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
Cross-shelf transport is important due to its role in the transport of nutrients, larvae, sediments, and pollutants. The role of coastal trapped waves(CTWs) and their contribution to the cross-shelf transport is prese...Cross-shelf transport is important due to its role in the transport of nutrients, larvae, sediments, and pollutants. The role of coastal trapped waves(CTWs) and their contribution to the cross-shelf transport is presently unknown. The impact of wind-driven CTWs on the structure of the cross-shelf currents and transport is investigated in the East China Sea(ECS) starting from theory. The cross-shelf currents are divided into four terms: the geostrophic balance(GB) term, the second-order wave(SOW) term, the bottom friction(BF) term and Ekman(EK) term, as well as three modes: the Kelvin wave(KW) mode, the first shelf wave(SW1) mode and the second shelf wave(SW2) mode. Comparison among these decompositions shows that(1) for the four terms, the effect of the GB and EK terms is continual, while that of the BF term is confi ned to 60–240 km of fshore, and the contribution of the SOW term can be ignored;(2) for the three modes, the KW and SW1 modes are dominant in cross-shelf transport. The results show that the total cross-shelf transport travels onshore under idealized wind stress on the order of 10^(-1), and it increases along the cross-shelf direction and peaks about-0.73 Sv at the continental shelf margin. With the increase of linear bottom friction coeffi cient, the cross-shelf transport declines with distance with the slope becoming more uniform.展开更多
Along the downwelling coast off Western Australia, late-austral-autumn/early-austral-winter chlorophyll a blooms are observed on the continental shelf south of the Shark Bay (26° S). The late-austral-autumn/early...Along the downwelling coast off Western Australia, late-austral-autumn/early-austral-winter chlorophyll a blooms are observed on the continental shelf south of the Shark Bay (26° S). The late-austral-autumn/early-austral-winter blooms are in phase with seasonal strengthening of the Leeuwin Current and its eddy field. From satellite altimeter and ocean color data , anticyclonic eddies are found to entrain the high phytoplankton biomass waters from the shelf and transport them offshore into the oligotrophic, subtropical marine environment. The late-austral-autumn/early-austral-winter blooms are highly linked with enhanced horizontal mixing by mesoscale eddies in the region, as derived from the finite-size Lyapunov exponent (FSLE) of the surface geostrophic flow field obtained from satellite altimeter data. The pathways of cross-shelf exchanges, which are mostly driven by the mesoscale eddies, are revealed with coalescing of the FSLE of the surface geostrophic flow field and the satellite chlorophyll a images.展开更多
Based on Marx-Planck coupled model simulations and in situ hydrography measurements, the volume transport of ocean currents and associated carbon fluxes across the continental margin from the continental shelf to the ...Based on Marx-Planck coupled model simulations and in situ hydrography measurements, the volume transport of ocean currents and associated carbon fluxes across the continental margin from the continental shelf to the deep ocean in the East China Sea during winter are estimated. Because cross-shelf currents in the Yellow and East China seas are much stronger in winter than in other seasons and are subducted into the subsurface Kuroshio, the cross-shelf burial of carbon takes place mainly in winter. The analyses show prominent cross-shelf transports during winter in the Yellow and East China seas, with annual mean offshore transport across a section from Taiwan to Cheju at 3.92 Sv(1 Sv=10~6 m^3 s^(-1)). Net transport across the section was0.82 Sv off the shelf, determined by the difference between Taiwan and Cheju strait transports. Net cross-shelf transports of dissolving inorganic carbon(DIC), dissolved organic carbon(DOC), and particulate organic carbon(POC) in winter were 98, 12,and 0.1 million tons, respectively. Under global greenhouse gas emission reduction(RCP4.5) and continuous increase(RCP8.5)scenarios, this cross-shelf transport has an increasing trend. The transports across the Taiwan-Cheju section in winter are predicted to increase by 0.54 and 0.65 Sv from 2006 to 2099, with rates of increase 15.3% and 19.6%, respectively. Associated with the transport increase, the cross-shelf fluxes of DIC, DOC and POC increase by as much as 15.4–25.2%. Cross-shelf carbon fluxes in the East China Sea during winter are evaluated for the first time under the global warming scenarios, showing the importance of cross-shelf transport in the carbon cycle of the China marginal seas.展开更多
