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1.
The deep-circulation current in the North Pacific carries lower circumpolar deep water (LCDW), which is characterized by high dissolved oxygen and low echo intensity of reflected sound pulses. Using the characteristics of LCDW, we examined a branch current of the deep circulation passing through the Main Gap of the Emperor Seamounts Chain (ESC) by analyzing conductivity temperature depth profiler (CTD) data and data of velocity and echo intensity from a lowered acoustic Doppler current profiler (LADCP), which were obtained along 170°E immediately west of the ESC, along 180°W and 175°W over the northern slope of the Hess Rise, and along 165°W. The velocity and water characteristics showed that the eastern branch current of the deep circulation, which has penetrated into the Northwest Pacific Basin (NWPB) through Wake Island Passage, bifurcates around 30°N, 170°E in the NWPB into the westward main stream and a northward branch current, and that the latter current proceeds along the western side of the ESC and passes through the Main Gap of the ESC, flowing eastward. The current in the Main Gap at 170°E flows southeastward with eastward velocity cores around 4000 dbar and at depths greater than 4800 dbar centered at 5400 dbar. The current in the deeper core is stronger and reaches a maximum velocity of approximately 10 cm s?1. The eastward current in the Main Gap enters the Northeast Pacific Basin (NEPB) and flows eastward along the northern slope of the Hess Rise. As the current flows downstream, the characteristics of LCDW carried by the current are diluted gradually. To the east of the Hess Rise, the branch current joins another branch current of the deep circulation from the south carrying less-modified LCDW. As a result, LCDW carried from the Main Gap is renewed by mixing with the less-modified LCDW coming from the south. Carrying the mixed LCDW, the confluence flows eastward south of 37°N at 165°W toward the northeastern region of the NEPB, where the LCDW overturns and changes to North Pacific Deep Water (NPDW). NPDW is probably carried by the westward current in the upper deep layer north of 37°N at 165°W.  相似文献   

2.

Oxidation of iron and manganese ions is predominant in the oxygen-rich deep western boundary current (DWBC) within the Pacific Ocean. By the faster removal of particulate iron hydroxide and manganese oxide, densities of the particulate matters are considered to be lower in the DWBC than the interior region. To detect the density variation of suspended particles between the DWBC and interior regions, we analyzed echo intensity (EI) measured in the western North Pacific by hydrographic casts with a 300 kHz lowered acoustic Doppler current profiler (LADCP) in a whole water column. At depths greater than 3000 m (~ 3000 dbar), EI is almost uniformly low between 12°N and 30°N but peaks sharply from 30°N to 35°N to a maximum north of 35°N. EI is found to be anomalously low in the DWBC compared to the background distribution. The DWBC pathways are identifiable by the low EI and high dissolved oxygen concentration. EI data by LADCPs and other acoustic instruments may be used to observe the temporal variations of the DWBC pathways.

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3.
The profiles of absolute current velocity obtained by using a lowered acoustic doppler current profiler (LADCP) are presented. In the course of the BSERP-3 expedition, the measurements were carried out in the regions of the Rim Current, anticyclonic eddy, and northwest shelf. In the core of the Rim Current, a unidirectional motion of waters is traced in layers below the main pycnocline down to depths greater than 500 m. Its characteristic velocity can be as high as 0.08 m/sec. It is shown that the direct action of the eddy is detected in the shelf region at distances larger than 20 km from the outer edge of the shelf in the zone bounded by an isobath of 100 m. The formation of multilayer vertical structures in the field of current velocities is revealed in the region of interaction of the anticyclonic eddy with irregularities of the bottom on the side of the shelf. A two-layer structure of currents with specific features in the layer of formed seasonal pycnocline is observed in the region of the shelf down to an isobath of 100 m. The profiles of the moduli of vertical shears of currents averaged over the casts ensemble are presented for the abyssal and shelf parts of the sea. It is shown that the shears induced by the geostrophic currents and wave processes in the region of the main pycnocline are comparable. Below the pycnocline, the shears are mainly determined by the wave processes. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 25–37, November–December, 2008.  相似文献   

4.
LADCP观测和资料后处理的关键技术   总被引:8,自引:4,他引:4  
针对LADCP这一崭新而又特殊的海流观测技术,系统地介绍了LADCP/CTD捆绑式测量、罗盘标定、测量设置和附加信息获取等LADCP观测中的主要技术问题。在对LADCP瓦迭式资料特点进行研究的基础上,阐释了LADCP资料后处理的关键技术:首先进行LADCP资料初处理和声速剖面校正,利用同ping剖面内相邻两水层的LADCP测量值之差等于两水层的真实速度之差这一特性,把LADCP的所有测量值转化为垂向切变流速,求出水柱内各水层的垂向切变率,对其按照一定的积分顺序进行深度积分,得到水柱内各水层相对于参考层的相对速度,利用底跟踪信息可以较直接地求出参考层的速度,也可以根据测量过程中LADCP和测船相对位置在入水时和出水时保持不变这一基本成立的假定通过GPS信息求出参考层的速度,从而得到整个水柱内各水层的绝对流速。为了提高处理结果的准确度,在资料后处理的每一处理步骤中都要特别注意相应的数据质量控制。  相似文献   

