2017 Vol. 39, No. 7
Display Method:
2017, 39(7): .
Abstract:
2017, 39(7): 1-11.
doi: 10.3969/j.issn.0253-4193.2017.07.001
Abstract:
Seafloor is an important boundary for underwater sound field, and its acoustic scattering property has significant influence to spatial structure and distribution of underwater sound field. In this paper, we systematically analyzed and summarized the present progress on the measuring techniques, mechanism and modeling of bottom acoustic scattering property in the world. In addition, some research directions and topics which should be paid more attention to in the future were put forwarded as well as some research difficulties. This work will have great contribution to further studying and understanding the present status and the future trend of the research on bottom acoustic scattering property.
Seafloor is an important boundary for underwater sound field, and its acoustic scattering property has significant influence to spatial structure and distribution of underwater sound field. In this paper, we systematically analyzed and summarized the present progress on the measuring techniques, mechanism and modeling of bottom acoustic scattering property in the world. In addition, some research directions and topics which should be paid more attention to in the future were put forwarded as well as some research difficulties. This work will have great contribution to further studying and understanding the present status and the future trend of the research on bottom acoustic scattering property.
2017, 39(7): 12-25.
doi: 10.3969/j.issn.0253-4193.2017.07.002
Abstract:
Ripple microtopography prevalently exist on coastal beds, which significantly change the bottom stress and then influence the sediment transport. Previous researchers mainly study the wave-dominant ripples and have applied them to the wave modelling. Wave-current combined flow is rarely discussed to generate ripples, and the combined flow-dominant ripples are rarely implemented to hydrodynamic and sediment models. We embedded the University of New South Wales sediment model into the POM model, and connected them with a wave-current interaction bottom boundary model coupled with a microtopography module under combined flow. We developed a wave-current-microtopography coupled model of sedimentology dynamics, and applied this coupled model to Jervis Bay, Australia. Developing stages and types are modeled, and the ripple height and length are simulated. The suspended sediment transport was analyzed under wave-dominant and combined flow separately. Simulated results show that the wave-dominant ripples have longer height and length. Therefore, ripples place an important role on suspended sediment when waves dominate. Through considering roughness that varies with microtopography, this model can predict the abrupt rising of suspended sediment concentration rather than setting an average uniform roughness.
Ripple microtopography prevalently exist on coastal beds, which significantly change the bottom stress and then influence the sediment transport. Previous researchers mainly study the wave-dominant ripples and have applied them to the wave modelling. Wave-current combined flow is rarely discussed to generate ripples, and the combined flow-dominant ripples are rarely implemented to hydrodynamic and sediment models. We embedded the University of New South Wales sediment model into the POM model, and connected them with a wave-current interaction bottom boundary model coupled with a microtopography module under combined flow. We developed a wave-current-microtopography coupled model of sedimentology dynamics, and applied this coupled model to Jervis Bay, Australia. Developing stages and types are modeled, and the ripple height and length are simulated. The suspended sediment transport was analyzed under wave-dominant and combined flow separately. Simulated results show that the wave-dominant ripples have longer height and length. Therefore, ripples place an important role on suspended sediment when waves dominate. Through considering roughness that varies with microtopography, this model can predict the abrupt rising of suspended sediment concentration rather than setting an average uniform roughness.
2017, 39(7): 26-35.
doi: 10.3969/j.issn.0253-4193.2017.07.003
Abstract:
It is necessary to analyze the characteristics of longshore current instability by using the nonlinear instability model when wave height reaches a finite amplitude. Building and verifying the nonlinear instability mathematical model of longshore current, this paper discusses the influences of model parameters and obtains the value of model parameters corresponding to the experimental result. The development process and its characteristics of longshore current instability in experiment are simulated and illustrated by the mathematical model. Key innovations include:(1) the smaller the bottom friction coefficient and lateral mixing coefficient, the sooner the instability occurrence, the bigger the fluctuation amplitude is; (2) the evolution processes of longshore current include five stages (linear, double period, larger period, wave group and irregular stages). The longshore current instability in the experiment occurs in stages of linear or double period. The vortex in double period stage forms by the vortexes in the linear stage which catch, match and merge one another. The match of vortex occurs in collision, the major energy transfers to trace wave and spreads along the coast at a slower rate of vortex.
