This volume aims at providing a platform for sharing valuable topics discussed at the 19th International Symposium on Geodynamics and Earth Tides,23-26 June 2021,Wuhan,China.The complete overview of all nineteen Sympo...This volume aims at providing a platform for sharing valuable topics discussed at the 19th International Symposium on Geodynamics and Earth Tides,23-26 June 2021,Wuhan,China.The complete overview of all nineteen Symposia is found in Table 1,where the times and venues are listed.展开更多
Since 2015, green tides have been blooming in offshore waters of Qinhuangdao, with serious impacts on the local ecological environment and tourism. Ulva australis, Bryopsis plumosa, and U. prolifera are the dominant s...Since 2015, green tides have been blooming in offshore waters of Qinhuangdao, with serious impacts on the local ecological environment and tourism. Ulva australis, Bryopsis plumosa, and U. prolifera are the dominant species of Qinhuangdao green tides, following a sequential succession pattern. Ulva prolifera is the dominant species,with the highest biomass and the greatest influence on the local ecological environment. To study the reason of green tide dominant species succession and U. profilera became the dominant species with the largest biomass,we compared and analyzed the growth and nutrient uptake capacity of the three algae. The results showed that temperature significantly affects the growth of the three species. Within the temperature range of the experimental setup, the optimum temperature for the growth of U. australis, B. plumosa and U. profilera is10℃, 15℃, and 20–25℃, respectively. Combined with the temperature variation trend during green tide bloom development, we believe that temperature is the key environmental factor for the succession of the dominant species. Ulva prolifera has a higher growth rate than U. australis and B. plumosa under the same nitrate,ammonium, and phosphate levels. Significant differences in the maximum absorption rate(R_(max)) and R_(max)/Ks(the relationship between uptake rate and substrate concentration) values indicated that U. prolifera had an apparent competitive advantage over U. australis and B. plumosa regarding nutrient uptake. Therefore, the strong growth and nutrient uptake capacities of U. prolifera might be the main reason for becoming the dominant species with the largest biomass in Qinhuangdao green tides.展开更多
The tidal triggering of earthquakes has been studied for many years.The discovery of slow earthquakes in the early 2000s,including slow slip,has urged scientists to investigate the tidal responses of these earthquakes...The tidal triggering of earthquakes has been studied for many years.The discovery of slow earthquakes in the early 2000s,including slow slip,has urged scientists to investigate the tidal responses of these earthquakes due to their sensitivity to weak stress perturbations.Previous studies have shown that slow earthquakes correlate with diurnal and semidiurnal tides and seasonal variations in surface loads more clearly than ordinary earthquakes.However,little is known about long-term responses to external stresses.In this paper,based on a widely accepted frictional law for faults,a mechanism is proposed by which nontidal variations in ocean bottom pressure,when combined with tides,pro mote the occurrence of slow earthquakes.Because slow earthquakes accompany a slip on the plate interface,this mechanism allows one to estimate slip modulations.A one-degree-of-freedom slip model is constructed and applied to Ise Bay in the Tonankai region of southwestern Japan,where large-scale ocean mass redistributions have occurred.The model calculated with parameters determined from the observation of tectonic tremors is quantitatively consistent with the slip during 1997-2013 inferred from GNSS data,suggesting that the decrease in the sea-level change in approximately 2006 could cause the accele ration of a slip observed after that.This result implies that the decreases in sea level in approximately 1996 and 2014 could also cause subsequent slip accelerations.These three slip acceleration periods temporally coincide with the increases in background seismicity in a shallower portion of the plate interface.These changes in seismicity are common to shallow earthquakes in the Tokai area,and a similar model can reproduce them.Further studies are expected to reveal causality between shallow earthquakes and long-term slip fluctuations based on modeling that considers changes in the frictional property along the plate interface.展开更多
We examine the cross-shelf variation of internal tides(ITs)west of the Dongsha Plateau in the northern South China Sea based on observations from 4 moorings deployed between August 2017 and September 2018.On the slope...We examine the cross-shelf variation of internal tides(ITs)west of the Dongsha Plateau in the northern South China Sea based on observations from 4 moorings deployed between August 2017 and September 2018.On the slope,the amplitude of diurnal baroclinic current ellipses are 5 times larger than that of barotropic currents.The baroclinic energy quickly dissipates during cross-shelf propagation,and barotropic currents become dominant on the shelf outside of the Zhujiang River Estuary,with the amplitude of semidiurnal barotropic current ellipses being 10 times larger than that of the baroclinic ones.Dynamic modal decomposition indicates the first baroclinic mode is dominant for both diurnal and semidiurnal ITs.The total horizontal kinetic energy(HKE)of the first three baroclinic modes shows spatiotemporal differences among the 4 moorings.On the slope,the HKE for diurnal ITs is stronger in summer and winter,but weaker in spring and autumn;for semidiurnal ITs there is a similar seasonal variation,but the HKE in winter is even stronger than that in summer.On the shallow shelf,both diurnal and semidiurnal ITs maintain a certain intensity in summer but almost disappear in winter.Further analysis shows that only the upper water column is affected by seasonal variation of stratification on the slope,variation of diurnal ITs is thus controlled by the semi-annual cycle of barotropic energy input from the Luzon Strait,while the incoherent baroclinic currents make a major contribution to the temporal variation of semidiurnal ITs.For the shelf region,the water column is well mixed in winter,and the baroclinic energy largely dissipates when ITs propagate to the shelf zone despite of a strong barotropic energy input from the Luzon Strait.展开更多
