2019 Vol. 41, No. 11
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2019, 41(11): .
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2019, 41(11): .
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2019, 41(11): 1-14.
doi: 10.3969/j.issn.0253-4193.2019.11.001
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Different researchers have studied mesoscale phenomena of Kuroshio Extension (KE) and north Pacific subtropical countercurrent (STCC) area independently, but they have never made comparisons and analysis of the phenomenon in the two areas. In this paper, the mesoscale phenomenon and the change process of energy in these two regions are unified analyzed and compared by using the 11 years data of sea surface anomaly of altimeter. Firstly, the ‘Okubo-Weiss algorithm’ is used to detect and analyze the eddy, and concluded that there are differences in distribution, amplitude, energy and lifetime between the cyclonic eddies and the anticyclonic eddies in these two regions. Secondly, the kinetic energy spectrum and energy cascade of mesoscale eddies in the two regions are discussed by using the method of kinetic energy spectrum analysis. The kinetic energy spectral density of both regions is concentrated in 2×10–3 circle/km to 4×10–3 circle/km. The propagation direction of most of mesoscale eddies in the KE region are more meridionally, while that in the STCC region are more zonally. The kinetic energy transfer terms of the two regions are mainly negative in the range of 2×10–3 circle/km to 3×10–3 circle/km, which implied that there is an energy source in this wavenumber, meanwhile, there is an inverse cascade.
Different researchers have studied mesoscale phenomena of Kuroshio Extension (KE) and north Pacific subtropical countercurrent (STCC) area independently, but they have never made comparisons and analysis of the phenomenon in the two areas. In this paper, the mesoscale phenomenon and the change process of energy in these two regions are unified analyzed and compared by using the 11 years data of sea surface anomaly of altimeter. Firstly, the ‘Okubo-Weiss algorithm’ is used to detect and analyze the eddy, and concluded that there are differences in distribution, amplitude, energy and lifetime between the cyclonic eddies and the anticyclonic eddies in these two regions. Secondly, the kinetic energy spectrum and energy cascade of mesoscale eddies in the two regions are discussed by using the method of kinetic energy spectrum analysis. The kinetic energy spectral density of both regions is concentrated in 2×10–3 circle/km to 4×10–3 circle/km. The propagation direction of most of mesoscale eddies in the KE region are more meridionally, while that in the STCC region are more zonally. The kinetic energy transfer terms of the two regions are mainly negative in the range of 2×10–3 circle/km to 3×10–3 circle/km, which implied that there is an energy source in this wavenumber, meanwhile, there is an inverse cascade.
2019, 41(11): 15-24.
doi: 10.3969/j.issn.0253-4193.2019.11.002
Abstract:
In order to study the real-time prediction method of ocean wave information, some theoretical derivation is made based on inverse scattering transformation of cubic Schrödinger equation, and a method to calculate eigenvalues from measured wave height time series is given. Then the calculated eigenvalues are used to predict spatial-temporal evolution of wave envelope. The predictions are then compared with measured time series, the results show the method has good effectiveness and accuracy. This method can provide support for big wave warning of ships or offshore platform, and time windows seeking for offshore operation under heavy sea.
In order to study the real-time prediction method of ocean wave information, some theoretical derivation is made based on inverse scattering transformation of cubic Schrödinger equation, and a method to calculate eigenvalues from measured wave height time series is given. Then the calculated eigenvalues are used to predict spatial-temporal evolution of wave envelope. The predictions are then compared with measured time series, the results show the method has good effectiveness and accuracy. This method can provide support for big wave warning of ships or offshore platform, and time windows seeking for offshore operation under heavy sea.
2019, 41(11): 25-34.
doi: 10.3969/j.issn.0253-4193.2019.11.003
Abstract:
Due to the narrow tube effect, ocean waves are large and usually mixed with swell in the Taiwan Strait. Much attention has been attracted by the swells, since they have important impacts on floating structures including the ships. The separation of wind-waves and swells is a fundamental step for the research on characteristics of swells, also is a hot topic with difficulties. But the generally accepted method of separation, which is two-dimensional spectral method, is hard to use in practice due to lack of data and limitations of observation. Thus the selection of one-dimensional spectral method with high accuracy becomes a key problem in the practical. Using the two-dimensional spectral data of three wave stations in the Taiwan Strait, results of separation are obtained. Considering results of separation as well as characteristics of wind-waves and swells in the Taiwan Strait, accuracies of different one-dimensional spectral methods are calculated and compared. The results show that the PM method as a whole is more accurate than other methods. Based on results of separation, a one-dimensional spectrum method is proposed which is a combination of the improved WH method and the PM method.
