Hydrographic data from eleven 1986 - 1991 cruises at zonal sections near 8°N from the Philippine coast to 130°E were used to examine thermohaline smictim and waer mass properties of the western boundary cnrr...Hydrographic data from eleven 1986 - 1991 cruises at zonal sections near 8°N from the Philippine coast to 130°E were used to examine thermohaline smictim and waer mass properties of the western boundary cnrrents there, especially those of the Mindanao Underconnt (MUC). The finding that the MLC consisted of two water masses with salinity of M.6 at 26.9 σt and 34.52 at 27. 2 σt which were remnants of the lower part of the southern Pacific Subtropical Waer (SPSW) and of the Antarctic Intermediate Water (AAIW) of South Pacific origin, respectively, showed that the MUC was not a local transient but originaed elsewhere. As the MUC flowed from 7 .5°N to 8°N, part of it carrying the SPSW turns anticyclonically and eastward. The Northem Pacilic Intermediate Watr (NPIW) often joins the MUC, which suggests that the NPIW carried by the MC partly to northward as a result of the shear between the MC and the MUC or other proceesses. The shear instability provides the energy for the irregular fluctuation of the MUC.展开更多
The simulation of an ocean general circulation model for the earth simulator （OFES） is transformed to an isopycnal coordinate to investigate the spatial structure and seasonal variability of the Mindanao Under- curr...The simulation of an ocean general circulation model for the earth simulator （OFES） is transformed to an isopycnal coordinate to investigate the spatial structure and seasonal variability of the Mindanao Under- current （MUC）. The results show that （1） potential density surfaces, δ0=26.5 and δ0=27.5, can be chosen to encompass the M UC layer. Southern Pacilic tropical water （SPTW）, Antarctic Intermediate Water （AAIW） and high potential density water （HPDW） constitute the MUC. （2） Climatologically, the MOC exists in the form of dual-core. In some months, the dual-core structure changes to a single-core structure. （3） Choosing section at 8°N for calculating the transport of the MUC transport is reliable. Potential density constraint provides a good method for calculating the transport of the MOC. （4） The annual mean transport of the MUC is 8.34 × 106 m3/s and varies considerably with seasons： stronger in late spring and weaker in winter.展开更多
通过分析1981—2010年的SODA2.2.4(Simple Ocean Data Assimilation)温盐数据,发现南极中层水在这个时期表现出了盐度减小的变化趋势,包括垂向盐度极小值处与沿27.2kg/m^3等密度面的盐度。但是这个淡化过程并不是渐进的,而是先在1996—2...通过分析1981—2010年的SODA2.2.4(Simple Ocean Data Assimilation)温盐数据,发现南极中层水在这个时期表现出了盐度减小的变化趋势,包括垂向盐度极小值处与沿27.2kg/m^3等密度面的盐度。但是这个淡化过程并不是渐进的,而是先在1996—2000年间达到了一个盐度异常的最大值,然后才进入快速减小阶段。盐度最小值处(27.2kg/m^3等密度面)盐度的EOF分解表明,南非以南海域以及东南大西洋海域的盐度减小幅度显著大于太平洋与印度洋水体,这隐含了厄加勒斯流系统对大西洋-印度洋通道上中层水体性质变化的重要影响。在形成机制上,本文从两个海气相互作用过程解释了上述的结果。南半球纬向风应力的EOF结果表明,亚南极锋以南的西风带在1979—2014年间是一个增强的变化趋势,由此产生的低盐南极表层水向北输送导致了上述的多年南极中层水淡化现象。这其中1998年风应力的极大值应当对应一个盐度异常的极小值,但在这里表现出的是盐度异常的最大值产生了一个矛盾的因果关系。进一步的分析表明,这个盐度异常最大值是海表面淡水输入量(降雨-蒸发)在相应时期大幅度减小的结果。展开更多
A streamfunction EOF method is applied to a time series of hydrographic sections in the Southern Ocean south of Australia to study water mass variations. Results show that there are large thermohaline variations north...A streamfunction EOF method is applied to a time series of hydrographic sections in the Southern Ocean south of Australia to study water mass variations. Results show that there are large thermohaline variations north of the Subantarctic Front (SAF) at 300–1500 dbar level, indicating upwelling and downwelling of the Antarctic Intermediate Water (AAIW) along isopycnal surfaces. Based on the latest altimeter product, Absolute Dynamic Topography, a mechanism due to frontal wave propagation is proposed to explain this phenomenon, and an index for frontal waves is defined. When the frontal wave is in positive (negative) phase, the SAF flows northeastward (southeastward) with the fresh AAIW downwelling (upwelling). Such mesoscale processes greatly enhance cross-frontal exchanges of water masses. Spectral analysis shows that frontal waves in the Southern Ocean south of Australia are dominated by a period of about 130 days with a phase speed of 4 cm/s and a wavelength of 450 km.展开更多