Since 2007,the large-scale green tide caused by Ulva prolifera(U.prolifera)have occurred as a recurrent phenomenon in the southern Yellow Sea of China.Field surveys and satellite remote sensing showed that the small s...Since 2007,the large-scale green tide caused by Ulva prolifera(U.prolifera)have occurred as a recurrent phenomenon in the southern Yellow Sea of China.Field surveys and satellite remote sensing showed that the small scattered patches of green tide algae were first observed along the Porphyra agriculture area of the Subei Shoal in late April.In this study,we attempted to identify the role of eutrophication in the origin of the green tide in the Subei Shoal and its adjacent area.Subei Shoal and its adjacent area are characterized by rich nutrients,especially NO_(3)^(-)-N,NH_(4)^(+)-N,PO_(4)^(3-)-P,and other bioavailable components(such as urea-N and amino acids).In the spring of 2017,the average concentrations of NO_(3)^(-)-N were 19.01±11.01μmolL^(-1),accounting for 86.68%of the dis-solved inorganic nitrogen(DIN).In addition,the average concentration of NH4^(+)-N was 2.51±1.60μmolL^(-1).PO_(4)^(3-)-P had an average concentration of 0.14±0.13μmolL-1.The average concentrations of urea-N and total hydrolyzed amino acids(THAA)were 1.73±1.36μmolL^(-1)and 1.33±0.80μmolL^(-1),respectively.Rich nutritive substances play a key role in the rapid production of U.prolifera and make the Jiangsu coastal water an incubator for green tide.展开更多
In this study,we estimate the absolute vertical land motions at three tidal stations with collocated Global Navigation Satellite System(GNSS)receivers over French Polynesia during the period 2007-2020,and obtain,as an...In this study,we estimate the absolute vertical land motions at three tidal stations with collocated Global Navigation Satellite System(GNSS)receivers over French Polynesia during the period 2007-2020,and obtain,as ancillary results,estimates of the absolute changes in sea level at the same locations.To verify our processing approach to determining vertical motion,we first modeled vertical motion at the International GNSS Service(IGS)THTI station located in the capital island of Tahiti and compared our estimate with previous independent determinations,with a good agreement.We obtained the following estimates for the vertical land motions at the tide gauges:Tubuai island,Austral Archipelago-0.92±0.17 mm/yr,Vairao village,Tahiti Iti:-0.49±0.39 mm/yr,Rikitea,Gambier Archipelago-0.43±0.17 mm/yr.The absolute variations of the sea level are:Tubuai island,Austral Archipelago 5.25±0.60 mm/yr,Vairao village,Tahiti Iti:3.62±0.52 mm/yr,Rikitea,Gambier Archipelago 1.52±0.23 mm/yr.We discuss these absolute values in light of the values obtained from altimetric measurements and other means in French Polynesia.展开更多
In 2022,Yellow Sea green tide caused by Ulva prolifera reached a historic minimum and the coastal areas of Shandong Peninsula were less affected.However,the largest amount of seaweed biomass has been washed ashore on ...In 2022,Yellow Sea green tide caused by Ulva prolifera reached a historic minimum and the coastal areas of Shandong Peninsula were less affected.However,the largest amount of seaweed biomass has been washed ashore on Lianyungang and Rizhao coasts since 2015.We studied the development pattern of Yellow Sea green tide in 2022,and analyzed the key environmental factors on the growth and drifting,then discussed the possible reasons that resulted in the massive stranding of green tide biomass in Lianyungang and Rizhao.Results show under the combined influence of the east to southeast winds and currents with shoreward anomalies,green tide drifted to the coastal waters between Shandong and Jiangsu provinces and the distribution areas located westward compared with previous years(2008–2021).Floating U.prolifera rafts from the coastal waters of Binhai and Sheyang drifted continuously into the coastal waters of Lianyungang and Rizhao,providing important supplements for Yellow Sea green tide.Because green tide in 2022 distributed close to the coastal waters,the abundant nutrients might support their continuous high growth rate.In addition,the amount of rainfall around Shandong Peninsula from late June to early July were significantly higher than in previous years,which might promote the development of green tide to some extent.展开更多
Ulva prolifera is the causative species of the annually occurring large-scale green tides in China since 2007.Its specific biological features on reproductivity strategies,as well as intra-species genetic diversity,ar...Ulva prolifera is the causative species of the annually occurring large-scale green tides in China since 2007.Its specific biological features on reproductivity strategies,as well as intra-species genetic diversity,are still largely unknown,especially at the genome level,despite their importance in understanding the formation and outbreak of massive green tides.In the present study,the restriction site-associated DNA genotyping approach(2b-RAD)was adopted to identify the genome-wide single-nucleotide polymorphisms(SNPs)of 54 individual thalli including samples collected from Subei Shoal in 2019 and Qingdao coast from 2019 to 2021.SNPs genotype results revealed that most of the thalli in 2019 and 2020 were haploid gametophytes,while only half of the thalli were gametophytes in 2021,indicating flexibility in the reproductive strategies for the formation of the green tides among different years and the dominance of asexual and vegetative reproductive mode for the floating period.Besides,population analysis was conducted,and it revealed a very low genetic diversity among samples from Subei Shoal and the Qingdao coast in the same year and a higher divergence among samples in different years.The results showed the efficiency of 2b-RAD in the exploration of SNPs in U.prolifera and provided the first genome-wide scale evidence for the origin of the large-scale green tides on the Qingdao coast.This study improved our understanding of the reproductive strategy and genetic diversity of the green tide causative species and will help further reveal the biological causes of the green tide in China.展开更多
