2014 Vol. 36, No. 5
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2014, 36(5): .
Abstract:
2014, 36(5): 1-7.
doi: 10.3969/j.issn.0253-4193.2014.05.001
Abstract:
As a kind of sustainable clean energy, ocean wave energy attracts more and more attention. Based on the wave model of WAVEWATCH Ⅲ, a regional wave model of China Sea is established in this paper with high resolution to investigate the wave energy distribution along the coastline of China. Referring to former research results, this paper detailed spatial and temporal distributions of China's ocean wave energy resource, providing data support for further development and utilization of wave energy.It proves that the wave energy resources along China Sea are characterized with low magnitude and unbalanced north-south distribution with Yangtze River estuary as the demarcation. Consequently, full investigations should be conducted to study the wave characters of project site before wave energy development ensuring that wave energy converters can be chosen appropriately, avoiding mass economic losses.
As a kind of sustainable clean energy, ocean wave energy attracts more and more attention. Based on the wave model of WAVEWATCH Ⅲ, a regional wave model of China Sea is established in this paper with high resolution to investigate the wave energy distribution along the coastline of China. Referring to former research results, this paper detailed spatial and temporal distributions of China's ocean wave energy resource, providing data support for further development and utilization of wave energy.It proves that the wave energy resources along China Sea are characterized with low magnitude and unbalanced north-south distribution with Yangtze River estuary as the demarcation. Consequently, full investigations should be conducted to study the wave characters of project site before wave energy development ensuring that wave energy converters can be chosen appropriately, avoiding mass economic losses.
2014, 36(5): 8-17.
doi: 10.3969/j.issn.0253-4193.2014.05.002
Abstract:
In 2012,the sea level anomaly high was the most prominent feature of sea level change in China coastal. The sea level was 122 mm higher than normal,53 mm higher than 2011,reached its highest level since 1980. Based on the 30 years water level,sea surface temperature,air temperature,barometric pressure and wind hydrological and meteorological data,the sea level anomaly high of 2012 in the China coastal area is investigated. The research results show: the coincidence of several long-period vibration made the sea level high during 2010 to 2012. In 2012,China coastal area air temperature and ocean temperature were higher than normal,the barometric pressure was 1.2 hpa lower than normal,reaching the lowest level in history; in 2012,SCSSM time was earlier than normal,and later than normal end,the South China Sea strongest southerly wind lead China Yellow Sea,East China Sea and South China Sea coastal waters for a long time accumulation,which caused sea level rise. In 2012,tropical cyclones landing time was focus,the number of typhoons affecting a wide range of northern regions were the most of history,especially in August 2012,there were six tropical cyclones affecting China's coastal area,sea level rise for the month obviously. In addition,the subtropical high was northerly,easterly and weakness,which also have some impact on the sea level rise of the East China Sea and South China Sea in 2012.
In 2012,the sea level anomaly high was the most prominent feature of sea level change in China coastal. The sea level was 122 mm higher than normal,53 mm higher than 2011,reached its highest level since 1980. Based on the 30 years water level,sea surface temperature,air temperature,barometric pressure and wind hydrological and meteorological data,the sea level anomaly high of 2012 in the China coastal area is investigated. The research results show: the coincidence of several long-period vibration made the sea level high during 2010 to 2012. In 2012,China coastal area air temperature and ocean temperature were higher than normal,the barometric pressure was 1.2 hpa lower than normal,reaching the lowest level in history; in 2012,SCSSM time was earlier than normal,and later than normal end,the South China Sea strongest southerly wind lead China Yellow Sea,East China Sea and South China Sea coastal waters for a long time accumulation,which caused sea level rise. In 2012,tropical cyclones landing time was focus,the number of typhoons affecting a wide range of northern regions were the most of history,especially in August 2012,there were six tropical cyclones affecting China's coastal area,sea level rise for the month obviously. In addition,the subtropical high was northerly,easterly and weakness,which also have some impact on the sea level rise of the East China Sea and South China Sea in 2012.
2014, 36(5): 18-29.
doi: 10.3969/j.issn.0253-4193.2014.05.003
Abstract:
Shallow water equation is widely used in tsunami early warning and researches,however,it is necessary to know the application scope and calculation efficiency of linear and nonlinear shallow water equations under different topographical and bathymetrical conditions. This paper mainly studied the linear and nonlinear characteristics of tsunami waves propagating in the South China Sea and the East China Sea with the continental shelf effects by using tsunami numerical forecasting model which were developed based on shallow water equations. Propagation characteristics of tsunami waves in the deep water show strong linear features（A/H<<1). The simulation of tsunami wave amplitude has high precision and efficiency under this linear system,whereas the characteristics of weak nonlinear and dispersion have small effect on the simulation of tsunami that can be ignored. Due to the variation of seafloor gradient and roughness effect,when tsunami waves propagates to the shallow water continental shelf,nonlinear effect on the waves will travel and accumulate rapidly. It shows a significant difference comparing to the tsunami wave simulations that uses linear and nonlinear shallow water equations. The results showed that in the South China Sea where the water depth is lower than 100 m,the nonlinear effects on waves following the first wave of a tsunami were evident and different but a small effect on the first wave. Hence,to use the linear system simulating tsunami wave amplitudes can meet the tsunami early warning requirements without the consideration of tsunami inundation. In the East China Sea,because of the continental shelf,it is critical to consider nonlinear characteristics since first wave and later phase wave of a tsunami were significant different which were simulated by linear and nonlinear tsunami numerical models respectively. This paper also highlighted the numerical comparison study of bottom friction term effect on tsunami initial wave amplitude. The results showed that bottom friction effected the area only with water depth less than 100 m. Finally,we preliminarily analyzed the effect of continental shelf width on maximum tsunami amplitude based on the sensitivity tests. It can be summarized when tsunami waves propagate and deform at continental shelf,the maximum tsunami amplitude must be weakened by the eastern China Sea continental shelf is not correct. Whether the tsunami amplitude will enlarge or reduce is mainly depends on the continental shelf width and the depth of outer margin of the continental shelf.
