2018 Vol. 40, No. 9
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2018, 40(9): .
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2018, 40(9): .
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2018, 40(9): 1-17.
doi: 10.3969/j.issn.0253-4193.2018.09.001
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By the natural and human activities, the phenomenon of marine hypoxia has become increasingly serious, threatening the marine ecological environment. And the problem of marine hypoxia has caused wide attention. In this paper, a three-dimensional hydrodynamic model (ROMS) was coupled to a biogeochemical model to simulate and analyze the ecological system of the East China Sea. In comparison with the observation data, the model results can reasonably capture the physical and biochemical dynamics off the Changjiang River Estuary. In addition, the sensitive experiments were also used to examine the role that physical forcing (river discharge, wind speed, wind direction) play in controlling hypoxia in waters adjacent to the Changjiang River Estuary. The results show that the wind and river discharge have significant influences on the hypoxia off the Changjiang River Estuary. The seasonal cycle of hypoxia was relatively insensitive to synoptic variability in river discharge, but integrated hypoxic areas were sensitive to the overall magnitude of river discharge. Increased in the magnitude of river discharge led to enhance stratification and surface chlorophyll concentration, thereby greatly increased hypoxic area off the Changjiang River Estuary. In contrast, decreased in the magnitude of river discharge reduced the stratification and surface chlorophyll concentration and hence significantly decreased the hypoxic area. And variations in wind speed and direction had the greatest impact on the seasonal cycle of hypoxia and large impacts on the annually integrated hypoxic areas.
By the natural and human activities, the phenomenon of marine hypoxia has become increasingly serious, threatening the marine ecological environment. And the problem of marine hypoxia has caused wide attention. In this paper, a three-dimensional hydrodynamic model (ROMS) was coupled to a biogeochemical model to simulate and analyze the ecological system of the East China Sea. In comparison with the observation data, the model results can reasonably capture the physical and biochemical dynamics off the Changjiang River Estuary. In addition, the sensitive experiments were also used to examine the role that physical forcing (river discharge, wind speed, wind direction) play in controlling hypoxia in waters adjacent to the Changjiang River Estuary. The results show that the wind and river discharge have significant influences on the hypoxia off the Changjiang River Estuary. The seasonal cycle of hypoxia was relatively insensitive to synoptic variability in river discharge, but integrated hypoxic areas were sensitive to the overall magnitude of river discharge. Increased in the magnitude of river discharge led to enhance stratification and surface chlorophyll concentration, thereby greatly increased hypoxic area off the Changjiang River Estuary. In contrast, decreased in the magnitude of river discharge reduced the stratification and surface chlorophyll concentration and hence significantly decreased the hypoxic area. And variations in wind speed and direction had the greatest impact on the seasonal cycle of hypoxia and large impacts on the annually integrated hypoxic areas.
2018, 40(9): 18-30.
doi: 10.3969/j.issn.0253-4193.2018.09.002
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Main SSTA modes of the global key regions simulated by the CESM global climate forecasting system are evaluated based on the HadISST、ERSST and OISST reanalysis datasets. It has shown that the model can able to simulate the main SSTA characteristics of the five key regions which are identified by the reanalysis datasets. The 1 month ahead hindcasting results of the five key regions show relative high predictability in the first two SSTA EOF modes, especially for the first mode (ENSO) of the tropical Pacific Ocean SSTA with a correlation coefficient 0.79 between the 3 months ahead hindcasting results and the reanalysis results which can provide valuable references for the ENSO forecasting. Many errors exist inevitably of the model which mainly show in the difference of the range and the location of the SSTA key regions in terms of space. It should be noted that the model shows a false IOD mode of the first tropical Indian Ocean SSTA mode. Meanwhile, three reanalysis datasets also show largest spatial differences of the first SSTA mode in the tropical Indian Ocean. Time series of the model all show anomalous high frequency signals and fluctuations, the magnitude of the errors are gradually increased by assimilation, 1 month ahead and 3 months ahead, it shows the rule that initial error accumulates gradually with integral. Phase of the first 5 years of the first tropical Atlantic Ocean SSTA mode deviates greatly with the reanalysis results, the results show great improved with the first 5 years excluded.