Since 2015, a novel green tide has been recurring in the coastal areas of Qinhuangdao at the western coast of the Bohai Sea in China, threatening the environment and ecosystem of the Beidaihe seaside holiday resort al...Since 2015, a novel green tide has been recurring in the coastal areas of Qinhuangdao at the western coast of the Bohai Sea in China, threatening the environment and ecosystem of the Beidaihe seaside holiday resort along the coast. Micro-propagules of the green algae including gametes, spores, micro-germlings and micro-vegetative fragments play an important role in the formation of green tides. They serve as a "seed source" of green macroalgae, and their distributions could reflect and influence the "algae source" of green tides. In this study,monthly surveys in the inshore and offshore areas of the Qinhuangdao coast were conducted from April to September 2016 and in January 2017 to investigate the tempo-spatial distribution patterns and the biomass variations of the green algae micro-propagules. The obtained results show that micro-propagules were mainly distributed in the inshore areas with a significantly decreasing abundance towards offshore areas. Their biomass was highest in July and August, and lowest in winter. The areas that were affected by the green tides showed a remarkably higher abundance of micro-propagules compared to other areas. These micro-propagules could serve as the "seed" source of green tides. Their distribution patterns indicate that the green tide in the coastal areas of Qinhuangdao originated locally.展开更多
The four leading tidal constituents M2, S2, K1 and O1 in the South China Sea are simulated by using POM. The model is forced with tide-generating potential and four leading tidal constituents at the open boundary. In ...The four leading tidal constituents M2, S2, K1 and O1 in the South China Sea are simulated by using POM. The model is forced with tide-generating potential and four leading tidal constituents at the open boundary. In order to simulate more exactly, TOPEX/Poseidon altimeter data are assimilated into the model and the open boundary is optimized. The computed co-tidal charts for M2 and K1 constituents are generally consistent with previous results in this region. The numerical simulation shows that energetic internal tides are generated over the bottom topography such as the Dongsha Islands, the Xisha Islands, the Zhongsha Islands, the Nansha Islands and the Luzon Strait.展开更多
An integrated investigation was carried out during late April to late May of 2014 in the coastal area of South Jiangsu Province to understand the early development of green tide in the Yellow Sea and discover the temp...An integrated investigation was carried out during late April to late May of 2014 in the coastal area of South Jiangsu Province to understand the early development of green tide in the Yellow Sea and discover the temporal and spatial distribution of green algal micro-propagules and macroalgae at the early stage of green tide. The results showed that green algal micro-propagules distributed in all stations from late April to late May, and micro-propagules of high density(> 300 ind. L^(-1)) concentrated in the adjacent Porphyra aquaculture area. Floating macroalgae were initially observed in the northern survey areas, and increased gradually. The dominant species was U. prolifera in the floating macroalgae, ranging between 90% and 100%. The seawater surface temperature and salinity in the above mentioned time period were suitable for the growth of macroalgae. This work can help government to strengthen management to reduce the blooms of macroalgae in the coastal area of South Jiangsu Province and also facilitate the decision-making for managers at the early stage of green tide.展开更多
The evolution of energy, energy flux and modal structure of the internal tides (ITs) in the northeastern South China Sea is examined using the measurements at two moorings along a cross-slope section from the deep con...The evolution of energy, energy flux and modal structure of the internal tides (ITs) in the northeastern South China Sea is examined using the measurements at two moorings along a cross-slope section from the deep continental slope to the shallow continental shelf. The energy of both diurnal and semidiurnal ITs clearly shows a ~14-day spring-neap cycle, but their phases lag that of barotropic tides, indicating that ITs are not generated on the continental slope. Observations of internal tidal energy flux suggest that they may be generated at the Luzon Strait and propagate west-northwest to the continental slope in the northwestern SCS. Because the continental slope is critical-supercritical with respect to diurnal ITs, about 4.6 kJ/m^2 of the incident energy and 8.7 kW/m of energy flux of diurnal ITs are reduced from the continental slope to the continental shelf. In contrast, the semidiurnal internal tides enter the shelf because of the sub-critical topography with respect to semidiurnal ITs. From the continental slope to the shelf, the vertical structure of diurnal ITs shows significant variation, with dominant Mode 1 on the deep slope and dominant higher modes on the shelf. On the contrary, the vertical structure of the semidiurnal ITs is stable, with dominant Mode 1.展开更多
A layered three-dimensional noalinear numerical model was constructed to simulate the generation and propagation of interanal tides over the continental slope. The simulation was split into external mode computation (...A layered three-dimensional noalinear numerical model was constructed to simulate the generation and propagation of interanal tides over the continental slope. The simulation was split into external mode computation (EMC) and internal mode computation (IMC) to minimize the computational load.IMC was carried out once afte EMC was implemented N time. As to EMC, a semi-implicit numerical scheme was applied in such a way that the pressure gradient terms and the velocity divergence terms were discretized semi-implicitly, but the other terms were discretized explicitly. Eulerian-Lagrangian explicit discretization are applied to the convective terms simultaneously. As a result, the stability of EMC did not depend on the wave celerity and time step was not limited by the CFL condition. More than that, use of the conjugate gradient accelerated Jacobi method further improved the computational efficiency of the model.展开更多
