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1.
Eitarou Oka Shota Katsura Hiroyuki Inoue Atsushi Kojima Moeko Kitamoto Toshiya Nakano Toshio Suga 《Journal of Oceanography》2017,73(4):479-490
The 137°E repeat hydrographic section for 50 winters during 1967–2016 has been analyzed to examine interannual to interdecadal variations and long-term changes of salinity and temperature in the surface and intermediate layers of the western North Pacific, with a particular focus on freshening in the subtropical gyre. Rapid freshening on both isobars and isopycnals began in the mid-1990s and persisted for the last 20 years in the upper main thermocline/halocline in the western subtropical gyre. In addition, significant decadal variability of salinity existed in the subtropical mode water (STMW), as previously reported for the shallower layers. An analysis of the 144°E repeat hydrographic section during 1984–2013 supplemented by Argo profiling float data in 2014 and 2015 revealed that the freshening trend and decadal variability observed at 137°E originated in the winter mixed layer in the Kuroshio Extension (KE) region and was transmitted southwestward to 137°E 1–2 years later in association with the subduction and advection of STMW. The mechanism of these changes and variations in the source region was further investigated. In addition to the surface freshwater flux in the KE region pointed out by previous studies, the decadal KE variability in association with the Pacific Decadal Oscillation likely contributes to the decadal salinity variability through water exchange between the subtropics and the subarctic across the KE. Interdecadal change in both the surface freshwater flux and the KE state, however, failed to explain the rapid freshening for the last 20 years. 相似文献
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3.
Abstract The surface distribution of salinity, temperature, nitrate‐nitrogen (N03‐N), and chlorophyll a in the southern New Zealand, Foveaux Strait region in February 1977, 1978, 1979, and 1980 was highly variable. The source of new nitrogen appears to be incursions of high‐salinity water west and east of Stewart Island. Although it seems likely that the source of this high‐nutrient, high‐salinity water is vertical, a horizontal advective source cannot be ruled out The chlorophyll a content of surface waters was not related directly to the NO3‐N concentrations. This lower food chain variability may be linked to variability in economically important species. Oysters grew twice as fast in the summer of 1978/79 as they did in 1979/80. But the mean chlorophyll a values were very similar for February of both years (2.5 and 2.2 μg 1?1, respectively). The elevated NO3‐N levels in 1979 may have resulted in much higher phytoplankton levels later that summer and resulted in the higher oyster growth rate that year. The mechanisms driving this variability have yet to be determined. 相似文献
4.
Decadal seesaw of the Central and Subtropical Mode Water formation associated with the Kuroshio Extension variability 总被引：1，自引：1，他引：0
Available Argo profiling float data from 2002 to 2011 were analyzed to examine the effect of the Kuroshio Extension (KE) current
system variability on the formation of the Central Mode Water. Just north of the upstream portion of the KE at 140–152°E,
formation of a lighter variety of the Central Mode Water in winter was active during the unstable period of the upstream KE
in 2006–2009 and was reduced when the upstream KE was in the stable period of 2002–2005 and 2010–2011. This decadal formation
variability is out of phase with that of the Subtropical Mode Water just south of the KE. 相似文献
5.