Shallow water equation is widely used in tsunami early warning and researches,however,it is necessary to know the application scope and calculation efficiency of linear and nonlinear shallow water equations under different topographical and bathymetrical conditions. This paper mainly studied the linear and nonlinear characteristics of tsunami waves propagating in the South China Sea and the East China Sea with the continental shelf effects by using tsunami numerical forecasting model which were developed based on shallow water equations. Propagation characteristics of tsunami waves in the deep water show strong linear features（A/H<<1). The simulation of tsunami wave amplitude has high precision and efficiency under this linear system,whereas the characteristics of weak nonlinear and dispersion have small effect on the simulation of tsunami that can be ignored. Due to the variation of seafloor gradient and roughness effect,when tsunami waves propagates to the shallow water continental shelf,nonlinear effect on the waves will travel and accumulate rapidly. It shows a significant difference comparing to the tsunami wave simulations that uses linear and nonlinear shallow water equations. The results showed that in the South China Sea where the water depth is lower than 100 m,the nonlinear effects on waves following the first wave of a tsunami were evident and different but a small effect on the first wave. Hence,to use the linear system simulating tsunami wave amplitudes can meet the tsunami early warning requirements without the consideration of tsunami inundation. In the East China Sea,because of the continental shelf,it is critical to consider nonlinear characteristics since first wave and later phase wave of a tsunami were significant different which were simulated by linear and nonlinear tsunami numerical models respectively. This paper also highlighted the numerical comparison study of bottom friction term effect on tsunami initial wave amplitude. The results showed that bottom friction effected the area only with water depth less than 100 m. Finally,we preliminarily analyzed the effect of continental shelf width on maximum tsunami amplitude based on the sensitivity tests. It can be summarized when tsunami waves propagate and deform at continental shelf,the maximum tsunami amplitude must be weakened by the eastern China Sea continental shelf is not correct. Whether the tsunami amplitude will enlarge or reduce is mainly depends on the continental shelf width and the depth of outer margin of the continental shelf.
2014, 36(5): 30-45.
doi: 10.3969/j.issn.0253-4193.2014.05.004
Abstract:
Based on subsurface sea temperature datasets in the tropical Pacific,we analyze the spatial patterns and formation mechanism of the second-type El Niño events,and discuss its relationship with the classic El Niño event,El Niño Modoki,WP-and CT-type El Niño events. Also revealed is the impact of the second-type El Niño events to the precipitation variations in China. Results are summarized as follows.（1) The second-type El Niño event is the third EOF mode of subsurface temperature anomalies（SOTA) in the tropical Pacific,which explains 4.7% of the total variance. At the warm phase of this mode,sea surface temperature anomalies（SSTA) is composed of an anomalous warming in the central tropical Pacific flanked by an SST to the east that is a cold tongue strengthening westward along the equator in the eastern Pacific. This mode has a interannual period of 3—4 year and 11 and 30—40 years long terms periods,with most mode peaks occurring in spring. The second-type El Niño events result from the combined effects of the anomalous sea surface wind stress in tropical Pacific and the wind stress curl on both sides of the equator,accompanied with anomalous Walker-circulation which are characterized by reversing vertical motions between the eastern Indian/western Pacific and the eastern Pacific/South America near the equator.（2) El Niño Modoki is shown to be closely associated the second-type El Niño event. It results from the air-sea interaction and catches primarily message of the second-type El Niño events.(3) The second-type El Niño events also influence the precipitation in China during spring and early summer. At its warm phase,an anomalous anti-cyclone develops over the East China Sea. Its southern flank results in anomalous northeast winds and reduced precipitation in the southern China. Its western flank transports more than normal vapor to the northern China,which confluences with the north winds,leading to more precipitation in this region. The opposite is valid at its cold phase. Moreover,we show that WP-and CT-type El Niño events are not independent El Niño types,but barely combinations of the classical El Niño and El Niño Modoki. Also addressed in this study are the physical processes of the influence of El Niño events on atmospheric circulation in summertime.
Based on subsurface sea temperature datasets in the tropical Pacific,we analyze the spatial patterns and formation mechanism of the second-type El Niño events,and discuss its relationship with the classic El Niño event,El Niño Modoki,WP-and CT-type El Niño events. Also revealed is the impact of the second-type El Niño events to the precipitation variations in China. Results are summarized as follows.（1) The second-type El Niño event is the third EOF mode of subsurface temperature anomalies（SOTA) in the tropical Pacific,which explains 4.7% of the total variance. At the warm phase of this mode,sea surface temperature anomalies（SSTA) is composed of an anomalous warming in the central tropical Pacific flanked by an SST to the east that is a cold tongue strengthening westward along the equator in the eastern Pacific. This mode has a interannual period of 3—4 year and 11 and 30—40 years long terms periods,with most mode peaks occurring in spring. The second-type El Niño events result from the combined effects of the anomalous sea surface wind stress in tropical Pacific and the wind stress curl on both sides of the equator,accompanied with anomalous Walker-circulation which are characterized by reversing vertical motions between the eastern Indian/western Pacific and the eastern Pacific/South America near the equator.（2) El Niño Modoki is shown to be closely associated the second-type El Niño event. It results from the air-sea interaction and catches primarily message of the second-type El Niño events.(3) The second-type El Niño events also influence the precipitation in China during spring and early summer. At its warm phase,an anomalous anti-cyclone develops over the East China Sea. Its southern flank results in anomalous northeast winds and reduced precipitation in the southern China. Its western flank transports more than normal vapor to the northern China,which confluences with the north winds,leading to more precipitation in this region. The opposite is valid at its cold phase. Moreover,we show that WP-and CT-type El Niño events are not independent El Niño types,but barely combinations of the classical El Niño and El Niño Modoki. Also addressed in this study are the physical processes of the influence of El Niño events on atmospheric circulation in summertime.