The spatial-temporal characteristics of internal tides (ITs) in the southwest Luzon Strait are examined, based on 9-month mooring current records from autumn 2008 to summer 2009. The results of spectral analysis sho...The spatial-temporal characteristics of internal tides (ITs) in the southwest Luzon Strait are examined, based on 9-month mooring current records from autumn 2008 to summer 2009. The results of spectral analysis show that the ITs in diurnal and semidiurnal frequencies are prominent at the mooring site, especially for the clockwise rotary component. The diurnal ITs are mostly dominated by the first mode except for that in spring when the second mode is relatively predominant. The semidiurnal ITs display a variable multimodal structure. Moreover, an apparent difference is detected in the kinetic energy of diurnal ITs. The energy is strongest in winter, and followed by that in summer, whereas the value is smallest in spring and autumn. It is suggested that the incoherent motions are responsible for the significant seasonal variations of diurnal ITs, reflecting interaction between diurnal ITs and the varying background conditions. However, the semidiumal ITs are independent of seasonal change, whose energy is smaller and only one-third of the diurnal energy in winter. Nevertheless, the abnormal variations of semidiurnal ITs are also related to the variable background conditions. The incoherent semidiurnal constituent accounts for about 37% of the total semidiurnal tidal kinetic energy, but the diurnal tidal motions contain fewer incoherent component (22.2%).展开更多
Green tides caused by the unusual accumulation of high floating Ulva prolifera have occurred regularly in the Yellow Sea since 2007.The primary source of the Yellow Sea green tides is the attached algae on the Pyropia...Green tides caused by the unusual accumulation of high floating Ulva prolifera have occurred regularly in the Yellow Sea since 2007.The primary source of the Yellow Sea green tides is the attached algae on the Pyropia aquaculture rafts in the Subei Shoal.Ulva prolifera and Blidingia(Italic)sp.are the main species observed on Pyropia aquaculture rafts in the Subei Shoal.We found that U.prolifera has strong buoyancy and a rapid growth rate,which may explain why it is the dominant species of green tides that occur in the China's sea area of the Yellow Sea.The growth rate of floating U.prolifera was about 20%–31%d–1,which was much higher than Blidingia(Italic)sp.There were about 1.7×104 t of attached algae on the Pyropia aquaculture rafts in May 2012.We found that 39%of attached algae could float when the tide rose in the Subei Shoal,and U.prolifera accounted for 63%of the floating algae.Our analysis estimated that about 4000 t of attached U.prolifera floated into the surrounding waters of the Subei Shoal during the recycling period of aquaculture rafts.These results suggest that the initial floating biomass of large-scale green tides in the Yellow Sea is determined by the U.prolifera biomass attached to Pyropia aquaculture rafts,further impacting the scale of the green tide。展开更多
By using a coordinate transformation,an exact solution of internal tides is obtained when the bot- tom slope is linear and the V(?)is(?)la frequency is constant.Consequently the dispersion relations of free waves are ...By using a coordinate transformation,an exact solution of internal tides is obtained when the bot- tom slope is linear and the V(?)is(?)la frequency is constant.Consequently the dispersion relations of free waves are presented.Compared with Baines solution,the solution derived here is more consistent with展开更多
Global ocean tides data were derived from Geosat altimeter data by means of the Quasi Harmonic Constituent Method (QHCM). Tidal solutions with resolution of 1°/3 in longitude and latitude were obtained for consti...Global ocean tides data were derived from Geosat altimeter data by means of the Quasi Harmonic Constituent Method (QHCM). Tidal solutions with resolution of 1°/3 in longitude and latitude were obtained for constituents M 2, S 2, O 1, K 1, M 4 and MS 4. The mean sea heights above the reference ellipsoid were also obtained consequently. The obtained tidal constants were compared with those from deep sea and island tide gauge data. The rms differences between the harmonic constants derived from Geosat altimetry and deep sea tide gauges for M 2, S 2, O 1 and K 1 ranged from 1.4 cm to 2.6 cm, although the GM altimeter data have significant errors due to instrument malfunction and other reasons. M 2 tide obtained was the most accurate one among all the tides. Comparison also showed that island tidal constants cannot represent well the tidal distribution in the ocean near the island, because of the significant local effect on tides.展开更多
The layered model in Part I was used to simulate the internal tide in a stratified, two layer, and rectangular sea area with step like topography. The internal tide current velocities of the upper and lower layers and...The layered model in Part I was used to simulate the internal tide in a stratified, two layer, and rectangular sea area with step like topography. The internal tide current velocities of the upper and lower layers and the interfacial elevations were computed and the effect of the upper layer water depth and density difference were studied. Numerical experiments verified that the model can correctly simulate internal tides. The model was also applied to the northwestern part of the South China Sea to simulate the internal tides there with real topography. The distributions of internal tide amplitude in interfaces were delineated.展开更多
There are obvious periodic oscillations in the observations of storm surges in the East China Sea . The storm surges are not only controlled by the wind stresses and isolated long wave caused by typhoons but also affe...There are obvious periodic oscillations in the observations of storm surges in the East China Sea . The storm surges are not only controlled by the wind stresses and isolated long wave caused by typhoons but also affected by the interaction between astronomical tides and storm surges . In the present paper we simulate the interaction between tides and storm surges by using a two dimensional numerical model. In our numerical experiments we use the data of the storm surge induced by Typhoon 8114 . The calculations tally with the measured data well. The results indicate that the periodic osculations occurring in the elevations of the surge are mainly caused by the interaction between the tide and the storm surge . The numerical experiments also indicate that the forecasting precision may be notably improved if the nonlinear interaction between tides and storm surges is taken into account.展开更多
基金the IAG:Commission 3,the IAG Sub-commission 3.1,2.6 and International Geodynamics and Earth Tide Service.The Symposium was sponsored by International Association of Geodesy(IAG),Chinese Academy of Sciences,National Natural Science Foundation of China,Innovation Academy for Precision Measurement Science and Technology(APM),State Key Laboratory of Geodesy and Earth's Dynamics,Huazhong University of Science and Technology.We are very grateful to the Scientific Committee,the local organizing committee and all the participants for successfully holding this meeting under the epidemic situation.