Yugo Shimizu Takanori Iwao Ichiro Yasuda Shin-Ichi Ito Tomowo Watanabe Kazuyuki Uehara Nobuyuki Shikama Toshiya Nakano 《Journal of Oceanography》2004,60(2):453-462
Six newly developed floats, which were set to drift on the 26.7 σθ isopycnal surface and to profile temperature, salinity and pressure above 1000 dbar once a week, were deployed in the Oyashio
and Kuroshio Extension (KE) in order to examine the circulation, formation site and time scale of newly formed North Pacific
Intermediate Water (NPIW). The floats were deployed in February or May 2001, and the data from their deployments to December
2002 are analyzed here. Four of the six floats were deployed near the KE axis at around the first meander crest, and they
moved eastward to 157°E–176°W at latitudes of 30°N–45°N. The other two floats deployed in the Oyashio water with low-potential
vorticity near the south coast of Hokkaido moved southward to reach the KE front and then moved eastward to the same region
as the first four floats. The temperature and salinity at 26.7 σθ measured by the profiling floats indicate that the source waters of NPIW, Oyashio and Kuroshio waters are drastically mixed
and modified in the mixed water region west of 160°E. The floats were separated into the three paths east of 160°E between
the Kuroshio Extension front and the north of Water-Mass front (nearly subarctic front). New NPIW is judged to be formed along
these three paths since the vertical profiles of temperature and salinity are quite smooth, having a salinity minimum at about
26.7σθ along each path. Kuroshio-Oyashio isopycnal mixing ratios of the new NPIW are 7:3, 6:4 and 5:5 at 26.7σθ along the southern, middle and northern paths, respectively. Potential vorticity converges to about 14–15 × 10−11 m−1s−1 along these paths. The time scale of new NPIW formation is estimated to be 1–1.5 years from the merger of Oyashio and Kuroshio
waters to the formation of the new NPIW.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
冬季黑潮延伸体海表温度对阿留申低压活动的双周期响应 总被引：1，自引：1，他引：0
Based on our previous work, the winter sea surface temperature(SST) in the Kuroshio Extension(KE) region showed significant variability over the past century with periods of ~6 a between 1930 and 1950 and ~10 a between1980 and 2009. How the activity of the Aleutian Low(AL) induces this dual-period variability over the two different timespans is further investigated here. For the ~6 a periodicity during 1930–1950, negative wind stress curl(WSC)anomalies in the central subtropical Pacific associated with an intensified AL generate positive sea surface height(SSH) anomalies. When these wind-induced SSH anomalies propagate westwards to the east of Taiwan, China two years later, positive velocity anomalies appear around the Kuroshio to the east of Taiwan and then the mean advection via this current of velocity anomalies leads to a strengthened KE jet and thus an increase in the KE SST one year later. For the ~10 a periodicity during 1980–2009, a negative North Pacific Oscillation-like dipole takes2–3 a to develop into a significant positive North Pacific Oscillation-like dipole, and this process corresponds to the northward shift of the AL. Negative WSC anomalies associated with this AL activity in the central North Pacific are able to induce the positive SSH anomalies. These oceanic signals then propagate westward into the KE region after 2–3 a, favoring a northward shift of the KE jet, thus leading to the warming of the KE SST. The feedbacks of the KE SST anomaly on the AL forcing are both negative for these two periodicities. These results suggest that the dual-period KE SST variability can be generated by the two-way KE-SST-AL coupling. 相似文献
7.
Mesoscale features in the eastward extension of the Kuroshio were investigated using assimilation of TOPEX/POSEIDON (T/P)
data into a three-layer quasi-geostrophic model. The T/P data exhibited an elongated state of the southern recirculation gyre
in 1993–95 and 1997, between whose two periods the gyre had a contracted state in 1995–96. A few stationary eddies were located
in the southern gyre during the contracted state. The baroclinic instability, which was indicated by the phase shift from
the uppermost-to the lowest-layer anomalies toward the downstream side, was evident near the Kuroshio Extension (KE) path.
Since the instability never appeared in the artificial model without bottom topography, the topographic barrier for the eastward
flow in the lowest layer was a necessary condition for the instability. The instability synchronized with the transition in
the western region of the KE axis from the elongated to the contracted states. This evolution was interpreted as if the baroclinic
instability played some part in the KE states and was a trigger for the transition from the elongated to the contracted states. 相似文献
8.
