Evidence for the Trapping and Amplification of Near-Inertial Motions in a Large Anticyclonic Ring in the Oyashio

Three ARGOS drift buoys were deployed in the Oyashio Current off the Kuril Islands near 45°N in fall, 1990, during a joint Russia/Canada study of western boundary current dynamics in the Subarctic Pacific Ocean. We here report on one buoy deployed within an anticyclonic warm core ring (WCR86B) which shows evidence of large amplitude inertial motions of near-diurnal frequency. During its first week within the ring the buoy drifted with a mean azimuthal current speed of 0.40–0.45 m s⁻¹ and a radius of rotation of 15–20 km. However, superimposed on the mean rotation of the ring at this time were “loops” of near-diurnal period, radius 7–8 km and speeds exceeding 1 m s⁻¹. During successive rotations the buoy spiraled outward, its mean period of rotation increased and the amplitude of the near-diurnal motions decreased. The large motions are explained by inertial wave trapping and amplification within the extremely large and weakly stratified eddy, wherein the negative vorticity of the eddy reduces the local inertial frequency to near-diurnal frequency. We here suggest that either tidal or wind forcing may generate these high-amplitude “loop” motions. This revised version was published online in August 2006 with corrections to the Cover Date.     

On the origin of the Tsushima Warm Current Water

ＯｎｔｈｅｏｒｉｇｉｎｏｆｔｈｅＴｓｕｓｈｉｍａＷａｒｍＣｕｒｒｅｎｔＷａｔｅｒ￥ＴａｎｇＹｕｘｉａｎｇａｎｄＨｅｕｎｇ－ＪａｅＬｉｅ（ＦｉｒｓｔｉｎｓｔｉｔｕｔｅＯｆＯｃｅａｎｏｇｒａｐｈｙ，ＳｔａｔｅＯｃｅａｎｉｃＡｄｍｉｎｉｓｔｒａｔｉｏｎ，Ｑ...     

Decadal Current Variations in the Southwestern Japan/East Sea

Absolute geostrophic velocities were calculated along TOPEX/Poseidon (T/P) groundtracks located in the Ulleung Basin of the southwestern Japan/East Sea (JES) from a combined analysis of nearly a decade of T/P data and two years of pressure-gauge-equipped inverted echo sounder (PIES) data obtained during the United States Office of Naval Research’s JES Program. Geostrophic velocities have been calculated daily for the Ulleung Basin from June 1999 to July 2001 from a three-dimensional mapping of temperature and salinity produced by PIES data interpreted via the Gravest Empirical Mode (GEM) technique combined with the Navy’s Modular Ocean Data Assimilation System (MODAS). These velocities were then used to convert T/P velocity anomalies to absolute velocities for the T/P time period of 1993 to 2002. Current intensities and variabilities associated with the East Korean Warm Current, Ulleung Warm Eddy, and Offshore Branch are examined. Spatial and temporal variations of the sea surface circulation are strong. Intensification of the currents generally occurred during the fall season. The flow pattern in individual years differed greatly from year to year and differed from climatology in important qualitative ways.     

Mean and Temporal Variability in Kuroshio Geostrophic Transport South of Taiwan (1993–2001)

Observations of the Kuroshio south of Taiwan have been carried out on a quarterly basis since late 1992 as part of the basin-wide High Resolution expendable bathythermograph/expendable conductivity-temperature-depth (XBT/XCTD) network. Mean geostrophic transport in the Kuroshio, 0–800 m, from 34 cruises is 22.0 Sv ± 1.5, consistent with previous results from moorings and geostrophic calculations in the upstream Kuroshio region. The mean core of the current has speed about 90 cm s⁻¹ and is located close to Taiwan. At this location the Kuroshio appears to be confined mainly to the upper 700 m, and there is no evident tight recirculation of the current. Eddy variability is substantial, and large eddies can be seen propagating westward for thousands of kilometers in TOPEX/Poseidon altimetric data, impinging on the current and altering its structure and transport. The annual range in transport is about 8 Sv ± 6, with maximum in summer. Interannual variability is about 12 Sv ± 6, with transport maxima in 1995 and 2000 and a minimum in 1997–1998. Interannual variability in the upstream Kuroshio may be uncorrelated with that in the downstream region south of Japan, where the transport is much greater. Our quarterly sampling aliases high frequency variability of the current, and an improved boundary-current observation program would include more frequent transects and occasional deeper measurements. This revised version was published online in August 2006 with corrections to the Cover Date.     

The wave plus current flow over vortex ripples at an arbitrary angle

This work concerns the wave plus current flow over a sand bed covered by vortex ripples, with the current and the waves coming from different angles. Experiments were performed in a basin, where current and waves were perpendicular, in order to determine the conditions (current strength) leading to a regular ripple pattern formation. Numerical simulations were conducted changing the direction between the waves and the current from 0° to 90° and the ratio between the current strength and the wave orbital velocity from 0.2 to 1.5. Close to the bed, the current aligns parallel to the ripple crests, leading to a veering current profile with the vertical coordinate. The current-related friction coefficient was calculated. It was found that it decreases as the angle approaches 90°, while it increases for decreasing values of the current with a trend that can be described by a power law.     