It is necessary to analyze the characteristics of longshore current instability by using the nonlinear instability model when wave height reaches a finite amplitude. Building and verifying the nonlinear instability mathematical model of longshore current, this paper discusses the influences of model parameters and obtains the value of model parameters corresponding to the experimental result. The development process and its characteristics of longshore current instability in experiment are simulated and illustrated by the mathematical model. Key innovations include:(1) the smaller the bottom friction coefficient and lateral mixing coefficient, the sooner the instability occurrence, the bigger the fluctuation amplitude is; (2) the evolution processes of longshore current include five stages (linear, double period, larger period, wave group and irregular stages). The longshore current instability in the experiment occurs in stages of linear or double period. The vortex in double period stage forms by the vortexes in the linear stage which catch, match and merge one another. The match of vortex occurs in collision, the major energy transfers to trace wave and spreads along the coast at a slower rate of vortex.
2017, 39(7): 36-42.
doi: 10.3969/j.issn.0253-4193.2017.07.004
Abstract:
Tidal asymmetry and tide-induced residual circulation play important roles in mass transport in estuarine and coastal seas. Previous studies have shown that the flood and ebb duration asymmetry corresponds well to the tidal velocity asymmetry in estuaries and embayments where standing tidal waves dominate. The tide-induced residual circulation is mainly from the nonlinear interaction between tides and bathymetry. This study takes the Yinggehai Coast as an example to study the tidal asymmetry and residual circulation in open coast with complex bathymetry, through combination of field observation and numerical simulation. Our results show that the flood duration is shorter than the ebb duration, while the velocity asymmetry manifests a complex spatial variability. The underlying mechanisms are that the velocity asymmetry is mainly induced by the interactions among K1, O1, and M2 and the interactions among the residual flow and tidal constituents. The former contribution results in a flood dominance, while the latter contribution results in a spatial distribution similar to the residual current. Overall, the interactions among the residual current and tidal constituents determine the pattern of the velocity asymmetry. For the tide-induced residual current, the Euler residual is greatly stronger than the Stokes one. There exist many clockwise and anti-clockwise eddies in the study site, and the clockwise eddies are generally associated with the tidal sand ridges well, while the anti-clockwise eddies are located in the deep troughs. The conservation of potential vorticity largely determines the residual circulation pattern, along with the bottom friction playing a critical role as well.
Tidal asymmetry and tide-induced residual circulation play important roles in mass transport in estuarine and coastal seas. Previous studies have shown that the flood and ebb duration asymmetry corresponds well to the tidal velocity asymmetry in estuaries and embayments where standing tidal waves dominate. The tide-induced residual circulation is mainly from the nonlinear interaction between tides and bathymetry. This study takes the Yinggehai Coast as an example to study the tidal asymmetry and residual circulation in open coast with complex bathymetry, through combination of field observation and numerical simulation. Our results show that the flood duration is shorter than the ebb duration, while the velocity asymmetry manifests a complex spatial variability. The underlying mechanisms are that the velocity asymmetry is mainly induced by the interactions among K1, O1, and M2 and the interactions among the residual flow and tidal constituents. The former contribution results in a flood dominance, while the latter contribution results in a spatial distribution similar to the residual current. Overall, the interactions among the residual current and tidal constituents determine the pattern of the velocity asymmetry. For the tide-induced residual current, the Euler residual is greatly stronger than the Stokes one. There exist many clockwise and anti-clockwise eddies in the study site, and the clockwise eddies are generally associated with the tidal sand ridges well, while the anti-clockwise eddies are located in the deep troughs. The conservation of potential vorticity largely determines the residual circulation pattern, along with the bottom friction playing a critical role as well.
2017, 39(7): 43-52.
doi: 10.3969/j.issn.0253-4193.2017.07.005
Abstract:
The ECMWF ORAS4 reanalysis is used to study the low-frequency variation in sea level in the tropical Pacific in this paper. The first mode of interannual sea level variation in the tropical Pacific reflects the burst of El Niño. The sea level change in the tropical eastern Pacific is opposite to that in the tropical western Pacific, and the principal component of the first mode is highly correlated with the Niño3.4 index. The second mode shows the warm water transport process during the El Niño. The locations where the warm water gathered in before El Niño, and the positions where the warm water started to transport to high latitude are different in the two types of El Niño events. Besides, there is a remarkable decadal change in the cycles of ENSO, and this is linked with the decadal variation in the tropical Pacific. The sea level trends are also affected by the decadal variation. The high rise (descend) rate after 1993 that observed by altimeter is caused by the phase-switching.
