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1.
Hydrographic surveys were carried out four times in the western channel of the Korea Strait in March and August 2003 and in
June and November 2004. The bottom cold water, which was lower than 10°C, appeared in the channel trough except in March 2003.
It flowed southwestward along the shelf of Korean coasts in August 2003 and in November 2004. The width and the maximum speed
of the intrusion current were about 20 km and approximately 25 cm s-1, respectively, off Ulsan, Korea. The volume transport of the bottom cold water was estimated 0.019 Sv (Sv≡106 m3 s-1) in August 2003 and 0.026 Sv in November 2004. 相似文献
2.
Kuh Kim Young-Gyu Kim Yang-Ki Cho Masaki Takematsu Yuri Volkov 《Journal of Oceanography》1999,55(2):103-109
Analysis of CTD data from four CREAMS expeditions carried out in summers of 1993–1996 produces distinct T-S relationships
for the western and eastern Japan Basin, the Ulleung Basin and the Yamato Basin. T-S characteristics are mainly determined
by salinity as it changes its horizontal pattern in three layers, which are divided by isotherms of 5°C and 1°C; upper warm
water, intermediate water and deep cold water. Upper warm water is most saline in the Ulleung Basin and the Yamato Basin.
Salinity of intermediate water is the highest in the eastern Japan Basin. Deep cold water has the highest salinity in the
Japan Basin. T-S curves in the western Japan Basin are characterized by a salinity jump around 1.2–1.4°C in the T-S plane,
which was previously found off the east coast of Korea associated with the East Sea Intermediate Water (Cho and Kim, 1994).
T-S curves for the Japan Basin undergo a large year-to-year variation for water warmer than 0.6°C, which occupies upper 400
m. It is postulated that the year-to-year variation in the Japan Basin is caused by convective overturning in winter.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
本文基于2017年634幅MODIS影像分析了安达曼海3个典型区域的内波空间分布特征，定量统计了波峰线长度、波包面积等特征参数，利用射线追踪法探讨了内波的潜在激发源并推算了内波的生成周期。研究表明，安达曼海北部海域的内波空间尺度较小，前导波波峰线的平均长度约为107 km，平均波包面积约为1 860 km2，内波的传播方向主要为东向以及西南向。安达曼海中部海域内波前导波波峰线的平均长度约为133 km，平均波包面积约为3 503 km2，超过70%的内波沿东偏北方向传播。苏门答腊岛北部海域内波前导波波峰线的平均长度约为131 km，平均波包面积约为2 997 km2，内波的传播方向主要为东向、东北向及东南向。安达曼海共有7个潜在内波激发源，内波的生成时间间隔介于11.5～13 h，具有明显的半日周期特征。 相似文献
4.
通过线性回归合成3颗卫星的遥感反射率,得到2006年7月27日—2006年8月8日期间有效数据量较多且时间连续的遥感反射率资料,并据此对长江口邻近海域近岸水舌向外海的扩展过程进行了分析。结果表明:在此期间存在一次明显的扩展过程,水舌的遥感反射率随离岸距离增加而降低,水舌主要沿纬度方向扩展,而在南、北方向摆动范围不大。该扩展过程分为伸展和消退两个阶段, 7月27日—8月2日期间,水舌逐天向东伸展,最远处到达124.4°E附近;在向东伸展途中,水舌宽度逐渐变窄但变化幅度较小;水舌内部遥感反射率的不同等值线均向东伸展,但向东伸展的程度不同,水舌边界的伸展速度变化较大(17.6~33.4 km/d),平均为每天24.5 km。从8月3日起水舌开始消退,至8月8日已完全消失;在消退过程中,水舌的范围缩小,遥感反射率下降,水舌轴线方向基本保持不变。结合相关资料对该过程的生消机理进行初步分析认为,在水舌扩展过程中,潮流的主要作用是阻碍沿岸水沿岸线方向运动,持续而强劲的南风对水舌的产生和伸展起重要作用,而东风则促使水舌消退。 相似文献
5.
