Using a Finite-Volume Community Ocean Model, we investigated the dynamic mechanism of the South China Sea Warm Current(SCSWC) in the northern South China Sea(NSCS) during winter monsoon relaxation. The model reproduce...Using a Finite-Volume Community Ocean Model, we investigated the dynamic mechanism of the South China Sea Warm Current(SCSWC) in the northern South China Sea(NSCS) during winter monsoon relaxation. The model reproduces the mean surface circulation of the NSCS during winter, while model-simulated subtidal currents generally capture its current pattern. The model shows that the current over the continental shelf is generally southwestward, under a strong winter monsoon condition, but a northeastward counter-wind current usually develops between 50-and 100-m isobaths, when the monsoon relaxes. Model experiments, focusing on the wind relaxation process, show that sea level is elevated in the northwestern South China Sea(SCS), related to the persistent northeasterly monsoon. Following wind relaxation, a high sea level band builds up along the mid-shelf, and a northeastward current develops, having an obvious vertical barotropic structure. Momentum balance analysis indicates that an along-shelf pressure gradient provides the initial driving force for the SCSWC during the first few days following wind relaxation. The SCSWC subsequently reaches a steady quasi-geostrophic balance in the cross-shelf direction, mainly linked to sea level adjustment over the shelf. Lagrangian particle tracking experiments show that both the southwestward coastal current and slope current contribute to the northeastward movement of the SCSWC during winter monsoon relaxation.展开更多
Using the data of 500 hPa geopotential height from 1951 to 1995, SST roughly in the same period and OLR data from 1974 to 1994, the relation between the anomalies of subtropical high (STH for short) and the tropical c...Using the data of 500 hPa geopotential height from 1951 to 1995, SST roughly in the same period and OLR data from 1974 to 1994, the relation between the anomalies of subtropical high (STH for short) and the tropical circulations including the Asian monsoon as well as the convective activity are studied. In order to study the physical process of the air-sea interaction related to STH anomaly, the correlation of STH with SST at various sea areas, lagged and simultaneous, has been calculated. Comparing the difference of OLR, wind fields, vertical circulations and SST anomalies in the strong and weak STH, we investigate the characteristics of global circulations and the SST distributions related to the anomalous STH at the western Pacific both in winter and summer. Much attention has been paid to the study of the air-sea interaction and the relationship between the East Asian monsoon and the STH in the western Pacific. A special vertical circulation, related to the STH anomalies is found, which connects the monsoon current to the west and the vertical flow influenced by the SST anomaly in the tropical eastern Pacific.展开更多
鲁汶流是东印度洋海区低盐暖水向极传输的主要途径,不仅显著调节低纬-高纬海区间的温盐分配,也极大影响澳大利亚西岸降水,理解其在地质历史时期的变化及影响因素,对于认识区域和全球气候变化具有重要意义。本次研究将鲁汶流区采集的SO18...鲁汶流是东印度洋海区低盐暖水向极传输的主要途径,不仅显著调节低纬-高纬海区间的温盐分配,也极大影响澳大利亚西岸降水,理解其在地质历史时期的变化及影响因素,对于认识区域和全球气候变化具有重要意义。本次研究将鲁汶流区采集的SO18588孔岩芯上部63 cm沉积物作为研究材料,并以1 cm为间隔对其进行采样,共计获得63个沉积物样品。通过对这些沉积物样品进行研究,发现在SO18588站处浮游有孔虫热带表层水种Trilobatus sacculifer的相对丰度比浮游有孔虫热带-亚热带表层水种Globigerinoides ruber的相对丰度更适合被用于指示鲁汶流强度变化;之后,利用浮游有孔虫热带表层水种T.sacculifer的相对丰度,重建了32 ka B. P.以来鲁汶流的强度变化,并与已发表的古海洋和古气候学记录进行了对比。结果显示,鲁汶流强度的冰期-间冰期变化受海平面升降和类厄尔尼诺-南方涛动气候态共同调控:冰期时海平面下降,类厄尔尼诺态强化,导致鲁汶流减弱;间冰期时,海平面上升,类拉尼娜态发育,造成鲁汶流增强。9.5~0 ka B. P.期间,鲁汶流强度的持续弱化,可能归因于澳洲冬季风的减弱和早全新世类拉尼娜格局向现代类厄尔尼诺格局转变所造成的厄尔尼诺事件频发;9.5 ka B. P.左右鲁汶流强度事件性地突然减弱,可能与海平面上升所导致的卡里马塔海峡贯通、印尼穿越流表层流被抑制有关。展开更多
The Beibu Gulf is at an important geographical location and rich in gas, oil and biological resources. The observed currents showed that the current in the upper layer was opposite to that in the lower layer in boreal...The Beibu Gulf is at an important geographical location and rich in gas, oil and biological resources. The observed currents showed that the current in the upper layer was opposite to that in the lower layer in boreal winter in the northern Beibu Gulf and it was northeastward in the lower layer. This northeastward current was reproduced by a 3 D baroclinic model in this study. It's found that the counter-wind deep current(referred to as ‘CWDC' hereinafter) strengthened from September to November but weakened from December to the following February. A closed meridional circulation in vertical direction was found in the northern Beibu Gulf, including CWDC, surface southwestward current, an upwelling, and a downwelling. The temporal variation process of the meridional circulation was similar to that of CWDC, with strength and range stronger in November and December than in other four months. Similar to the variation process of CWDC, the monsoon wind changed from weak easterly wind in September to strong northeasterly wind in November and December, and it was transformed into weak southeasterly wind in February again. The sensitive experiments showed that CWDC and the meridional circulation were controlled by the monsoon wind and were adjusted by heat flux-and tide-induced mixing, respectively. According to the momentum balance equation, it can be revealed the counter-wind deep current is a compensation current which is induced by the surface elevation gradient balanced by the Coriolis force, vertical diffusion and baroclinic pressure gradient.展开更多