文摘This volume aims at providing a platform for sharing valuable topics discussed at the 19th International Symposium on Geodynamics and Earth Tides,23-26 June 2021,Wuhan,China.The complete overview of all nineteen Symposia is found in Table 1,where the times and venues are listed.
基金The Fund of Key Laboratory of Ecological Prewarning,Protection and Restoration of Bohai Sea,Ministry of Natural Resources under contract No.2022107the Qingdao Postdoctoral Applied Research Project under contract No.QDBSH202001。
文摘Since 2015, green tides have been blooming in offshore waters of Qinhuangdao, with serious impacts on the local ecological environment and tourism. Ulva australis, Bryopsis plumosa, and U. prolifera are the dominant species of Qinhuangdao green tides, following a sequential succession pattern. Ulva prolifera is the dominant species,with the highest biomass and the greatest influence on the local ecological environment. To study the reason of green tide dominant species succession and U. profilera became the dominant species with the largest biomass,we compared and analyzed the growth and nutrient uptake capacity of the three algae. The results showed that temperature significantly affects the growth of the three species. Within the temperature range of the experimental setup, the optimum temperature for the growth of U. australis, B. plumosa and U. profilera is10℃, 15℃, and 20–25℃, respectively. Combined with the temperature variation trend during green tide bloom development, we believe that temperature is the key environmental factor for the succession of the dominant species. Ulva prolifera has a higher growth rate than U. australis and B. plumosa under the same nitrate,ammonium, and phosphate levels. Significant differences in the maximum absorption rate(R_(max)) and R_(max)/Ks(the relationship between uptake rate and substrate concentration) values indicated that U. prolifera had an apparent competitive advantage over U. australis and B. plumosa regarding nutrient uptake. Therefore, the strong growth and nutrient uptake capacities of U. prolifera might be the main reason for becoming the dominant species with the largest biomass in Qinhuangdao green tides.
基金partly supported by JSPS KAKENHI Grant Numbers JP16H02219, JP21H01187, JP21H05204, JP21K14022 and JP21H05203JST Grant Number JPMJMI18A1。
文摘The tidal triggering of earthquakes has been studied for many years.The discovery of slow earthquakes in the early 2000s,including slow slip,has urged scientists to investigate the tidal responses of these earthquakes due to their sensitivity to weak stress perturbations.Previous studies have shown that slow earthquakes correlate with diurnal and semidiurnal tides and seasonal variations in surface loads more clearly than ordinary earthquakes.However,little is known about long-term responses to external stresses.In this paper,based on a widely accepted frictional law for faults,a mechanism is proposed by which nontidal variations in ocean bottom pressure,when combined with tides,pro mote the occurrence of slow earthquakes.Because slow earthquakes accompany a slip on the plate interface,this mechanism allows one to estimate slip modulations.A one-degree-of-freedom slip model is constructed and applied to Ise Bay in the Tonankai region of southwestern Japan,where large-scale ocean mass redistributions have occurred.The model calculated with parameters determined from the observation of tectonic tremors is quantitatively consistent with the slip during 1997-2013 inferred from GNSS data,suggesting that the decrease in the sea-level change in approximately 2006 could cause the accele ration of a slip observed after that.This result implies that the decreases in sea level in approximately 1996 and 2014 could also cause subsequent slip accelerations.These three slip acceleration periods temporally coincide with the increases in background seismicity in a shallower portion of the plate interface.These changes in seismicity are common to shallow earthquakes in the Tokai area,and a similar model can reproduce them.Further studies are expected to reveal causality between shallow earthquakes and long-term slip fluctuations based on modeling that considers changes in the frictional property along the plate interface.
基金The Key-Area Research and Development Project of Guangdong Province under contract No.2020B1111020003the Science and Technology Plan Projects of Guangdong Province under contract No.2021B1212050025the Science and Technology Development Fund of the South China Sea Bureau,Ministry of Natural Resources under contract No.202205.
文摘We examine the cross-shelf variation of internal tides(ITs)west of the Dongsha Plateau in the northern South China Sea based on observations from 4 moorings deployed between August 2017 and September 2018.On the slope,the amplitude of diurnal baroclinic current ellipses are 5 times larger than that of barotropic currents.The baroclinic energy quickly dissipates during cross-shelf propagation,and barotropic currents become dominant on the shelf outside of the Zhujiang River Estuary,with the amplitude of semidiurnal barotropic current ellipses being 10 times larger than that of the baroclinic ones.Dynamic modal decomposition indicates the first baroclinic mode is dominant for both diurnal and semidiurnal ITs.The total horizontal kinetic energy(HKE)of the first three baroclinic modes shows spatiotemporal differences among the 4 moorings.On the slope,the HKE for diurnal ITs is stronger in summer and winter,but weaker in spring and autumn;for semidiurnal ITs there is a similar seasonal variation,but the HKE in winter is even stronger than that in summer.On the shallow shelf,both diurnal and semidiurnal ITs maintain a certain intensity in summer but almost disappear in winter.Further analysis shows that only the upper water column is affected by seasonal variation of stratification on the slope,variation of diurnal ITs is thus controlled by the semi-annual cycle of barotropic energy input from the Luzon Strait,while the incoherent baroclinic currents make a major contribution to the temporal variation of semidiurnal ITs.For the shelf region,the water column is well mixed in winter,and the baroclinic energy largely dissipates when ITs propagate to the shelf zone despite of a strong barotropic energy input from the Luzon Strait.
基金supported by the Joint Fund between NSFC and Shandong Province(No.U1906210)the China National Key Research and Development Program(No.2016YFC1402101).