Due to the narrow tube effect, ocean waves are large and usually mixed with swell in the Taiwan Strait. Much attention has been attracted by the swells, since they have important impacts on floating structures including the ships. The separation of wind-waves and swells is a fundamental step for the research on characteristics of swells, also is a hot topic with difficulties. But the generally accepted method of separation, which is two-dimensional spectral method, is hard to use in practice due to lack of data and limitations of observation. Thus the selection of one-dimensional spectral method with high accuracy becomes a key problem in the practical. Using the two-dimensional spectral data of three wave stations in the Taiwan Strait, results of separation are obtained. Considering results of separation as well as characteristics of wind-waves and swells in the Taiwan Strait, accuracies of different one-dimensional spectral methods are calculated and compared. The results show that the PM method as a whole is more accurate than other methods. Based on results of separation, a one-dimensional spectrum method is proposed which is a combination of the improved WH method and the PM method.
2019, 41(11): 35-39.
doi: 10.3969/j.issn.0253-4193.2019.11.004
Abstract:
Although many on-site measures and numerical simulations indicate that ocean ridges can trap tsunami waves and guide them toward the far-field area, causing serious disasters, few studies have elaborated its mechanism. Based on the ray theory, this paper derives analytical solutions of the ray trajectory for trapped waves over the exponential ocean ridge. Furthermore, the completely trapped condition for tsunamis generated at top of the ridge is proposed. Based on such critical condition, the formulation of the trapped efficiency is derived to evaluate the ratio of the energy trapped by the ocean ridge to the total tsunami energy.
Although many on-site measures and numerical simulations indicate that ocean ridges can trap tsunami waves and guide them toward the far-field area, causing serious disasters, few studies have elaborated its mechanism. Based on the ray theory, this paper derives analytical solutions of the ray trajectory for trapped waves over the exponential ocean ridge. Furthermore, the completely trapped condition for tsunamis generated at top of the ridge is proposed. Based on such critical condition, the formulation of the trapped efficiency is derived to evaluate the ratio of the energy trapped by the ocean ridge to the total tsunami energy.
2019, 41(11): 40-50.
doi: 10.3969/j.issn.0253-4193.2019.11.005
Abstract:
Based on the survey data of temperature and salinity, concentration mixture analysis method is used to analyze water masses at 10°N section in the tropical central and eastern Pacific. From top to bottom, the water masses are the Eastern Equatorial Tropical Water Mass (E-ETWM), the North Pacific Central Water (NPCW), the California Current System waters (CCS), the South Pacific Central Water (SPCW), the Pacific Subarctic Water Mass (PSWM) and the Pacific Deep Water (PDW). It is found that the upwelling is induced by the constant positive wind stress curl throughout the year in the sea area from 9°N to 10°N under the influence of the intertropical convergence zone (ITCZ), then the four ventilated subduction water masses of the NPCW, the CCS, the SPCW and the PSWM are pumped into the subsurface and intermediate layer and distributed at different levels. Previous studies have only pointed out that the above four water masses will sink and move towards the equator after the formation of surface ventilation. This study further clarify the dynamic mechanism of the four water masses moving equatorwards as it subduction. What’s more, we reveal their corresponding depths at the 10°N section in the tropical central and eastern Pacific. The results reveal the cycling process between the tropical central and eastern Pacific water masses and the upper and intermediate layer water masses in the subtropical, subpolar regions in the North Pacific and subtropical region in South Pacific, which are of great scientific value to understand the exchange and redistribution of matter and energy between high, middle and low latitudes in the North Pacific.
Based on the survey data of temperature and salinity, concentration mixture analysis method is used to analyze water masses at 10°N section in the tropical central and eastern Pacific. From top to bottom, the water masses are the Eastern Equatorial Tropical Water Mass (E-ETWM), the North Pacific Central Water (NPCW), the California Current System waters (CCS), the South Pacific Central Water (SPCW), the Pacific Subarctic Water Mass (PSWM) and the Pacific Deep Water (PDW). It is found that the upwelling is induced by the constant positive wind stress curl throughout the year in the sea area from 9°N to 10°N under the influence of the intertropical convergence zone (ITCZ), then the four ventilated subduction water masses of the NPCW, the CCS, the SPCW and the PSWM are pumped into the subsurface and intermediate layer and distributed at different levels. Previous studies have only pointed out that the above four water masses will sink and move towards the equator after the formation of surface ventilation. This study further clarify the dynamic mechanism of the four water masses moving equatorwards as it subduction. What’s more, we reveal their corresponding depths at the 10°N section in the tropical central and eastern Pacific. The results reveal the cycling process between the tropical central and eastern Pacific water masses and the upper and intermediate layer water masses in the subtropical, subpolar regions in the North Pacific and subtropical region in South Pacific, which are of great scientific value to understand the exchange and redistribution of matter and energy between high, middle and low latitudes in the North Pacific.