2014, 36(5): 46-53.
doi: 10.3969/j.issn.0253-4193.2014.05.005
Abstract:
Typhoon track forecast error should include distance error and direction error, but in previous operational application and scientific research in favor only consider the distance error between observation position and forecast position of the corresponding time. In this paper the method of assessing the typhoon track error was improved. A new method of characterization of typhoon track error multiple-factor error method is established based on the distance error. The tropical cyclone（TC) best track data which compiled by Chinese Meteorological Administration（CMA) were as the standard, the TC tracks in the western North Pacific forecasted by CMA, U S Joint Typhoon Warning Center and Japan Meteorological Agency in 2008 and 2009, were analyzed by using the new multiple-factor method that attributes TC track forecast error, and with the distance error method which uses generally was compared. The results show that the quite obvious difference exists between the multiple-factor error analysis method and distance error analysis method. The multiple-factor error method superiority is quite obvious. It is an useful exploration to the more scientific assessment method for typhoon track forecast error. It has a certain practice application value.
Typhoon track forecast error should include distance error and direction error, but in previous operational application and scientific research in favor only consider the distance error between observation position and forecast position of the corresponding time. In this paper the method of assessing the typhoon track error was improved. A new method of characterization of typhoon track error multiple-factor error method is established based on the distance error. The tropical cyclone（TC) best track data which compiled by Chinese Meteorological Administration（CMA) were as the standard, the TC tracks in the western North Pacific forecasted by CMA, U S Joint Typhoon Warning Center and Japan Meteorological Agency in 2008 and 2009, were analyzed by using the new multiple-factor method that attributes TC track forecast error, and with the distance error method which uses generally was compared. The results show that the quite obvious difference exists between the multiple-factor error analysis method and distance error analysis method. The multiple-factor error method superiority is quite obvious. It is an useful exploration to the more scientific assessment method for typhoon track forecast error. It has a certain practice application value.
2014, 36(5): 54-60.
doi: 10.3969/j.issn.0253-4193.2014.05.006
Abstract:
Ambient sea-noise data were collected for three month period,using submersible buoy system in the South China Sea. Broad-band ambient-noise signals from the sixteen hydrophones were amplified and recorded for 2min every 1h. The results of data processing show a strong wind dependence in the upper frequency bands from approximately 800 Hz to 5 kHz,and the greater the wind speed,the better the correlation. The noise is correlated more with wind speed than with wave height. The wind-generated spectrum level producing virtually constant noise intensity in the midwater,however,due to the length of the hydrophone failed to cover the entire depth,the distribution of the noise at the near-surface and near-bottom unable to given. In the frequencies above 400 Hz ambient-noise spectrum level ranged with the entire wind speeds. In addition it was found that the ambient-noise spectrum shown to be linearly dependent upon the logarithm of wind speed.
Ambient sea-noise data were collected for three month period,using submersible buoy system in the South China Sea. Broad-band ambient-noise signals from the sixteen hydrophones were amplified and recorded for 2min every 1h. The results of data processing show a strong wind dependence in the upper frequency bands from approximately 800 Hz to 5 kHz,and the greater the wind speed,the better the correlation. The noise is correlated more with wind speed than with wave height. The wind-generated spectrum level producing virtually constant noise intensity in the midwater,however,due to the length of the hydrophone failed to cover the entire depth,the distribution of the noise at the near-surface and near-bottom unable to given. In the frequencies above 400 Hz ambient-noise spectrum level ranged with the entire wind speeds. In addition it was found that the ambient-noise spectrum shown to be linearly dependent upon the logarithm of wind speed.
2014, 36(5): 61-67.
doi: 10.3969/j.issn.0253-4193.2014.05.007
Abstract:
In this paper,a novel algorithm is present for oil spill detecting from look-alikes on SAR image. It based on Fourier fractal and feature selection. Fractal characteristics have an infinite number of details,and it has self-affine characteristics in different scales. These geometric characteristics are identical with oil film and look-alikes surface very well. The feature space of this method is composed by Fourier fractal characteristics. By using the differential evolution feature selection method,we select important eigen values（IEs) from total sample space. By using ANN and IEs,we classify the sample space. Experimental results show that classify accuracy rate reach the 100% when using selected eigenvectors. The algorithm gets the purpose of dimension reduction while select the important feature. This idea can be applied to other high-dimensional feature-based recognition system.
In this paper,a novel algorithm is present for oil spill detecting from look-alikes on SAR image. It based on Fourier fractal and feature selection. Fractal characteristics have an infinite number of details,and it has self-affine characteristics in different scales. These geometric characteristics are identical with oil film and look-alikes surface very well. The feature space of this method is composed by Fourier fractal characteristics. By using the differential evolution feature selection method,we select important eigen values（IEs) from total sample space. By using ANN and IEs,we classify the sample space. Experimental results show that classify accuracy rate reach the 100% when using selected eigenvectors. The algorithm gets the purpose of dimension reduction while select the important feature. This idea can be applied to other high-dimensional feature-based recognition system.
2014, 36(5): 68-76.
doi: 10.3969/j.issn.0253-4193.2014.05.008
Abstract:
Using the two-dimensional shallow water equations,the paper simulated the tidal field of Laizhou bay based on three charts surveyed in 1958,1984 and 2002 respectively. The models were used to study the evolution rule and to reveal the effect on the tidal dynamics by the Yellow River Sandspit formation and evolution over the past 50 years. Results show that,the high-velocity zones have developed outside of the sandspit,and on the periphery of the high-velocity zones,there are the tidal shear fronts which can be divided into inner-ebb-outer-flood type（IEOF) and the inner-flood-outer-ebb type（IFOE). Acompannied with the sandspit extension toward the the Laizhou bay constantly,distribution of the tide field have converted to the rayonnant model with the sandspit as the center,the arc high-velocity zone moved to the open seas with the increases of range and velocity,the tidal shear fronts lasted longer,spaced shorter,and its length from north to south had clear growth too. But the high-velocity zones and tidal shear fronts are always in the north of the Qingtuizi. Under the combined action of the arc high-velocity zone and tidal shear front,compared with the results of the coastal geomorphology evolution in the same period,a majority of the Yellow River sediment migrated and settled in the north sea area of the Qingtuozi merely. It is the main driving factors that lead to the different geomorphical evolution between the south and west coast.