文摘Since 2007,the large-scale green tide caused by Ulva prolifera(U.prolifera)have occurred as a recurrent phenomenon in the southern Yellow Sea of China.Field surveys and satellite remote sensing showed that the small scattered patches of green tide algae were first observed along the Porphyra agriculture area of the Subei Shoal in late April.In this study,we attempted to identify the role of eutrophication in the origin of the green tide in the Subei Shoal and its adjacent area.Subei Shoal and its adjacent area are characterized by rich nutrients,especially NO_(3)^(-)-N,NH_(4)^(+)-N,PO_(4)^(3-)-P,and other bioavailable components(such as urea-N and amino acids).In the spring of 2017,the average concentrations of NO_(3)^(-)-N were 19.01±11.01μmolL^(-1),accounting for 86.68%of the dis-solved inorganic nitrogen(DIN).In addition,the average concentration of NH4^(+)-N was 2.51±1.60μmolL^(-1).PO_(4)^(3-)-P had an average concentration of 0.14±0.13μmolL-1.The average concentrations of urea-N and total hydrolyzed amino acids(THAA)were 1.73±1.36μmolL^(-1)and 1.33±0.80μmolL^(-1),respectively.Rich nutritive substances play a key role in the rapid production of U.prolifera and make the Jiangsu coastal water an incubator for green tide.
基金the University of French Polynesiafunding by several successive“Decision Aide a la Recherche”(DAR)grants to the Geodesy Observatory of Tahiti from the French Space Agency(CNES)+2 种基金fundings from the local government of French Polynesia(Observatoire Polynesien du Rechauffement Climatique)funding by“National Natural Science Foundation of China”(Grand No.41931075)funding by“the Fundamental Research Funds for the Central Universities"(Grand No.2042022kf1198)。
文摘In this study,we estimate the absolute vertical land motions at three tidal stations with collocated Global Navigation Satellite System(GNSS)receivers over French Polynesia during the period 2007-2020,and obtain,as ancillary results,estimates of the absolute changes in sea level at the same locations.To verify our processing approach to determining vertical motion,we first modeled vertical motion at the International GNSS Service(IGS)THTI station located in the capital island of Tahiti and compared our estimate with previous independent determinations,with a good agreement.We obtained the following estimates for the vertical land motions at the tide gauges:Tubuai island,Austral Archipelago-0.92±0.17 mm/yr,Vairao village,Tahiti Iti:-0.49±0.39 mm/yr,Rikitea,Gambier Archipelago-0.43±0.17 mm/yr.The absolute variations of the sea level are:Tubuai island,Austral Archipelago 5.25±0.60 mm/yr,Vairao village,Tahiti Iti:3.62±0.52 mm/yr,Rikitea,Gambier Archipelago 1.52±0.23 mm/yr.We discuss these absolute values in light of the values obtained from altimetric measurements and other means in French Polynesia.
基金Supported by the National Key R&D Program of China(No.2022YFC3106005)the Shandong Provincial Natural Science Foundation(No.ZR2021MD122)+1 种基金the MNR Key Laboratory of Eco-Environmental Science and Technology,China(No.MEEST-2023-04)the Shandong Provincial Key Laboratory of Marine Ecological Environment and Disaster Prevention and Mitigation(No.201708)。
文摘In 2022,Yellow Sea green tide caused by Ulva prolifera reached a historic minimum and the coastal areas of Shandong Peninsula were less affected.However,the largest amount of seaweed biomass has been washed ashore on Lianyungang and Rizhao coasts since 2015.We studied the development pattern of Yellow Sea green tide in 2022,and analyzed the key environmental factors on the growth and drifting,then discussed the possible reasons that resulted in the massive stranding of green tide biomass in Lianyungang and Rizhao.Results show under the combined influence of the east to southeast winds and currents with shoreward anomalies,green tide drifted to the coastal waters between Shandong and Jiangsu provinces and the distribution areas located westward compared with previous years(2008–2021).Floating U.prolifera rafts from the coastal waters of Binhai and Sheyang drifted continuously into the coastal waters of Lianyungang and Rizhao,providing important supplements for Yellow Sea green tide.Because green tide in 2022 distributed close to the coastal waters,the abundant nutrients might support their continuous high growth rate.In addition,the amount of rainfall around Shandong Peninsula from late June to early July were significantly higher than in previous years,which might promote the development of green tide to some extent.
基金Supported by the Laoshan Laboratory (No.LSKJ202204005)the Mount Tai Scholar Climbing Plan to Song SUNthe Open Fund of CAS Key Laboratory of Marine Ecology and Environmental Sciences,Institute of Oceanology,Chinese Academy of Sciences (No.KLMEES201801)
文摘Ulva prolifera is the causative species of the annually occurring large-scale green tides in China since 2007.Its specific biological features on reproductivity strategies,as well as intra-species genetic diversity,are still largely unknown,especially at the genome level,despite their importance in understanding the formation and outbreak of massive green tides.In the present study,the restriction site-associated DNA genotyping approach(2b-RAD)was adopted to identify the genome-wide single-nucleotide polymorphisms(SNPs)of 54 individual thalli including samples collected from Subei Shoal in 2019 and Qingdao coast from 2019 to 2021.SNPs genotype results revealed that most of the thalli in 2019 and 2020 were haploid gametophytes,while only half of the thalli were gametophytes in 2021,indicating flexibility in the reproductive strategies for the formation of the green tides among different years and the dominance of asexual and vegetative reproductive mode for the floating period.Besides,population analysis was conducted,and it revealed a very low genetic diversity among samples from Subei Shoal and the Qingdao coast in the same year and a higher divergence among samples in different years.The results showed the efficiency of 2b-RAD in the exploration of SNPs in U.prolifera and provided the first genome-wide scale evidence for the origin of the large-scale green tides on the Qingdao coast.This study improved our understanding of the reproductive strategy and genetic diversity of the green tide causative species and will help further reveal the biological causes of the green tide in China.