2019, 41(11): 51-63.
doi: 10.3969/j.issn.0253-4193.2019.11.006
Abstract:
Sea surface temperature (SST) is an important expression of air-sea interaction, and accurate simulation of SST is also the foundation of ocean internal temperature prediction. This paper attempts to diagnose the contribution of radiation fields on SST simulation by comparing the results of SST driven by two different surface forcing modes employing the Regional Ocean Model System (ROMS). According to the EOF analysis method, a correction scheme on CFSR surface atmospheric forcing radiation data is proposed, and therefrom, a high frequency revised dataset of CFSR radiation flux is obtained. The comparison tests show that surface forcing derived from the COARE 3.0 formula mode improves simulating performance of SST, as the RMSE decreases by 39% comparing to direct forcing mode. Comparing the thermal radiation fields of the two forcing modes, it is found that latent radiation is the main reason for different performances of SST simulation, and following by the effect of sensible heat radiation difference. Correction of both two radiation fields could improve the SST simulation results significantly; and correction of longwave radiation shows a more significant effect in winter which is still weaker than that of correction of latent radiation. In comprehensive, the accurate dataset of surface forcing field is more effective than change the choice of forcing mode.
Sea surface temperature (SST) is an important expression of air-sea interaction, and accurate simulation of SST is also the foundation of ocean internal temperature prediction. This paper attempts to diagnose the contribution of radiation fields on SST simulation by comparing the results of SST driven by two different surface forcing modes employing the Regional Ocean Model System (ROMS). According to the EOF analysis method, a correction scheme on CFSR surface atmospheric forcing radiation data is proposed, and therefrom, a high frequency revised dataset of CFSR radiation flux is obtained. The comparison tests show that surface forcing derived from the COARE 3.0 formula mode improves simulating performance of SST, as the RMSE decreases by 39% comparing to direct forcing mode. Comparing the thermal radiation fields of the two forcing modes, it is found that latent radiation is the main reason for different performances of SST simulation, and following by the effect of sensible heat radiation difference. Correction of both two radiation fields could improve the SST simulation results significantly; and correction of longwave radiation shows a more significant effect in winter which is still weaker than that of correction of latent radiation. In comprehensive, the accurate dataset of surface forcing field is more effective than change the choice of forcing mode.
2019, 41(11): 64-74.
doi: 10.3969/j.issn.0253-4193.2019.11.007
Abstract:
Boron is a common element in vent fluids of seafloor hydrothermal fields. Due to its typical fluid-mobility and distinct isotope compositions in different reservoirs, boron has been largely applied to trace metal sources, water/rock interaction and sediment contribution to hydrothermal fluids. Up to date, the B contents and its isotope compositions in hydrothermal fluids from the major seafloor hydrothermal fields have been studied sufficiently, but the comparisons of B behavior in different geological settings are relatively limited and the reasons causing the systematic differences in elements and isotope compositions of hydrothermal fluids are still unclear. In this paper, the sources of B in hydrothermal fluids from different geological settings were calculated based on B contents and its isotope compositions, meanwhile, the causes of systematic differences in B isotope compositions between mid-ocean ridge and back-arc basin hydrothermal fluids were discussed. Results show that the δ11B values of hydrothermal end member fluids from different hydrothermal fields have large variations, which mainly results from the mixing of B from difference sources in different proportions. Boron in mid-ocean ridge and sediment-starve back-arc basin hydrothermal fluids are mainly from the mixing of seawater and basement-derived B, the contribution of magmatic volatiles to sediment-starve back-arc basin hydrothermal systems is the major causes of B isotope composition differences in these two geological settings. Moreover, the differences in geochemical compositions of basement rocks and degrees of water/rock interaction also cause the differences in B isotope compositions to some extent. While the δ11B values of hydrothermal end member fluids from sediment-covered hydrothermal fields are extremely low and contribution of sediment-derived B to hydrothermal fluid is the major cause of this phenomenon. Moreover, sediment absorption also causes the B isotope variation to some extent. In sediment-covered mid-ocean ridge hydrothermal fields, the B isotope compositions of hydrothermal fluids are also influenced by the incorporation of sediment-derived B and have relatively lower δ11B values. Compared with the Okinawa Trough, the degrees of sediment absorption in sediment-covered mid-ocean ridge hydrothermal fluids are more intensely. Based on these analysis, we put forward the mechanism causing systematic differences in B isotope compositions of hydrothermal fluids from mid-ocean ridge and back-arc basins.