Main SSTA modes of the global key regions simulated by the CESM global climate forecasting system are evaluated based on the HadISST、ERSST and OISST reanalysis datasets. It has shown that the model can able to simulate the main SSTA characteristics of the five key regions which are identified by the reanalysis datasets. The 1 month ahead hindcasting results of the five key regions show relative high predictability in the first two SSTA EOF modes, especially for the first mode (ENSO) of the tropical Pacific Ocean SSTA with a correlation coefficient 0.79 between the 3 months ahead hindcasting results and the reanalysis results which can provide valuable references for the ENSO forecasting. Many errors exist inevitably of the model which mainly show in the difference of the range and the location of the SSTA key regions in terms of space. It should be noted that the model shows a false IOD mode of the first tropical Indian Ocean SSTA mode. Meanwhile, three reanalysis datasets also show largest spatial differences of the first SSTA mode in the tropical Indian Ocean. Time series of the model all show anomalous high frequency signals and fluctuations, the magnitude of the errors are gradually increased by assimilation, 1 month ahead and 3 months ahead, it shows the rule that initial error accumulates gradually with integral. Phase of the first 5 years of the first tropical Atlantic Ocean SSTA mode deviates greatly with the reanalysis results, the results show great improved with the first 5 years excluded.
2018, 40(9): 31-42.
doi: 10.3969/j.issn.0253-4193.2018.09.003
Abstract:
The relationship between coral growth rate and sea surface temperature anomaly (SSTA) was used to reconstruct the SSTA in the central South China Sea Since 1780. Our reconstruction shows that SSTA over the period 1780-1890, which correspond to the latter part of Little Ice Age, was cold relatively, the average SSTA was -0.2℃, the coldest SSTA was -1℃ in 1837. After 1890, the SSTA increased most fast between 1971 to 1998, the highest SSTA was 2℃ in 1998, but there was a downward trend after 1998, which is basically synchronous with the change of land temperature in Northern Hemisphere. The spectral analysis shows a significant period of 26-34 a for the SSTA in the central of South China Sea, with the phase transitions correspond to the decadal shifts of the Pacific Decadal Oscillation. The wavelet analysis indicated that the interdecadal oscillation of the SSTA in the central South China Sea was not stable over the past 234 years. After entering the Current Warm Period, the interdecadal variability has enhanced distinctly, which may be related to the changes in the internal variability of the ocean associated with the global warming. Our result, together with the change in the decadal-scale SST variability of the tropical southwest Pacific in the 1890, suggested that the internal variability of the tropical Pacific has changed since 1890.
The relationship between coral growth rate and sea surface temperature anomaly (SSTA) was used to reconstruct the SSTA in the central South China Sea Since 1780. Our reconstruction shows that SSTA over the period 1780-1890, which correspond to the latter part of Little Ice Age, was cold relatively, the average SSTA was -0.2℃, the coldest SSTA was -1℃ in 1837. After 1890, the SSTA increased most fast between 1971 to 1998, the highest SSTA was 2℃ in 1998, but there was a downward trend after 1998, which is basically synchronous with the change of land temperature in Northern Hemisphere. The spectral analysis shows a significant period of 26-34 a for the SSTA in the central of South China Sea, with the phase transitions correspond to the decadal shifts of the Pacific Decadal Oscillation. The wavelet analysis indicated that the interdecadal oscillation of the SSTA in the central South China Sea was not stable over the past 234 years. After entering the Current Warm Period, the interdecadal variability has enhanced distinctly, which may be related to the changes in the internal variability of the ocean associated with the global warming. Our result, together with the change in the decadal-scale SST variability of the tropical southwest Pacific in the 1890, suggested that the internal variability of the tropical Pacific has changed since 1890.