A winter onshore warm tongue extending from the Yellow Sea Warm Current to the southern Jiangsu coast, and an of fshore cold tongue extending from the southern Jiangsu coast to the southwest of Jeju Island(South Korea...A winter onshore warm tongue extending from the Yellow Sea Warm Current to the southern Jiangsu coast, and an of fshore cold tongue extending from the southern Jiangsu coast to the southwest of Jeju Island(South Korea), are newly identified based on the sea-surface temperature from satellite remote sensing, and further confirmed by the distribution of suspended sediments. In addition, there are two obvious thermal fronts associated with the onshore warm tongue and off shore cold tongue. The narrow gap between the two thermal fronts is supposed to be the pathway for the off shore transport of cold coastal water and suspended sediments. The concurrence of onshore warm and of fshore cold tongues suggests the concurrence of onshore and off shore currents in the western Yellow Sea in winter, which seems to be inconsistent with the previously accepted view that, in winter, the Yellow Sea Coastal Current flows from the Old Huanghe Delta to the southwest of Jeju Island. This distinctive phenomenon helps establish an updated view of the circulation in the western Yellow Sea in winter.展开更多
基于普林斯顿海洋模式(POM),利用全球海洋温盐集(WOA13)气候态温盐数据对南海环流进行诊断计算,分析东沙海区冬季气候态跨陆坡运动特征。诊断结果表明:跨陆坡运动的水平和垂向断面分布,反映出该海区跨陆坡运动存在反对称结构,即东沙岛...基于普林斯顿海洋模式(POM),利用全球海洋温盐集(WOA13)气候态温盐数据对南海环流进行诊断计算,分析东沙海区冬季气候态跨陆坡运动特征。诊断结果表明:跨陆坡运动的水平和垂向断面分布,反映出该海区跨陆坡运动存在反对称结构,即东沙岛以东向陆架方向运动、以西向外洋方向运动。根据正压涡度平衡方程逐项分析,探讨了东沙海区跨陆坡运动的动力机制,研究表明:地形与斜压联合效应项(joint effect of baroclinicity and bottom relief,JEBAR)和地转位势涡度平流项(advection of the geostrophic potential vorticity,APV)主导了涡度平衡,平流项和扩散项作用次之,且JEBAR、APV及平流扩散各项在东沙岛东西两侧均表现为正负号相反分布;相比而言,海表风应力项和海底摩擦力项的影响为小量。东沙海区密度场相对于地形的不均匀分布,使得东沙以东JEBAR分布为正、以西JEBAR分布为负,这种分布是导致反对称的跨陆坡运动发生的主要内在机制,且东沙岛地形和不均匀密度场分布是这种动力机制得以维持的主要原因。展开更多
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 National Natural Science Foundation of China(Nos.41476022,41506044)the Program for Innovation Research and Entrepreneurship Team in Jiangsu Province+1 种基金the National Program on Global Change and Air-Sea Interaction(No.GASI-IPOVAI-05)the Startup Foundation for Introducing Talent of Nanjing University of Information Science and Technology(Nos.2013r121,2014r072)
文摘Cross-shelf transport is important due to its role in the transport of nutrients, larvae, sediments, and pollutants. The role of coastal trapped waves(CTWs) and their contribution to the cross-shelf transport is presently unknown. The impact of wind-driven CTWs on the structure of the cross-shelf currents and transport is investigated in the East China Sea(ECS) starting from theory. The cross-shelf currents are divided into four terms: the geostrophic balance(GB) term, the second-order wave(SOW) term, the bottom friction(BF) term and Ekman(EK) term, as well as three modes: the Kelvin wave(KW) mode, the first shelf wave(SW1) mode and the second shelf wave(SW2) mode. Comparison among these decompositions shows that(1) for the four terms, the effect of the GB and EK terms is continual, while that of the BF term is confi ned to 60–240 km of fshore, and the contribution of the SOW term can be ignored;(2) for the three modes, the KW and SW1 modes are dominant in cross-shelf transport. The results show that the total cross-shelf transport travels onshore under idealized wind stress on the order of 10^(-1), and it increases along the cross-shelf direction and peaks about-0.73 Sv at the continental shelf margin. With the increase of linear bottom friction coeffi cient, the cross-shelf transport declines with distance with the slope becoming more uniform.
基金supported by Strategic Research Fund for Marine Environment
文摘Along the downwelling coast off Western Australia, late-austral-autumn/early-austral-winter chlorophyll a blooms are observed on the continental shelf south of the Shark Bay (26° S). The late-austral-autumn/early-austral-winter blooms are in phase with seasonal strengthening of the Leeuwin Current and its eddy field. From satellite altimeter and ocean color data , anticyclonic eddies are found to entrain the high phytoplankton biomass waters from the shelf and transport them offshore into the oligotrophic, subtropical marine environment. The late-austral-autumn/early-austral-winter blooms are highly linked with enhanced horizontal mixing by mesoscale eddies in the region, as derived from the finite-size Lyapunov exponent (FSLE) of the surface geostrophic flow field obtained from satellite altimeter data. The pathways of cross-shelf exchanges, which are mostly driven by the mesoscale eddies, are revealed with coalescing of the FSLE of the surface geostrophic flow field and the satellite chlorophyll a images.