基金The National Key Research and Development Program of China under contract Nos 2016YFC1402104 and2016YFC1402106the National Natural Science Foundation of China under contract No.41606190+2 种基金the Shandong Natural Science Foundation under contract No.ZR2016DB22the Foundation of Key Laboratory of Integrated Monitoring and Applied Technologies for Marine Harmful Algal Blooms,SOA under contract No.MATHAB201806the Creative Team Project of the Laboratory for Marine Ecology and Environmental Science,Qingdao National Laboratory for Marine Science and Technology under contract No.LMEESCTSP-2018-3
文摘Since 2015, a novel green tide has been recurring in the coastal areas of Qinhuangdao at the western coast of the Bohai Sea in China, threatening the environment and ecosystem of the Beidaihe seaside holiday resort along the coast. Micro-propagules of the green algae including gametes, spores, micro-germlings and micro-vegetative fragments play an important role in the formation of green tides. They serve as a "seed source" of green macroalgae, and their distributions could reflect and influence the "algae source" of green tides. In this study,monthly surveys in the inshore and offshore areas of the Qinhuangdao coast were conducted from April to September 2016 and in January 2017 to investigate the tempo-spatial distribution patterns and the biomass variations of the green algae micro-propagules. The obtained results show that micro-propagules were mainly distributed in the inshore areas with a significantly decreasing abundance towards offshore areas. Their biomass was highest in July and August, and lowest in winter. The areas that were affected by the green tides showed a remarkably higher abundance of micro-propagules compared to other areas. These micro-propagules could serve as the "seed" source of green tides. Their distribution patterns indicate that the green tide in the coastal areas of Qinhuangdao originated locally.
文摘The four leading tidal constituents M2, S2, K1 and O1 in the South China Sea are simulated by using POM. The model is forced with tide-generating potential and four leading tidal constituents at the open boundary. In order to simulate more exactly, TOPEX/Poseidon altimeter data are assimilated into the model and the open boundary is optimized. The computed co-tidal charts for M2 and K1 constituents are generally consistent with previous results in this region. The numerical simulation shows that energetic internal tides are generated over the bottom topography such as the Dongsha Islands, the Xisha Islands, the Zhongsha Islands, the Nansha Islands and the Luzon Strait.
基金supported by the National Natural Science Foundation of China (41276119)NSFC-Shandong Joint Fund for Marine Science Research Centers (Grant No.U1406403)
文摘An integrated investigation was carried out during late April to late May of 2014 in the coastal area of South Jiangsu Province to understand the early development of green tide in the Yellow Sea and discover the temporal and spatial distribution of green algal micro-propagules and macroalgae at the early stage of green tide. The results showed that green algal micro-propagules distributed in all stations from late April to late May, and micro-propagules of high density(> 300 ind. L^(-1)) concentrated in the adjacent Porphyra aquaculture area. Floating macroalgae were initially observed in the northern survey areas, and increased gradually. The dominant species was U. prolifera in the floating macroalgae, ranging between 90% and 100%. The seawater surface temperature and salinity in the above mentioned time period were suitable for the growth of macroalgae. This work can help government to strengthen management to reduce the blooms of macroalgae in the coastal area of South Jiangsu Province and also facilitate the decision-making for managers at the early stage of green tide.
基金The State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract No.LTO1915the National Natural Science Foundation of China under contract Nos 41630970,41876016,41676022 and 41521005the Instrument Developing Project of the CAS under contract No.YZ201432
文摘The evolution of energy, energy flux and modal structure of the internal tides (ITs) in the northeastern South China Sea is examined using the measurements at two moorings along a cross-slope section from the deep continental slope to the shallow continental shelf. The energy of both diurnal and semidiurnal ITs clearly shows a ~14-day spring-neap cycle, but their phases lag that of barotropic tides, indicating that ITs are not generated on the continental slope. Observations of internal tidal energy flux suggest that they may be generated at the Luzon Strait and propagate west-northwest to the continental slope in the northwestern SCS. Because the continental slope is critical-supercritical with respect to diurnal ITs, about 4.6 kJ/m^2 of the incident energy and 8.7 kW/m of energy flux of diurnal ITs are reduced from the continental slope to the continental shelf. In contrast, the semidiurnal internal tides enter the shelf because of the sub-critical topography with respect to semidiurnal ITs. From the continental slope to the shelf, the vertical structure of diurnal ITs shows significant variation, with dominant Mode 1 on the deep slope and dominant higher modes on the shelf. On the contrary, the vertical structure of the semidiurnal ITs is stable, with dominant Mode 1.
文摘A layered three-dimensional noalinear numerical model was constructed to simulate the generation and propagation of interanal tides over the continental slope. The simulation was split into external mode computation (EMC) and internal mode computation (IMC) to minimize the computational load.IMC was carried out once afte EMC was implemented N time. As to EMC, a semi-implicit numerical scheme was applied in such a way that the pressure gradient terms and the velocity divergence terms were discretized semi-implicitly, but the other terms were discretized explicitly. Eulerian-Lagrangian explicit discretization are applied to the convective terms simultaneously. As a result, the stability of EMC did not depend on the wave celerity and time step was not limited by the CFL condition. More than that, use of the conjugate gradient accelerated Jacobi method further improved the computational efficiency of the model.