2018, 40(9): 43-53.
doi: 10.3969/j.issn.0253-4193.2018.09.004
Abstract:
Several oil fields and oil-bearing structures had been found in carbonate buried hills in Weixi'nan Sag of the Beibuwan Basin during the last forty years. In this paper, a comprehensive analysis had been made to study the carbonate reservoir characteristics and its main controlling factors based on core and thin-section observation, drilling and logging information and seismic data. Carbonate buried hills were found distributed around the area between No.1 and No.2 Fault Belt. The carbonate strata in No.1 Fault Belt were mainly light grey limestone, dolomitic limestone and dolomitite interaction of Huanglong formation in upper Carboniferous, which deposited in the environment of bioclastic lime bank of carbonate platform and platform margin. Fissure, dissolved pore and cave constituted its main reservoir space. The carbonate strata in No.2 Fault Belt was mainly grey and dark grey limestone of Shidengzi member and Menggong'ao member in lower Carboniferous, which deposited in the environment of lime bank of intra-platform and bioclastic lime bank of platform margin. And fissure was its main reservoir type. The development degree of carbonate reservoir in buried hills was mainly controlled by sedimentary environment, groundwater activity, paleotectonic stress and overlying strata. Affected by these factors together, carbonate buried hills in Weixi'nan Sag developed good reservoir condition with multiple reservoir types of pore, fissure and karst cave.
Several oil fields and oil-bearing structures had been found in carbonate buried hills in Weixi'nan Sag of the Beibuwan Basin during the last forty years. In this paper, a comprehensive analysis had been made to study the carbonate reservoir characteristics and its main controlling factors based on core and thin-section observation, drilling and logging information and seismic data. Carbonate buried hills were found distributed around the area between No.1 and No.2 Fault Belt. The carbonate strata in No.1 Fault Belt were mainly light grey limestone, dolomitic limestone and dolomitite interaction of Huanglong formation in upper Carboniferous, which deposited in the environment of bioclastic lime bank of carbonate platform and platform margin. Fissure, dissolved pore and cave constituted its main reservoir space. The carbonate strata in No.2 Fault Belt was mainly grey and dark grey limestone of Shidengzi member and Menggong'ao member in lower Carboniferous, which deposited in the environment of lime bank of intra-platform and bioclastic lime bank of platform margin. And fissure was its main reservoir type. The development degree of carbonate reservoir in buried hills was mainly controlled by sedimentary environment, groundwater activity, paleotectonic stress and overlying strata. Affected by these factors together, carbonate buried hills in Weixi'nan Sag developed good reservoir condition with multiple reservoir types of pore, fissure and karst cave.
2018, 40(9): 54-64.
doi: 10.3969/j.issn.0253-4193.2018.09.005
Abstract:
South Asia underwent three stages including Gondwana intercontinental rifting, Gondwana cracking and plates drifting and the collision between Indian plate and Eurasian plate, and formed three types of basin that is passive continental margin basin, subduction-collision zone basin and cratonic basin. The passive continental margin basin is widely distributed, forming a major basin group in the region. The characteristics of hydrocarbon accumulation in different basin types are studied through the analysis of petroleum geological conditions such as the source, reservoir and seal. According to the remaining recoverable reserves and prospective resource in basin, analyze the resource potential of sedimentary basins in the South Asia. It is believed that the oil and gas resources in the passive continental marginal basin have the greatest potential, and the Krishna-Godavari Basin, Bombay Basin and Cauvery Basin are optimized as favorable ones for hydrocarbon exploration in the South Asia.
South Asia underwent three stages including Gondwana intercontinental rifting, Gondwana cracking and plates drifting and the collision between Indian plate and Eurasian plate, and formed three types of basin that is passive continental margin basin, subduction-collision zone basin and cratonic basin. The passive continental margin basin is widely distributed, forming a major basin group in the region. The characteristics of hydrocarbon accumulation in different basin types are studied through the analysis of petroleum geological conditions such as the source, reservoir and seal. According to the remaining recoverable reserves and prospective resource in basin, analyze the resource potential of sedimentary basins in the South Asia. It is believed that the oil and gas resources in the passive continental marginal basin have the greatest potential, and the Krishna-Godavari Basin, Bombay Basin and Cauvery Basin are optimized as favorable ones for hydrocarbon exploration in the South Asia.