The Argo float observations are used to investigate the mesoscale characteristics of the Antarctic Intermediate Water （AAIW） in the South Pacific in this paper. It is shown that a subsurface mesoscale phenomenon is ...The Argo float observations are used to investigate the mesoscale characteristics of the Antarctic Intermediate Water （AAIW） in the South Pacific in this paper. It is shown that a subsurface mesoscale phenomenon is probably touched by an Argo float during the float＇s ascent-descent cycles and is identified by the horizontal salinity gradient between the vertical temperature-salinity profiles. This shows that the transportation of the AAIW may be accompanied with the rich mesoscale characteristics. To derive the spatial length, time, and propagation characteristics of the mesoscale variability of the AAIW, the gridded temperature-salinity dataset ENACT/ENSEMBLE Version 3 constructed on the in-situ observations in the South Pacific since 2005 is used. The Empirical Mode Decomposition method is applied to decompose the isopycnal-averaged salinity anomaly from 26.8 cr0-27.4 ao, where the AAIW mainly resides, into the basin scale and two mesoscale modes. It is found that the first mesoscale mode with the length scale on the order of 1 000 km explains nearly 50% variability of the mesoscale characteristics of the AAIW. Its westward-propagation speeds are slower in the mid-latitude （around 1 cm/s） and faster in the low latitude （around 6 cm/s）, but with an increasing in the latitude band on 25^-30~S. The second mesoscale mode is of the length scale on the order of 500 km, explaining about 30% variability of the mesoscale characteristics of the AAIW. Its westward-propagation speed keeps nearly unchanged （around 0.5 cm/s）. These results presented the stronger turbulent motion of the subsurface ocean on the spatial scale, and also described the significant role of Argo program for the better understanding of the deep ocean.展开更多
On the basis of the salinity distribution of isopycnal（σ_0=27.2 kg/m^3） surface and in salinity minimum, the Antarctic Intermediate Water（AAIW） around South Australia can be classified into five types correspondi...On the basis of the salinity distribution of isopycnal（σ_0=27.2 kg/m^3） surface and in salinity minimum, the Antarctic Intermediate Water（AAIW） around South Australia can be classified into five types corresponding to five regions by using in situ CTD observations. Type 1 is the Tasman AAIW, which has consistent hydrographic properties in the South Coral Sea and the North Tasman Sea. Type 2 is the Southern Ocean（SO） AAIW, parallel to and extending from the Subantarctic Front with the freshest and coldest AAIW in the study area. Type 3 is a transition between Type 1 and Type 2. The AAIW transforms from fresh to saline with the latitude declining（equatorward）. Type 4, the South Australia AAIW, has relatively uniform AAIW properties due to the semienclosed South Australia Basin. Type 5, the Southeast Indian AAIW, progressively becomes more saline through mixing with the subtropical Indian intermediate water from south to north. In addition to the above hydrographic analysis of AAIW, the newest trajectories of Argo（Array for real-time Geostrophic Oceanography） floats were used to constructed the intermediate（1 000 m water depth） current field, which show the major interocean circulation of AAIW in the study area. Finally, a refined schematic of intermediate circulation shows that several currents get together to complete the connection between the Pacific Ocean and the Indian Ocean. They include the South Equatorial Current and the East Australia Current in the Southwest Pacific Ocean, the Tasman Leakage and the Flinders Current in the South Australia Basin, and the extension of Flinders Current in the southeast Indian Ocean.展开更多
文摘Hydrographic data from eleven 1986 - 1991 cruises at zonal sections near 8°N from the Philippine coast to 130°E were used to examine thermohaline smictim and waer mass properties of the western boundary cnrrents there, especially those of the Mindanao Underconnt (MUC). The finding that the MLC consisted of two water masses with salinity of M.6 at 26.9 σt and 34.52 at 27. 2 σt which were remnants of the lower part of the southern Pacific Subtropical Waer (SPSW) and of the Antarctic Intermediate Water (AAIW) of South Pacific origin, respectively, showed that the MUC was not a local transient but originaed elsewhere. As the MUC flowed from 7 .5°N to 8°N, part of it carrying the SPSW turns anticyclonically and eastward. The Northem Pacilic Intermediate Watr (NPIW) often joins the MUC, which suggests that the NPIW carried by the MC partly to northward as a result of the shear between the MC and the MUC or other proceesses. The shear instability provides the energy for the irregular fluctuation of the MUC.
