2019 Vol. 41, No. 1
Display Method:
2019, 41(1): .
Abstract:
2019, 41(1): .
Abstract:
2019, 41(1): 1-10.
doi: 10.3969/j.issn.0253-4193.2019.01.001
Abstract:
On the basis of spot investigation data and satellite remote sensing data in eastern Hainan Island of July 2014 and 2015, we investigated the variation of upwelling in eastern Hainan Island under the influence of ENSO. Results show that 2015 is a strong El Niño year, and the low temperature, high salinity water is deeper from the surface than 2014, but more shallow in the offshore, and the climbing phenomenon of the upwelling is more obvious. The 27.5℃ isothermal of temperature and the 34 isograms of salinity can climb up to 15-25 m in the whole section. Influenced by southwesterly wind, the low temperature-high salinity water climb up along the terrain, which is the typically wind-driven upwelling. 2014 is a normal year, the low temperature-high salinity water is more shallow from the surface than 2015 (except the offshore), the low temperature-high salinity phenomenon is more obvious than 2015 in the same depth, but the climb phenomenon of the upwelling is not obvious. The 27.5℃ isothermal of temperature and the 34 isograms of salinity climb in less than 10 m. Prevailing wind is southeasterly wind, which suppresses the form of upwelling. The low temperature-high salinity water lifting is formed on the whole terrain, which is not suit to the characteristic of the typically wind-driven upwelling. This shows that the form of upwelling in eastern Hainan Island in 2014 may be associated with the thermocline lift caused by circulation changes off the coast.
On the basis of spot investigation data and satellite remote sensing data in eastern Hainan Island of July 2014 and 2015, we investigated the variation of upwelling in eastern Hainan Island under the influence of ENSO. Results show that 2015 is a strong El Niño year, and the low temperature, high salinity water is deeper from the surface than 2014, but more shallow in the offshore, and the climbing phenomenon of the upwelling is more obvious. The 27.5℃ isothermal of temperature and the 34 isograms of salinity can climb up to 15-25 m in the whole section. Influenced by southwesterly wind, the low temperature-high salinity water climb up along the terrain, which is the typically wind-driven upwelling. 2014 is a normal year, the low temperature-high salinity water is more shallow from the surface than 2015 (except the offshore), the low temperature-high salinity phenomenon is more obvious than 2015 in the same depth, but the climb phenomenon of the upwelling is not obvious. The 27.5℃ isothermal of temperature and the 34 isograms of salinity climb in less than 10 m. Prevailing wind is southeasterly wind, which suppresses the form of upwelling. The low temperature-high salinity water lifting is formed on the whole terrain, which is not suit to the characteristic of the typically wind-driven upwelling. This shows that the form of upwelling in eastern Hainan Island in 2014 may be associated with the thermocline lift caused by circulation changes off the coast.
2019, 41(1): 11-20.
doi: 10.3969/j.issn.0253-4193.2019.01.002
Abstract:
Based on the observations of full depth in the North Passage (NP) during the flood season in 2015, an analysis of horizontal flow, residual flow structure and boundary layer features in the middle-lower sections of NP was further conducted. The research reveals that the tidal current vectors during spring tide shows clear vertical variations. A lateral water transport to the north of the channel appears in the study site. The lateral flow velocity (depth-averaged) varies from -0.10 m/s to 0.39 m/s during spring tide while -0.13 m/s to 0.25 m/s during neap tide. Lateral advection plays an important role in the longitudinal mass transport and hydrodynamics. There is a significant variation in the residual flow vertical distribution, with an approximately zero value at the bottom. The residual flow is stronger in the neap tide. Suspended bed sediments can be seen as a supply for the turbidity maximum. There are great errors in the logarithmic velocity fitting law based on the traditional "six points" method. To gain the precise bottom boundary layer parameters, we need to focus on the high-resolution velocity profile in the 1 m water column above the bed.
Based on the observations of full depth in the North Passage (NP) during the flood season in 2015, an analysis of horizontal flow, residual flow structure and boundary layer features in the middle-lower sections of NP was further conducted. The research reveals that the tidal current vectors during spring tide shows clear vertical variations. A lateral water transport to the north of the channel appears in the study site. The lateral flow velocity (depth-averaged) varies from -0.10 m/s to 0.39 m/s during spring tide while -0.13 m/s to 0.25 m/s during neap tide. Lateral advection plays an important role in the longitudinal mass transport and hydrodynamics. There is a significant variation in the residual flow vertical distribution, with an approximately zero value at the bottom. The residual flow is stronger in the neap tide. Suspended bed sediments can be seen as a supply for the turbidity maximum. There are great errors in the logarithmic velocity fitting law based on the traditional "six points" method. To gain the precise bottom boundary layer parameters, we need to focus on the high-resolution velocity profile in the 1 m water column above the bed.
2019, 41(1): 21-31.
doi: 10.3969/j.issn.0253-4193.2019.01.003
Abstract:
Residual water level (i.e. the tidally averaged water level) is mainly controlled by the tide-river interaction, and understanding its formation and evolution is important with regard to water resources management in estuaries. In this study, based on the three-dimensional baroclinic hydrodynamic numerical results under different tide-river conditions and the Chebyshev polynomial decomposition approach, the impact of the baroclinic gradient on residual water level variation was explored for given idealized geometry with a convergent width and a linear bed slope. Model results show that the variation of residual water level along the estuary axis is determined by freshwater discharge, tidal amplitude, convergent topography and baroclinic gradient. In particular, the influence of the baroclinic gradient on the residual water level is featured by an accumulative effect over the whole backwater zone, with a significant spring-neap and wet-dry changes. Information of water level and velocity field are provided by numerical model, making use of Chebyshev polynomial decomposition, it is possible to decompose the residual water level into different components, linking to tide, river and tide-river interaction, respectively. When compared with the residual water level induced by baroclinic gradient, it is shown that, the residual water level in backwater zone is primarily controlled by the tide-river interaction. Effect of baroclinic gradient on the residual water level becomes important during the neap tide and may become the dominant factor on the residual water level.