南极绕极流的经向输运

南极绕极流(ACC)是南大洋中最显著的流动，流量超过130×106m3/s (Nowlin et al.，1986)。传统认为，由于以东向运动为主的ACC的存在极大地阻碍了南大洋中上层的南北向物质和能量的交换，绕极流区的经向输运是非常小的。但是近些年的研究发现，穿过ACC的通量并不是可以忽略不计的，它对维持南极和亚南极区的动力和热力平衡起着重要作用，在全球气候系统中也有着深刻的影响(Doos et al.，1994)。     

2002年4～5月琉球群岛两侧海流的研究

基于日本气象厅“长风丸”调查船在2002年4～5月航次期间的CTD资料,结合卫星风场资料,采用改进逆方法计算了琉球群岛两侧海域各断面的流速和流量分布,并分析卫星跟踪浮标资料和同期的卫星高度计资料,得出下面一些主要结论:(1)黑潮流速在PN断面上只有一个流核.通过断面PN的净东北向流量约为34.7×106m3/s,此流量包括台湾暖流、东海黑潮和黑潮以东的反气旋涡的流量.(2)黑潮流速在断面TK上有两个流核,通过断面TK净东向的流量为25.6×106m3/s,黑潮通过海峡后流向断面ASUKA.(3)冲绳岛东南海区琉球海流的流量约为8.8×106m3/s,并流向断面AM.(4)奄美大岛以东的北向海流的流量为12.7×106m3/s,并流向断面ASUKA.在断面ASUKA东南部出现一个中尺度反气旋涡,直径约240 km,其流量约为28.5×106m3/s.(5)四国以南黑潮第一层水体基本来源于通过吐噶喇海峡的黑潮,第二、三层水体来自吐噶喇海峡和奄美大岛以东海域的流量大致相当,而第四层的流量则主要来自于奄美大岛以东海域.(6)浮标资料显示,奄美大岛以东的海流部分来自于断面AM以东海区,并通过断面ASUKA.     

灵山岛西北侧适养区近底层流特征初步分析

传统观念的底层流是指离底大于或等于２ｍ的海流。离底小于２ｍ的流场特征，至今研究甚少。近年来，随着养殖业的蓬勃发展，对其了解的需求愈来愈迫切。１近底层流观测全国海岛资源综合调查时，按“青岛市海岛办”的要求，在灵山岛西北侧适养区（水深１２ｍ）布设了一个近底层（离底２０ｃｍ）流观测站（３５℃４６＇Ｎ，１２０℃９＇Ｅ），连续观测１５昼夜。观测期间适逢１９９０年５号台风在江苏省北部登陆，该站测得１１．９ｍ／ｓ的风速。观测仪器使用国产ＨＪＬ１－１型印刷海流计。测流时将海流计悬挂于特制三角架中央，由潜水员精确…     

Kinematic metrics of the Loop Current in the Gulf of Mexico from satellite altimetry

We analyzed a 20-year time series (January 1st, 1993 through December 31st, 2012) of Loop Current (LC) surface area derived from satellite altimetry in the eastern Gulf of Mexico to estimate kinematical metrics of this potent flow. On average the LC intrudes to its maximum northward position about 216 ± 126 days after the previous eddy separation; and ∼30 ± 31 days later sheds a large anticyclonic eddy. When the northern extent of the LC intrusion following the previous eddy separation is greater than 27°N, the current retreats very quickly until it sheds another eddy with the entire separation process occurring on the order of 30 days. To first order the change in areal extent of the LC during intrusion into the Gulf occurs at an average rate of 225 km² day⁻¹, which corresponds to an intrusion velocity of 1.7 cm s⁻¹ of the LC front, and adds Caribbean water to the Gulf at a rate of 2.6 ± 0.7 Sv.     

黄海暖流源区附近温盐结构及其季节变化

为探究不同季节下黄海暖流在源区的状态,利用韩国海洋数据中心(Korea Oceanographic Data Center)发布的水文数据,对黄海暖流源区附近温盐结构及其季节变化进行了分析。结果表明:年平均状态下对马暖流在济州岛东南存在向西向入侵的趋势,其入侵存在明显的季节变化:秋季最强,冬、春季开始减弱,夏季最弱。济州岛西侧,约在33°30′N、125°30′E处存在一支伸向西北的高盐舌,该高盐舌盐度同样具有明显的季节变化:冬季最强,春季开始减弱,夏季降至最低,秋季盐度开始缓慢回升。黄海区盐度的变化要滞后于对马暖流区盐度变化。冬季朝鲜沿岸水南下入侵程度最强,能到达34°N以南的位置。