,where three sets with 303 sediment samples including suspended sediment near the bottom,surface deposition with a vertical thickness of 1 to 2 cm,and subsurface deposition with a vertical thickness of 2 to 10 cm were simultaneously taken by grabber instrument. Thereafter,based on the collected sediment samples,the empirical orthogonal function method was applied to discuss the exchange process of the suspended load near the bottom and bed sediments. The results are shown as follows: the spatial distribution patterns of the suspended load near the bottom of the Changjiang Estuary are mainly composed of silt with a small difference in spatial distributions. The spatial distribution patterns of surface bed sediments and subsurface bed sediments are similar with regional characteristics. Their spatial distributions are more complex than that of the suspended load near the bottom. In the central district of Nanhui Shoal,sediments were characterized by coarse silt and fine sand,and the sediments distributed in other areas were characterized by silt. Furthermore,the first mode of the sediments by EOF could mainly reflect the sediments movement of fine particle size,and the second mode mainly reflects the sediments movement of coarse particle size. The vertical exchange between the suspended load and the surface bed sediments with main grain size is silt components. However,during the exchange process between the surface bed sediments and subsurface bed sediments in the central district of Nanhui Shoal,the dominant exchange component is coarse silt,and fine sand exchange occurred in other regions. Taken altogether,grain size with silt components of the Changjiang Estuary should play a dominant role in bed sediments exchange process.
The large estuarine sediment dynamic process has been the core content of the land ocean interactions in the coastal zone research. The vertical exchange for sediments in the different water depth of the estuary is a key in the analysis of estuarine dynamics and deposition mechanism. Here,a large-scale and dense sediment samples cruise of the Changjiang (Yangtze) Estuary was carried out in December 2011,where three sets with 303 sediment samples including suspended sediment near the bottom,surface deposition with a vertical thickness of 1 to 2 cm,and subsurface deposition with a vertical thickness of 2 to 10 cm were simultaneously taken by grabber instrument. Thereafter,based on the collected sediment samples,the empirical orthogonal function method was applied to discuss the exchange process of the suspended load near the bottom and bed sediments. The results are shown as follows: the spatial distribution patterns of the suspended load near the bottom of the Changjiang Estuary are mainly composed of silt with a small difference in spatial distributions. The spatial distribution patterns of surface bed sediments and subsurface bed sediments are similar with regional characteristics. Their spatial distributions are more complex than that of the suspended load near the bottom. In the central district of Nanhui Shoal,sediments were characterized by coarse silt and fine sand,and the sediments distributed in other areas were characterized by silt. Furthermore,the first mode of the sediments by EOF could mainly reflect the sediments movement of fine particle size,and the second mode mainly reflects the sediments movement of coarse particle size. The vertical exchange between the suspended load and the surface bed sediments with main grain size is silt components. However,during the exchange process between the surface bed sediments and subsurface bed sediments in the central district of Nanhui Shoal,the dominant exchange component is coarse silt,and fine sand exchange occurred in other regions. Taken altogether,grain size with silt components of the Changjiang Estuary should play a dominant role in bed sediments exchange process.
2014, 36(7): 111-117.
doi: 10.3969/j.issn.0253-4193.2014.04.012
Abstract:
To describe a longitudinal wave velocity of seafloor sediments,a ratio of the density variation (RDV) and a ratio of the effective elastic modulus variation (REEMV) are introduced,and then we conclude that the ratio of density variation is a composite parameter consisting of porosity,seawater density and density of solid phase of seafloor sediment. The longitudinal wave velocity can be expressed as a Taylor polynomial function of both the RDV and the REEMV. On basis of univariate analysis,the longitudinal wave velocity can be also written as a product of a reference wave velocity and a modulation function,and the theoretical results show that the reference wave velocity is determined by the physical properties of seafloor sediments,and a theoretical model of the composite parameter-longitudinal wave velocity is attained. By means of the model,the analysis of the some main presented empirical formulas of longitudinal wave velocity as a function of porosity shows that the reference wave velocity of these formulas are different each other but the modulation functions derived from these formulas are mutually equivalent. It shows that the proposed relationship between longitudinal wave velocity and physical-mechanical properties of seafloor sediments has turned out to be valid.