2018, 40(9): 65-77.
doi: 10.3969/j.issn.0253-4193.2018.09.006
Abstract:
The 2D wave and current coupled model is established and applied to simulate the morphological evolution of the Modaoment Estuary in monthly scale. The main findings are as follows:(1)In the dry season, the siltation dominates in the estuary without wave,however, siltation turns into erosion in the estuary with current and wave coupled. In the flood season, the siltation dominates in the estuary without wave except erosion in the west main tributary, with current and wave coupled, the siltation still dominates except that siltation turns into erosion in the inner slope and center of the mouth bar with the amount of the siltation reduced. (2)The magnitude of the monthly morphological change is centimeter level with the significant seasonal variation. The siltation dominates in the Modaomen Estuary without wave both the dry season and the flood season, with the larger siltation in the flood season. After the wave and current coupled, siltation dominates in the flood season while erosion dominates in the dry season. (3)Spatially, the outer slope of the mouth bar is silted in the flood season, and eroded in the dry season, the inner slope of the mouth bar is eroded both the flood season and the dry season, the top of the mouth bar is silted in the flood season and little changed in the dry season. In addition, the tidal induced bottom shear stress is dominant in the inner slope of the mouth bar, and wave induced bottom shear stress is dominant in the outer slope of the mouth bar.
The 2D wave and current coupled model is established and applied to simulate the morphological evolution of the Modaoment Estuary in monthly scale. The main findings are as follows:(1)In the dry season, the siltation dominates in the estuary without wave,however, siltation turns into erosion in the estuary with current and wave coupled. In the flood season, the siltation dominates in the estuary without wave except erosion in the west main tributary, with current and wave coupled, the siltation still dominates except that siltation turns into erosion in the inner slope and center of the mouth bar with the amount of the siltation reduced. (2)The magnitude of the monthly morphological change is centimeter level with the significant seasonal variation. The siltation dominates in the Modaomen Estuary without wave both the dry season and the flood season, with the larger siltation in the flood season. After the wave and current coupled, siltation dominates in the flood season while erosion dominates in the dry season. (3)Spatially, the outer slope of the mouth bar is silted in the flood season, and eroded in the dry season, the inner slope of the mouth bar is eroded both the flood season and the dry season, the top of the mouth bar is silted in the flood season and little changed in the dry season. In addition, the tidal induced bottom shear stress is dominant in the inner slope of the mouth bar, and wave induced bottom shear stress is dominant in the outer slope of the mouth bar.
2018, 40(9): 78-89.
doi: 10.3969/j.issn.0253-4193.2018.09.007
Abstract:
Submarine sand waves, vital to seabed stability, are an important consideration for oceanic engineering projects such as oil pipe lines and submarine cables. The properties of surface sediment and the evolvement of submarine sand waves in a specified area in the South China Sea are studied using both a hydrological model and field observational data. The bottom flow field data between 2010 and 2011 in the study area are simulated by the Regional Ocean Model System (ROMS). The migration of submarine sand waves is calculated using Rubin's formula along with typhoon data and bottom flow field data, which allows for the analysis of sand wave response under the influence of typhoons. The migration direction calculated by Rubin's formula and bottom flow are very similar to collected data. The migration distance of different positions is between 0.0 m and 21.8 m, which reciprocates cumulatively. This shows that Rubin's formula can predict the progress of submarine sand waves with the bottom flow simulated by ROMS. The migration distances of 2 sites in the study area are 2.0 m and 2.9 m during the Typhoon "Fanapi". The proportion of the calculated migration distance by the typhoon is 9.17% and 26.36% of the annual migration distance, respectively, which proves that the typhoon can make a significant impact on submarine sand waves.
Submarine sand waves, vital to seabed stability, are an important consideration for oceanic engineering projects such as oil pipe lines and submarine cables. The properties of surface sediment and the evolvement of submarine sand waves in a specified area in the South China Sea are studied using both a hydrological model and field observational data. The bottom flow field data between 2010 and 2011 in the study area are simulated by the Regional Ocean Model System (ROMS). The migration of submarine sand waves is calculated using Rubin's formula along with typhoon data and bottom flow field data, which allows for the analysis of sand wave response under the influence of typhoons. The migration direction calculated by Rubin's formula and bottom flow are very similar to collected data. The migration distance of different positions is between 0.0 m and 21.8 m, which reciprocates cumulatively. This shows that Rubin's formula can predict the progress of submarine sand waves with the bottom flow simulated by ROMS. The migration distances of 2 sites in the study area are 2.0 m and 2.9 m during the Typhoon "Fanapi". The proportion of the calculated migration distance by the typhoon is 9.17% and 26.36% of the annual migration distance, respectively, which proves that the typhoon can make a significant impact on submarine sand waves.