5.
ADCP观测得到的2008年4月吕宋海峡流速剖面结构   总被引:1,自引:0,他引:1       下载免费PDF全文
基于2008年4月22—26日吕宋海峡调查航次的下放式声学多普勒流速剖面仪(LADCP)和船载ADCP(SADCP)等观测资料,并采用潮波模式模拟结果去除潮流对观测资料的影响,观测结果表明:调查期间黑潮入侵南海的位置与1992年春季比较接近,其分支位于调查海区中部C2、C7、C8和C9站,表层黑潮在C8站分离为两支,分别流向C9和C2站,C9站北向流明显比C8站减弱。在C2站,黑潮分支位于400m层以浅,其最大西向流速为77cm/s,而在C7、C8和C9站黑潮分支位于500m层以浅,黑潮在入侵南海的过程中其核心深度逐渐变浅。上层黑潮明显作反气旋弯曲。本调查航次的观测结果在定性上支持吕宋海峡水交换有"三明治"垂直结构的特性。  相似文献   

6.
This paper describes results from a geophysical study in the Vestbakken Volcanic Province, located on the central parts of the western Barents Sea continental margin, and adjacent oceanic crust in the Norwegian-Greenland Sea. The results are derived mainly from interpretation and modeling of multichannel seismic, ocean bottom seismometer and land station data along a regional seismic profile. The resulting model shows oceanic crust in the western parts of the profile. This crust is buried by a thick Cenozoic sedimentary package. Low velocities in the bottom of this package indicate overpressure. The igneous oceanic crust shows an average thickness of 7.2 km with the thinnest crust (5–6 km) in the southwest and the thickest crust (8–9 km) close to the continent-ocean boundary (COB). The thick oceanic crust is probably related to high mantle temperatures formed by brittle weakening and shear heating along a shear system prior to continental breakup. The COB is interpreted in the central parts of the profile where the velocity structure and Bouguer anomalies change significantly. East of the COB Moho depths increase while the vertical velocity gradient decreases. Below the assumed center for Early Eocene volcanic activity the model shows increased velocities in the crust. These increased crustal velocities are interpreted to represent Early Eocene mafic feeder dykes. East of the zone of volcanoes velocities in the crust decrease and sedimentary velocities are observed at depths of more than 10 km. The amount of crustal intrusions is much lower in this area than farther west. East of the Kn?legga Fault crystalline basement velocities are brought close to the seabed. This fault marks the eastern limit of thick Cenozoic and Mesozoic packages on central parts of the western Barents Sea continental margin.  相似文献   

7.
An inverse calculation using hydrographic section data collected from October to December 2000 yields velocity structure and transports of the Kuroshio in the Okinawa Trough region of the East China Sea (ECS) and south of central Japan, and of the Ryukyu Current (RC) southeast of the Ryukyu Islands. The results show the Kuroshio flowing from the ECS, through the Tokara Strait (TK), with a subsurface maximum velocity of 89 cm s−1 at 460 dbar. In a section (TI) southeast of Kyushu, a subsurface maximum velocity of 92 cm s−1 at 250 dbar is found. The results also show the RC flowing over the continental slope from the region southeast of Okinawa (OS) to the region east of Amami-Ohshima (AE) with a subsurface maximum velocity of 67 cm s−1 at 400 dbar, before joining the Kuroshio southeast of Kyushu (TI). The volume transport around the subsurface velocity maximum southeast of Kyushu (TI) balances well with the sum of those in TK and AE. The temperature-salinity relationships found around these velocity cores are very similar, indicating that the same water mass is involved. These results help demonstrate the joining of the RC with the Kuroshio southeast of Kyushu. The net volume transport of the Kuroshio south of central Japan is estimated to be 64∼79 Sv (1 Sv ≡ 106 m3s−1), of which 27 Sv are supplied by the Kuroshio from the ECS and 13 Sv are supplied by the RC from OS. The balance (about 24∼39 Sv) is presumably supplied by the Kuroshio recirculation south of Shikoku, Japan.  相似文献   

8.
The results obtained with the use of a lowered acoustic Doppler current profiler (LADCP) are presented. The use of the LADCP from a vessel was the first in the history of the study of the Black Sea. The measurements were carried out in the northeastern Black Sea under the auspices of the Black Sea Ecosystem Recovery Program (BSERP) in May 2004. The effect of the computation parameters on the quality and accuracy of the calculations of velocity profiles was studied. It was shown that the use of optimal parameters and reliable navigation data and setting the instrument as close to the bottom as possible could essentially enhance the accuracy of the measurements. The current velocity calculations from the LADCP data were compared with the data on the vessel drift under calm weather. The accuracy of the calculations reached 6–8 cm/s. Recommendations on the choice of the optimal parameters for processing the data on the current velocity are presented.  相似文献   

9.
Within the framework of the linear theory of long waves, with regard for the turbulent viscosity, we study the development of tidal currents in a basin of variable depth with two straits. The problem is solved numerically. The velocity field on the strait-basin boundary is regarded as known. The numerical analysis is performed for different depths of the straits. We study the influence of the geometric characteristics of the basin on the amplitudes of the profile of free surface and wave velocity and establish the dependences of the wave characteristics on the period of current velocities in the strait and the parameters of the basin. In particular, it is shown that the increase in the period of current velocities in the strait leads to significant changes in the level and structure of currents. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 3–12, July–August, 2007.  相似文献   

10.
The Western Drake Passage current system is investigated using the CTD, LADCP, and SADCP data of the cross Drake section carried out in January 2010. A complicated current structure consisting of the six Antarctic Circumpolar Current (ACC) jets as well as the system of slope and abyssal currents was revealed. The most interesting result is the identification of the abyssal quasi-geostrophic spurts in the northern part that probably are generated by abyssal eddy fragments, which are an imperative part of the meandering ACC.  相似文献   

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