The ECMWF ORAS4 reanalysis is used to study the low-frequency variation in sea level in the tropical Pacific in this paper. The first mode of interannual sea level variation in the tropical Pacific reflects the burst of El Niño. The sea level change in the tropical eastern Pacific is opposite to that in the tropical western Pacific, and the principal component of the first mode is highly correlated with the Niño3.4 index. The second mode shows the warm water transport process during the El Niño. The locations where the warm water gathered in before El Niño, and the positions where the warm water started to transport to high latitude are different in the two types of El Niño events. Besides, there is a remarkable decadal change in the cycles of ENSO, and this is linked with the decadal variation in the tropical Pacific. The sea level trends are also affected by the decadal variation. The high rise (descend) rate after 1993 that observed by altimeter is caused by the phase-switching.
2017, 39(7): 53-69.
doi: 10.3969/j.issn.0253-4193.2017.07.006
Abstract:
The possible influence of sea surface temperature (SST) anomalies over the tropical Pacific on the Arctic sea ice and their possible mechanisms are researched from atmospheric circulation and net surface heat flux by using monthly data of HadISST and NCEP/NCAR spanning from 1950 to 2015. The main results obtained show that during summer and autumn of ENSO development phase, EP and CP El Niño events have no apparent connection with the Arctic sea ice anomalies. However, strong signals are detected when it happens to La Niña and there are distinctive differences between EP and CP events.Sea ice reduce in Barents/Kara Sea in EP La Niña but increase in East Siberia/Chukchi Sea in CP La Niña. During summer and autumn of EP La Niña's development, SST anomalies over the tropical Pacific leads to negative SLP in Barents/Kara Sea by teleconnection wave trains and forms AO-like pattern together with positive SLP in middle latitude. It changes the wind which brings warm advection and southerly anomalies helps to transfer more warm water from North Atlantic, high water vapor content at the same time enhance the income of net surface heat flux and result in the decrease of sea ice in Barents/Kara Sea. In the situation of CP La Niña, East Siberia/Chukchi Sea are dominated by north wind in summer because of a cyclonic circulation in the eastern side, sea ice are transported here from North Pole and thus sea ice concentration increased, effect of net surface heat flux is small.
The possible influence of sea surface temperature (SST) anomalies over the tropical Pacific on the Arctic sea ice and their possible mechanisms are researched from atmospheric circulation and net surface heat flux by using monthly data of HadISST and NCEP/NCAR spanning from 1950 to 2015. The main results obtained show that during summer and autumn of ENSO development phase, EP and CP El Niño events have no apparent connection with the Arctic sea ice anomalies. However, strong signals are detected when it happens to La Niña and there are distinctive differences between EP and CP events.Sea ice reduce in Barents/Kara Sea in EP La Niña but increase in East Siberia/Chukchi Sea in CP La Niña. During summer and autumn of EP La Niña's development, SST anomalies over the tropical Pacific leads to negative SLP in Barents/Kara Sea by teleconnection wave trains and forms AO-like pattern together with positive SLP in middle latitude. It changes the wind which brings warm advection and southerly anomalies helps to transfer more warm water from North Atlantic, high water vapor content at the same time enhance the income of net surface heat flux and result in the decrease of sea ice in Barents/Kara Sea. In the situation of CP La Niña, East Siberia/Chukchi Sea are dominated by north wind in summer because of a cyclonic circulation in the eastern side, sea ice are transported here from North Pole and thus sea ice concentration increased, effect of net surface heat flux is small.
2017, 39(7): 70-79.
doi: 10.3969/j.issn.0253-4193.2017.07.007
Abstract:
A superimposed wind field is constructed using empirical wind fields and NCEP reanalyzed wind fields from the advantages and disadvantages of the two, and the simulation result is good compared with the real wind field data. Eight typhoons greatly affecting the South China Sea is simulated using WAVEWATCH Ⅲ based on the superimposed wind field data, the superimposed wind field has shown higher accurate and more reliable in simulating typhoon-induced waves.
A superimposed wind field is constructed using empirical wind fields and NCEP reanalyzed wind fields from the advantages and disadvantages of the two, and the simulation result is good compared with the real wind field data. Eight typhoons greatly affecting the South China Sea is simulated using WAVEWATCH Ⅲ based on the superimposed wind field data, the superimposed wind field has shown higher accurate and more reliable in simulating typhoon-induced waves.