2018, 40(9): 90-102.
doi: 10.3969/j.issn.0253-4193.2018.09.008
Abstract:
Coastal aeolian is a typical product of sea, land and air interaction. Based on a comprehensive observation of beach aeolian sand in the Yuandangao beach of Pingtan Island, Fujian Province, this paper aims to explore and summarize the vertical distribution, entrainment and transport characteristics of beach aeolian sand influenced by tide. The main conclusions are as follows:(1) The vertical distribution of wind-sand flow in intertidal zone is almost entirely(98.9%) in the range of 0-30 cm, and the specific distribution function varies with different particle size; (2) The threshold velocity of beach aeolian sand is significantly higher than that of inland desert, and the changing process of it in the tidal circulation mainly reflects the interaction between average surface moisture and fetch length; (3) The wind-blown sand flux of intertidal zone involves the interaction of average surface moisture, fetch length and wind speed, and the dominant factors of its changing process vary in different stages of ebb and flow; (4) Entrainment of sand from a dry source and transport across a moist surface is one of the typical beach aeolian sand transport mode, with a short delivered distance at a time, and a highly relayed way of overall transport.
Coastal aeolian is a typical product of sea, land and air interaction. Based on a comprehensive observation of beach aeolian sand in the Yuandangao beach of Pingtan Island, Fujian Province, this paper aims to explore and summarize the vertical distribution, entrainment and transport characteristics of beach aeolian sand influenced by tide. The main conclusions are as follows:(1) The vertical distribution of wind-sand flow in intertidal zone is almost entirely(98.9%) in the range of 0-30 cm, and the specific distribution function varies with different particle size; (2) The threshold velocity of beach aeolian sand is significantly higher than that of inland desert, and the changing process of it in the tidal circulation mainly reflects the interaction between average surface moisture and fetch length; (3) The wind-blown sand flux of intertidal zone involves the interaction of average surface moisture, fetch length and wind speed, and the dominant factors of its changing process vary in different stages of ebb and flow; (4) Entrainment of sand from a dry source and transport across a moist surface is one of the typical beach aeolian sand transport mode, with a short delivered distance at a time, and a highly relayed way of overall transport.
2018, 40(9): 103-112.
doi: 10.3969/j.issn.0253-4193.2018.09.009
Abstract:
In this paper, we first retrieve ocean surface wind speed from C-2PO model without incidence angle input using selected 142 quad-polarized synthetic aperture radar (SAR) images. Subsequently, wind speed computed from geophysical function model (GMF) CMOD5.N with incidence angle measured from the advanced scatterometer (ASCAT) using the same SAR images. Compared with national data buoy center (NDBC) buoy-measured wind speed, the results show that the ocean surface wind speed retrieve from CMOD5.N GMF and C-2PO model both have a high accuracy, and with the root-mean-square (RMS) error are1.68 m/s and 1.74 m/s, respectively. In addition, the wind speeds retrieval RMS error of CMOD5.N GMF is perform better than C-2PO model at low wind speed section (0-10 m/s). After that, taken one SAR image with low wind speed, three reasons of this phenomenon are presented in this paper based on SAR system imaging mechanism.
In this paper, we first retrieve ocean surface wind speed from C-2PO model without incidence angle input using selected 142 quad-polarized synthetic aperture radar (SAR) images. Subsequently, wind speed computed from geophysical function model (GMF) CMOD5.N with incidence angle measured from the advanced scatterometer (ASCAT) using the same SAR images. Compared with national data buoy center (NDBC) buoy-measured wind speed, the results show that the ocean surface wind speed retrieve from CMOD5.N GMF and C-2PO model both have a high accuracy, and with the root-mean-square (RMS) error are1.68 m/s and 1.74 m/s, respectively. In addition, the wind speeds retrieval RMS error of CMOD5.N GMF is perform better than C-2PO model at low wind speed section (0-10 m/s). After that, taken one SAR image with low wind speed, three reasons of this phenomenon are presented in this paper based on SAR system imaging mechanism.