Residual water level (i.e. the tidally averaged water level) is mainly controlled by the tide-river interaction, and understanding its formation and evolution is important with regard to water resources management in estuaries. In this study, based on the three-dimensional baroclinic hydrodynamic numerical results under different tide-river conditions and the Chebyshev polynomial decomposition approach, the impact of the baroclinic gradient on residual water level variation was explored for given idealized geometry with a convergent width and a linear bed slope. Model results show that the variation of residual water level along the estuary axis is determined by freshwater discharge, tidal amplitude, convergent topography and baroclinic gradient. In particular, the influence of the baroclinic gradient on the residual water level is featured by an accumulative effect over the whole backwater zone, with a significant spring-neap and wet-dry changes. Information of water level and velocity field are provided by numerical model, making use of Chebyshev polynomial decomposition, it is possible to decompose the residual water level into different components, linking to tide, river and tide-river interaction, respectively. When compared with the residual water level induced by baroclinic gradient, it is shown that, the residual water level in backwater zone is primarily controlled by the tide-river interaction. Effect of baroclinic gradient on the residual water level becomes important during the neap tide and may become the dominant factor on the residual water level.
2019, 41(1): 32-40.
doi: 10.3969/j.issn.0253-4193.2019.01.004
Abstract:
Oceanic surface information with large scale, real-time, high resolution has been collected by satellite remote sensing instruments, including sea surface temperature (SST) and sea surface height (SSH), which could be assimilated in ocean model to enhance the simulation. In this paper, an experiment in South China Sea is conducted based on ROMS and 4DVAR method, by assimilating the AVHRR SST and AVISO sea level anomalies (SLA) data. To confirm the efficiency of the assimilation, the HYCOM reanalysis data and Argo in situ profile are applied to validate the SSH, current and temperature-salinity (T-S) field of the assimilation. The results show that the simulation is enhanced after the SST and SSH assimilation. The capability of mesoscale characteristics detection in SSH outcomes is promoted, and the absolute bias (Abias) and root mean square error (RMSE) are 0.054 m and 0.066 m, compared with the HYCOM surface elevation. Considering the velocity evaluation with HYCOM, the averaged Abias of the eastward and northward velocity at 10 m layer is 0.12 m/s and 0.011 m/s, accompanied with a promotion of 0.01 m/s. Meanwhile, the assimilation results agree with the Argo T-S profiles well, the averaged Abias of T-S is 0.45℃, 0.077, while the RMSE is 0.91℃ and 0.11, respectively. Moreover, the analysis of single T-S profile indicates that the assimilation results achieve a comparable accuracy with HYCOM.
Oceanic surface information with large scale, real-time, high resolution has been collected by satellite remote sensing instruments, including sea surface temperature (SST) and sea surface height (SSH), which could be assimilated in ocean model to enhance the simulation. In this paper, an experiment in South China Sea is conducted based on ROMS and 4DVAR method, by assimilating the AVHRR SST and AVISO sea level anomalies (SLA) data. To confirm the efficiency of the assimilation, the HYCOM reanalysis data and Argo in situ profile are applied to validate the SSH, current and temperature-salinity (T-S) field of the assimilation. The results show that the simulation is enhanced after the SST and SSH assimilation. The capability of mesoscale characteristics detection in SSH outcomes is promoted, and the absolute bias (Abias) and root mean square error (RMSE) are 0.054 m and 0.066 m, compared with the HYCOM surface elevation. Considering the velocity evaluation with HYCOM, the averaged Abias of the eastward and northward velocity at 10 m layer is 0.12 m/s and 0.011 m/s, accompanied with a promotion of 0.01 m/s. Meanwhile, the assimilation results agree with the Argo T-S profiles well, the averaged Abias of T-S is 0.45℃, 0.077, while the RMSE is 0.91℃ and 0.11, respectively. Moreover, the analysis of single T-S profile indicates that the assimilation results achieve a comparable accuracy with HYCOM.
2019, 41(1): 41-50.
doi: 10.3969/j.issn.0253-4193.2019.01.005
Abstract:
In general, a pair of clockwise and anti-clockwise vortexes will develop at the right and left sides of a headland (facing to the sea), respectively. These vortexes play important roles in sediment transport, sea bed change and pollutants' dispersion. The islands in the ocean will also induce island wakes. When the islands are close to the headland, the island wakes may interact with the vortexes induced by the headlands. In this study, we take the Puqian Bay, Hainan Island, as an example to investigate the construction of an artificial island at the bay mouth on the vortexes in the coastal bay, and further examine its effect on the sea bed erosion and accretion. This study is mainly conducted through using the COAWST model. The model is carefully calibrated by the observation data of water elevation and current. The model results indicate that there develops a large-scale clockwise vortex in the bay during the spring tide, while this vortex disappears during the neap tide. The construction of the artificial island does not change the vortex pattern as a whole, however, locally there develop several clockwise and anti-clockwise vortexes around the island. The sea bed is in a state of weak accretion under the tidal action, while the artificial island strengthens this pattern in most of the bay, except in the waterway between the island and coastline. It is hoped that this study will benefit coastal development management.