Boron is a common element in vent fluids of seafloor hydrothermal fields. Due to its typical fluid-mobility and distinct isotope compositions in different reservoirs, boron has been largely applied to trace metal sources, water/rock interaction and sediment contribution to hydrothermal fluids. Up to date, the B contents and its isotope compositions in hydrothermal fluids from the major seafloor hydrothermal fields have been studied sufficiently, but the comparisons of B behavior in different geological settings are relatively limited and the reasons causing the systematic differences in elements and isotope compositions of hydrothermal fluids are still unclear. In this paper, the sources of B in hydrothermal fluids from different geological settings were calculated based on B contents and its isotope compositions, meanwhile, the causes of systematic differences in B isotope compositions between mid-ocean ridge and back-arc basin hydrothermal fluids were discussed. Results show that the δ11B values of hydrothermal end member fluids from different hydrothermal fields have large variations, which mainly results from the mixing of B from difference sources in different proportions. Boron in mid-ocean ridge and sediment-starve back-arc basin hydrothermal fluids are mainly from the mixing of seawater and basement-derived B, the contribution of magmatic volatiles to sediment-starve back-arc basin hydrothermal systems is the major causes of B isotope composition differences in these two geological settings. Moreover, the differences in geochemical compositions of basement rocks and degrees of water/rock interaction also cause the differences in B isotope compositions to some extent. While the δ11B values of hydrothermal end member fluids from sediment-covered hydrothermal fields are extremely low and contribution of sediment-derived B to hydrothermal fluid is the major cause of this phenomenon. Moreover, sediment absorption also causes the B isotope variation to some extent. In sediment-covered mid-ocean ridge hydrothermal fields, the B isotope compositions of hydrothermal fluids are also influenced by the incorporation of sediment-derived B and have relatively lower δ11B values. Compared with the Okinawa Trough, the degrees of sediment absorption in sediment-covered mid-ocean ridge hydrothermal fluids are more intensely. Based on these analysis, we put forward the mechanism causing systematic differences in B isotope compositions of hydrothermal fluids from mid-ocean ridge and back-arc basins.
2019, 41(11): 75-88.
doi: 10.3969/j.issn.0253-4193.2019.11.008
Abstract:
The sedimentary environment of the South Yellow Sea (SYS) is complex under the interaction of sea and land. It has always been the focus and difficulty for sedimentary mechanism researches. In this study, multi-index records, including 196 samples of grain size and bulk organic matter indexes (TOC, TN, TOC/TN, and δ13Corg) of a gravity Core Z1 from the central South Yellow Sea mud area were obtained. Five layers of AMS14C age were determined and the highest resolution was 11 a/cm. Our results reveal that the sedimentary processes of central SYS since 6.1 ka BP could be generally divided into three stages: (1) During 6.1–5.2 ka BP, the sediments had the coarsest mean grain size and were mainly residual sand and terrestrial coarse-grained matters, the content of organic matter was very low and primarily terrigenous materials. The variation of mean grain size and organic matter content were both influenced by strong East Asian Monsoon. The low preservation efficiency of organic matter in turbulent marine environment and the remarkable dilution effect of large quantity of terrestrial input were other reasons for lower organic content. (2) During 5.2–3.9 ka BP, the sediment mean grain size was thinner with fluctuating amplitude, the organic matter was increasing and mainly marine materials. They were concerned with weakening East Asian Winter Monsoon. The increase of marine organic matter was related to the increasing influence of Yellow Sea Warm Current. (3) Since 3.9 ka BP, the mean grain size of the sediments was the smallest and relatively constant, the organic matter content was continuously increased to 1.9 ka BP, and then stabilize. They were chiefly controlled by the modern circulation system and East Asian Winter Monsoon. The mean grain size and the overall organic matter indexes explain the complexity of sedimentary environment evolution of the central South Yellow Sea mud area. High-resolution records of sedimentary environment evolution obtained in this study could provide data for sedimentary mechanism researches, moreover, which have certain instruction significance on paleoclimate and paleoceanography of the SYS.
The sedimentary environment of the South Yellow Sea (SYS) is complex under the interaction of sea and land. It has always been the focus and difficulty for sedimentary mechanism researches. In this study, multi-index records, including 196 samples of grain size and bulk organic matter indexes (TOC, TN, TOC/TN, and δ13Corg) of a gravity Core Z1 from the central South Yellow Sea mud area were obtained. Five layers of AMS14C age were determined and the highest resolution was 11 a/cm. Our results reveal that the sedimentary processes of central SYS since 6.1 ka BP could be generally divided into three stages: (1) During 6.1–5.2 ka BP, the sediments had the coarsest mean grain size and were mainly residual sand and terrestrial coarse-grained matters, the content of organic matter was very low and primarily terrigenous materials. The variation of mean grain size and organic matter content were both influenced by strong East Asian Monsoon. The low preservation efficiency of organic matter in turbulent marine environment and the remarkable dilution effect of large quantity of terrestrial input were other reasons for lower organic content. (2) During 5.2–3.9 ka BP, the sediment mean grain size was thinner with fluctuating amplitude, the organic matter was increasing and mainly marine materials. They were concerned with weakening East Asian Winter Monsoon. The increase of marine organic matter was related to the increasing influence of Yellow Sea Warm Current. (3) Since 3.9 ka BP, the mean grain size of the sediments was the smallest and relatively constant, the organic matter content was continuously increased to 1.9 ka BP, and then stabilize. They were chiefly controlled by the modern circulation system and East Asian Winter Monsoon. The mean grain size and the overall organic matter indexes explain the complexity of sedimentary environment evolution of the central South Yellow Sea mud area. High-resolution records of sedimentary environment evolution obtained in this study could provide data for sedimentary mechanism researches, moreover, which have certain instruction significance on paleoclimate and paleoceanography of the SYS.