Using the two-dimensional shallow water equations,the paper simulated the tidal field of Laizhou bay based on three charts surveyed in 1958,1984 and 2002 respectively. The models were used to study the evolution rule and to reveal the effect on the tidal dynamics by the Yellow River Sandspit formation and evolution over the past 50 years. Results show that,the high-velocity zones have developed outside of the sandspit,and on the periphery of the high-velocity zones,there are the tidal shear fronts which can be divided into inner-ebb-outer-flood type（IEOF) and the inner-flood-outer-ebb type（IFOE). Acompannied with the sandspit extension toward the the Laizhou bay constantly,distribution of the tide field have converted to the rayonnant model with the sandspit as the center,the arc high-velocity zone moved to the open seas with the increases of range and velocity,the tidal shear fronts lasted longer,spaced shorter,and its length from north to south had clear growth too. But the high-velocity zones and tidal shear fronts are always in the north of the Qingtuizi. Under the combined action of the arc high-velocity zone and tidal shear front,compared with the results of the coastal geomorphology evolution in the same period,a majority of the Yellow River sediment migrated and settled in the north sea area of the Qingtuozi merely. It is the main driving factors that lead to the different geomorphical evolution between the south and west coast.
2014, 36(5): 77-89.
doi: 10.3969/j.issn.0253-4193.2014.05.009
Abstract:
Forty years of geological and geophysical investigation and research made us clear that Chinese Historical Sea Lines（abbreviated as CHSL) in the South China Sea（SCS) not only demonstrated our sovereign right,but also a combination of giant geological boundaries between continental blocks,islands and countries. This paper will focus on the geological rationality of the CHSL in SCS,based on the investigation of geophysical features,regional geological structures,origin and evolution. The main conclusions are: the location of the eastern CHSL is consistent with the Manila Trench in topography. The west side of the trench is the Central Sea Basin of the SCS,with 4 km to 8 km oceanic crust. The east side of the trench is Philippine Archipelago. Based on paleomagnetic analysis,this archipelago was originally a small continental block located in the south latitude. It drifted northward to the present location along the Manila Trench since Middle to Late Eocene（about 16 Ma to 10 Ma),and thrusted on the oceanic crust of the Central Basin of South China Sea due to the combined action of Pacific Plate and Australia Plate. Thus,the Philippine Archipelago was outside source island arc block. The Huangyan Island is located west of the Manila Trench. It's a volcanic island of oceanic crust of central sea basin of South China Sea. It doesn't belong to the Philippine Archipelago. The location of the southern CHSLs of the SCS in topography is consistent with Nansha Trough. Accompanied with the Nansha Block splitting southward from the northern margin,the oceanic crust of proto South China Sea moved southward and subducted beneath the Kalimantan Continent along the Trough. Thus,Nansha Block was absolutely a different geological source continental block from the Kalimantan Continent. The location of the western CHSLs of South China Sea is the same in topography features as a giant East Vietnam Fault. The Fault might be related to the southward shift of the Xisha,Zhongsha and Nansha Block from north of the SCS. The north edge of Nansha block showed steep and straight normal faults,meaning that the Central basin of the South China Sea was mainly evolved by extension. Multi-channel seismic profiles,drilled records as well as the dredged samples showed that the stratigraphic divisions of several Nansha basins,Zhongsha and Xisha Block were very similar to and might be fully compared with that of the Pearl River Mouth Basin on the northern continental margin and paleo South China Continental Plate,so the Xisha,Zhongsha and Nansha Block originally belonged to the South China Continent,latterly it was split away and moved southward to present location owing to the evolution of South China Sea.
Forty years of geological and geophysical investigation and research made us clear that Chinese Historical Sea Lines（abbreviated as CHSL) in the South China Sea（SCS) not only demonstrated our sovereign right,but also a combination of giant geological boundaries between continental blocks,islands and countries. This paper will focus on the geological rationality of the CHSL in SCS,based on the investigation of geophysical features,regional geological structures,origin and evolution. The main conclusions are: the location of the eastern CHSL is consistent with the Manila Trench in topography. The west side of the trench is the Central Sea Basin of the SCS,with 4 km to 8 km oceanic crust. The east side of the trench is Philippine Archipelago. Based on paleomagnetic analysis,this archipelago was originally a small continental block located in the south latitude. It drifted northward to the present location along the Manila Trench since Middle to Late Eocene（about 16 Ma to 10 Ma),and thrusted on the oceanic crust of the Central Basin of South China Sea due to the combined action of Pacific Plate and Australia Plate. Thus,the Philippine Archipelago was outside source island arc block. The Huangyan Island is located west of the Manila Trench. It's a volcanic island of oceanic crust of central sea basin of South China Sea. It doesn't belong to the Philippine Archipelago. The location of the southern CHSLs of the SCS in topography is consistent with Nansha Trough. Accompanied with the Nansha Block splitting southward from the northern margin,the oceanic crust of proto South China Sea moved southward and subducted beneath the Kalimantan Continent along the Trough. Thus,Nansha Block was absolutely a different geological source continental block from the Kalimantan Continent. The location of the western CHSLs of South China Sea is the same in topography features as a giant East Vietnam Fault. The Fault might be related to the southward shift of the Xisha,Zhongsha and Nansha Block from north of the SCS. The north edge of Nansha block showed steep and straight normal faults,meaning that the Central basin of the South China Sea was mainly evolved by extension. Multi-channel seismic profiles,drilled records as well as the dredged samples showed that the stratigraphic divisions of several Nansha basins,Zhongsha and Xisha Block were very similar to and might be fully compared with that of the Pearl River Mouth Basin on the northern continental margin and paleo South China Continental Plate,so the Xisha,Zhongsha and Nansha Block originally belonged to the South China Continent,latterly it was split away and moved southward to present location owing to the evolution of South China Sea.