In general, a pair of clockwise and anti-clockwise vortexes will develop at the right and left sides of a headland (facing to the sea), respectively. These vortexes play important roles in sediment transport, sea bed change and pollutants' dispersion. The islands in the ocean will also induce island wakes. When the islands are close to the headland, the island wakes may interact with the vortexes induced by the headlands. In this study, we take the Puqian Bay, Hainan Island, as an example to investigate the construction of an artificial island at the bay mouth on the vortexes in the coastal bay, and further examine its effect on the sea bed erosion and accretion. This study is mainly conducted through using the COAWST model. The model is carefully calibrated by the observation data of water elevation and current. The model results indicate that there develops a large-scale clockwise vortex in the bay during the spring tide, while this vortex disappears during the neap tide. The construction of the artificial island does not change the vortex pattern as a whole, however, locally there develop several clockwise and anti-clockwise vortexes around the island. The sea bed is in a state of weak accretion under the tidal action, while the artificial island strengthens this pattern in most of the bay, except in the waterway between the island and coastline. It is hoped that this study will benefit coastal development management.
2019, 41(1): 51-57.
doi: 10.3969/j.issn.0253-4193.2019.01.006
Abstract:
As the only semi-enclosed inland sea of China, the Bohai Sea has higher seismicity level and therefore is exposed to tsunami hazard. This study aimed to evaluate the tsunami hazard along the coast of the Bohai Sea by using the probabilistic method. Firstly, we established the magnitude-frequency relationship based on the historical earthquakes catalog in this area. Then, an earthquake catalog of 100 000 years was generated through the stochastic Monte Carlo simulation. At last, based on tsunami simulation of these events and the statistical results of the maximum wave amplitude catalog, the probabilistic tsunami hazard maps of specific return periods along the Bohai Sea coasts and tsunami hazard curves for important cities surrounding the Bohai Sea were plotted. The results indicated that part of the Bohai Bay and Laizhou Bay have higher tsunami hazard than Liaodong Bay, with a moderate threat level of 1-3 m.
As the only semi-enclosed inland sea of China, the Bohai Sea has higher seismicity level and therefore is exposed to tsunami hazard. This study aimed to evaluate the tsunami hazard along the coast of the Bohai Sea by using the probabilistic method. Firstly, we established the magnitude-frequency relationship based on the historical earthquakes catalog in this area. Then, an earthquake catalog of 100 000 years was generated through the stochastic Monte Carlo simulation. At last, based on tsunami simulation of these events and the statistical results of the maximum wave amplitude catalog, the probabilistic tsunami hazard maps of specific return periods along the Bohai Sea coasts and tsunami hazard curves for important cities surrounding the Bohai Sea were plotted. The results indicated that part of the Bohai Bay and Laizhou Bay have higher tsunami hazard than Liaodong Bay, with a moderate threat level of 1-3 m.
2019, 41(1): 58-71.
doi: 10.3969/j.issn.0253-4193.2019.01.007
Abstract:
In this paper, two kinds of biogenic sediments, calcareous ooze and siliceous ooze, which are the most common types of biogenic sediment in the Indian Ocean, were analyzed to explore the concentration distribution of the major and trace elements, rare earth elements and Y (REY) in the bulk samples and different particle size components. The composition characteristics, material sources and enrichment mechanism of REY in these two kind sediments were discussed. The results show that the siliceous ooze is riched in CaO and Sr, and the siliceous ooze is enriched with SiO2, Al2O3 and Fe2O3. The average content of ∑REY in calcareous ooze is 40.56×10-6, which is enriched in the fine sediment, and the light rare earth element (LREE) is slightly enriched in this kind sediment. When that normalized by PAAS, REY all showed negative anomalies of Ce, positive anomalies of Eu and Y in both the bulk sediment and different particle size components. REY in the calcareous ooze reserve the composition of seawater, which is dominated by autogenous origin and also influenced by hydrothermal fluid and oceanic basalt weathering materials. Meanwhile, the content of ∑REY in the siliceous ooze is 248.54×10-6, which is also enriched in fine sediments (>4φ). LREE is relatively enriched too. The ∑REY content in the sediments of the study site is near the boundary grade, but the HREY content in the fine sediments reaches the industrial grade. REY in the fine-grained components of this kind sediment mainly comes from the adsorption of clay minerals and iron-manganese oxides which come from the terrestrial or pyroclastic materials, while the REY source in the coarse-grained fraction is related to the biological effects. The enrichment of REY in siliceous ooze is associated with apatite in sediments, but REY from some different sources may be redistributed into the minerals such as apatite and phillipsite during diagenetic process.