2019, 41(11): 89-100.
doi: 10.3969/j.issn.0253-4193.2019.11.009
Abstract:
On the basis of particle size analysis, heavy mineral analysis was carried out in different size fractions with a spacing of 0.5Φ of the Changjiang River Estuary surface sediment. Heavy mineral similarity value calculated between the each grain group and wide window grain size group (1.5Φ to 6Φ). The results show that the surface sediments of the Changjiang River Estuary have a large grain size span, ranging from coarse sand to mud, and the silt content is high. Intrasample variability of heavy mineral contents, species and compositions is ubiquitous, intersample variability has certain regularity. There are about 30 kinds of heavy minerals in the Changjiang River Estuary, about ten kinds of minerals in the coarse-grained fractions, the number of heavy minerals in fine-grained fractions has increased to more than twenty. 3.5Φ to 4.5Φ is a fraction with numerous and complex heavy minerals. Mica is rich in the coarse-grained grade (<3Φ), and the heavy mineral combination is mica+hornblende, but almost absent in fine grains of >4Φ. The amphibole group almost exist all range of grain sizes and the content is high in grain of 3Φ to 5Φ. Epidote group, stable minerals, and especially Fe-metallic minerals increase at fine grain of >3.5Φ. The heavy minerals combination is hornblende+epidote+limonite in the Changjiang River Estuary, sphene is the characteristic mineral. Similarity analysis shows that the main grain size and the wide grain size of the sediment have similarities in the characteristics of heavy minerals, which is the most suitable size for replacing the heavy minerals of the whole sediment. The heavy mineral characteristics are deeply affected by the particle size distribution in the Changjiang River Estuary. Mineral type, mineral combination and indice, and the hydrodynamic and provenance implications must be combined with the grain size analysis.
On the basis of particle size analysis, heavy mineral analysis was carried out in different size fractions with a spacing of 0.5Φ of the Changjiang River Estuary surface sediment. Heavy mineral similarity value calculated between the each grain group and wide window grain size group (1.5Φ to 6Φ). The results show that the surface sediments of the Changjiang River Estuary have a large grain size span, ranging from coarse sand to mud, and the silt content is high. Intrasample variability of heavy mineral contents, species and compositions is ubiquitous, intersample variability has certain regularity. There are about 30 kinds of heavy minerals in the Changjiang River Estuary, about ten kinds of minerals in the coarse-grained fractions, the number of heavy minerals in fine-grained fractions has increased to more than twenty. 3.5Φ to 4.5Φ is a fraction with numerous and complex heavy minerals. Mica is rich in the coarse-grained grade (<3Φ), and the heavy mineral combination is mica+hornblende, but almost absent in fine grains of >4Φ. The amphibole group almost exist all range of grain sizes and the content is high in grain of 3Φ to 5Φ. Epidote group, stable minerals, and especially Fe-metallic minerals increase at fine grain of >3.5Φ. The heavy minerals combination is hornblende+epidote+limonite in the Changjiang River Estuary, sphene is the characteristic mineral. Similarity analysis shows that the main grain size and the wide grain size of the sediment have similarities in the characteristics of heavy minerals, which is the most suitable size for replacing the heavy minerals of the whole sediment. The heavy mineral characteristics are deeply affected by the particle size distribution in the Changjiang River Estuary. Mineral type, mineral combination and indice, and the hydrodynamic and provenance implications must be combined with the grain size analysis.
2019, 41(11): 101-116.
doi: 10.3969/j.issn.0253-4193.2019.11.010
Abstract:
Shallow seismic profiles, 16 sediment vibrocores, and AMS 14C ages of foraminifers and a freshwater snail (Parafossarulus striatulus (Benson)) were used to recognize the depositional architecture, the accumulation depths, and the sediment compositions of the northern flank of the abandoned subaqueous Yellow River Delta off the Lianyungang coast, western South Yellow Sea, and further to classify the geographical units and their distribution. The facies of the adjacent shallow transgressive deposits were also distinguished to recognize their paleo-environments. Results show that the subaqueous deposits are divided geographically into two units of delta front and prodelta. Both of them juxtapose along the Lianyungang coast. The delta front is located off the coast between the Liezi River and New Huaihe River mouths. It is a fan-like clinoform, prograding towards NNE and inclining towards NW. It contains two lobes named the Guanhe Lobe and its eastern lobe. Both of them make up the main depocenters. The delta front is mainly composed of sandy deposits, with some muds or sandy muds in the eastern interdistributary bay between the two lobes. The prodelta is located northwest of the delta front, extending off the Liezi River mouth towards Haizhou Bay. It is accumulated by thin mud deposits with vertically homogeneous distribution. Two cores in its northern portion reveal the thicknesses of 1.8 m and 1.5 m, respectively. The transgressive sand sheet is located north of the subaqueous delta, with a thickness of ~20 cm. It is widely present in the study area. Off the Lianyungang coast, however, it is covered by Yellow River-derived sediments and thus underlies the abandoned Yellow River Delta. This sand sheet is characterized by an erosional and relict morphology. Land–sea transition facies are widely present below these transgressive sands, which were formed during the MIS 3 of the Late Pleistocene. It consists of yellow silts or sandy silts, containing many foraminifera and ostracoda as well as freshwater snails.