本文利用1993-2015年AVISO卫星高度计融合数据，统计分析了从黑潮延伸体流轴脱落涡旋的空间分布特征、运动属性以及季节、年际和类年代际变化。研究结果表明，23年间共追踪到242个气旋涡，276个反气旋涡，脱落的涡旋主要分布在沙茨基海隆以西区域。从脱落涡旋的源地空间分布来看，气旋涡的形成区域有两个高值区，一个位于黑潮延伸体流轴稳定弯曲处，即144°~146°E之间的上游区域；另一个位于沙茨基海隆西侧156°E处。而反气旋涡的形成区域也有两个高值区，一个位于沙茨基海隆以西的下游区域，另一个位于148°E处。这些在上游和下游脱落的涡旋大多向西移动，其中有88%的涡旋再次被流轴吸收。脱落涡旋的数量显示出了明显的年际和类年代际变化。在流轴的上下游区域，类年代际和年际变化分别占主导地位。并且在上游区域，脱落涡旋的类年代际变化与黑潮延伸体的强度呈负相关。在季节变化上，夏季脱落形成的涡旋最多，冬季最少。 相似文献
9.
We investigate sea level changes in the western North Pacific for twenty-first century climate projections by analyzing the output from 15 coupled models participating in the Coupled Model Intercomparison Project phase 3 (CMIP3). Projected changes in the wind stress due to those in sea level pressure (SLP) result in the projected sea level changes. In the western North Pacific (30?50°N, 145?170°E), the inter-model standard deviation of the sea level change relative to the global mean is comparable to that based on the multi-model ensemble (MME) mean. Whereas a positive SLP change in the eastern North Pacific (40?50°N, 170?150°W) induces a large northward shift of the Kuroshio Extension (KE), a negative SLP change in this region induces a strong intensification of the KE. Large inter-model variability of the SLP projection in the eastern North Pacific causes a large uncertainty of the sea level projection in the western North Pacific. Models with a larger northward shift (intensification) of the KE exhibit a poleward shift (an intensification) of the Aleutian Low (AL) larger than that for the MME mean. However, models that exhibit a larger intensification of the AL do not necessarily show a larger intensification of the KE. Our analysis suggests that the SLP change that induces an intensification of the KE is associated with a teleconnection from the equatorial Pacific, and that the SLP change that induces a northward shift of the KE is characterized by a zonal mean change. 相似文献
10.
Basil R. Stanton 《新西兰海洋与淡水研究杂志》2013,47(3):645-654
In the region between 30°S and northern New Zealand, vertical salinity profiles through the core of the Antarctic Intermediate Water (AAIW) show a high degree of spatial and temporal variability, and this variability is much larger than that found in nearby ocean areas. Characteristic features are interleaving of salinity layers and large changes in the salinity minimum between adjacent stations. Quantifying the changes through the calculation of an intrusion index highlights the degree of variability and the importance of boundary mixing along the New Zealand slope. However, the main cause of the variability is the meeting and mixing of higher salinity AAIW, arriving from the north‐west (having travelled around the subtropical gyre) with lower salinity AAIW arriving by more direct entry from the north‐east. These waters meet in the region through the action of the meso‐scale eddy field. Present data indicate that where strong salinity interleaving occurs, the length scales are of the order of 10 km and the time scales are of the order of a few days. Resolution of the processes at work will require studies on finer scales than presently available. 相似文献
11.
过去的研究认为,黑潮延伸体的年代际振荡受来自其下游的太平洋年代际振荡（PDO）相关联的信号主导,但最近的观测表明这种调控机制在2017年9月之后不再成立。与此同时,黑潮延伸体的上游即日本南部黑潮正在发生一次大弯曲事件。利用26年（1993–2018年）的卫星高度计提供的海表高度距平数据和自组织映射（SOM）方法,本文研究了日本南部黑潮与黑潮延伸体的时空模态及其因果关系。结果表明,SOM能有效地提取两个海区的典型空间模态,且它们的演变轨迹表明当日本南部黑潮处于大弯曲（离岸型非大弯曲）路径时,黑潮延伸体趋于稳定（不稳定）态。基于SOM识别得到的海表面高度距平（SLA）特征区及特征时间模态,我们进一步利用一种最近发展的定量因果分析方法研究了两个流系之间的因果关系。研究发现,当黑潮大弯曲发生时,日本南部黑潮和黑潮延伸体之间存在双向因果,但因果关键区不同。前者对后者的影响集中在纪伊半岛东南侧及黑潮延伸体“两脊一槽”区域,而后者对前者的影响则集中在黑潮延伸体“两脊一槽”区域及黑潮再循环流区域。这说明黑潮大弯曲的发展对黑潮延伸体的稳定性有重要作用,同时黑潮延伸体通过调制南部再循环流影响日本南部黑潮的路径。不同的是,当离岸型非大弯曲路径发生时,只有从日本南部黑潮向黑潮延伸体的单向因果关系,且因果性主要集中在伊豆海脊及再循环流区域。这与该时期海表高度负异常沿日本南岸不断向位于下游的黑潮延伸体再循环流的传播有关,它使得黑潮延伸体变得不稳定。 相似文献
12.