2014, 36(5): 90-97.
doi: 10.3969/j.issn.0253-4193.2014.05.010
Abstract:
Segmenting the seafloor sonar gray image,and extracting characteristic vector unit with principal component analysis,the selection of the mean,standard deviation,contrast,correlation coefficient,energy and homogeneity is as training characteristic vector,to build wavelet neural network. Using genetic algorithm to optimize the wavelet neural network initial weights and wavelet parameters,the three of sediment types sand,rocks,mud were been training,and get three sediment test accuracy of 90% or more,far better than single wavelet neural network training test accuracy. Experiments show that wavelet neural network based on genetic algorithm can be effectively used for seabed sediment sonar image recognition and classification,and overcome that the wavelet neural network training shortcomings easy to fall into local minimum.
Segmenting the seafloor sonar gray image,and extracting characteristic vector unit with principal component analysis,the selection of the mean,standard deviation,contrast,correlation coefficient,energy and homogeneity is as training characteristic vector,to build wavelet neural network. Using genetic algorithm to optimize the wavelet neural network initial weights and wavelet parameters,the three of sediment types sand,rocks,mud were been training,and get three sediment test accuracy of 90% or more,far better than single wavelet neural network training test accuracy. Experiments show that wavelet neural network based on genetic algorithm can be effectively used for seabed sediment sonar image recognition and classification,and overcome that the wavelet neural network training shortcomings easy to fall into local minimum.
2014, 36(5): 98-106.
doi: 10.3969/j.issn.0253-4193.2014.05.011
Abstract:
Core sediment samples collected from the mud area of Bohai Sea（BS) were analyzed for the concentration and depositional flux of black carbon（BC). By combining with 210Pb radionuclide dating,the relationship between centennial scale variation of BC depositional flux and human activities adjacent to the BS was discussed. The results showed that:（1) the concentration and flux of BC ranged from 0.24 to 0.49 mg/g and from 0.026 to 0.053 mg/(cm2·a),with mean values of（0.32±0.07) mg/g and（0.040±0.008) mg/(cm2·a),respectively. BC concentration was equivalent to those in other China seas（like the East China Sea),but significantly lower than the heavily polluted areas,such as America bays and Swedish continental shelf;（2) BC flux peaked around 1950s to mid-1970s and early 1990s to late 1990s,which each could be attributed to the sharply increased biomass burning and fossil fuels（coal and oil) combustion. However,the lower value and the decreasing trend of BC flux occurred in the period of late 1970s to late 1980s and the initial period of the 21st century could be explained by the diversion of the Huanghe River and the utilization of clean technology for energy consumption as well as pollution control strategies,respectively;（3) By comparing the present results and other studies in various seas and lakes around the world,it was confirmed that BC sedimentary record in core sediment could be used as a good geochemical indicator to reveal the influence history of anthropogenic activities on regional ecological environment.
Core sediment samples collected from the mud area of Bohai Sea（BS) were analyzed for the concentration and depositional flux of black carbon（BC). By combining with 210Pb radionuclide dating,the relationship between centennial scale variation of BC depositional flux and human activities adjacent to the BS was discussed. The results showed that:（1) the concentration and flux of BC ranged from 0.24 to 0.49 mg/g and from 0.026 to 0.053 mg/(cm2·a),with mean values of（0.32±0.07) mg/g and（0.040±0.008) mg/(cm2·a),respectively. BC concentration was equivalent to those in other China seas（like the East China Sea),but significantly lower than the heavily polluted areas,such as America bays and Swedish continental shelf;（2) BC flux peaked around 1950s to mid-1970s and early 1990s to late 1990s,which each could be attributed to the sharply increased biomass burning and fossil fuels（coal and oil) combustion. However,the lower value and the decreasing trend of BC flux occurred in the period of late 1970s to late 1980s and the initial period of the 21st century could be explained by the diversion of the Huanghe River and the utilization of clean technology for energy consumption as well as pollution control strategies,respectively;（3) By comparing the present results and other studies in various seas and lakes around the world,it was confirmed that BC sedimentary record in core sediment could be used as a good geochemical indicator to reveal the influence history of anthropogenic activities on regional ecological environment.
2014, 36(5): 107-123.
doi: 10.3969/j.issn.0253-4193.2014.05.012
Abstract:
There distributed numerous aseismic ridges and seamount chains in global seafloor. Of them, some remarkable ridges close to subduction zones exist in Pacific Ocean, Indian Ocean and Atlantic Ocean. In addition to Barracuda and Tiburon ridges（close to the Lesser Antilles arc) originating from transform fault, the genesis of most intra-plate aseismic ridges and seamount chains is related to mantle geodynamics（different from plate tectonics). At plate convergent margins, these aseismic ridges and seamount chains, together with normal oceanic crust formed in spreading mid-oceanic ridges, have been or are subducted beneath continental arc or intra-oceanic arc. The geological effects（e.g, structure, morphology, earthquake and magmatism) of the subduction of aseismic ridges and seamount chains on supra-subduction zones（SSZ) are obviously different from those of normal oceanic crust. The subduction of aseismic ridges and seamount chains often cause locally abnormal elevations of upper plate, enhancing subduction-induced erosion, landward displacement of trench, and the enhancement of intensity of earthquakes. Meanwhile, when aseismic ridges and seamount chains are subducted, they not only affect mantle geochemistry due to its entrained enriched geochemical characteristics, but play a significant role on geochemistry of arc and back-arc lavas and the formation of hydrothermal deposits on the SSZ setting. Finally, this paper point out possible research areas related to the subduction of aseimic ridges and seamount chains in China as follows, such as possible effects of subduction of the Huangyandao seamount chain on Luzon arc, effects of subduction of several aseismic ridges in the Indian Ocean on local areas of Tibetan Plateau, and effects of subduction of the Cocos ridge on the Costa Rica seismogenesis（targeted area of IODP leg 344), and some aseismic ridges（close to the Subduction zone) dispersed in west Pacific, etc.