Ursula Schauer Eberhard Fahrbach 《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(12):401
The generation and downstream modification of a cold dense Arctic shelf water plume were studied with moored current meters, thermistor chains and conductivity/temperature sensors deployed from August 1993 to September 1994 south of the Storfjord in the Svalbard Archipelago. These observations are compared to similar time series from 1991/92. In 1993/94, bottom water with temperatures close to the freezing point drained continuously from Storfjord between March and September with a mean speed of 0.14 m s−1. About 1.5 months after the plume front had left the Storfjord, it reached the shelf break, 150 km away. The plume had increased its width from 15 km to about 35 km, but its thickness of 50 m remained almost constant and it left the shelf edge at a similar speed. The increased volume transport and the change of temperature/salinity properties indicate an entrainment of 110% of ambient Atlantic water into the plume on its way from the production area to the shelf edge.The maximum salinity of the cold plume was 0.2 lower in 1993/94 than in 1991/92, whilst the temperature/salinity-range of the surrounding Atlantic water remained unchanged. Probably as a dynamic consequence, the speed of the plume was considerably lower in 1993/94. The lower salinity of the plume in 1993/94 is a result of both the 30% less ice formation in Storfjord, caused by lower heat flux and less open water, and a lower surface salinity at the beginning of ice formation. During 1993/94, the Storfjord plume was too light to sink below 700 m. 相似文献
6.
7.
The hydrographic structure of the region of large meander of the Kuroshio and the large cold water mass, which were formed in 1975, was observed down to the ocean bottom, during three cruises of the R/VHakuho Maru in September 1975, September 1976, and December 1977. The analysis of observed data indicates the following common features: the horizontal gradient of the specific volume anomaly exists down to a 3,500 db surface, corresponding to the existence of baroclinic geostrophic current down to this depth. These facts demonstrate that the current of the Kuroshio is not confined to the upper layer during periods of existence of the large meander. On a T-S diagram, the Kuroshio water and the water in the large cold water mass can be discriminated down to a 5°C surface, but there is evidence of mixing due to conspicuous interleaving between the two water masses, near the thermocline. Below the thermocline, water types defined by points on the T-S diagram can be traced from a deeper level in the Kuroshio water to a shallower level in the cold water mass, indicating that in the deeper layers the Kuroshio water continues to be uplifted toward the center of the cold water mass. The same inference is also obtained from the distribution of dissolved oxygen. 相似文献
8.
- Starting from satellite remote sensing data, the dynamical processes of shear waves occurring at the boundary between the western boundary current and the shelf slope water are studied and dynamically analyzed in this study. The average wavelength is 75 km, and the average amplitude (from crest to trough )17 km. the average phase speed 100 cms-1 for the shear waves along the north wall of the Gulf Stream to the east of Cape Hatteras measured from NOAA satellite IR (infrared ) images. The average wavelength of shear waves along the north wall of the Kuroshio Current is 57 km, and the average amplitude 17 km. For the shear waves occurring along the west wall of the Gulf Stream to the south of Cape Hatteras, the average wavelength is 131 km, and the average amplitude 33 km measured from Seasat SAR (synthetic aperture radar )images. The time for one cycle of shear wave event is about one week.In order to explore the dynamical mechanisms of shear waves, we solved the vorticity equation for a stratified flu 相似文献
9.
From 1980 to 1995, in August, the bottom layer of Osaka Bay was occupied by cold, nutrient-rich water compared with that observed
during both previous and subsequent decades. To investigate the mechanisms for the intrusion of bottom-layer cold water into
Osaka Bay, the intrusion into Osaka Bay via the Kii Channel is simulated using a finite-volume coastal ocean model with unstructured
triangular cell grids. The initial conditions, boundary conditions, and surface temperature given to the model are obtained
from daily reanalysis data provided by the Japan Coastal Ocean Predictability Experiment. The model shows that cold water
uplifted on the eastern side of the Kii Peninsula is propagated westward at 1.0 m/s as a coastal boundary current; it reaches
the Kii Channel mouth when the Kuroshio axis is located around 74 km south of Cape Shionomisaki. However, the modeled cold
water mass at the Kii Channel mouth does not intrude further to the north of the Kii Channel; therefore, another mechanism
is required to explain the cold-water intrusion into the bottom layer of Osaka Bay. A plausible explanation is the estuarine
circulation established by the freshwater supply at the bay head. When the river runoff is included in the model without forced
vertical mixing, the temperature in Osaka Bay decreases 6.6 days later than the temperature decreases at the Kii Channel mouth.
Furthermore, the shoreward current speed in the bottom layer of the modeled estuarine circulation is 15 cm/s, which provides
the mechanism required for the cold water mass to pass the Kii Channel. 相似文献
10.