In this paper, two kinds of biogenic sediments, calcareous ooze and siliceous ooze, which are the most common types of biogenic sediment in the Indian Ocean, were analyzed to explore the concentration distribution of the major and trace elements, rare earth elements and Y (REY) in the bulk samples and different particle size components. The composition characteristics, material sources and enrichment mechanism of REY in these two kind sediments were discussed. The results show that the siliceous ooze is riched in CaO and Sr, and the siliceous ooze is enriched with SiO2, Al2O3 and Fe2O3. The average content of ∑REY in calcareous ooze is 40.56×10-6, which is enriched in the fine sediment, and the light rare earth element (LREE) is slightly enriched in this kind sediment. When that normalized by PAAS, REY all showed negative anomalies of Ce, positive anomalies of Eu and Y in both the bulk sediment and different particle size components. REY in the calcareous ooze reserve the composition of seawater, which is dominated by autogenous origin and also influenced by hydrothermal fluid and oceanic basalt weathering materials. Meanwhile, the content of ∑REY in the siliceous ooze is 248.54×10-6, which is also enriched in fine sediments (>4φ). LREE is relatively enriched too. The ∑REY content in the sediments of the study site is near the boundary grade, but the HREY content in the fine sediments reaches the industrial grade. REY in the fine-grained components of this kind sediment mainly comes from the adsorption of clay minerals and iron-manganese oxides which come from the terrestrial or pyroclastic materials, while the REY source in the coarse-grained fraction is related to the biological effects. The enrichment of REY in siliceous ooze is associated with apatite in sediments, but REY from some different sources may be redistributed into the minerals such as apatite and phillipsite during diagenetic process.
2019, 41(1): 72-86.
doi: 10.3969/j.issn.0253-4193.2019.01.008
Abstract:
Process, response and hydrodynamic mechanism of the interaction between turbidity flows and bottom currents are the frontier and weak research of marine sedimentology. Based on 3D seismic data, in this paper, the author found that the evenly spaced unidirectionally migrating channels (UMCs) appear in the Meishan Formation in southwest Beijiao Sag. The results show that unidirectional migration channels with high amplitude are developed in bathyal environment and turbidity flows from South Uplift cut and result in negative geomorphic unit, i.e., channels. These channels are divided into two units of erosional surface (ES) and channel sand-levee mud complexs (CS-LMCs). Trucation reflections under ES on the steep bank are more obvious than the counterparts on the gentle bank. Amplitude of CS-LMCs from steep bank to gentle bank gradually become to weak. Different to unidirectional migration canyons, these channels migrated to the opposite flow direction of bottom current, upstream of bottom current, in the Mid-Miocene. The author proposed the conceptional model of UMCs:channels resulted from turbidity-flow incisions are reshaped by bottom currents, resulting in steep bank corresponding to upsteam of bottom currents and gentle bank corresponding to downsteam of bottom currents. Meanwhile, bottom currents deflect the upper party of turbidity to flow towards gentle bank, which results in higher and lower deposit rate in gentle bank and steep bank, respectively. In this circumstance, the channels persistently migrate towards the upsteam of bottom currents. South Uplift provenance, bottom current associated with intermediate water in South China Sea, paleoclimate and sea-level fluctuation, and paleotopography of Beijiao Uplift are main control factors for unidirectional channel migration. We first found that unidirectionally migrating channels with high amplitude were a novel new type of interaction between turbidity flow and bottom current, which is of great significance to paleocean, paleoclimate, and exploration for oil and gas and gives importance to geologist.
Process, response and hydrodynamic mechanism of the interaction between turbidity flows and bottom currents are the frontier and weak research of marine sedimentology. Based on 3D seismic data, in this paper, the author found that the evenly spaced unidirectionally migrating channels (UMCs) appear in the Meishan Formation in southwest Beijiao Sag. The results show that unidirectional migration channels with high amplitude are developed in bathyal environment and turbidity flows from South Uplift cut and result in negative geomorphic unit, i.e., channels. These channels are divided into two units of erosional surface (ES) and channel sand-levee mud complexs (CS-LMCs). Trucation reflections under ES on the steep bank are more obvious than the counterparts on the gentle bank. Amplitude of CS-LMCs from steep bank to gentle bank gradually become to weak. Different to unidirectional migration canyons, these channels migrated to the opposite flow direction of bottom current, upstream of bottom current, in the Mid-Miocene. The author proposed the conceptional model of UMCs:channels resulted from turbidity-flow incisions are reshaped by bottom currents, resulting in steep bank corresponding to upsteam of bottom currents and gentle bank corresponding to downsteam of bottom currents. Meanwhile, bottom currents deflect the upper party of turbidity to flow towards gentle bank, which results in higher and lower deposit rate in gentle bank and steep bank, respectively. In this circumstance, the channels persistently migrate towards the upsteam of bottom currents. South Uplift provenance, bottom current associated with intermediate water in South China Sea, paleoclimate and sea-level fluctuation, and paleotopography of Beijiao Uplift are main control factors for unidirectional channel migration. We first found that unidirectionally migrating channels with high amplitude were a novel new type of interaction between turbidity flow and bottom current, which is of great significance to paleocean, paleoclimate, and exploration for oil and gas and gives importance to geologist.
2019, 41(1): 87-97.
doi: 10.3969/j.issn.0253-4193.2019.01.009
Abstract:
The channel complex systems of the Middle Miocene in the Rovuma Basin, East Africa exhibits complex filling characteristics and space-time evolution. The distribution of various hierarchies in channel complex system is analyzed under seismic resolution by several seismic techniques, such as 3D visualization, horizontal coherence slice, interval slice of root mean square amplitude, and the vertical and lateral evolution models are established. The channel complex system in Middle Miocene in the Rovuma Basin is composed with four identified hierarchies including channel complex system, channel complex set, channel complex and channel. The channel complex system evolves from strongly restricted to locally restricted along the direction of turbidity currents. The channel complex system is differentiated into three independent channel complex sets in the distal. The channel complex set shows four depositional patterns, two patterns are consistent and synchronous with the channel complex system, the other two patterns are weak confined and unconfined channel complex sets. Deep water deposition in channel complex systems is mainly affected by the sea level change, slope gradient and bottom current, the sedimentary scale, transport distance, deposition position, extension direction and external morphology change with time and space. The channel complex system presents a complex multi-level filling feature. The vertical overlap patterns vary with the location of the deposits. The late distribution of early channel complex set affect the development of the later channel complex set.
