Dune fields at the northern margin of the East Asian monsoon （EAM）, are mosaics of mobile and vegetation-stabilized aeolian dunes. These sand dunes are highly sensitive to environmental change, thus the distribution...Dune fields at the northern margin of the East Asian monsoon （EAM）, are mosaics of mobile and vegetation-stabilized aeolian dunes. These sand dunes are highly sensitive to environmental change, thus the distribution and the timing of their development may provide important clues to past environmental dynamics. Due to the strong wind erosion and dune migration, long and continuous stratigraphic records are seldom preserved. Synthesizing a large body of events, ultimately producing a relatively complete and high-resolution record, may be a proper method to investigate the dune development history and climate change. In this study, we synthesized a large body of luminescence ages for aeolian deposits from the Mu Us, Otindag, Horqin dune fields at the northern margin of the EAM. The results show that these dune fields, as a whole experienced a most extensive mobility during the early Holocene, followed by a widespread shift toward limited mobility and soil development in the mid-Holocene, and widespread reactivation occurred during late Holocene. The dune developments are directly linked to the effective moisture change controlled by the EAM changes, which respond to the low latitude summer insolation variation. The increased subsidence at the margin contrary to the core EAM, the delay from the feedback of the soil-vegetation-air coupled system, the increased evaporation due to the high temperature all play partial role in the lag of the margin EAM effective moisture change to the low latitude summer insolation. The asynchronous end of the wetter mid-Holocene mainly responds to the southeastwardly shift of the precipitation belt, while the regional sensitivity, response speed and internal feedback also contributed. The correspondence between dune records and North Atlantic drift-ice records of the rapid climate changes implies a close relationship between North Atlantic climate and the frequent dune activity at the northern margin of EAM.展开更多
天山北坡地处多个大气环流系统的过渡区,气候变化敏感,其长时间尺度的气候演变过程、水热组合方式等问题仍在讨论中,客观把握上述问题对深入认识亚欧大陆内部气候变化格局与过程具有重要意义。本研究以那拉提剖面为研究对象,基于AMS14C...天山北坡地处多个大气环流系统的过渡区,气候变化敏感,其长时间尺度的气候演变过程、水热组合方式等问题仍在讨论中,客观把握上述问题对深入认识亚欧大陆内部气候变化格局与过程具有重要意义。本研究以那拉提剖面为研究对象,基于AMS14C年代-深度模型,以花粉为古气候代用指标,重建了天山北坡末次冰消期至早、中全新世的气候变化过程并探讨了其驱动机制。(1)14327—11578 cal yr B.P.期间花粉组合以荒漠草原成分为主,其主成分分析第1轴得分指示有效湿度偏低,并存在气候突变现象;11578—9457 cal yr B.P.期间演替为森林草原群落,气候以冷湿为特征;9457—8602 cal yr B.P.期间退化为草原,气候转为暖干;8602—6369 cal yr B.P.期间发育针阔混交林,气候偏暖湿。(2)天山北坡末次冰消期至早、中全新世,温度变化与高低纬、海陆间长尺度的记录相一致,冬季太阳辐射是影响温度变化的主要因素;海面温度升高,不仅使西风环流水汽含量增加,还引发北大西洋涛动偏于正相,西部扰动加强,给天山北坡带来更多降水。(3)天山北坡12900—11500 cal yr B.P.期间以干旱为特征的气候突变从起讫时间、湿度变化等特征分析是对“新仙女木事件”的响应,北美洲劳伦泰德冰盖融冰减缓了北大西洋经向翻转环流,叠加北大西洋涛动负相位、西风环流减弱等因素,使到达研究区的水汽减少。展开更多
Using observational data of Argos satellite-tracked drifters from 1988 to 2012, we analyzed seasonal characteristics of the surface Kuroshio branch(KB) intrusion into the South China Sea(SCS). The analysis results are...Using observational data of Argos satellite-tracked drifters from 1988 to 2012, we analyzed seasonal characteristics of the surface Kuroshio branch(KB) intrusion into the South China Sea(SCS). The analysis results are as follows.The surface KB originates from the southern Balintang Channel(BLTC) and Babuyan Channel(BBYC). It begins in late September, reaches peak strength in November–December, and declines at the end of March. The mean speed of drifters along the KB path during their traverse of the Luzon Strait(LS) was 43% faster than during the two days before entering the LS for the flow originating from the southern BLTC, but there was a 24% increase in speed for the flow from the BBYC. The observations show that in winter, monthly-mean sea-level anomalies(SLAs) were positive southwest of Taiwan Island and extended to the northern LS. The SLAs were negative northwest of Luzon Island and extended to the southern LS, which acted like a pump, forcing a part of Kuroshio water westward into the SCS. The condition under which the KB forms was solved by a set of simplified motion equations. The results indicate that whether the KB can form depends upon the sea-level gradient at the central LS and region to the west, as well as the location, speed and direction of Kuroshio surface water when it enters the LS.展开更多
An accelerating charged particle exerts a force upon itself. If we model the particle as a spherical shell of radius R, and calculate the force of one piece of this shell on another and eventually integrate over the w...An accelerating charged particle exerts a force upon itself. If we model the particle as a spherical shell of radius R, and calculate the force of one piece of this shell on another and eventually integrate over the whole particle, there will be a net force on the particle due to the breakdown of Newton’s third law. This symmetry breaking mechanism relies on the finite size of the particle;thus, as Feynman has stated, conceptually this mechanism doesn’t make good sense for point particles. Nonetheless, in the point particle limit, two terms survive in the self-force series: R0 and R-1 terms. The R0 term can alternatively be attributed to the well-known radiation reaction but the origin of R-1 term is not clear. In this study, we will show that this new term can be accounted for by an inductive mechanism in which the changing magnetic field induces an inductive force on the particle. Using this inductive mechanism, we derive R-1 term in an extremely easy way.展开更多