The history of the East Asian monsoon(EAM)since Last Glacial Maximum is reconstructed based on records in a sediment core retrieved from the northern South China Sea.The provenance of organic carbon and the EAM’s evo...The history of the East Asian monsoon(EAM)since Last Glacial Maximum is reconstructed based on records in a sediment core retrieved from the northern South China Sea.The provenance of organic carbon and the EAM’s evolution are investigated using combined organic carbon,grain size,and AMS 14 C dating analysis.Responding to the strong winter monsoon,the marine organic matter was dominated in the sediments,andδ13 C of organic matter was high during the last glacial period.During the Holocene,the primary productivity decreased and the dilution effect of riverine inorganic clastics strengthened.Accordingly,the total organic carbon contents andδ13 C values decreased,and terrestrial organic matter content increased in the core sediments.The 4μm grain size fraction,as the environmental sensitive grain size component,is determined to reconstruct the paleoclimatic records.During the last glacial period,the contents of 4μm grain size component were mainly controlled by the sea level changes.Upon the Holocene,the influence of the sea level changes weakened and the roles of current system and provenance strengthened.The correlation between the EAM and solar insolation forcing is also discussed in this paper.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.41606005,41430963)the National Science Foundation for Post-Doctoral Scientists of China(No.2015M582133)the Fundamental Research Funds for the Central Universities(No.201713023)
文摘Using a Finite-Volume Community Ocean Model, we investigated the dynamic mechanism of the South China Sea Warm Current(SCSWC) in the northern South China Sea(NSCS) during winter monsoon relaxation. The model reproduces the mean surface circulation of the NSCS during winter, while model-simulated subtidal currents generally capture its current pattern. The model shows that the current over the continental shelf is generally southwestward, under a strong winter monsoon condition, but a northeastward counter-wind current usually develops between 50-and 100-m isobaths, when the monsoon relaxes. Model experiments, focusing on the wind relaxation process, show that sea level is elevated in the northwestern South China Sea(SCS), related to the persistent northeasterly monsoon. Following wind relaxation, a high sea level band builds up along the mid-shelf, and a northeastward current develops, having an obvious vertical barotropic structure. Momentum balance analysis indicates that an along-shelf pressure gradient provides the initial driving force for the SCSWC during the first few days following wind relaxation. The SCSWC subsequently reaches a steady quasi-geostrophic balance in the cross-shelf direction, mainly linked to sea level adjustment over the shelf. Lagrangian particle tracking experiments show that both the southwestward coastal current and slope current contribute to the northeastward movement of the SCSWC during winter monsoon relaxation.
文摘Using the data of 500 hPa geopotential height from 1951 to 1995, SST roughly in the same period and OLR data from 1974 to 1994, the relation between the anomalies of subtropical high (STH for short) and the tropical circulations including the Asian monsoon as well as the convective activity are studied. In order to study the physical process of the air-sea interaction related to STH anomaly, the correlation of STH with SST at various sea areas, lagged and simultaneous, has been calculated. Comparing the difference of OLR, wind fields, vertical circulations and SST anomalies in the strong and weak STH, we investigate the characteristics of global circulations and the SST distributions related to the anomalous STH at the western Pacific both in winter and summer. Much attention has been paid to the study of the air-sea interaction and the relationship between the East Asian monsoon and the STH in the western Pacific. A special vertical circulation, related to the STH anomalies is found, which connects the monsoon current to the west and the vertical flow influenced by the SST anomaly in the tropical eastern Pacific.