The channel complex systems of the Middle Miocene in the Rovuma Basin, East Africa exhibits complex filling characteristics and space-time evolution. The distribution of various hierarchies in channel complex system is analyzed under seismic resolution by several seismic techniques, such as 3D visualization, horizontal coherence slice, interval slice of root mean square amplitude, and the vertical and lateral evolution models are established. The channel complex system in Middle Miocene in the Rovuma Basin is composed with four identified hierarchies including channel complex system, channel complex set, channel complex and channel. The channel complex system evolves from strongly restricted to locally restricted along the direction of turbidity currents. The channel complex system is differentiated into three independent channel complex sets in the distal. The channel complex set shows four depositional patterns, two patterns are consistent and synchronous with the channel complex system, the other two patterns are weak confined and unconfined channel complex sets. Deep water deposition in channel complex systems is mainly affected by the sea level change, slope gradient and bottom current, the sedimentary scale, transport distance, deposition position, extension direction and external morphology change with time and space. The channel complex system presents a complex multi-level filling feature. The vertical overlap patterns vary with the location of the deposits. The late distribution of early channel complex set affect the development of the later channel complex set.
2019, 41(1): 98-107.
doi: 10.3969/j.issn.0253-4193.2019.01.010
Abstract:
The geomorphic features in the Zhujiang River Estuary have changed tremendously due to natural processes and human activities over the last century, and these changes have led to the variations in the hydrodynamic environment such as the reduced tidal prism in the estuary. In this paper, the relation between geomorphic features and the tidal prism was analyzed. In order to identify how the historical landform change affects the tidal prism, we investigated the morphology change in the Lingdingyang Estuary through the analyses of historical topographic maps and nautical charts. The shape index and fractal dimension were introduced as indicators to reflect coastline changes that affect the tides. The tidal dissipation rate and tidal influx were found to represent the tidal prism. The results show that the tidal influx in the Lingdingyang has declined by 14.50% since 1906 under the morphological change. The tidal dissipation rate weakens subject to the morphological changes and the tidal dissipation rate decreases by 0.23. Meanwhile, the tidal reduction capability is weakened due to the coastline change, which has become the straight artificial coastline under the embankment construction especially since 1971.
The geomorphic features in the Zhujiang River Estuary have changed tremendously due to natural processes and human activities over the last century, and these changes have led to the variations in the hydrodynamic environment such as the reduced tidal prism in the estuary. In this paper, the relation between geomorphic features and the tidal prism was analyzed. In order to identify how the historical landform change affects the tidal prism, we investigated the morphology change in the Lingdingyang Estuary through the analyses of historical topographic maps and nautical charts. The shape index and fractal dimension were introduced as indicators to reflect coastline changes that affect the tides. The tidal dissipation rate and tidal influx were found to represent the tidal prism. The results show that the tidal influx in the Lingdingyang has declined by 14.50% since 1906 under the morphological change. The tidal dissipation rate weakens subject to the morphological changes and the tidal dissipation rate decreases by 0.23. Meanwhile, the tidal reduction capability is weakened due to the coastline change, which has become the straight artificial coastline under the embankment construction especially since 1971.
2019, 41(1): 108-120.
doi: 10.3969/j.issn.0253-4193.2019.01.011
Abstract:
The characteristics of erosion-deposition variation before and after the construction of Rudong Sunshine Island are analyzed from various aspects such as typical sections, isobaths and regional settings, based on the underwater topographic data and the fixed-point hydrological observation data in recent years, and 11 kinds of response relationship between engineering construction and environment of the Sunshine Island are established. In addition, the effects of engineering construction on topographic and geomorphological changes over the surrounding waters of the Sunshine Island are studied. Based on the response relationship, the cause of formation is discussed also. The result shows that the erosion-deposition state of local areas of tidal ridge and tidal channel has changed in some extent in five years before and after engineering, which may be due to the changes brought to the local hydrodynamic conditions by the engineering construction. It also dicoveries that the tidal ridge had some tendency to move southward, despite it hasn't changed the stability of Channel-sand System as a whole. In view of this, long-term monitoring and dynamic analysis of tidal sand ridges and tidal channels around Sunshine Island need to be strengthened.
The characteristics of erosion-deposition variation before and after the construction of Rudong Sunshine Island are analyzed from various aspects such as typical sections, isobaths and regional settings, based on the underwater topographic data and the fixed-point hydrological observation data in recent years, and 11 kinds of response relationship between engineering construction and environment of the Sunshine Island are established. In addition, the effects of engineering construction on topographic and geomorphological changes over the surrounding waters of the Sunshine Island are studied. Based on the response relationship, the cause of formation is discussed also. The result shows that the erosion-deposition state of local areas of tidal ridge and tidal channel has changed in some extent in five years before and after engineering, which may be due to the changes brought to the local hydrodynamic conditions by the engineering construction. It also dicoveries that the tidal ridge had some tendency to move southward, despite it hasn't changed the stability of Channel-sand System as a whole. In view of this, long-term monitoring and dynamic analysis of tidal sand ridges and tidal channels around Sunshine Island need to be strengthened.