To describe a longitudinal wave velocity of seafloor sediments,a ratio of the density variation (RDV) and a ratio of the effective elastic modulus variation (REEMV) are introduced,and then we conclude that the ratio of density variation is a composite parameter consisting of porosity,seawater density and density of solid phase of seafloor sediment. The longitudinal wave velocity can be expressed as a Taylor polynomial function of both the RDV and the REEMV. On basis of univariate analysis,the longitudinal wave velocity can be also written as a product of a reference wave velocity and a modulation function,and the theoretical results show that the reference wave velocity is determined by the physical properties of seafloor sediments,and a theoretical model of the composite parameter-longitudinal wave velocity is attained. By means of the model,the analysis of the some main presented empirical formulas of longitudinal wave velocity as a function of porosity shows that the reference wave velocity of these formulas are different each other but the modulation functions derived from these formulas are mutually equivalent. It shows that the proposed relationship between longitudinal wave velocity and physical-mechanical properties of seafloor sediments has turned out to be valid.
2014, 36(7): 118-124.
doi: 10.3969/j.issn.0253-4193.2014.04.013
Abstract:
In this paper, the sediment motion at north passage has been analyzed on the basis of the observations of water current and sediment concentration before and after the third phase engineering of the deep waterways in Changjiang Estuary. The result shows that:the distribution of the sediment concentration of north passage in both flood and dry season appears low-high-low pattern from the upper stream to the down stream where the midstream region of north passage has the highest sediment concentration. The correlation of sediment concentration and water current averaged in a tide cycle is poor in the flood season so that the sediment advection.plays a more important role in north passage while in the dry season, the correlation is good so that the sediment suspension plays more. The main form of sediment transport in north passage is the lagrangian advection. The net sediment transport in the flood season is bigger than the dry season. The tidal pumping effect as well as the vertical-circulation effect are big in the midstream of north passage in the flood season while in the dry season, they are so small that make the water and sediment move nearly in the same direction excluding the upper stream of north passage. The reason that the tidal pumping effect as well as the vertical-circulation effect play an important roles in the midstream of north passage is that the sediment exchanging is very frequent in the midstream of north passage where there exist a high concentration of sediment flowed into north passage generated from both the mouth bar of south passage and Jiuduansha tidal shoal in a flood tide.
In this paper, the sediment motion at north passage has been analyzed on the basis of the observations of water current and sediment concentration before and after the third phase engineering of the deep waterways in Changjiang Estuary. The result shows that:the distribution of the sediment concentration of north passage in both flood and dry season appears low-high-low pattern from the upper stream to the down stream where the midstream region of north passage has the highest sediment concentration. The correlation of sediment concentration and water current averaged in a tide cycle is poor in the flood season so that the sediment advection.plays a more important role in north passage while in the dry season, the correlation is good so that the sediment suspension plays more. The main form of sediment transport in north passage is the lagrangian advection. The net sediment transport in the flood season is bigger than the dry season. The tidal pumping effect as well as the vertical-circulation effect are big in the midstream of north passage in the flood season while in the dry season, they are so small that make the water and sediment move nearly in the same direction excluding the upper stream of north passage. The reason that the tidal pumping effect as well as the vertical-circulation effect play an important roles in the midstream of north passage is that the sediment exchanging is very frequent in the midstream of north passage where there exist a high concentration of sediment flowed into north passage generated from both the mouth bar of south passage and Jiuduansha tidal shoal in a flood tide.
2014, 36(7): 125-132.
doi: 10.3969/j.issn.0253-4193.2014.04.014
Abstract:
In order to improve the consistency of sea surface wind speed (SSWS) data from different satellite altimeters,the SSWS data from the HY-2A,T/P,GFO,Jason-1,Envisat,Jason-2,and CryoSat-2 satellite altimeter are collected,and compared with NDBC buoy data. Then,the calibration formulas are given,and the calibration results are investigated. The results show that both the mean values (MVs) and root mean squares (RMSs) of the differences between the SSWS data from the satellite altimeters and the buoys decrease after the calibrations,and the case of the HY-2A satellite altimeter is most remarkable. The MVs are within ±0.2 m/s,and the RMSs are below 1.6m/s except the HY-2A,GFO,and Jason-1 satellite altimeters. Therefore,the calibration formulas presented in this paper are useful for reducing the differences between the SSWS data from the satellite altimeters and the buoys (especially for HY-2A satellite altimeter).
In order to improve the consistency of sea surface wind speed (SSWS) data from different satellite altimeters,the SSWS data from the HY-2A,T/P,GFO,Jason-1,Envisat,Jason-2,and CryoSat-2 satellite altimeter are collected,and compared with NDBC buoy data. Then,the calibration formulas are given,and the calibration results are investigated. The results show that both the mean values (MVs) and root mean squares (RMSs) of the differences between the SSWS data from the satellite altimeters and the buoys decrease after the calibrations,and the case of the HY-2A satellite altimeter is most remarkable. The MVs are within ±0.2 m/s,and the RMSs are below 1.6m/s except the HY-2A,GFO,and Jason-1 satellite altimeters. Therefore,the calibration formulas presented in this paper are useful for reducing the differences between the SSWS data from the satellite altimeters and the buoys (especially for HY-2A satellite altimeter).