Shallow seismic profiles, 16 sediment vibrocores, and AMS 14C ages of foraminifers and a freshwater snail (Parafossarulus striatulus (Benson)) were used to recognize the depositional architecture, the accumulation depths, and the sediment compositions of the northern flank of the abandoned subaqueous Yellow River Delta off the Lianyungang coast, western South Yellow Sea, and further to classify the geographical units and their distribution. The facies of the adjacent shallow transgressive deposits were also distinguished to recognize their paleo-environments. Results show that the subaqueous deposits are divided geographically into two units of delta front and prodelta. Both of them juxtapose along the Lianyungang coast. The delta front is located off the coast between the Liezi River and New Huaihe River mouths. It is a fan-like clinoform, prograding towards NNE and inclining towards NW. It contains two lobes named the Guanhe Lobe and its eastern lobe. Both of them make up the main depocenters. The delta front is mainly composed of sandy deposits, with some muds or sandy muds in the eastern interdistributary bay between the two lobes. The prodelta is located northwest of the delta front, extending off the Liezi River mouth towards Haizhou Bay. It is accumulated by thin mud deposits with vertically homogeneous distribution. Two cores in its northern portion reveal the thicknesses of 1.8 m and 1.5 m, respectively. The transgressive sand sheet is located north of the subaqueous delta, with a thickness of ~20 cm. It is widely present in the study area. Off the Lianyungang coast, however, it is covered by Yellow River-derived sediments and thus underlies the abandoned Yellow River Delta. This sand sheet is characterized by an erosional and relict morphology. Land–sea transition facies are widely present below these transgressive sands, which were formed during the MIS 3 of the Late Pleistocene. It consists of yellow silts or sandy silts, containing many foraminifera and ostracoda as well as freshwater snails.
2019, 41(11): 117-126.
doi: 10.3969/j.issn.0253-4193.2019.11.011
Abstract:
In order to study the formation, development and evolutionary mechanism of the only known marine blue hole in China, also the deepest one in the world, we used the LISST-100X and CTD carried by remote operated vehicle for the measurement of suspended matter and the profile of temperature and salinity in the Sansha Yongle Blue Hole in May 2017. We acquired the data of the volume concentration of suspended matter, temperature, salinity and dissolved oxygen, then we conducted the study of the vertical distribution characteristics of suspended matter. The results indicate that the water below 90 m of the cave is anaerobic and the concentration of suspended matter presents 5 cycle changes. The results also indicate that there are three thermoclines and three haloclines in the Sansha Yongle Blue Hole, and there is a good correspondence between them. The total concentration of suspended matter in the surface water is about 20 μL/L, and the average concentration of suspended matter is 5.93 μL/L. CyclothemⅠlies at 5 m in shallow water layer; cyclothemⅡlies between 10 m and 43 m below the water surface, partially corresponding to the first thermocline and halocline water depth (10–20 m); cyclothem Ⅲ lies between 70 meters to 110 m at depth, completely corresponding to the second thermocline and halocline (water depth 70–110 m); cyclothem Ⅳ lies between 130 m to 150 m, completely corresponding to the third thermocline and halocline (water depth 130–150 m); cyclothemⅤlies in 260 m and then deep to 300 m. The suspended matter concentration on the surface is high, as is mainly affected by the sediment input from the surrounding coral reefs. The vertical distribution characteristics of suspended matter in the Sansha Yongle Blue Hole is mainly controlled and affected by hydrodynamic force, cave morphology, thermocline, halocline, dissolved oxygen content and plankton.
In order to study the formation, development and evolutionary mechanism of the only known marine blue hole in China, also the deepest one in the world, we used the LISST-100X and CTD carried by remote operated vehicle for the measurement of suspended matter and the profile of temperature and salinity in the Sansha Yongle Blue Hole in May 2017. We acquired the data of the volume concentration of suspended matter, temperature, salinity and dissolved oxygen, then we conducted the study of the vertical distribution characteristics of suspended matter. The results indicate that the water below 90 m of the cave is anaerobic and the concentration of suspended matter presents 5 cycle changes. The results also indicate that there are three thermoclines and three haloclines in the Sansha Yongle Blue Hole, and there is a good correspondence between them. The total concentration of suspended matter in the surface water is about 20 μL/L, and the average concentration of suspended matter is 5.93 μL/L. CyclothemⅠlies at 5 m in shallow water layer; cyclothemⅡlies between 10 m and 43 m below the water surface, partially corresponding to the first thermocline and halocline water depth (10–20 m); cyclothem Ⅲ lies between 70 meters to 110 m at depth, completely corresponding to the second thermocline and halocline (water depth 70–110 m); cyclothem Ⅳ lies between 130 m to 150 m, completely corresponding to the third thermocline and halocline (water depth 130–150 m); cyclothemⅤlies in 260 m and then deep to 300 m. The suspended matter concentration on the surface is high, as is mainly affected by the sediment input from the surrounding coral reefs. The vertical distribution characteristics of suspended matter in the Sansha Yongle Blue Hole is mainly controlled and affected by hydrodynamic force, cave morphology, thermocline, halocline, dissolved oxygen content and plankton.