There distributed numerous aseismic ridges and seamount chains in global seafloor. Of them, some remarkable ridges close to subduction zones exist in Pacific Ocean, Indian Ocean and Atlantic Ocean. In addition to Barracuda and Tiburon ridges（close to the Lesser Antilles arc) originating from transform fault, the genesis of most intra-plate aseismic ridges and seamount chains is related to mantle geodynamics（different from plate tectonics). At plate convergent margins, these aseismic ridges and seamount chains, together with normal oceanic crust formed in spreading mid-oceanic ridges, have been or are subducted beneath continental arc or intra-oceanic arc. The geological effects（e.g, structure, morphology, earthquake and magmatism) of the subduction of aseismic ridges and seamount chains on supra-subduction zones（SSZ) are obviously different from those of normal oceanic crust. The subduction of aseismic ridges and seamount chains often cause locally abnormal elevations of upper plate, enhancing subduction-induced erosion, landward displacement of trench, and the enhancement of intensity of earthquakes. Meanwhile, when aseismic ridges and seamount chains are subducted, they not only affect mantle geochemistry due to its entrained enriched geochemical characteristics, but play a significant role on geochemistry of arc and back-arc lavas and the formation of hydrothermal deposits on the SSZ setting. Finally, this paper point out possible research areas related to the subduction of aseimic ridges and seamount chains in China as follows, such as possible effects of subduction of the Huangyandao seamount chain on Luzon arc, effects of subduction of several aseismic ridges in the Indian Ocean on local areas of Tibetan Plateau, and effects of subduction of the Cocos ridge on the Costa Rica seismogenesis（targeted area of IODP leg 344), and some aseismic ridges（close to the Subduction zone) dispersed in west Pacific, etc.
2014, 36(5): 124-129.
doi: 10.3969/j.issn.0253-4193.2014.05.013
Abstract:
This paper analyzes and evaluates the seabed stability based on the marine geohazards in order to reflect the appropriate level of the geological environment of China's offshore to the human engineering activities. This paper proposes the concept of the evaluation of the seabed stability, and the indicator system of the evaluation of the seabed stability is set based on the earthquake zonation, engineering geology zonation, topography zonation, direct geohazards and restricted geohazards. And the weighted value of all evaluation indicators has been determined by using analytic hierarchy process. The seabed of China's offshore is divided into 6'×6' grid cells and the evaluation result is calculated by the map layer data of the marine geohazards map, earthquake zonation map, topography map and other digital layers with fuzzy comprehensive evaluation method. The seabed stability of China's offshore is divided into five grades from stable status to unstable status.
This paper analyzes and evaluates the seabed stability based on the marine geohazards in order to reflect the appropriate level of the geological environment of China's offshore to the human engineering activities. This paper proposes the concept of the evaluation of the seabed stability, and the indicator system of the evaluation of the seabed stability is set based on the earthquake zonation, engineering geology zonation, topography zonation, direct geohazards and restricted geohazards. And the weighted value of all evaluation indicators has been determined by using analytic hierarchy process. The seabed of China's offshore is divided into 6'×6' grid cells and the evaluation result is calculated by the map layer data of the marine geohazards map, earthquake zonation map, topography map and other digital layers with fuzzy comprehensive evaluation method. The seabed stability of China's offshore is divided into five grades from stable status to unstable status.
2014, 36(5): 130-135.
doi: 10.3969/j.issn.0253-4193.2014.05.014
Abstract:
Breaking wave has significant influence on the offshore coastal topography and offshore structures. Based on the physical model experiments,the bed form and pore water pressure are analyzed in the wave broken zone under the solitary wave and regular wave. Under breaking wave impact,the seabed surface scour is more heavily. Sandbar and sandpit are formed at the wave broken zone,and their scales are larger and the amplitudes of pore water pressure are higher under the solitary wave compared with regular wave. At the same time,effect of the variation of wave surface on the pore water pressure was studied. It is found that the duration curves of wave surface changing are similar to the duration curves of pore water pressure and it is more similar to the duration curves of pore water pressure gradient. It shows that the variation of wave surface can mostly reflect the variation of pore water pressure gradient on the seabed. Based on the discuss of the coupling effect between wave and seabed,it is found that topography variation may lead to waves appear different broken types at the wave broken zone,it was concluded from analysis that the pore water pressure amplitude under the plunging wave is bigger than spilling wave.
Breaking wave has significant influence on the offshore coastal topography and offshore structures. Based on the physical model experiments,the bed form and pore water pressure are analyzed in the wave broken zone under the solitary wave and regular wave. Under breaking wave impact,the seabed surface scour is more heavily. Sandbar and sandpit are formed at the wave broken zone,and their scales are larger and the amplitudes of pore water pressure are higher under the solitary wave compared with regular wave. At the same time,effect of the variation of wave surface on the pore water pressure was studied. It is found that the duration curves of wave surface changing are similar to the duration curves of pore water pressure and it is more similar to the duration curves of pore water pressure gradient. It shows that the variation of wave surface can mostly reflect the variation of pore water pressure gradient on the seabed. Based on the discuss of the coupling effect between wave and seabed,it is found that topography variation may lead to waves appear different broken types at the wave broken zone,it was concluded from analysis that the pore water pressure amplitude under the plunging wave is bigger than spilling wave.