A set of simultaneous long-term, deep current measurements was taken using a moored array in the mid-ocean of the western North Pacific near 30°N, 146°E. Five current meters at three stations provided good quality records over 84 days. Low-frequency current fluctuations with meridional dominance are clearly seen in the deep layer records. They are consistent with signals of a mesoscale current fluctuation which has a period of about 100 days, an east-west wave length of about 200 km, and a westward phase propagation with a speed of about 2 cm sec–1. Bottom intensification of the east component of low-frequency current fluctuations is also observed. 相似文献
11.
The effects of intra-seasonal wind forcing on the mean field of the tropical Pacific Ocean has been studied using an ocean general circulation model (GCM). Idealized intra-seasonal zonal wind forcing with zero mean, which propagates eastward, induces net eastward jets at the equator that shift the warm water pool to the east. The mean temperature of the upper 200 m of the ocean increases off the equator and decreases at the equator. The change is independent of the propagation speed of the intra-seasonal wind forcing. The magnitude of the change depends on the amplitude and the period of the forcing, and the ocean structure, while the spatial pattern is independent of these parameters. A simple shallow water model is used to explain these changes. It is found that the term responsible for the enhanced eastward Equatorial jet is the Reynolds stress term, which arises from a phase shift of the zonal current due to friction. The resultant convergence of eastward momentum on the equator and geostrophic adjustment of the interface to the change of zonal current brings about the thermal redistribution of the upper ocean seen in the GCM. 相似文献
12.
13.
Ship and satellite observations taken over the last thirty years show that mesoscale patterns of sea surface temperature (SST) in the California Current System are consistently found throughout the year and usually occur in approximately the same geographical locations. Typically, these patterns are more pronounced in fall/winter than in spring/summer. The temporal and spatial characteristics of these persistent feature were examined with satellite infrared (IR) measurements during winter 1980–1981. In January 1981, a ship surveyed the vertical structure of several physical, chemical, and biological parameters beneath one of these SST features centered near 32°N, 124°W. The surface IR pattern had a length scale of 200 km and a time scale of about 100 days. It disintegrated following the first two storms of the winter season. Motion studies of the pattern in late October indicated an anticyclonic rotation with maximum velocities of 50 cm s?1 at 50 km from the axis of rotation. As a unit, the pattern advected southward with an average speed of 1 cm s?1. Thermal fronts, determined from the satellite imagery, were strongest (0.4°C km?1) along the rim of the pattern and were advected anticyclonically with the pattern; their length scales were 20–30 km in the along-front direction and less than 10 km wide. The hydrographic data revealed a three-layer structure beneath the surface pattern; a 75 m deep surface layer, a cold-core region from 75 to 200 m depth, and a warm-core eddy extending from 250 to 1450 m. The anticyclonic motion of the surface layer was caused by a geostrophic adjustment to the surface dynamic height anomaly produced by the subsurface warm-core eddy. The IR pattern observed from space reflects the horizontal structure of the surface layer and is consistent with a theoretical model of a mean horizontal SST gradient perturbed by a subsurface density anomaly. Ship of opportunity SST observations collected by the National Marine Fisheries are shown to resolve mesoscale patterns. For December 1980, the SST pattern near 32°N, 124°W represented a 2°C warm anomaly compared with the 20-year mean monthly SST pattern. 相似文献
14.
Alberto G Figueiredo 《Marine Geology》1980,35(4):367-376
The result of two sequential oceanographic stations of 36 hours each in the area of sand ridges are presented. One station was located in the trough between two sand ridges and the other was at the crest of a sand ridge. At these stations salinity and temperature of the sea water, currents, winds, waves, and barometric pressure were measured each hour.During the observations, a cold front passed; this generated westerly winds that grew in speed from 24 to 52 km h?1. The average height of the wind generated waves grew from 1.0 to 1.5 m and their periods increased from 7 to 10 s, and the speed of the northeast directed surface current increased from 40 to 82 cm s?1. A bottom current (also directed northeast) increased from 26 to 34 cm s?1.After the cold front had passed, the wind backed to the southeast and decreased in speed from 26 to zero km h?1. The surface current in a northwest direction decreased from 29 to 8 cm s?1. A bottom current (also directed northwest) decreased from 22 to 3 cm s?1. Later, swells from the southeast appeared and their periods increased from 5 to 9 s and their heights grew from 1.0 to 1.5 m. After 3 hours, the speeds of the surface and bottom currents increased from 8 to 72 cm s?1 and 3 to 62 cm s?1 respectively.This cold front induced strong winds and storm-wave currents able to erode sediments (assuming a threshold velocity of 20 cm s?1) and transport them in a north-northeast direction.The origin and the maintenance of these sand ridges is thought to be a function of sediments eroded from troughs and piled up at ridge crests during a storm condition. Some eroded sediments are transported north of Verga lighthouse where they are deposited on a smooth bottom. 相似文献
15.