2017, 39(7): 80-91.
doi: 10.3969/j.issn.0253-4193.2017.07.008
Abstract:
To speculate about the hydrodynamic process and sediment transport within the intertidal zone, we conducted a two-day survey in the Eastern Chongming Island in April, 2014 during a spring tide. Four tripods were deployed in three main morphological domains:one in the salt marshes, one in the mudflats and two in the tidal creeks. Our results show that:(1) the median particle size of surficial sediment in the creeks is 21.7 μm and is finer than that in the salt marshes and mudflats which is 33.0 μm. The particle size of suspended sediment decreases landward; (2) the dominant currents are rectilinear currents in the tidal creeks while are often rotational flows in the flats. The average vertical velocity in the lateral, creek, salt marsh, and mudflat is 15.4 cm/s, 34.6 cm/s, 11.3 cm/s, and 28.9 cm/s, respectively; (3) the highest suspended sediment concentration appears in the early flood periods in the tidal creeks while occurs during slack water or in the middle of the ebb periods in the flats. The suspended sediment in the tidal creeks mostly derives from adjacent sea rather than resuspension which is the main suspended sediment source in the flats; (4) over a tidal cycle, net landward sediment transport is observed in the creeks and the average sediment flux per tidal cycle could be 4.0 t/m. There is also a net import of sediment with 1.0 t/m per tidal cycle driven through the salt marsh. On the contrary, the net sediment flux in the mudflat is seaward along the creek and the dominant sediment transport in the mudflat is perpendicular to the creek rather than along the creek which the lateral, creek and salt marsh are. Our results also indicate that the salt marshes experience deposition while the mudflats are eroded in our study site.
To speculate about the hydrodynamic process and sediment transport within the intertidal zone, we conducted a two-day survey in the Eastern Chongming Island in April, 2014 during a spring tide. Four tripods were deployed in three main morphological domains:one in the salt marshes, one in the mudflats and two in the tidal creeks. Our results show that:(1) the median particle size of surficial sediment in the creeks is 21.7 μm and is finer than that in the salt marshes and mudflats which is 33.0 μm. The particle size of suspended sediment decreases landward; (2) the dominant currents are rectilinear currents in the tidal creeks while are often rotational flows in the flats. The average vertical velocity in the lateral, creek, salt marsh, and mudflat is 15.4 cm/s, 34.6 cm/s, 11.3 cm/s, and 28.9 cm/s, respectively; (3) the highest suspended sediment concentration appears in the early flood periods in the tidal creeks while occurs during slack water or in the middle of the ebb periods in the flats. The suspended sediment in the tidal creeks mostly derives from adjacent sea rather than resuspension which is the main suspended sediment source in the flats; (4) over a tidal cycle, net landward sediment transport is observed in the creeks and the average sediment flux per tidal cycle could be 4.0 t/m. There is also a net import of sediment with 1.0 t/m per tidal cycle driven through the salt marsh. On the contrary, the net sediment flux in the mudflat is seaward along the creek and the dominant sediment transport in the mudflat is perpendicular to the creek rather than along the creek which the lateral, creek and salt marsh are. Our results also indicate that the salt marshes experience deposition while the mudflats are eroded in our study site.
2017, 39(7): 92-101.
doi: 10.3969/j.issn.0253-4193.2017.07.009
Abstract:
Based on the data of grain size and trace elements coupled with high-precise AMS14C dating, this paper dealed with the provenance and sediment environment evolution of the middle Okinawa Trough for the last 5 300 a with the sample from the Core HOBAB2-S2. The analysis on REE and trace elements showed their affinities to the terrigenous sediments in the study area. In combination with REE parameters of potential sediment sources, the sediments were mainly originated from Taiwan. The grain size was used to be the indicators of sediment environment, especially the vigor of local current(the current was mainly referred to Kuroshio Current in this paper). The conclusions were summarized as follows. Four periods were divided. During the first period(5.30-3.81 ka BP), grain size was getting finer, which indicated the Kuroshio Current weakened gradually. In the period of 3.18-2.70 ka BP, the garin size showed distinct change and we can deduce that the sediments suffered a relative volatility period. During the third period, from 2.70 ka BP to 0.97 ka BP, the environment was stable inferred from the grain size with little changes. Since 0.97 ka BP, the sediments grain size was larger than before and indicated the enhance of the strength of Kuroshio Current.