2019, 41(11): 127-141.
doi: 10.3969/j.issn.0253-4193.2019.11.012
Abstract:
Coastal boulders, with durable and easily visible, have been widely used as markers to confirm the existence and estimate the magnitude of marine hydrodynamic extreme events, which is valuable for risk prediction and coastal management. A detailed survey of large boulder accumulations was carried out at Dadonghai and Xiaodonghai sites on the southern coast of Hainan Island. The size, position and distance from the shoreline of 24 boulders were measured by Riegl VZ4000 3D terrestial laser (TLS) scanner and traditional methods, respectively, in order to determine their volume parameters, mass as well as the conditions under which they were transported landward to their present positions. The results were then analyzed with hydrodynamic models to evaluate the characteristics of the transporting waves and flow speeds. Storm waves would be responsible for the detachment and transportation of these largest boulders. The maximum intensity of typhoon hitting this area should not be less than that of super Typhoon Baoxia. The results indicate that the TLS technology has the advantages of convenience, speed and accuracy to measure hydrodynamic process of coastal boulders than that of traditional methods. The study insists on the potential for reconstructing the history of paleostorm activity in the South China Sea and predicting the occurrence trend of marine extreme wave disasters in the coastal areas of Hainan Island in the future.
Coastal boulders, with durable and easily visible, have been widely used as markers to confirm the existence and estimate the magnitude of marine hydrodynamic extreme events, which is valuable for risk prediction and coastal management. A detailed survey of large boulder accumulations was carried out at Dadonghai and Xiaodonghai sites on the southern coast of Hainan Island. The size, position and distance from the shoreline of 24 boulders were measured by Riegl VZ4000 3D terrestial laser (TLS) scanner and traditional methods, respectively, in order to determine their volume parameters, mass as well as the conditions under which they were transported landward to their present positions. The results were then analyzed with hydrodynamic models to evaluate the characteristics of the transporting waves and flow speeds. Storm waves would be responsible for the detachment and transportation of these largest boulders. The maximum intensity of typhoon hitting this area should not be less than that of super Typhoon Baoxia. The results indicate that the TLS technology has the advantages of convenience, speed and accuracy to measure hydrodynamic process of coastal boulders than that of traditional methods. The study insists on the potential for reconstructing the history of paleostorm activity in the South China Sea and predicting the occurrence trend of marine extreme wave disasters in the coastal areas of Hainan Island in the future.
2019, 41(11): 142-149.
doi: 10.3969/j.issn.0253-4193.2019.11.013
Abstract:
The evolution of estuarine large-scale tidal flat is highly related to costal engineerings, e.g., navigation, ecological and et al. Thus it is one of the key topics in the studies of estuarine geomorphology as well as engineering. The patterns of riverbed evolution and the driven mechanisms were analyzed based on the high resolution monitor results of topography with a single-beam bathymetry system in the coast of the reclamation area of East Hengsha Shoal during 2011 to 2017. Meanwhile, the sediment discharge, the estuarine engineering project, the extreme climate event and et al., are also included. The results are summarized into four aspects. (1) The East Hengsha shoal showed a trend of siltation in middle area and a trend of scouring in surrounding area. The whole evolution pattern experienced from “growing wide-not-high” before the project to “growing high-not-wide” after the project. (2) The sediment source of the siltation is marine dominanted, while the dynamics source of that is driven by the circulation induced from the divergence of flood and ebb current. (3) The groin of the Deep Water Project and the reclamation in the East Hengsha shoal are the main reasons of intermediate deposition in the study area. (4) The evolution of shoal-channel pattern is sensitive to anthropogenic activity. The embankment project along the shore line holds on the swing of river channel, but aggravates the erosion of local banks. In the future, more attention should be paid to the evolution of the internal ditches to prevent their connectivity, which may cause serious problem on the stability of the embankment and the beach.