2018, 40(9): 113-124.
doi: 10.3969/j.issn.0253-4193.2018.09.010
Abstract:
With climate change occurrence, such as global warming, polar sea ice has been drawn increasing attentions. Synthetic aperture radar (SAR) can monitor earth independent on sunlight and cloud. GaoFen-3 is a C-band SAR of the GaoFen series satellites, which has multiple imaging modes and can obtain data globally. SAR plays an important role in monitoring polar sea ice due to the advantage of all-weather operation and high spatial resolution. Bases on the GaoFen-3 horizontal-vertical data, we proposed an automatic method to discriminate sea ice and sea water, using the support vector machine classification method. The detected sea ice shows good agreement with visual inspection. The successful development of this algorithm supports the Gaofen-3 SAR for operational service of monitoring polar sea ice.
With climate change occurrence, such as global warming, polar sea ice has been drawn increasing attentions. Synthetic aperture radar (SAR) can monitor earth independent on sunlight and cloud. GaoFen-3 is a C-band SAR of the GaoFen series satellites, which has multiple imaging modes and can obtain data globally. SAR plays an important role in monitoring polar sea ice due to the advantage of all-weather operation and high spatial resolution. Bases on the GaoFen-3 horizontal-vertical data, we proposed an automatic method to discriminate sea ice and sea water, using the support vector machine classification method. The detected sea ice shows good agreement with visual inspection. The successful development of this algorithm supports the Gaofen-3 SAR for operational service of monitoring polar sea ice.
2018, 40(9): 125-136.
doi: 10.3969/j.issn.0253-4193.2018.09.011
Abstract:
Emphasis has been laid on polarimetric SAR oil spill detection in this study. For the research of the oil spill detection of different radar bands polarimetric SAR, SIR-C/X polarimetric SAR data acquired synchronously are adopted to reduce the effect of observation and environment conditions. Research of the identification capability of co-polarization phase difference, conformity coefficient and decomposition parameters on oil slick and the discrepancy of diverse dark phenomena such as biogenic slick and low wind area have been carried out using the SIR-C/X multi-polarization data. The analysis results indicate that C band is superior to L band in oil slick identification and the detection of the discrepancy of diverse dark phenomena. For L band, the anisotropy parameter has better performance than co-polarization phase difference and conformity coefficient. And co-polarization phase difference and conformity coefficient are better than decomposition parameters anisotropy and entropy in C band, with averaged scattering angle in helping to filter out biogenic slick and low wind area.
Emphasis has been laid on polarimetric SAR oil spill detection in this study. For the research of the oil spill detection of different radar bands polarimetric SAR, SIR-C/X polarimetric SAR data acquired synchronously are adopted to reduce the effect of observation and environment conditions. Research of the identification capability of co-polarization phase difference, conformity coefficient and decomposition parameters on oil slick and the discrepancy of diverse dark phenomena such as biogenic slick and low wind area have been carried out using the SIR-C/X multi-polarization data. The analysis results indicate that C band is superior to L band in oil slick identification and the detection of the discrepancy of diverse dark phenomena. For L band, the anisotropy parameter has better performance than co-polarization phase difference and conformity coefficient. And co-polarization phase difference and conformity coefficient are better than decomposition parameters anisotropy and entropy in C band, with averaged scattering angle in helping to filter out biogenic slick and low wind area.
2018, 40(9): 137-147.
doi: 10.3969/j.issn.0253-4193.2018.09.012
Abstract:
The response of beach to storm and the restoration after storm have always been a hotspot in researches on sandy beach. Based on the topography investigation of Dongsha Beach in Zhujiajian Island, Zhejiang Province, the profile variations of Dongsha Beach under the influence of tropical storm Nakri were analyzed, and the restoration in one year after storm was discussed. The results show that Dongsha Beach almost all suffered erosion during the tropical storm Nakri resulting from storm wave was shoreward wave, the total erosional volume per unit of 12 sections was 73.46 m3/m, and the erosion extent of straight zone's sections were more serious than the two shadow zones' sections. As the beach was on the left side of the storm direction, and Nakri was far from Dongsha Beach, Dongsha Beach had been generally eroded at low intensity. During the recovery process of Dongsha Beach after this storm, geomorphic adjustment and erosion conditions between different parts were distinct. The lower headland shadow zone of beach tended to be stable, the straight zone and the upper headland shadow zone could not recover as the situation before storm due to the seasonal adjustment of beach.