基金The National Natural Science Foundation of China under contract Nos 41276022,U1133001,41230962,41206010 and 41206008the Open Fund of the Key Laboratory of Ocean Circulation and Waves,Chinese Academy of Sciences under contract No.KLOCW1506Guangdong Province Key Laboratory for Coastal Ocean Variation and Disaster Prediction Technologies,Guangdong Ocean University under contract No.GLOD1401
文摘The spatial-temporal characteristics of internal tides (ITs) in the southwest Luzon Strait are examined, based on 9-month mooring current records from autumn 2008 to summer 2009. The results of spectral analysis show that the ITs in diurnal and semidiurnal frequencies are prominent at the mooring site, especially for the clockwise rotary component. The diurnal ITs are mostly dominated by the first mode except for that in spring when the second mode is relatively predominant. The semidiurnal ITs display a variable multimodal structure. Moreover, an apparent difference is detected in the kinetic energy of diurnal ITs. The energy is strongest in winter, and followed by that in summer, whereas the value is smallest in spring and autumn. It is suggested that the incoherent motions are responsible for the significant seasonal variations of diurnal ITs, reflecting interaction between diurnal ITs and the varying background conditions. However, the semidiumal ITs are independent of seasonal change, whose energy is smaller and only one-third of the diurnal energy in winter. Nevertheless, the abnormal variations of semidiurnal ITs are also related to the variable background conditions. The incoherent semidiurnal constituent accounts for about 37% of the total semidiurnal tidal kinetic energy, but the diurnal tidal motions contain fewer incoherent component (22.2%).
基金The National Key R&D Program of China under contract Nos 2016YFC1402104 and 2016YFC1402106the National Natural Science Foundation of China under contract No.41606190+2 种基金the Shandong Natural Science Foundation under contract No.ZR2016DB22the Foundation of Key Laboratory of Integrated Monitoring and Applied Technologies for Marine Harmful Algal Blooms,SOA under contract No.MATHAB 201806the Creative Team Project of the Laboratory for Marine Ecology and Environmental Science,Qingdao National Laboratory for Marine Science and Technology under contract No.LMEES-CTSP-2018-3
文摘Green tides caused by the unusual accumulation of high floating Ulva prolifera have occurred regularly in the Yellow Sea since 2007.The primary source of the Yellow Sea green tides is the attached algae on the Pyropia aquaculture rafts in the Subei Shoal.Ulva prolifera and Blidingia(Italic)sp.are the main species observed on Pyropia aquaculture rafts in the Subei Shoal.We found that U.prolifera has strong buoyancy and a rapid growth rate,which may explain why it is the dominant species of green tides that occur in the China's sea area of the Yellow Sea.The growth rate of floating U.prolifera was about 20%–31%d–1,which was much higher than Blidingia(Italic)sp.There were about 1.7×104 t of attached algae on the Pyropia aquaculture rafts in May 2012.We found that 39%of attached algae could float when the tide rose in the Subei Shoal,and U.prolifera accounted for 63%of the floating algae.Our analysis estimated that about 4000 t of attached U.prolifera floated into the surrounding waters of the Subei Shoal during the recycling period of aquaculture rafts.These results suggest that the initial floating biomass of large-scale green tides in the Yellow Sea is determined by the U.prolifera biomass attached to Pyropia aquaculture rafts,further impacting the scale of the green tide。
基金National Education Committee Foundation Programs 9142305 and 9342305National Natural Science Foundation Program 49376257National Special Research Program 85-927-05-03
文摘By using a coordinate transformation,an exact solution of internal tides is obtained when the bot- tom slope is linear and the V(?)is(?)la frequency is constant.Consequently the dispersion relations of free waves are presented.Compared with Baines solution,the solution derived here is more consistent with
文摘Global ocean tides data were derived from Geosat altimeter data by means of the Quasi Harmonic Constituent Method (QHCM). Tidal solutions with resolution of 1°/3 in longitude and latitude were obtained for constituents M 2, S 2, O 1, K 1, M 4 and MS 4. The mean sea heights above the reference ellipsoid were also obtained consequently. The obtained tidal constants were compared with those from deep sea and island tide gauge data. The rms differences between the harmonic constants derived from Geosat altimetry and deep sea tide gauges for M 2, S 2, O 1 and K 1 ranged from 1.4 cm to 2.6 cm, although the GM altimeter data have significant errors due to instrument malfunction and other reasons. M 2 tide obtained was the most accurate one among all the tides. Comparison also showed that island tidal constants cannot represent well the tidal distribution in the ocean near the island, because of the significant local effect on tides.
文摘The layered model in Part I was used to simulate the internal tide in a stratified, two layer, and rectangular sea area with step like topography. The internal tide current velocities of the upper and lower layers and the interfacial elevations were computed and the effect of the upper layer water depth and density difference were studied. Numerical experiments verified that the model can correctly simulate internal tides. The model was also applied to the northwestern part of the South China Sea to simulate the internal tides there with real topography. The distributions of internal tide amplitude in interfaces were delineated.
文摘There are obvious periodic oscillations in the observations of storm surges in the East China Sea . The storm surges are not only controlled by the wind stresses and isolated long wave caused by typhoons but also affected by the interaction between astronomical tides and storm surges . In the present paper we simulate the interaction between tides and storm surges by using a two dimensional numerical model. In our numerical experiments we use the data of the storm surge induced by Typhoon 8114 . The calculations tally with the measured data well. The results indicate that the periodic osculations occurring in the elevations of the surge are mainly caused by the interaction between the tide and the storm surge . The numerical experiments also indicate that the forecasting precision may be notably improved if the nonlinear interaction between tides and storm surges is taken into account.