2019, 41(1): 121-133.
doi: 10.3969/j.issn.0253-4193.2019.01.012
Abstract:
As a typical small and medium-sized river, the source to sink process of fine sediment from the Yalu River catchment to the mud deposition of the offshore eastern Liaodong Peninsula is characterized by a unique mechanism. Among other methods, remote sensing is an effective means to understand the process and mechanism of sediment transport in estuarine-continental shelf. In this paper, we measured the surface suspended sediment concentration (SSC) in the eastern coast offshore of the Liaodong Peninsula, and then established a relationship between the measured SSC and the Remote Sensing Reflectance (Rrs) of GOCI images to retrieve the long-term spatio-temporal distribution of surface SSC (April 2011 to March 2017). The effect of tidal current, strong wind and flood on the variations of surface SSC is further analyzed. The SSC transport pattern from the Yalu River to the mud deposition along eastern coast offshore of Liaodong Peninsula is finally discussed. The results show that the distribution of the surface SSC in the study area displays great spatial differences. Near the estuary, the surface SSC is of highest value and is greater than 500 g/m3. While in other areas, the SSC value is less than 20 g/m3. Concerning the seasonal variation, the surface SSC value in the dry season is higher than that in the flood season, which is mainly due to the enhanced wind waves by strong winds in the dry season. Although the surface SSC value is low in the flood season, it still significantly increased during the flood period of the Yalu River catchment. In addition, as a typical small and medium-sized source-sink conveying system, the sediment transport mechanism from the Yalu River to the mud deposition along eastern coast offshore of Liaodong Peninsula is generally characterized by "deposit in summer and transport in winter".
As a typical small and medium-sized river, the source to sink process of fine sediment from the Yalu River catchment to the mud deposition of the offshore eastern Liaodong Peninsula is characterized by a unique mechanism. Among other methods, remote sensing is an effective means to understand the process and mechanism of sediment transport in estuarine-continental shelf. In this paper, we measured the surface suspended sediment concentration (SSC) in the eastern coast offshore of the Liaodong Peninsula, and then established a relationship between the measured SSC and the Remote Sensing Reflectance (Rrs) of GOCI images to retrieve the long-term spatio-temporal distribution of surface SSC (April 2011 to March 2017). The effect of tidal current, strong wind and flood on the variations of surface SSC is further analyzed. The SSC transport pattern from the Yalu River to the mud deposition along eastern coast offshore of Liaodong Peninsula is finally discussed. The results show that the distribution of the surface SSC in the study area displays great spatial differences. Near the estuary, the surface SSC is of highest value and is greater than 500 g/m3. While in other areas, the SSC value is less than 20 g/m3. Concerning the seasonal variation, the surface SSC value in the dry season is higher than that in the flood season, which is mainly due to the enhanced wind waves by strong winds in the dry season. Although the surface SSC value is low in the flood season, it still significantly increased during the flood period of the Yalu River catchment. In addition, as a typical small and medium-sized source-sink conveying system, the sediment transport mechanism from the Yalu River to the mud deposition along eastern coast offshore of Liaodong Peninsula is generally characterized by "deposit in summer and transport in winter".
2019, 41(1): 134-141.
doi: 10.3969/j.issn.0253-4193.2019.01.013
Abstract:
An approach is developed to standard catch per unit effort (CPUE) in the Northwest Pacific Ocean during 1998-2016 by considering environmental factors, including sea surface temperature (SST), sea surface height anomaly (SSHA), and chlorophyll a (Chl a) concentration of Ommastrephes bartramii habitat (35°~45° N,140°~165° E). It is found that the range of SST for high frequency of fishing (97.8%) is 10.2-22.2℃; the range of SSHA for high frequency of fishing (97.3%) is -15.9-28.2 cm; the range of Chl a concentration for high frequency of fishing (95.2%) is 0.0-1.0 mg/m3. The nominal CPUE is consistent with the yearly environmental based-CPUE. However, the nominal CPUE is significant less than environmental based-CPUE, because the highly concentrated fishing results in the effective fishing effort less than nominal fishing effort. We suggest that the environmental based-CPUE is more representative and closer to actual abundance indices of Ommastrephes bartramii, and we should consider environmental based-CPUE in the stock assessment and management for Ommastrephes bartramii in the Northwest Pacific Ocean in the future.
An approach is developed to standard catch per unit effort (CPUE) in the Northwest Pacific Ocean during 1998-2016 by considering environmental factors, including sea surface temperature (SST), sea surface height anomaly (SSHA), and chlorophyll a (Chl a) concentration of Ommastrephes bartramii habitat (35°~45° N,140°~165° E). It is found that the range of SST for high frequency of fishing (97.8%) is 10.2-22.2℃; the range of SSHA for high frequency of fishing (97.3%) is -15.9-28.2 cm; the range of Chl a concentration for high frequency of fishing (95.2%) is 0.0-1.0 mg/m3. The nominal CPUE is consistent with the yearly environmental based-CPUE. However, the nominal CPUE is significant less than environmental based-CPUE, because the highly concentrated fishing results in the effective fishing effort less than nominal fishing effort. We suggest that the environmental based-CPUE is more representative and closer to actual abundance indices of Ommastrephes bartramii, and we should consider environmental based-CPUE in the stock assessment and management for Ommastrephes bartramii in the Northwest Pacific Ocean in the future.