基金The Major Project of the National Natural Science Foundation of China under contract No.40890152the National Basic Research Program of China under contract No.2012CB417404National Natural Science Foundation of China under contract Nos 41221063 and 41130859
文摘The simulation of an ocean general circulation model for the earth simulator （OFES） is transformed to an isopycnal coordinate to investigate the spatial structure and seasonal variability of the Mindanao Under- current （MUC）. The results show that （1） potential density surfaces, δ0=26.5 and δ0=27.5, can be chosen to encompass the M UC layer. Southern Pacilic tropical water （SPTW）, Antarctic Intermediate Water （AAIW） and high potential density water （HPDW） constitute the MUC. （2） Climatologically, the MOC exists in the form of dual-core. In some months, the dual-core structure changes to a single-core structure. （3） Choosing section at 8°N for calculating the transport of the MUC transport is reliable. Potential density constraint provides a good method for calculating the transport of the MOC. （4） The annual mean transport of the MUC is 8.34 × 106 m3/s and varies considerably with seasons： stronger in late spring and weaker in winter.
文摘通过分析1981—2010年的SODA2.2.4(Simple Ocean Data Assimilation)温盐数据,发现南极中层水在这个时期表现出了盐度减小的变化趋势,包括垂向盐度极小值处与沿27.2kg/m^3等密度面的盐度。但是这个淡化过程并不是渐进的,而是先在1996—2000年间达到了一个盐度异常的最大值,然后才进入快速减小阶段。盐度最小值处(27.2kg/m^3等密度面)盐度的EOF分解表明,南非以南海域以及东南大西洋海域的盐度减小幅度显著大于太平洋与印度洋水体,这隐含了厄加勒斯流系统对大西洋-印度洋通道上中层水体性质变化的重要影响。在形成机制上,本文从两个海气相互作用过程解释了上述的结果。南半球纬向风应力的EOF结果表明,亚南极锋以南的西风带在1979—2014年间是一个增强的变化趋势,由此产生的低盐南极表层水向北输送导致了上述的多年南极中层水淡化现象。这其中1998年风应力的极大值应当对应一个盐度异常的极小值,但在这里表现出的是盐度异常的最大值产生了一个矛盾的因果关系。进一步的分析表明,这个盐度异常最大值是海表面淡水输入量(降雨-蒸发)在相应时期大幅度减小的结果。
基金supported by the National Natural Science Foundation of China (Grant No. 41006114)the National Science and Technology Major Project (Grant No. 2012YQ12003907)+2 种基金the National Key Basic Research Program of China (Grant Nos. 2012CB417401 and 2013CB956202)the CAS Strategic Priority Research Program (Grant No. XDA11010101)the NSFC-Shandong Joint Fund for Marine Science Research Center (Grant No. U1406401)
文摘A streamfunction EOF method is applied to a time series of hydrographic sections in the Southern Ocean south of Australia to study water mass variations. Results show that there are large thermohaline variations north of the Subantarctic Front (SAF) at 300–1500 dbar level, indicating upwelling and downwelling of the Antarctic Intermediate Water (AAIW) along isopycnal surfaces. Based on the latest altimeter product, Absolute Dynamic Topography, a mechanism due to frontal wave propagation is proposed to explain this phenomenon, and an index for frontal waves is defined. When the frontal wave is in positive (negative) phase, the SAF flows northeastward (southeastward) with the fresh AAIW downwelling (upwelling). Such mesoscale processes greatly enhance cross-frontal exchanges of water masses. Spectral analysis shows that frontal waves in the Southern Ocean south of Australia are dominated by a period of about 130 days with a phase speed of 4 cm/s and a wavelength of 450 km.