Based on the data of grain size and trace elements coupled with high-precise AMS14C dating, this paper dealed with the provenance and sediment environment evolution of the middle Okinawa Trough for the last 5 300 a with the sample from the Core HOBAB2-S2. The analysis on REE and trace elements showed their affinities to the terrigenous sediments in the study area. In combination with REE parameters of potential sediment sources, the sediments were mainly originated from Taiwan. The grain size was used to be the indicators of sediment environment, especially the vigor of local current(the current was mainly referred to Kuroshio Current in this paper). The conclusions were summarized as follows. Four periods were divided. During the first period(5.30-3.81 ka BP), grain size was getting finer, which indicated the Kuroshio Current weakened gradually. In the period of 3.18-2.70 ka BP, the garin size showed distinct change and we can deduce that the sediments suffered a relative volatility period. During the third period, from 2.70 ka BP to 0.97 ka BP, the environment was stable inferred from the grain size with little changes. Since 0.97 ka BP, the sediments grain size was larger than before and indicated the enhance of the strength of Kuroshio Current.
2017, 39(7): 102-109.
doi: 10.3969/j.issn.0253-4193.2017.07.010
Abstract:
The drilling of well CSDP-02 of the "Continental Shelf Drilling Program" creates a new situation for the exploration of Mesozoic-Paleozoic reservoir on the central uplift of the South Yellow Sea Basin. In this study, based on the spectrum analysis of Mesozoic-Paleozoic strata, as well as the multi-trace seismic, logging and core data of Well CSDP-02, S-transform is applied to multi-trace seismic data from Mesozoic-Paleozoic strata of the central uplift to get different instantaneous frequency volumes. The results show that, the three possible reservoirs of Qinglong Formation, Dalong-Longtan Formation and Chihsia Formation-Carboniferous all show low frequency anomalies with a Spectrum analysis showing low frequency low intensity or high frequency low intensity anomalies. At high frequency section, the reservoirs standout from surrounding geology and shallow layers are also bright at such high frequency, which will deteriorate the likelihood to identify the anomalies of target layer from iso-frequency sections. Compared with core description of Well CSDP-02, the low frequency anomalies are related with oil immersion layer observed from well sample, which has a great significance for the exploration of Mesozoic-Paleozoic layer of the South Yellow Sea Basin.
The drilling of well CSDP-02 of the "Continental Shelf Drilling Program" creates a new situation for the exploration of Mesozoic-Paleozoic reservoir on the central uplift of the South Yellow Sea Basin. In this study, based on the spectrum analysis of Mesozoic-Paleozoic strata, as well as the multi-trace seismic, logging and core data of Well CSDP-02, S-transform is applied to multi-trace seismic data from Mesozoic-Paleozoic strata of the central uplift to get different instantaneous frequency volumes. The results show that, the three possible reservoirs of Qinglong Formation, Dalong-Longtan Formation and Chihsia Formation-Carboniferous all show low frequency anomalies with a Spectrum analysis showing low frequency low intensity or high frequency low intensity anomalies. At high frequency section, the reservoirs standout from surrounding geology and shallow layers are also bright at such high frequency, which will deteriorate the likelihood to identify the anomalies of target layer from iso-frequency sections. Compared with core description of Well CSDP-02, the low frequency anomalies are related with oil immersion layer observed from well sample, which has a great significance for the exploration of Mesozoic-Paleozoic layer of the South Yellow Sea Basin.
2017, 39(7): 110-123.
doi: 10.3969/j.issn.0253-4193.2017.07.011
Abstract:
Mesoscale eddies are a prominent dynamic phenomenon in the ocean with complex and continuous changes during lifecycles. It has become a research focus to investigate eddy propagation characteristics using data driven techniques. From the perspective that eddy trajectories collectively create a spatial network, this study presents a community detection method to uncover latent clusters of eddy activities. The creation of the mobility network is achieved by dividing the study area, the South China Sea, into regular grids and projecting eddy trajectories obtained from 1992 to 2011 to this grid-like network with stop locations as nodes and transitions as edges. The trajectories are preprocessed and generalized at four different granularities:trajectory partitions (TP), origin-destination transitions (OD), minimum description length (MDL), and regeneration of strong processes (RSP). Then, a fast unfolding algorithm is applied to the networks created at different granularities to discover potential communities. Finally, the relationships between different communities are visually analyzed using the chord diagram. The results show that the RSP data of eddy tracks overcome the data insufficiency in TP-network, and the method is able to identify major paths and clustering patterns of eddy activities throughout the life from the RSP data.