2019, 41(1): 142-150.
doi: 10.3969/j.issn.0253-4193.2019.01.014
Abstract:
To achieve continuous survey of seabed macro seepage, the application of a navigation marine direct current resistivity survey method is initiated in this paper. To guarantee the feasibility of the proposed method, geoelectric models have been built based on the existing in-situ observation and resistivity characteristics of gas-bearing water. In this case, resistivity sections imagine with different design parameters are obtained by numerical simulation and laboratory tests; the anomaly characteristics of resistivity sections are analyzed and the detection effect of the method is evaluated. And on this basis, the design of detection system design and experimental test are further carried out. The study results indicate that the cable of navigation 2D electrical imaging system could be composed of 2 current electrodes and 8 voltage electrodes, and the spacing between electrodes must be less than 0.05 m; then measurement can be achieved by means of parallel acquisition of dipole-dipole array. Gas distribution area shows obvious high-resistivity anomaly. The pattern of this anomaly can be categorized into 7 types, which were jointly determined by the factors of travel speed, the length of the arrangement and the lateral width of the gas distribution area. There is a positive exponential relation between the maximum value of resistivity can be detected and the rate of gas eruption. Conclusively, the navigation 2D electrical imaging method is an demonstrated method which could effectively detect the range of gas distribution and the rate of gas eruption in a quick manner.
To achieve continuous survey of seabed macro seepage, the application of a navigation marine direct current resistivity survey method is initiated in this paper. To guarantee the feasibility of the proposed method, geoelectric models have been built based on the existing in-situ observation and resistivity characteristics of gas-bearing water. In this case, resistivity sections imagine with different design parameters are obtained by numerical simulation and laboratory tests; the anomaly characteristics of resistivity sections are analyzed and the detection effect of the method is evaluated. And on this basis, the design of detection system design and experimental test are further carried out. The study results indicate that the cable of navigation 2D electrical imaging system could be composed of 2 current electrodes and 8 voltage electrodes, and the spacing between electrodes must be less than 0.05 m; then measurement can be achieved by means of parallel acquisition of dipole-dipole array. Gas distribution area shows obvious high-resistivity anomaly. The pattern of this anomaly can be categorized into 7 types, which were jointly determined by the factors of travel speed, the length of the arrangement and the lateral width of the gas distribution area. There is a positive exponential relation between the maximum value of resistivity can be detected and the rate of gas eruption. Conclusively, the navigation 2D electrical imaging method is an demonstrated method which could effectively detect the range of gas distribution and the rate of gas eruption in a quick manner.
2019, 41(1): 151-159.
doi: 10.3969/j.issn.0253-4193.2019.01.015
Abstract:
A typhoon intensity estimation technique based on scatterometer wind data is proposed in this study. The mean of sea surface wind speed computed in a circular area of the typhoon, is used to determine the typhoon intensity. This technique is verified by typhoon cases from the HY-2 satellite scatterometer data. The verification results indicate that the method proposed in this study can overcome the problems with underestimated wind speed retrieved from typical scatterometers. And the method is proved to be effective for determining typhoon intensity for cases under severe typhoon category, as compared with historical typhoon records.
A typhoon intensity estimation technique based on scatterometer wind data is proposed in this study. The mean of sea surface wind speed computed in a circular area of the typhoon, is used to determine the typhoon intensity. This technique is verified by typhoon cases from the HY-2 satellite scatterometer data. The verification results indicate that the method proposed in this study can overcome the problems with underestimated wind speed retrieved from typical scatterometers. And the method is proved to be effective for determining typhoon intensity for cases under severe typhoon category, as compared with historical typhoon records.
2019, 41(1): 160-171.
doi: 10.3969/j.issn.0253-4193.2019.01.016
Abstract:
The seafloor surficial sediments have multiphase, multi-particle and multi-morphological structures, which lead to complex and diverse acoustic wave propagation process. Based on the analysis of the characteristics of compressional wave velocity and shear wave velocity, the scientific problems and key technical problems to be solved are pointed out. On the basis of analyzing the research status of sound velocity characteristics at home and abroad, this paper suggests that a systematic and controllable experimental measurement method to solve the four problems existing in current measurement. With a comprehensive analysis on the relationship between compressional wave velocity and shear wave velocity including their regression relation and theoretical analysis, differences on measuring scale, measuring frequency, and measurement status are discussed for current three kinds of methods including geoacoustic inversion, samples acoustic measurement, and in-situ acoustic measurement. And also the methods on the consistency of explanation for measurement results of different measurement methods and measurement techniques are discussed, to obtain the real seabed sediment acoustic characteristics of different types and different regions. Finally, six technical demands are presented such as the laboratory measurement of physical and mechanical parameter measurement, acoustic analysis of fluid solid coupling characteristics, in-situ measurement and monitoring of submarine sediments, error analysis and correction between sampling analysis and in-situ measurement, and the surface acoustic measurement technology of deep sediments, with the aim to improve the accuracy of acoustic detection of the sea and the seafloor, and promote development of ocean engineering.