Atlantic Water flow through the Barents and Kara Seas 总被引：2，自引：0，他引：2
Ursula Schauer Harald Loeng Bert Rudels Vladimir K. Ozhigin Wolfgang Dieck 《Deep Sea Research Part I: Oceanographic Research Papers》2002,49(12)
The pathway and transformation of water from the Norwegian Sea across the Barents Sea and through the St. Anna Trough are documented from hydrographic and current measurements of the 1990s. The transport through an array of moorings in the north-eastern Barents Sea was between 0.6 Sv in summer and 2.6 Sv in winter towards the Kara Sea and between zero and 0.3 Sv towards the Barents Sea with a record mean net flow of 1.5 Sv. The westward flow originates in the Fram Strait branch of Atlantic Water at the Eurasian continental slope, while the eastward flow constitutes the Barents Sea branch, continuing from the western Barents Sea opening.About 75% of the eastward flow was colder than 0°C. The flow was strongly sheared, with the highest velocities close to the bottom. A deep layer with almost constant temperature of about −0.5°C throughout the year formed about 50% of the flow to the Kara Sea. This water was a mixture between warm saline Atlantic Water and cold, brine-enriched water generated through freezing and convection in polynyas west of Novaya Zemlya, and possibly also at the Central Bank. Its salinity is lower than that of the Atlantic Water at its entrance to the Barents Sea, because the ice formation occurs in a low salinity surface layer. The released brine increases the salinity and density of the surface layer sufficiently for it to convect, but not necessarily above the salinity of the Atlantic Water. The freshwater west of Novaya Zemlya primarily stems from continental runoff and at the Central Bank probably from ice melt. The amount of fresh water compares to about 22% of the terrestrial freshwater supply to the western Barents Sea. The deep layer continues to the Kara Sea without further change and enters the Nansen Basin at or below the core depth of the warm, saline Fram Strait branch. Because it is colder than 0°C it will not be addressed as Atlantic Water in the Arctic Ocean.In earlier decades, the Atlantic Water advected from Fram Strait was colder by almost 2 K as compared to the 1990s, while the dense Barents Sea water was colder by up to 1 K only in a thin layer at the bottom and the salinity varied significantly. However, also with the resulting higher densities, deep Eurasian Basin water properties were met only in the 1970s. The very low salinities of the Great Salinity Anomaly in 1980 were not discovered in the outflow data. We conclude that the thermal variability of inflowing Atlantic water is damped in the Barents Sea, while the salinity variation is strongly modified through the freshwater conditions and ice growth in the convective area off Novaya Zemlya. 相似文献
16.
Masayuki Takahashi Isao Koike Takashi Ishimaru Toshiro Saino Ken Furuya Yoshihiko Fujita Akihiko Hattori Shun-ei Ichimura 《Journal of Oceanography》1980,36(4):209-216
Water plumes, 20 km long or less, identified by low temperature, high salinity and high nutrient concentrations, were observed on the eastern side of Izu Islands where the Kuroshio Current or its branch flowed eastward. The T-S diagrams and the vertical profiles of oceanographic variables indicated that the water plumes resulted from the upwelling of subsurface water. A newly formed plume, characterized by a sharp temperature front and high nutrient concentrations, contained less chlorophyll than did old plumes. It is suggested that the upwelling plumes are maintained for a period long enough to allow luxuriant growth of phytoplankton. 相似文献
17.