基金supported by the Major Science Research Plan of China for Global Change Research(Grant No.2012CB956001)the Special Program for Marine of the Chinese Academy of Sciences(Grant Nos.XDA11010205&XDA11010304)+4 种基金the National Natural Science Foundation of China(Grant Nos.41421005&41576016)the Key Foundation for International Cooperation(Grant No.41720104008)the“Science Plan of Aoshan”Project of Qingdao National Laboratory for Marine Science and Technology(Grant No.2016ASKJ04)the Special Program of State Oceanic Administration(Grant No.GASI-03-01-01-05)the Project of Joint Funds of Shandong Province(Grant Nos.2014GJJS0101and U1406401)
文摘Based on Marx-Planck coupled model simulations and in situ hydrography measurements, the volume transport of ocean currents and associated carbon fluxes across the continental margin from the continental shelf to the deep ocean in the East China Sea during winter are estimated. Because cross-shelf currents in the Yellow and East China seas are much stronger in winter than in other seasons and are subducted into the subsurface Kuroshio, the cross-shelf burial of carbon takes place mainly in winter. The analyses show prominent cross-shelf transports during winter in the Yellow and East China seas, with annual mean offshore transport across a section from Taiwan to Cheju at 3.92 Sv(1 Sv=10~6 m^3 s^(-1)). Net transport across the section was0.82 Sv off the shelf, determined by the difference between Taiwan and Cheju strait transports. Net cross-shelf transports of dissolving inorganic carbon(DIC), dissolved organic carbon(DOC), and particulate organic carbon(POC) in winter were 98, 12,and 0.1 million tons, respectively. Under global greenhouse gas emission reduction(RCP4.5) and continuous increase(RCP8.5)scenarios, this cross-shelf transport has an increasing trend. The transports across the Taiwan-Cheju section in winter are predicted to increase by 0.54 and 0.65 Sv from 2006 to 2099, with rates of increase 15.3% and 19.6%, respectively. Associated with the transport increase, the cross-shelf fluxes of DIC, DOC and POC increase by as much as 15.4–25.2%. Cross-shelf carbon fluxes in the East China Sea during winter are evaluated for the first time under the global warming scenarios, showing the importance of cross-shelf transport in the carbon cycle of the China marginal seas.
基金Supported by the Strategy Program of Chinese Academy of Sciences(Nos.XDA10020104,XDA10020305)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.41421005)+2 种基金the National Natural Science Foundation of China(Nos.41476019,41606040)the NSFC-Shandong Joint Fund for Marine Science Research Centers(No.U1406401)the High Performance Computing Center,Institute of Oceanology,Chinese Academy of Sciences in Qingdao
文摘A winter onshore warm tongue extending from the Yellow Sea Warm Current to the southern Jiangsu coast, and an of fshore cold tongue extending from the southern Jiangsu coast to the southwest of Jeju Island(South Korea), are newly identified based on the sea-surface temperature from satellite remote sensing, and further confirmed by the distribution of suspended sediments. In addition, there are two obvious thermal fronts associated with the onshore warm tongue and off shore cold tongue. The narrow gap between the two thermal fronts is supposed to be the pathway for the off shore transport of cold coastal water and suspended sediments. The concurrence of onshore warm and of fshore cold tongues suggests the concurrence of onshore and off shore currents in the western Yellow Sea in winter, which seems to be inconsistent with the previously accepted view that, in winter, the Yellow Sea Coastal Current flows from the Old Huanghe Delta to the southwest of Jeju Island. This distinctive phenomenon helps establish an updated view of the circulation in the western Yellow Sea in winter.
文摘基于普林斯顿海洋模式(POM),利用全球海洋温盐集(WOA13)气候态温盐数据对南海环流进行诊断计算,分析东沙海区冬季气候态跨陆坡运动特征。诊断结果表明:跨陆坡运动的水平和垂向断面分布,反映出该海区跨陆坡运动存在反对称结构,即东沙岛以东向陆架方向运动、以西向外洋方向运动。根据正压涡度平衡方程逐项分析,探讨了东沙海区跨陆坡运动的动力机制,研究表明:地形与斜压联合效应项(joint effect of baroclinicity and bottom relief,JEBAR)和地转位势涡度平流项(advection of the geostrophic potential vorticity,APV)主导了涡度平衡,平流项和扩散项作用次之,且JEBAR、APV及平流扩散各项在东沙岛东西两侧均表现为正负号相反分布;相比而言,海表风应力项和海底摩擦力项的影响为小量。东沙海区密度场相对于地形的不均匀分布,使得东沙以东JEBAR分布为正、以西JEBAR分布为负,这种分布是导致反对称的跨陆坡运动发生的主要内在机制,且东沙岛地形和不均匀密度场分布是这种动力机制得以维持的主要原因。