Using AVISO satellite altimeter observations during 1993–2015 and a manual eddy detection method, a total of 276 anticyclonic rings and 242 cyclonic rings shed from the Kuroshio Extension(KE) were identified, and their three-dimensional(3D) anomaly structures were further reconstructd based on the Argo float data and the Japan Agency for Marine-Earth Science and Technology(JAMSTEC) cruise and buoy data through an interpolation method. It is found that the cyclonic(anticyclonic) rings presented consistent negative(positive) anomalies of potential temperature;meanwhile the relevant maximum anomaly center became increasingly shallow for the cyclonic rings whereas it went deeper for the anticyclonic rings as the potential temperature anomaly decreased from the west to the east. The above deepening or shoaling trend is associated with the zonal change of the depth of the main thermocline. Moreover, the composite cold ring between 140° and 150°E was found to exhibit a double-core vertical structure due to the existence of mode water with low potential vorticity. Specifically, a relatively large negative(positive) salinity anomaly and a small positive(negative) one appeared for the composite cyclonic(anticyclonic) ring at the depth above and below 600 m, respectively. The underlying driving force for the temperature and salinity anomaly of the composite rings was also attempted, which varies depending on the intensity of the background current and the temperature and salinity fields in different areas of the KE region, and the rings’ influences on the temperature and salinity could reach deeper than 1 000 m on average. 相似文献
13.
Monthly Variations of Water Masses in the Yellow and East China Seas, November 6, 1998 总被引：4，自引：0，他引：4
The monthly water mass variations in the Yellow Sea and the East China Sea are investigated using over 40 years of historical
temperature and salinity observations via a cluster analysis that incorporates geographical distance and depth separation
in addition to the temperature and salinity. Results delineate monthly variations in the major water masses and provide some
insight into formation mechanisms and intermixing. The major water masses include the Kuroshio-East China Sea water (KE),
the Yellow Sea surface water (YSS) and bottom cold water (YSB), mixed water (MW), and coastal water (CW). The distribution
of the KE water mass reveals the intrusion pattern into the area west of Cheju. A separate mixed water type appears between
the KE water mass and the Yellow Sea water masses during winter. The formation mechanism of the YSB appears to be the surface
cooling and active mixing in winter. In the East China Sea, during summer, surface water is differentiated from the subsurface
water while there is no differentiation during winter. In the Yellow Sea, a three layer system exists in the summer and fall
(May–November) while a two layer system exists during the rest of the year. A fresh water mass generated by Yangtze River
discharge (YD) is present over the northern East China Sea and the southern Yellow Sea during summer.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
本文利用Argo海水盐度资料、海流同化数据和同期大气再分析数据，探讨热带太平洋盐度趋势变化和相关动力过程。Argo资料显示，2015?2017年热带太平洋出现显著的盐度异常(SAE)，这是改变长期趋势的主要原因，表现为表层显著淡化和次表层咸化特征。这种盐度异常具有明显的区域性特征和垂直结构的差异，体现在热带太平洋北部海区(NTP)和南太平洋辐合区(SPCZ)表层淡化，盐度最大变幅为0.71～0.92，淡化可以达到混合层底；热带太平洋南部海区(STP)次表层咸化，最大变幅为0.46，主要发生在温跃层附近，期间盐度异常沿着等位密面从西向东扩展。平流和挟卷是与SAE密切相关的海洋动力过程，两者在NTP淡化海域有着持续而较为显著的影响，在SPCZ淡化、STP咸化海域后期贡献也较大，其中盐度平流对热带太平洋海区盐度变化起主要贡献。NTP淡化海区表层淡水通量和STP咸化海区密度补偿引起的混合也是SAE的重要影响因素。 相似文献
15.