The evolution of estuarine large-scale tidal flat is highly related to costal engineerings, e.g., navigation, ecological and et al. Thus it is one of the key topics in the studies of estuarine geomorphology as well as engineering. The patterns of riverbed evolution and the driven mechanisms were analyzed based on the high resolution monitor results of topography with a single-beam bathymetry system in the coast of the reclamation area of East Hengsha Shoal during 2011 to 2017. Meanwhile, the sediment discharge, the estuarine engineering project, the extreme climate event and et al., are also included. The results are summarized into four aspects. (1) The East Hengsha shoal showed a trend of siltation in middle area and a trend of scouring in surrounding area. The whole evolution pattern experienced from “growing wide-not-high” before the project to “growing high-not-wide” after the project. (2) The sediment source of the siltation is marine dominanted, while the dynamics source of that is driven by the circulation induced from the divergence of flood and ebb current. (3) The groin of the Deep Water Project and the reclamation in the East Hengsha shoal are the main reasons of intermediate deposition in the study area. (4) The evolution of shoal-channel pattern is sensitive to anthropogenic activity. The embankment project along the shore line holds on the swing of river channel, but aggravates the erosion of local banks. In the future, more attention should be paid to the evolution of the internal ditches to prevent their connectivity, which may cause serious problem on the stability of the embankment and the beach.
2019, 41(11): 150-155.
doi: 10.3969/j.issn.0253-4193.2019.11.014
Abstract:
Wind speed is one of the important ocean state parameters. Accurate extraction of sea surface wind speed is an important guarantee for achieving marine environmental monitoring and coastal engineering applications. At present, as an emerging marine environment monitoring device, high frequency radar still has challenges in wind speed extraction. This paper proposes a wind speed extraction method based on artificial neural network which can be trained by historical sea state data measured by buoys to achieve non-linear mapping among wind and effective wave height, wave period, wind direction, and time. The test results show the stability of the trained network both in time and space and the trained network was applied to the wind speed inversion of the high frequency surface wave radar, OSMAR-S. The correlation coefficient between the inversion wind speed and the measured wind speed of the buoy reaches 0.849, and the root mean square error is 2.11 m/s. This result is significantly better than the conventional SMB method which inverts the wind speed from wave height, and verifies the feasibility of this method in high frequency radar wind speed inversion.
Wind speed is one of the important ocean state parameters. Accurate extraction of sea surface wind speed is an important guarantee for achieving marine environmental monitoring and coastal engineering applications. At present, as an emerging marine environment monitoring device, high frequency radar still has challenges in wind speed extraction. This paper proposes a wind speed extraction method based on artificial neural network which can be trained by historical sea state data measured by buoys to achieve non-linear mapping among wind and effective wave height, wave period, wind direction, and time. The test results show the stability of the trained network both in time and space and the trained network was applied to the wind speed inversion of the high frequency surface wave radar, OSMAR-S. The correlation coefficient between the inversion wind speed and the measured wind speed of the buoy reaches 0.849, and the root mean square error is 2.11 m/s. This result is significantly better than the conventional SMB method which inverts the wind speed from wave height, and verifies the feasibility of this method in high frequency radar wind speed inversion.
2019, 41(11): 156-162.
doi: 10.3969/j.issn.0253-4193.2019.11.015
Abstract:
There is an increasing amount of beach debris worldwide which have serious impacts on the marine environment, especially to the marine ecosystem health and biological habitats. It has been one of the great technological difficulties on how to monitor and identify beach debris efficiently during the process of the accurately disposing beach debris. Therefore, in this paper, a new recognition method of beach debris was proposed based on field beach debris experiment on Nanhui Beach by combination of LiDAR (light detection and ranging) with record full waveform data and the Back Propagation (BP) neural network model. The results reveal that the echo amplitude and width extracted from full-waveform data can be used to identify beach debris because of their distinct waveform features. Meanwhile, beach debris can be effectively classified into foam, cloth, metal, paper and plastic with the highly accuracy rate of 79% by the BP neural network recognition. Moreover, it can be found that some beach debris are difficult to identify owing to the same material composition for these debris, which may disturb the recognition rate of BP neural network to great degree. Therefore, it can be expected that a new monitoring tool for beach debris identification by LiDAR will be popular in future.
There is an increasing amount of beach debris worldwide which have serious impacts on the marine environment, especially to the marine ecosystem health and biological habitats. It has been one of the great technological difficulties on how to monitor and identify beach debris efficiently during the process of the accurately disposing beach debris. Therefore, in this paper, a new recognition method of beach debris was proposed based on field beach debris experiment on Nanhui Beach by combination of LiDAR (light detection and ranging) with record full waveform data and the Back Propagation (BP) neural network model. The results reveal that the echo amplitude and width extracted from full-waveform data can be used to identify beach debris because of their distinct waveform features. Meanwhile, beach debris can be effectively classified into foam, cloth, metal, paper and plastic with the highly accuracy rate of 79% by the BP neural network recognition. Moreover, it can be found that some beach debris are difficult to identify owing to the same material composition for these debris, which may disturb the recognition rate of BP neural network to great degree. Therefore, it can be expected that a new monitoring tool for beach debris identification by LiDAR will be popular in future.
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