文摘鲁汶流是东印度洋海区低盐暖水向极传输的主要途径,不仅显著调节低纬-高纬海区间的温盐分配,也极大影响澳大利亚西岸降水,理解其在地质历史时期的变化及影响因素,对于认识区域和全球气候变化具有重要意义。本次研究将鲁汶流区采集的SO18588孔岩芯上部63 cm沉积物作为研究材料,并以1 cm为间隔对其进行采样,共计获得63个沉积物样品。通过对这些沉积物样品进行研究,发现在SO18588站处浮游有孔虫热带表层水种Trilobatus sacculifer的相对丰度比浮游有孔虫热带-亚热带表层水种Globigerinoides ruber的相对丰度更适合被用于指示鲁汶流强度变化;之后,利用浮游有孔虫热带表层水种T.sacculifer的相对丰度,重建了32 ka B. P.以来鲁汶流的强度变化,并与已发表的古海洋和古气候学记录进行了对比。结果显示,鲁汶流强度的冰期-间冰期变化受海平面升降和类厄尔尼诺-南方涛动气候态共同调控:冰期时海平面下降,类厄尔尼诺态强化,导致鲁汶流减弱;间冰期时,海平面上升,类拉尼娜态发育,造成鲁汶流增强。9.5~0 ka B. P.期间,鲁汶流强度的持续弱化,可能归因于澳洲冬季风的减弱和早全新世类拉尼娜格局向现代类厄尔尼诺格局转变所造成的厄尔尼诺事件频发;9.5 ka B. P.左右鲁汶流强度事件性地突然减弱,可能与海平面上升所导致的卡里马塔海峡贯通、印尼穿越流表层流被抑制有关。
基金jointly supported by the National Natural Science Foundation of China (Nos. 41566001, 41406044 and 41576024)Guangxi Natural Science Foundation (Nos. 2015GXNSFCA139023, 2018JJD150011, 2016JJF15001 and 2015GXNSFAA139247)+5 种基金Guangxi Science and Technology Development Program (Guikegong 1598016-8)Guangxi Science and Technology Major Project (Guike AA18118025)Guangxi Key Research and Development Program (Guike AB16380282)Guangxi Key Laboratory of Marine Disaster in the Beibu Gulf, Qinzhou University (No. 2017KF02)the Fundamental Research Funds of Guangxi Academy of Sciences (No. 2017YJJ23005)supported by Vietnam State-Level Project KC09.14/16-20
文摘The Beibu Gulf is at an important geographical location and rich in gas, oil and biological resources. The observed currents showed that the current in the upper layer was opposite to that in the lower layer in boreal winter in the northern Beibu Gulf and it was northeastward in the lower layer. This northeastward current was reproduced by a 3 D baroclinic model in this study. It's found that the counter-wind deep current(referred to as ‘CWDC' hereinafter) strengthened from September to November but weakened from December to the following February. A closed meridional circulation in vertical direction was found in the northern Beibu Gulf, including CWDC, surface southwestward current, an upwelling, and a downwelling. The temporal variation process of the meridional circulation was similar to that of CWDC, with strength and range stronger in November and December than in other four months. Similar to the variation process of CWDC, the monsoon wind changed from weak easterly wind in September to strong northeasterly wind in November and December, and it was transformed into weak southeasterly wind in February again. The sensitive experiments showed that CWDC and the meridional circulation were controlled by the monsoon wind and were adjusted by heat flux-and tide-induced mixing, respectively. According to the momentum balance equation, it can be revealed the counter-wind deep current is a compensation current which is induced by the surface elevation gradient balanced by the Coriolis force, vertical diffusion and baroclinic pressure gradient.
基金supported by the National Programme on Global Change and Air-Sea Interaction (Nos. GASI-GEO GE-03 and GASI-04-01-02)the National Natural Science Foundation of China (Nos. 41476047, 41106045, 41506064 and 41427803)
文摘The history of the East Asian monsoon(EAM)since Last Glacial Maximum is reconstructed based on records in a sediment core retrieved from the northern South China Sea.The provenance of organic carbon and the EAM’s evolution are investigated using combined organic carbon,grain size,and AMS 14 C dating analysis.Responding to the strong winter monsoon,the marine organic matter was dominated in the sediments,andδ13 C of organic matter was high during the last glacial period.During the Holocene,the primary productivity decreased and the dilution effect of riverine inorganic clastics strengthened.Accordingly,the total organic carbon contents andδ13 C values decreased,and terrestrial organic matter content increased in the core sediments.The 4μm grain size fraction,as the environmental sensitive grain size component,is determined to reconstruct the paleoclimatic records.During the last glacial period,the contents of 4μm grain size component were mainly controlled by the sea level changes.Upon the Holocene,the influence of the sea level changes weakened and the roles of current system and provenance strengthened.The correlation between the EAM and solar insolation forcing is also discussed in this paper.