The response of beach to storm and the restoration after storm have always been a hotspot in researches on sandy beach. Based on the topography investigation of Dongsha Beach in Zhujiajian Island, Zhejiang Province, the profile variations of Dongsha Beach under the influence of tropical storm Nakri were analyzed, and the restoration in one year after storm was discussed. The results show that Dongsha Beach almost all suffered erosion during the tropical storm Nakri resulting from storm wave was shoreward wave, the total erosional volume per unit of 12 sections was 73.46 m3/m, and the erosion extent of straight zone's sections were more serious than the two shadow zones' sections. As the beach was on the left side of the storm direction, and Nakri was far from Dongsha Beach, Dongsha Beach had been generally eroded at low intensity. During the recovery process of Dongsha Beach after this storm, geomorphic adjustment and erosion conditions between different parts were distinct. The lower headland shadow zone of beach tended to be stable, the straight zone and the upper headland shadow zone could not recover as the situation before storm due to the seasonal adjustment of beach.
2018, 40(9): 148-158.
doi: 10.3969/j.issn.0253-4193.2018.09.013
Abstract:
Rare earth elements (REEs) and major elements in Core STD235 sediments from the northeastern South China Sea (SCS) were analyzed. Combined with the results, the sediment provenance and the relationship between the vertical variations of REE parameters and climate change were discussed. REE chemical characteristics showed that the sediments in the investigated site had the same main provenance and were dominated by the terrestrial contribution during the last 20 ka. The UCC-normalized REE pattern and REE parameters of sediments from Core STD235 are close to sediments from southeastern Taiwan Rivers, indicating that sediments were primarily derived from the southeastern Taiwan rivers. Further analysis implied that the southwestern Taiwan rivers might also make contribution to the core STD235. The sediments might be transported by the North Pacific Deep Water and Kuroshio through the Luzon Strait into SCS. Synthetically analysis potentially denotes the climatic environment variations should be the main factor causing the vertical variations of REE indexes. The analysis indicated the stronger chemical weathering intensity during the last interglacial period than that during the last glacial period on the source areas of the sediment, implying a warmer and wetter climate in Taiwan during the last interglacial period. The variations of chemical weathering intensity recorded in sediments might be associated with changes of environment and climate on the source areas. It is speculated that the controlling factors of environment and climate on Taiwan Island were similar to the south China, and the East Asian monsoon system might be the primary cause of the regional environment and climate changes. In addition, abrupt changes in almost of all proxies of the Core STD235 sediments from about 16 ka BP to 13 ka BP occurred and indicated a stronger chemical weathering, which implied the environmental and climatic condition on source area changed to warm and humid climate during that period.
Rare earth elements (REEs) and major elements in Core STD235 sediments from the northeastern South China Sea (SCS) were analyzed. Combined with the results, the sediment provenance and the relationship between the vertical variations of REE parameters and climate change were discussed. REE chemical characteristics showed that the sediments in the investigated site had the same main provenance and were dominated by the terrestrial contribution during the last 20 ka. The UCC-normalized REE pattern and REE parameters of sediments from Core STD235 are close to sediments from southeastern Taiwan Rivers, indicating that sediments were primarily derived from the southeastern Taiwan rivers. Further analysis implied that the southwestern Taiwan rivers might also make contribution to the core STD235. The sediments might be transported by the North Pacific Deep Water and Kuroshio through the Luzon Strait into SCS. Synthetically analysis potentially denotes the climatic environment variations should be the main factor causing the vertical variations of REE indexes. The analysis indicated the stronger chemical weathering intensity during the last interglacial period than that during the last glacial period on the source areas of the sediment, implying a warmer and wetter climate in Taiwan during the last interglacial period. The variations of chemical weathering intensity recorded in sediments might be associated with changes of environment and climate on the source areas. It is speculated that the controlling factors of environment and climate on Taiwan Island were similar to the south China, and the East Asian monsoon system might be the primary cause of the regional environment and climate changes. In addition, abrupt changes in almost of all proxies of the Core STD235 sediments from about 16 ka BP to 13 ka BP occurred and indicated a stronger chemical weathering, which implied the environmental and climatic condition on source area changed to warm and humid climate during that period.
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