2014, 36(5): 136-141.
doi: 10.3969/j.issn.0253-4193.2014.05.015
Abstract:
In nearshore waters,the spatial and temporal scales of waves,tides current and circulation have great difference. It is difficult to combine these factors' effects to predict the transport of sediment. This paper proposed a concept of ocean waves significant velocity,which combine the effects of wave,tide and ocean current by the horizontal kinetic energy superposition principle. Through comparing the relation between shear stress at the water-sediment interface and sediment carrying capacity,with the condition of equilibrium of sediment flux,a new formula of sediment carrying capacity which connected to the ocean waves significant velocity is derived. The sediment carrying capacity is related to the critical velocity that is increased with the water depth and reduced with the relative roughness. Finally,the field data of 30 observation stations and 590 simulation data have been used to verify this paper's formula. The results show that the new formula is good agreement with the field and simulation data. The formula of sediment carrying capacity could be used to simulate the nearshore sediment transport.
In nearshore waters,the spatial and temporal scales of waves,tides current and circulation have great difference. It is difficult to combine these factors' effects to predict the transport of sediment. This paper proposed a concept of ocean waves significant velocity,which combine the effects of wave,tide and ocean current by the horizontal kinetic energy superposition principle. Through comparing the relation between shear stress at the water-sediment interface and sediment carrying capacity,with the condition of equilibrium of sediment flux,a new formula of sediment carrying capacity which connected to the ocean waves significant velocity is derived. The sediment carrying capacity is related to the critical velocity that is increased with the water depth and reduced with the relative roughness. Finally,the field data of 30 observation stations and 590 simulation data have been used to verify this paper's formula. The results show that the new formula is good agreement with the field and simulation data. The formula of sediment carrying capacity could be used to simulate the nearshore sediment transport.
2014, 36(5): 142-151.
doi: 10.3969/j.issn.0253-4193.2014.05.016
Abstract:
A certain scale of linear submarine sands which are referred to as tidal sand ridges occurs off the Minjiang Estuary and the Jiulongjiang Estuary in Fujian. Based on the survey data by multi-beam acoustic sounding,sub-bottom profile as well as sediment grain sizes analysis,we studied the features of the tidal sand ridges. The results show that the sand ridges off the Minjiang Estuary are oriented NE-SW,and some of them are connected. The sand ridges off the Jiulongjiang Estuary are oriented ENE-WSW,and some appear to diverge on the end. According to the analysis of marine hydrodynamic environment affects,and the relation among the ridges scale,depth and relative distance to the estuary,the main body of the sand ridges is basically steady. They have been reformed by the recent hydrodynamics as evidenced by similar sand waves on both sides of flanks. The interaction by recent tidal current,wave and residual current leads to a relatively smooth surface on top and both flanks of the sand ridges. It's indicated that the tidal sands primarily originated from estuarine coarse sandy shoals on the paleo-channel system and were subsequently modified into the linear forms during the period of Holocene transgression when sea-level rise was decelerated.
A certain scale of linear submarine sands which are referred to as tidal sand ridges occurs off the Minjiang Estuary and the Jiulongjiang Estuary in Fujian. Based on the survey data by multi-beam acoustic sounding,sub-bottom profile as well as sediment grain sizes analysis,we studied the features of the tidal sand ridges. The results show that the sand ridges off the Minjiang Estuary are oriented NE-SW,and some of them are connected. The sand ridges off the Jiulongjiang Estuary are oriented ENE-WSW,and some appear to diverge on the end. According to the analysis of marine hydrodynamic environment affects,and the relation among the ridges scale,depth and relative distance to the estuary,the main body of the sand ridges is basically steady. They have been reformed by the recent hydrodynamics as evidenced by similar sand waves on both sides of flanks. The interaction by recent tidal current,wave and residual current leads to a relatively smooth surface on top and both flanks of the sand ridges. It's indicated that the tidal sands primarily originated from estuarine coarse sandy shoals on the paleo-channel system and were subsequently modified into the linear forms during the period of Holocene transgression when sea-level rise was decelerated.
2014, 36(5): 152-160.
doi: 10.3969/j.issn.0253-4193.2014.05.017
Abstract:
Through statistical analyzing the scientific investigate acoustic-physical data of the submarine coral sand in southern South China Sea,the paper shows that the analysis result of the compression wave velocity decrease with the porosity or water content increasing,and the compression wave velocity increase with the grain medium diameter or wet density increasing. On the basis of Biot's sound velocity formula and Wyllie's acoustic model about loose and saturation porosity water sediment,the paper explain the influence mechanism of physical-mechanical factors for the compression wave velocity of submarine coral sand,expound the cause of the sound velocity increase or decrease with the factor change of solid phase and liquid phase,analyze the precision difference of estimating submarine coral sand sound velocity of the several empirical formulas,and obtain the preliminary conclusions of needing to establishes the sound velocity empirical formulas fit for submarine coral sand and other single type seafloor sediment.
Through statistical analyzing the scientific investigate acoustic-physical data of the submarine coral sand in southern South China Sea,the paper shows that the analysis result of the compression wave velocity decrease with the porosity or water content increasing,and the compression wave velocity increase with the grain medium diameter or wet density increasing. On the basis of Biot's sound velocity formula and Wyllie's acoustic model about loose and saturation porosity water sediment,the paper explain the influence mechanism of physical-mechanical factors for the compression wave velocity of submarine coral sand,expound the cause of the sound velocity increase or decrease with the factor change of solid phase and liquid phase,analyze the precision difference of estimating submarine coral sand sound velocity of the several empirical formulas,and obtain the preliminary conclusions of needing to establishes the sound velocity empirical formulas fit for submarine coral sand and other single type seafloor sediment.