Mesoscale eddies are a prominent dynamic phenomenon in the ocean with complex and continuous changes during lifecycles. It has become a research focus to investigate eddy propagation characteristics using data driven techniques. From the perspective that eddy trajectories collectively create a spatial network, this study presents a community detection method to uncover latent clusters of eddy activities. The creation of the mobility network is achieved by dividing the study area, the South China Sea, into regular grids and projecting eddy trajectories obtained from 1992 to 2011 to this grid-like network with stop locations as nodes and transitions as edges. The trajectories are preprocessed and generalized at four different granularities:trajectory partitions (TP), origin-destination transitions (OD), minimum description length (MDL), and regeneration of strong processes (RSP). Then, a fast unfolding algorithm is applied to the networks created at different granularities to discover potential communities. Finally, the relationships between different communities are visually analyzed using the chord diagram. The results show that the RSP data of eddy tracks overcome the data insufficiency in TP-network, and the method is able to identify major paths and clustering patterns of eddy activities throughout the life from the RSP data.
2017, 39(7): 124-130.
doi: 10.3969/j.issn.0253-4193.2017.07.012
Abstract:
In this paper, which is based on the Jason-2 altimeter data, with the data of the significant wave height (SWH), wind speed (U) and sea state bias (SSB) combination of 1-6 cycle in 12 different seasons in the cycle data as the training set, select the other 3 cycles of Jason-2 data as the test set. By the test analysis, the BP neural network model which corresponds to 3 cycles for estimating the SSB is established. The model is applied to the estimations of SSB in the HY-2 altimeter, and the performances of the model can be evaluated by the goodness of fit between U and SWH by SSB, explained variance and residual contrast analysis. It suggests that the BP neutral network model can be effectively applied to the HY-2 estimations of SSB and significantly better than the traditional parameter model of sea state bias.
In this paper, which is based on the Jason-2 altimeter data, with the data of the significant wave height (SWH), wind speed (U) and sea state bias (SSB) combination of 1-6 cycle in 12 different seasons in the cycle data as the training set, select the other 3 cycles of Jason-2 data as the test set. By the test analysis, the BP neural network model which corresponds to 3 cycles for estimating the SSB is established. The model is applied to the estimations of SSB in the HY-2 altimeter, and the performances of the model can be evaluated by the goodness of fit between U and SWH by SSB, explained variance and residual contrast analysis. It suggests that the BP neutral network model can be effectively applied to the HY-2 estimations of SSB and significantly better than the traditional parameter model of sea state bias.
2017, 39(7): 131-142.
doi: 10.3969/j.issn.0253-4193.2017.07.013
Abstract:
This paper analyzes the sedimentary environment of Gaizhou Shoal in recent 30 years based on the grain size analyses and 137Cs and 210Pb dating of sediment samples from the core, collected from the north of Gaizhou Shoal, combining with remote sensing images of 1988, 1994, 1999 and 2013. The results show that the type of sediment are sandy silt and silt with poor sorted, fine skewed and platykurtic. The deposition rate of Gaizhou Shoal in recent 30 years is rapid with 2.83 cm/a. The annual runoff and sediment discharge of Liaohe River decreased after the building of Panshan sluice in 1969, and the grain size of sediment of Gaizhou Shoal was restricted by runoff, tidal current and wave while the runoff was the main factor. Liaohe River was closured in 1999, and then the effect of runoff weakened while the effect of tidal current enhanced. The development process of Gaizhou Shoal was affected by runoff, tidal current, wave and human activities, but the main form of Gaizhou Shoal has no significant change in recent 30 years, while the northern increased and connected with the main shoal, and the southern was birdfoot because of wave reforming.
This paper analyzes the sedimentary environment of Gaizhou Shoal in recent 30 years based on the grain size analyses and 137Cs and 210Pb dating of sediment samples from the core, collected from the north of Gaizhou Shoal, combining with remote sensing images of 1988, 1994, 1999 and 2013. The results show that the type of sediment are sandy silt and silt with poor sorted, fine skewed and platykurtic. The deposition rate of Gaizhou Shoal in recent 30 years is rapid with 2.83 cm/a. The annual runoff and sediment discharge of Liaohe River decreased after the building of Panshan sluice in 1969, and the grain size of sediment of Gaizhou Shoal was restricted by runoff, tidal current and wave while the runoff was the main factor. Liaohe River was closured in 1999, and then the effect of runoff weakened while the effect of tidal current enhanced. The development process of Gaizhou Shoal was affected by runoff, tidal current, wave and human activities, but the main form of Gaizhou Shoal has no significant change in recent 30 years, while the northern increased and connected with the main shoal, and the southern was birdfoot because of wave reforming.
Email alert
RSS