本文利用Argo盐度、SODA海流量、OAFlux蒸发量和TRMM降水量等数据,采用盐度收支方程定量给出了印度洋混合层盐度的收支,揭示了整个印度洋净淡水通量项、平流项、垂向卷夹项的分布、季节变化特征及其对混合层盐度变化的主要贡献。结果表明,就多年平均而言,平流项负贡献（15.14%）大于正贡献（9.89%）,说明平流输送把低盐水输送到高盐海域,导致印度洋高盐海域混合层的盐度降低。净淡水通量项的分布和季节变化与降水量基本一致,且正贡献（13.70%）大于负贡献（7.81%）,说明净淡水通量项使印度洋的混合层盐度升高（因为多年平均蒸发量大于降水量）。盐度季节变化显著海域的进一步分析表明,6?11月,西南季风漂流把赤道西印度洋的低盐水（相对阿拉伯海高盐水而言）输送到阿拉伯海西部海域,导致该海域的盐度降低。平流输送把孟加拉湾湾口和中部的高盐水带到北部海域,是导致北部海域盐度升高的主要原因。 相似文献
16.
利用WOD09和Argo剖面资料,结合SODA、OFES、GPCP和WHOI等资料分析了吕宋海峡西侧海域混合层盐度1984—2010年间的长期变化趋势和年代际变化特征,并利用混合层盐度平衡方程探讨了其变化机理。研究结果表明:(1)吕宋海峡西侧海域的盐度整体上呈现下降趋势,线性趋势为-0.020/a;(2)以1999年为界,吕宋海峡西侧海域的盐度在1999年之前为正距平,最大正距平值可达0.14,平均值为0.05,在1999年之后为负距平,最大负距平值为-0.22,平均值为-0.06;(3)影响该海域混合层盐度的长期变化趋势和年代际变化的主要因素为平流作用,特别是黑潮入侵的变化。 相似文献
17.
Using a gridded array for real-time geostrophic oceanography(Argo) program float dataset, the features of upperocean salinity stratification in the tropical Pacific Ocean are studied. The salinity component of the squared Brunt-V?is?l? frequency N~2( N_S~2) is used to represent salinity stratification. Layer-max N_S~2(LMN), defined as the N_S~2 maximum over the upper 300 m depth, and halocline depth(HD), defined as the depth where the N_S~2 maximum is located, are used to specifically describe the intensity of salinity stratification. Salinity stratification in the Topical Pacific Ocean has both spatial and temporal variability. Over the western and eastern equatorial Pacific, the LMN has a large magnitude with a shallow HD, and both have completely opposite distributions outside of the equatorial region. An obvious seasonal cycle in the LMN occurs in the north side of eastern equatorial Pacific and freshwater flux forcing dominates the seasonal variations, followed by subsurface forcing.At the eastern edge of the western Pacific warm pool around the dateline, significant interannual variation of salinity stratification occurs and is closely related to the El Ni?o Southern Oscillation event. When an El Ni?o event occurs, the precipitation anomaly freshens sea surface and the thermocline shoaling induced by the westerly wind anomaly lifts salty water upward, together contribute to the positive salinity stratification anomaly over the eastern edge of the warm pool. The interannual variations in ocean stratification can slightly affect the propagation of first baroclinic gravity waves. 相似文献
18.