《African Journal of Marine Science》2013,35(2):375-388
In July 1998, a bottom-mounted Acoustic Doppler Current Profiler was deployed at 36m depth in the centre of the Tsitsikamma National Park on the eastern Agulhas Bank, South Africa. The purpose was to investigate transport of chokka squid Loligo vulgaris reynaudii paralarvae hatched on the inshore spawning grounds (<60m) and ichthyoplankton spawned within the park. Analysis of the first 12 months of data (July 1998–June 1999) shows that surface flow was mainly eastward (alongshore), with a maximum velocity (u-component) of +115cm s?1 and an average of +24cm s?1. Generally, velocity decreased with depth, with a maximum bottom velocity (u-component) of +65cm s?1 and an average of +10cm s?1. Data from a nearby thermistor array show that the water column was usually isothermal during winter (July–September), with bottom flow in the same direction as the surface layer. In summer (December–March), vertical stratification was most intense, and surface and bottom flows differed in velocity and direction. Potential net monthly displacements calculated for three depths (5m, 23m and 31m) indicate that passive, neutrally buoyant biological material (e.g. squid paralarvae, fish eggs and larvae) would likely be transported eastwards in the surface layer for eight of the 12 months, and would generally exceed distances of 220km month–1. Displacement in the bottom layer was more evenly distributed between east and west, with net monthly (potential) transport typically 70–100km, but reaching a maximum of 200km. Wind-driven coastal upwelling, prevalent during the summer, causes the surface layer of the coastal counter-current to flow offshore for several days, resulting in potential displacement distances of 40km from the coast. These results suggest that squid paralarvae hatched on the inshore spawning grounds are not generally transported towards the 'cold ridge', a prominent semi-permanent oceanographic feature of cold, nutrient-rich upwelled water, where food is abundant, and that fish larvae, whether from the surface or bottom layer, are exported beyond the boundaries of the Tsitsikamma National Park. 相似文献
18.
A high-frequency multifrequency coastal radar operating at four frequencies between 4.8 and 21.8 MHz was used as part of the third Chesapeake Bay Outflow Plume Experiment (COPE-3) during October and November, 1997. The radar system surveyed the open ocean east of the coast and just south of the mouth of Chesapeake Bay from two sites separated by about 20 km. Measurements were taken once an hour, and the eastward and northward components of ocean currents were estimated at four depths ranging from about 0.5 m to 2.5 m below the surface for each location on a 2 by 2 km grid. Direction of arrival of the signals was estimated using the MUSIC algorithm. The radar measurements were compared to currents measured by several moored acoustic Doppler current profilers (ADCPs) with range bins 2-14 m below the water surface. The vertical structure of the current was examined by utilizing four different radar wavelengths, which respond to ocean currents at different depths, and by using several ADCP range bins separated by 1-m intervals. The radar and ADCP current estimates were highly correlated and showed similar depth behavior, and there was significant correlation between radar current estimates at different wavelengths and wind speed 相似文献
19.
Current records obtained in the inshore region along the Fukushima coast are analyzed. The existence of periodical current fluctuations whose period is about 100 hours and whose amplitude is as large as 15–25cm s–1 is recognized. Auto-spectral analyses are made also for sea level, atmospheric pressure and wind records. Each spectrum has significant peaks at the similar period to the current spectrum. The wind spectrum has a broad peak compared with the current. The periodical current fluctuations propagate southward with speed of 3–5 km h–1. These propagation speeds seem to correspond to those of the second-and third-mode shelf waves. 相似文献
20.
《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(3):415-438
The mesoscale dynamics of the Scottish side of the Faroe–Shetland Channel have been investigated using synoptic in situ and remote sensing observations. A cold core cyclonic eddy, identified from an AVHRR image, had a diameter of about 50 km and surface current speeds of up to 50 cm s-1; it appeared to be attached to the 800 m isobath as it moved north-eastward along the edge of the channel at about 8 cm s-1. Speeds in the slope current were about 50 cm s-1 but increased to 70 cm s-1 where the current was compressed by the eddy. Offshore, over the 1000 m isobath in the cooler water, speeds in the current were slower (ca. 20 cm s-1). North-west of the Shetlands the offshore edge of the slope current was deflected across the channel for a distance of about 70 km from the shelf edge. The speed of drifters in the slope current increased to over 60 cm s-1 as they moved anti-cyclonically around this deflection. CTD profiles suggest that the movement of the surface waters was mirrored in the deep water of the channel. The deflection carried a very large quantity of North Atlantic Water into the central part of the channel; its cause and ultimate fate are not known, although it is likely to have had a significant impact on the dynamics of the channel. 相似文献