基金financially supported by the National Science Foundation of China(Grant No.41102102)"Strategic Priority Research Program"of the Chinese Academy of Sciences(Grant No.XDB03020300)the Key Research Program of the Chinese Academy of Sciences(Grant No.KZZD-EW-04-03)
文摘Dune fields at the northern margin of the East Asian monsoon （EAM）, are mosaics of mobile and vegetation-stabilized aeolian dunes. These sand dunes are highly sensitive to environmental change, thus the distribution and the timing of their development may provide important clues to past environmental dynamics. Due to the strong wind erosion and dune migration, long and continuous stratigraphic records are seldom preserved. Synthesizing a large body of events, ultimately producing a relatively complete and high-resolution record, may be a proper method to investigate the dune development history and climate change. In this study, we synthesized a large body of luminescence ages for aeolian deposits from the Mu Us, Otindag, Horqin dune fields at the northern margin of the EAM. The results show that these dune fields, as a whole experienced a most extensive mobility during the early Holocene, followed by a widespread shift toward limited mobility and soil development in the mid-Holocene, and widespread reactivation occurred during late Holocene. The dune developments are directly linked to the effective moisture change controlled by the EAM changes, which respond to the low latitude summer insolation variation. The increased subsidence at the margin contrary to the core EAM, the delay from the feedback of the soil-vegetation-air coupled system, the increased evaporation due to the high temperature all play partial role in the lag of the margin EAM effective moisture change to the low latitude summer insolation. The asynchronous end of the wetter mid-Holocene mainly responds to the southeastwardly shift of the precipitation belt, while the regional sensitivity, response speed and internal feedback also contributed. The correspondence between dune records and North Atlantic drift-ice records of the rapid climate changes implies a close relationship between North Atlantic climate and the frequent dune activity at the northern margin of EAM.
文摘天山北坡地处多个大气环流系统的过渡区,气候变化敏感,其长时间尺度的气候演变过程、水热组合方式等问题仍在讨论中,客观把握上述问题对深入认识亚欧大陆内部气候变化格局与过程具有重要意义。本研究以那拉提剖面为研究对象,基于AMS14C年代-深度模型,以花粉为古气候代用指标,重建了天山北坡末次冰消期至早、中全新世的气候变化过程并探讨了其驱动机制。(1)14327—11578 cal yr B.P.期间花粉组合以荒漠草原成分为主,其主成分分析第1轴得分指示有效湿度偏低,并存在气候突变现象;11578—9457 cal yr B.P.期间演替为森林草原群落,气候以冷湿为特征;9457—8602 cal yr B.P.期间退化为草原,气候转为暖干;8602—6369 cal yr B.P.期间发育针阔混交林,气候偏暖湿。(2)天山北坡末次冰消期至早、中全新世,温度变化与高低纬、海陆间长尺度的记录相一致,冬季太阳辐射是影响温度变化的主要因素;海面温度升高,不仅使西风环流水汽含量增加,还引发北大西洋涛动偏于正相,西部扰动加强,给天山北坡带来更多降水。(3)天山北坡12900—11500 cal yr B.P.期间以干旱为特征的气候突变从起讫时间、湿度变化等特征分析是对“新仙女木事件”的响应,北美洲劳伦泰德冰盖融冰减缓了北大西洋经向翻转环流,叠加北大西洋涛动负相位、西风环流减弱等因素,使到达研究区的水汽减少。
基金The National Key Research and Development Program of China under contract Nos 2016YFC1401403,2016YFB0201103 and 2017YFA0604101the Strategic Priority Research Program of Chinese Academy of Sciences under contract No.XDA11020301+1 种基金the National Natural Science Foundation of China under contract No.41206025the China Ocean Mineral Resources R&D Association Program under contract No.DY135-E2-1-06
文摘Using observational data of Argos satellite-tracked drifters from 1988 to 2012, we analyzed seasonal characteristics of the surface Kuroshio branch(KB) intrusion into the South China Sea(SCS). The analysis results are as follows.The surface KB originates from the southern Balintang Channel(BLTC) and Babuyan Channel(BBYC). It begins in late September, reaches peak strength in November–December, and declines at the end of March. The mean speed of drifters along the KB path during their traverse of the Luzon Strait(LS) was 43% faster than during the two days before entering the LS for the flow originating from the southern BLTC, but there was a 24% increase in speed for the flow from the BBYC. The observations show that in winter, monthly-mean sea-level anomalies(SLAs) were positive southwest of Taiwan Island and extended to the northern LS. The SLAs were negative northwest of Luzon Island and extended to the southern LS, which acted like a pump, forcing a part of Kuroshio water westward into the SCS. The condition under which the KB forms was solved by a set of simplified motion equations. The results indicate that whether the KB can form depends upon the sea-level gradient at the central LS and region to the west, as well as the location, speed and direction of Kuroshio surface water when it enters the LS.
文摘An accelerating charged particle exerts a force upon itself. If we model the particle as a spherical shell of radius R, and calculate the force of one piece of this shell on another and eventually integrate over the whole particle, there will be a net force on the particle due to the breakdown of Newton’s third law. This symmetry breaking mechanism relies on the finite size of the particle;thus, as Feynman has stated, conceptually this mechanism doesn’t make good sense for point particles. Nonetheless, in the point particle limit, two terms survive in the self-force series: R0 and R-1 terms. The R0 term can alternatively be attributed to the well-known radiation reaction but the origin of R-1 term is not clear. In this study, we will show that this new term can be accounted for by an inductive mechanism in which the changing magnetic field induces an inductive force on the particle. Using this inductive mechanism, we derive R-1 term in an extremely easy way.