The seafloor surficial sediments have multiphase, multi-particle and multi-morphological structures, which lead to complex and diverse acoustic wave propagation process. Based on the analysis of the characteristics of compressional wave velocity and shear wave velocity, the scientific problems and key technical problems to be solved are pointed out. On the basis of analyzing the research status of sound velocity characteristics at home and abroad, this paper suggests that a systematic and controllable experimental measurement method to solve the four problems existing in current measurement. With a comprehensive analysis on the relationship between compressional wave velocity and shear wave velocity including their regression relation and theoretical analysis, differences on measuring scale, measuring frequency, and measurement status are discussed for current three kinds of methods including geoacoustic inversion, samples acoustic measurement, and in-situ acoustic measurement. And also the methods on the consistency of explanation for measurement results of different measurement methods and measurement techniques are discussed, to obtain the real seabed sediment acoustic characteristics of different types and different regions. Finally, six technical demands are presented such as the laboratory measurement of physical and mechanical parameter measurement, acoustic analysis of fluid solid coupling characteristics, in-situ measurement and monitoring of submarine sediments, error analysis and correction between sampling analysis and in-situ measurement, and the surface acoustic measurement technology of deep sediments, with the aim to improve the accuracy of acoustic detection of the sea and the seafloor, and promote development of ocean engineering.
2019, 41(1): 172-182.
doi: 10.3969/j.issn.0253-4193.2019.01.017
Abstract:
The accurate information of subaqueous topography and seabed substrata are of great significant for marine engineering construction, benthic habitat mapping, and management of marine protected areas (MPAs). The bathymetric and backscatter data of 880 km2 in the Joseph Bonaparte Gulf, Northern Australia were collected by using a multi-beam echo-sounder system (Kongsberg's 300 kHz EM3002), and 54 samples of seabed sediments were collected simultaneously. The Random Forest Decision Tree (RFDT) was chosen as the modelling method for prediction. The results show that:(1) Improvement of the predicted accuracy for bed sediment classification is made when the parameters of RDFT are set as "number of trees" 200, "minimum size node to split" 2 and the "maximum splitting levels" 5 in this paper. (2) The highest accuracy of 83.3% is predicted from the incidence angle (backscatter) of 13° and 37°, and the coarse sediment, such as sandy gravel and gravelly sand are mainly distributed in the area with stronger backscatter intensity, but the fine sediment, such as gravelly muddy sand and (gravelly) muddy sand are distributed in the shallow area. However, it is noteworthy that the predicted accuracy of sediment classification may decrease when bathymetry data is chosen as the characteristic variable with the backscatter.
The accurate information of subaqueous topography and seabed substrata are of great significant for marine engineering construction, benthic habitat mapping, and management of marine protected areas (MPAs). The bathymetric and backscatter data of 880 km2 in the Joseph Bonaparte Gulf, Northern Australia were collected by using a multi-beam echo-sounder system (Kongsberg's 300 kHz EM3002), and 54 samples of seabed sediments were collected simultaneously. The Random Forest Decision Tree (RFDT) was chosen as the modelling method for prediction. The results show that:(1) Improvement of the predicted accuracy for bed sediment classification is made when the parameters of RDFT are set as "number of trees" 200, "minimum size node to split" 2 and the "maximum splitting levels" 5 in this paper. (2) The highest accuracy of 83.3% is predicted from the incidence angle (backscatter) of 13° and 37°, and the coarse sediment, such as sandy gravel and gravelly sand are mainly distributed in the area with stronger backscatter intensity, but the fine sediment, such as gravelly muddy sand and (gravelly) muddy sand are distributed in the shallow area. However, it is noteworthy that the predicted accuracy of sediment classification may decrease when bathymetry data is chosen as the characteristic variable with the backscatter.
2019, 41(1): 183-190.
doi: 10.3969/j.issn.0253-4193.2019.01.018
Abstract:
The concentration of chlorophyll a in water is an important indicator for study in phytoplankton biomass and primary productivity. Therefore, the long-term monitoring of chlorophyll a in the estuary area has important ecological significance. Remote sensing technology can obtain large-scale observation results of long time series. Using Landsat TM/ETM+ remote sensing images from 1986 to 2015, we constructed a quantitative inversion model based on field measured data and obtained the spatial-temporal distribution of chlorophyll a concentration in Jiaozhou Bay over the past 30 years. The variation pattern of chlorophyll a is stable; chlorophyll a is higher in the northwest and lower in the southeast. The mean value of chlorophyll a concentration shows a slight upward trend. Taking advantage of sea surface temperature, land use classification and landscape pattern index retrieved from remote sensing images, the influence factors of spatial-temporal distribution of chlorophyll a concentration of Jiaozhou Bay are analyzed. The chlorophyll a concentration is closely related to the sea surface temperature. In addition, it is also influenced by human factors, such as the landscape pattern index of aquiculture area and construction of large artificial facilities.
The concentration of chlorophyll a in water is an important indicator for study in phytoplankton biomass and primary productivity. Therefore, the long-term monitoring of chlorophyll a in the estuary area has important ecological significance. Remote sensing technology can obtain large-scale observation results of long time series. Using Landsat TM/ETM+ remote sensing images from 1986 to 2015, we constructed a quantitative inversion model based on field measured data and obtained the spatial-temporal distribution of chlorophyll a concentration in Jiaozhou Bay over the past 30 years. The variation pattern of chlorophyll a is stable; chlorophyll a is higher in the northwest and lower in the southeast. The mean value of chlorophyll a concentration shows a slight upward trend. Taking advantage of sea surface temperature, land use classification and landscape pattern index retrieved from remote sensing images, the influence factors of spatial-temporal distribution of chlorophyll a concentration of Jiaozhou Bay are analyzed. The chlorophyll a concentration is closely related to the sea surface temperature. In addition, it is also influenced by human factors, such as the landscape pattern index of aquiculture area and construction of large artificial facilities.
Email alert
RSS