2014, 36(5): 161-169.
doi: 10.3969/j.issn.0253-4193.2014.05.018
Abstract:
For spectral wave mode,how to adequately describe the island terrain features and accurate computation of the physical processes such as wave diffraction,refraction and bottom friction due to the presence of shoals and channels or islands,is a key task in an archipelago or reef area.Nested multi-grid scheme,islands sub-grid topographic effect calculation scheme,fitted coordinate grids,unstructured grids,and dynamic adaptive quadtree grid technology embodied islands reefs complex terrain has made satisfactory effect. The complementary advantages of phase-resolving models could be perfect ocean wave spectrum model in order to improve the wave calculation accuracy of the nearshore wave physical process in wave spectrum model.A spectral wave model coupling a quadtree-adaptive discretization of the two spatial dimensions in spherical coordinates will be established; Based on phase-resolving models such of the mild-slope equation by taking into account high-order derivatives of the bottom profile and the current,the introduction of new diffraction,reflection and bottom friction effects will be exported correction factor for spectral wave model which is a frontier and exploratory development for ocean wave refined forecast in archipelago or reef ocean regions.
For spectral wave mode,how to adequately describe the island terrain features and accurate computation of the physical processes such as wave diffraction,refraction and bottom friction due to the presence of shoals and channels or islands,is a key task in an archipelago or reef area.Nested multi-grid scheme,islands sub-grid topographic effect calculation scheme,fitted coordinate grids,unstructured grids,and dynamic adaptive quadtree grid technology embodied islands reefs complex terrain has made satisfactory effect. The complementary advantages of phase-resolving models could be perfect ocean wave spectrum model in order to improve the wave calculation accuracy of the nearshore wave physical process in wave spectrum model.A spectral wave model coupling a quadtree-adaptive discretization of the two spatial dimensions in spherical coordinates will be established; Based on phase-resolving models such of the mild-slope equation by taking into account high-order derivatives of the bottom profile and the current,the introduction of new diffraction,reflection and bottom friction effects will be exported correction factor for spectral wave model which is a frontier and exploratory development for ocean wave refined forecast in archipelago or reef ocean regions.
2014, 36(5): 170-176.
doi: 10.3969/j.issn.0253-4193.2014.05.019
Abstract:
The rip current is one of the most significant factors affecting nearshore engineering and coastal evolution,and has very important significance for the pollutant emission and swimming safety. Based on the published literatures about the laboratory and field measurements,the theoretical analysis,generation mechanisms and the numerical simulations,the research progresses in this subject at home and abroad are reviewed in detail. Several opinions on the existing problems are summered and the future developments are proposed.
The rip current is one of the most significant factors affecting nearshore engineering and coastal evolution,and has very important significance for the pollutant emission and swimming safety. Based on the published literatures about the laboratory and field measurements,the theoretical analysis,generation mechanisms and the numerical simulations,the research progresses in this subject at home and abroad are reviewed in detail. Several opinions on the existing problems are summered and the future developments are proposed.
2014, 36(5): 177-185.
doi: 10.3969/j.issn.0253-4193.2014.05.020
Abstract:
Composition and assemblage characteristics of heavy minerals were analyzed in core OS03-1 sediment collected from the Academy of Sciences Rise of southeastern Okhotsk Sea. The results show that the dominant minerals are hyperthene,epidote and common hornblende,and characteristic minerals are titanomagnetite and augite; the sediments are mostly ice-rafted debris（IRD) and volcanogenic matter. IRD were mainly derived from the western and northern Okhotsk Sea,and a little from Kamchatka peninsula. Volcanogenic matter was mainly from Kamchatka Peninsula and Kurile Islands. Three tephra layers were identified. The first layer is characterized by special color,grain size and mineral composition,which was same to the well studied K2 tephra layer and deposited at 26.0 ka BP. The third layer could be recognized by color,but was clearly diluted by terrigenous sediment. The second tephra layer couldn't be distinguished by color and grain size because of mixing with terrigenous sediment. The study also shows that composition and assemblage of heavy minerals are both effective indicators of sediment sources,and credible indentifying index of tephra,especially those diluted by terrigenous matter.
Composition and assemblage characteristics of heavy minerals were analyzed in core OS03-1 sediment collected from the Academy of Sciences Rise of southeastern Okhotsk Sea. The results show that the dominant minerals are hyperthene,epidote and common hornblende,and characteristic minerals are titanomagnetite and augite; the sediments are mostly ice-rafted debris（IRD) and volcanogenic matter. IRD were mainly derived from the western and northern Okhotsk Sea,and a little from Kamchatka peninsula. Volcanogenic matter was mainly from Kamchatka Peninsula and Kurile Islands. Three tephra layers were identified. The first layer is characterized by special color,grain size and mineral composition,which was same to the well studied K2 tephra layer and deposited at 26.0 ka BP. The third layer could be recognized by color,but was clearly diluted by terrigenous sediment. The second tephra layer couldn't be distinguished by color and grain size because of mixing with terrigenous sediment. The study also shows that composition and assemblage of heavy minerals are both effective indicators of sediment sources,and credible indentifying index of tephra,especially those diluted by terrigenous matter.
2014, 36(5): 186-189.
doi: 10.3969/j.issn.0253-4193.2014.05.021
Abstract:
The recorded data by cyclic triaxial testing are discrete and limited, the relationships of data need to be fitted for easy use, however the present expirical equation is not available for testing data. To obtain the value of shear modulus and damping ratio for different shear strain, the piecewise polynomial fitting method is applied to normalized shear modulus and damping ratio versus shear strain based on least-square principle. The value of shear strain is converted to avoid the equation set ill-conditioned due to the great difference in shear strain magnitude. The fitting results is satisfactory by using the piecewise lower polynomial order fitting.
The recorded data by cyclic triaxial testing are discrete and limited, the relationships of data need to be fitted for easy use, however the present expirical equation is not available for testing data. To obtain the value of shear modulus and damping ratio for different shear strain, the piecewise polynomial fitting method is applied to normalized shear modulus and damping ratio versus shear strain based on least-square principle. The value of shear strain is converted to avoid the equation set ill-conditioned due to the great difference in shear strain magnitude. The fitting results is satisfactory by using the piecewise lower polynomial order fitting.
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