为考察海水淡化产生的浓盐水对胶州湾盐度分布的影响,利用POM模式,建立了胶州湾盐度扩散模型,分别以现有海水淡化量和2010年规划海水淡化量所排放的浓盐水量为输入条件,模拟计算了胶州湾盐度的分布和变化。模拟显示,2010年2月、5月、8月和10月胶州湾整个湾内平均盐度分别为30.9895,30.8040,30.0221和30.2306,较2008年分别增加约0.0276,0.0274,0.0212和0.0205。浓盐水排放位置附近局部海域盐度增加明显,如黄岛浓盐水排放点附近海域,2月大潮涨潮时盐度超过31.55的水域面积较2008年增加0.24 km2,并且出现0.08 km2盐度超过32.00的水域;2月大潮落潮时盐度超过31.55水域面积比2008年增加0.53 km2左右,盐度超过32.00的面积增加约0.16 km2。2月、5月、8月和10月最高值分别达到40.23,36.66,37.94和37.87。结合前期室内实验结果可以看出,2月份的盐度最高值超过对胶州湾浮游植物生长有明显影响的非检测浓度(38.62)。这表明,按2010年规划的海水淡化规模所产生的排海浓盐水尽管对整个胶州湾的盐度分布影响不大,但会导致局部海域盐度明显增加,从而可能会对该海域浮游植物生长造成一定影响。 相似文献
19.
两个西边界流延伸体区域中尺度涡统计特征分析 总被引：3，自引：2，他引：1
黑潮和湾流是世界大洋中最典型的两支西边界流，黑潮延伸体（Kuroshio Extention，KE）和湾流延伸体（Gulf Stream Extention，GSE）区域中尺度涡活动十分活跃。本文综合利用卫星高度计资料和Argo浮标资料，对KE和GSE区域中尺度涡的表层特征及其对温盐影响进行了统计研究和对比分析。结果表明:黑潮和湾流主轴附近为涡旋频率的高值区，主轴南北两侧分别以气旋涡和反气旋涡数量占多，主轴附近的涡旋强度明显大于其他区域；两个区域的涡旋以西向移动为主，气旋涡和反气旋涡都具有向南（赤道）偏离的趋势；两个区域的涡旋数量都以夏、秋季较多，涡旋强度都在春、夏季较大，且GSE区域涡旋强度明显大于KE区域；气旋涡（反气旋涡）引起内部明显的温度负（正）异常，KE区域气旋涡（反气旋涡）内部呈"负-正"（"正-负"）上下层相反的盐度异常分布，GSE区域气旋涡（反气旋涡）在各层呈现较为一致的盐度负（正）异常；两个区域中尺度涡对温盐场的平均影响深度可达1 000×104 Pa以上。 相似文献
20.
From the moored buoy observation at \(33.9^{\circ }\)N, \(144.9^{\circ }\)E south of the Kuroshio Extension (KE), we obtained Eulerian time series of dissolved oxygen concentration (DO) at 200, 400, and 600 m depths from June 2012 to March 2013. We observed ventilation by meso- and submesoscale processes that transport water southward across the KE jet. First, the cyclonic mesoscale eddy in June 2012 substantially depressed DO at depths of 400 and 600 m but maintained DO at 200 m, suggesting near-surface lateral transport of high-DO water derived from the north of the KE. Second, subduction of high-DO (>230 \({\upmu }\)mol kg\(^{-1}\)) water to a depth of 600 m was observed from early February to March 2013, associated with a mesoscale/submesoscale meandering of the KE jet. In mid-March 2013, shipboard hydrographic data were collected where the water mass at the mooring site would be advected by the eastward current on the southern flank of the KE. Based on these data, the subduction event was identified as an intrusion of an anomalously thick water mass from approximately 400–900 dbar. Ventilation of the subtropical mode water at a depth of 200 m around a subsurface DO maximum layer was detected as a rapid rise in DO in January 2013. This occurred after a significant seasonal decrease in DO at a rate of \(-0.130 \pm 0.007\) \({\upmu }\)mol kg\(^{-1}\) day\(^{-1}\) from July to December 2012. 相似文献