2014, 36(7): 133-141.
doi: 10.3969/j.issn.0253-4193.2014.04.015
Abstract:
The selected area in this paper is located in the south of the Cheju Island. The study area is part of the Yellow Sea Trough extends to the Okinawa Trough and it's in the pathway of the Yellow Warm Current which is one of the branches of the Kuroshio Warm Current. Its seabed sonar image processing analysis and acoustic seabed classification research,contribute to a comprehensive understanding of the characteristics of the channel seabed bedforms surface texture and sediment distribution pattern. With the high-precision multibeam echo sounder sonar data in the research area,we apply image processing techniques and methods and get the seabed sonar image,then we can do quantitative description and analysis to the seabed surface texture features. Based on multibeam echo sounder backscatter strength data and 19 geological seabed sediment sample data,a statistical model which presents the relationship between seabed backscatter signal and sediment type is set up. Using improved Learning Vector Quantization neural network methods,a fast and accurate automatic identification for three seabed sediment types (TS,YS,STY) implementation is feasible.
The selected area in this paper is located in the south of the Cheju Island. The study area is part of the Yellow Sea Trough extends to the Okinawa Trough and it's in the pathway of the Yellow Warm Current which is one of the branches of the Kuroshio Warm Current. Its seabed sonar image processing analysis and acoustic seabed classification research,contribute to a comprehensive understanding of the characteristics of the channel seabed bedforms surface texture and sediment distribution pattern. With the high-precision multibeam echo sounder sonar data in the research area,we apply image processing techniques and methods and get the seabed sonar image,then we can do quantitative description and analysis to the seabed surface texture features. Based on multibeam echo sounder backscatter strength data and 19 geological seabed sediment sample data,a statistical model which presents the relationship between seabed backscatter signal and sediment type is set up. Using improved Learning Vector Quantization neural network methods,a fast and accurate automatic identification for three seabed sediment types (TS,YS,STY) implementation is feasible.
2014, 36(7): 142-148.
doi: 10.3969/j.issn.0253-4193.2014.04.016
Abstract:
There exist a series of submarine mounds (50 to 100 m higher above the surrounding seafloor) on the deepwater (600 to 1000 m) slope area between the southwestern Dongsha Islands and the eastern Baiyun sag, revealed by some Multi-channel seismic reflection and CHIRP subbottom profiles. The strata within these mounds have suffered folding and showed chaotic or weak reflections and seriously acoustic masking effects. CHIRP subbottom profiles also showed gas plumes up to 50 m have been developed within the mounds, which reflect there may exist ongoing muddy volcanism. Sedimentary studies showed that some biogenic carbonate nodules distributed on the surface of the mounds. Based on evidences mentioned above, it can be inferred that these mounds southwest of Dongsha Islands are mud volcanoes which may be an important prospecting area for gas hydrates. These mud volcanoes showed characteristics of tectonically compression and banded distribution, which are different from gas hydrate-bearing non-mud volcanoes in the Shenhu area and the Jiulong Methane Reef area and mud volcanoes in other typical passive continental margins in the world. The origin and the potential for gas hydrates of the mounds southwest Dongsha islands are still in debate, and need to be further studied.
There exist a series of submarine mounds (50 to 100 m higher above the surrounding seafloor) on the deepwater (600 to 1000 m) slope area between the southwestern Dongsha Islands and the eastern Baiyun sag, revealed by some Multi-channel seismic reflection and CHIRP subbottom profiles. The strata within these mounds have suffered folding and showed chaotic or weak reflections and seriously acoustic masking effects. CHIRP subbottom profiles also showed gas plumes up to 50 m have been developed within the mounds, which reflect there may exist ongoing muddy volcanism. Sedimentary studies showed that some biogenic carbonate nodules distributed on the surface of the mounds. Based on evidences mentioned above, it can be inferred that these mounds southwest of Dongsha Islands are mud volcanoes which may be an important prospecting area for gas hydrates. These mud volcanoes showed characteristics of tectonically compression and banded distribution, which are different from gas hydrate-bearing non-mud volcanoes in the Shenhu area and the Jiulong Methane Reef area and mud volcanoes in other typical passive continental margins in the world. The origin and the potential for gas hydrates of the mounds southwest Dongsha islands are still in debate, and need to be further studied.
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