基金The National Natural Science Foundation of China under contract No.41176029the Basic Scientific Fund for National Public Research Institute of China under contract No.GY02-2012G25
文摘The Argo float observations are used to investigate the mesoscale characteristics of the Antarctic Intermediate Water （AAIW） in the South Pacific in this paper. It is shown that a subsurface mesoscale phenomenon is probably touched by an Argo float during the float＇s ascent-descent cycles and is identified by the horizontal salinity gradient between the vertical temperature-salinity profiles. This shows that the transportation of the AAIW may be accompanied with the rich mesoscale characteristics. To derive the spatial length, time, and propagation characteristics of the mesoscale variability of the AAIW, the gridded temperature-salinity dataset ENACT/ENSEMBLE Version 3 constructed on the in-situ observations in the South Pacific since 2005 is used. The Empirical Mode Decomposition method is applied to decompose the isopycnal-averaged salinity anomaly from 26.8 cr0-27.4 ao, where the AAIW mainly resides, into the basin scale and two mesoscale modes. It is found that the first mesoscale mode with the length scale on the order of 1 000 km explains nearly 50% variability of the mesoscale characteristics of the AAIW. Its westward-propagation speeds are slower in the mid-latitude （around 1 cm/s） and faster in the low latitude （around 6 cm/s）, but with an increasing in the latitude band on 25^-30~S. The second mesoscale mode is of the length scale on the order of 500 km, explaining about 30% variability of the mesoscale characteristics of the AAIW. Its westward-propagation speed keeps nearly unchanged （around 0.5 cm/s）. These results presented the stronger turbulent motion of the subsurface ocean on the spatial scale, and also described the significant role of Argo program for the better understanding of the deep ocean.
基金The Chinese Polar Environment Comprehensive Investigation and Assessment Programs under contract Nos CHINARE-04-04 and CHINARE-04-01
文摘On the basis of the salinity distribution of isopycnal（σ_0=27.2 kg/m^3） surface and in salinity minimum, the Antarctic Intermediate Water（AAIW） around South Australia can be classified into five types corresponding to five regions by using in situ CTD observations. Type 1 is the Tasman AAIW, which has consistent hydrographic properties in the South Coral Sea and the North Tasman Sea. Type 2 is the Southern Ocean（SO） AAIW, parallel to and extending from the Subantarctic Front with the freshest and coldest AAIW in the study area. Type 3 is a transition between Type 1 and Type 2. The AAIW transforms from fresh to saline with the latitude declining（equatorward）. Type 4, the South Australia AAIW, has relatively uniform AAIW properties due to the semienclosed South Australia Basin. Type 5, the Southeast Indian AAIW, progressively becomes more saline through mixing with the subtropical Indian intermediate water from south to north. In addition to the above hydrographic analysis of AAIW, the newest trajectories of Argo（Array for real-time Geostrophic Oceanography） floats were used to constructed the intermediate（1 000 m water depth） current field, which show the major interocean circulation of AAIW in the study area. Finally, a refined schematic of intermediate circulation shows that several currents get together to complete the connection between the Pacific Ocean and the Indian Ocean. They include the South Equatorial Current and the East Australia Current in the Southwest Pacific Ocean, the Tasman Leakage and the Flinders Current in the South Australia Basin, and the extension of Flinders Current in the southeast Indian Ocean.
