共查询到20条相似文献，搜索用时 31 毫秒
1.
E. Wolanski P. Colin J. Naithani E. Deleersnijder Y. Golbuu 《Estuarine, Coastal and Shelf Science》2004,60(4):705-716
Three years of temperature data along two transects extending to 90 m depth, at Palau, Micronesia, show twice-a-day thermocline vertical displacements of commonly 50–100 m, and on one occasion 270 m. The internal wave occurred at a number of frequencies. There were a number of spectral peaks at diurnal and semi-diurnal frequencies, as well as intermediate and sub-inertial frequencies, less so at the inertial frequency. At Palau the waves generally did not travel around the island because there was no coherence between internal waves on either side of the island. The internal waves at a site 30 km offshore were out-of-phase with those on the island slopes, suggesting that the waves were generated on the island slope and then radiated away. Palau Island was thus a source of internal wave energy for the surrounding ocean. A numerical model suggests that the tidal and low-frequency currents flowing around the island form internal waves with maximum wave amplitude on the island slope and that these waves radiate away from the island. The model also suggests that the headland at the southern tip of Palau prevents the internal waves to rotate around the island. The large temperature fluctuations (commonly daily fluctuations ≈10 °C, peaking at 20 °C) appear responsible for generating a thermal stress responsible for a biologically depauperate biological community on the island slopes at depths between 60 and 120 m depth. 相似文献
2.
P. V. Hareesh Kumar S. Lekshmi P. S. V. Jagadeesh K. Anilkumar G. V. Krishnakumar A. D. Rao 《Marine Geodesy》2013,36(2-3):232-244
Time series of temperature and salinity collected from a station in the NE Arabian Sea during March, April, May, October, and November was utilized to explain the behavior of internal tides. Analysis revealed the existence of semi-diurnal internal tides and high frequency (HF) internal waves (IW). It was observed that the amplitudes of HF IWs were determined by the degree of stratification in the thermocline. Corresponding to an increase in the density gradient in thermocline (0.016 kg/m4 in April to 0.14 kg/m4 in October), the temperature fluctuations due to internal tides increased from <0.2°C to >1.5°C, respectively. Brunt-Vaiisala frequency also showed similar variations (～10 cph to 22 cph). Within the thermocline, semi-diurnal internal tides caused fluctuations of >10m in the isotherm depths. A linear regression equation was fitted to parameterize the amplitude of HF IWs and its upper frequency limit in terms of thermocline gradient. The IW and one-dimensional models simulated the presence of internal tides and diurnal cycling in the temperature field, respectively. Coupling of these models showed improvement in the simulation of temperature. 相似文献
3.
Yuji Kashino Iwao Ueki Yoshifumi Kuroda Andri Purwandani 《Journal of Oceanography》2007,63(4):545-559
We investigated variability in the ocean surface-subsurface layer north of New Guinea using Triangle Trans-Ocean Buoy Network (TRITON) buoys at 2°N, 138°E and 0°N, 138°E during the period from October 1999 to July 2004. Both North and South Pacific waters were observed below the subsurface at these stations. The variability in the subsurface waters was particularly high at 2°N, 138°E. Clear interannual variability occurred near the surface; the water type differed before and after onset of the 2002–03 El Niño. Before summer 2001, water that appeared to be advected from the central equatorial Pacific occupied the near surface layer. After autumn 2001, waters advected by the New Guinea Coastal Current were observed near the surface. Intraseasonal and seasonal variations were also observed below the subsurface. With regard to seasonal variability, the salinity of the subsurface saline water, the South Pacific Tropical Water, was generally high during the boreal summer-autumn, when the New Guinea Coastal Undercurrent was strong. Intraseasonal fluctuations on a scale of 20 to 60 days were also seen and may have been associated with intrinsic oceanic variability, such as ocean eddies, near the stations. Ocean variability in the thermocline layer between 100 and 200 m greatly affects the surface dynamic height variability; water variability before 2001 and variability in the pycnocline depth after 2002 are important factors affecting the thermocline. 相似文献
4.
The vertical characters of temperature, salinity and density fluctuations in shallow region of the East China Sea are analysed by using 12 CTD short records with 1-hour intervals. The average S,t and p profiles can be divided into three distinctive layers: the thermocline, and the layers above and below it. The fluctuations of t, S and p are basically caused by internal waves, but there are somewhat intrusions or entrainments at the thermocline boundaries. The vertical displacement of the thermocline centre is up to more than 6.35m and the thermocline thickness changes from 3.5 to 8.0 m. Their varature with time are intermittent and rather irregular. The vertical wavenumber spectra of temperature fluctuations have been estimated by using the maximum entropy method, indicating that energy is mainly contained in the low-wavenumber range (<0.13cpm) with two sharp peaks probably corresponding to the first and second modes of internal waves, whose dependence is estimated to be less than β-2. There exist dep 相似文献
5.
Rory O.R.Y. Thompson 《Progress in Oceanography》1977,7(4):135-162
A theory of Rossby waves makes a number of predictions about motions below the thermocline at Site D (39°10'N, 70°W). An experiment was made to test these predictions. Kinetic energy spectra show most of the energy is associated with periods of a week to a few months. The Reynolds' stress is negative for these periods. There is high coherence and on phase shift between 1000 m and 2000 m depths. Most of the wave-number estimates point to the south-west quadrant, consistent with westward propagation and with momentum flux into the Gulf Stream and energy flux out of it. There is enough consistency between statistics based on successive 8-month records to conclude that statistics based on a single 8-month record near Site D are meaningful. In an 8-month array of twenty-six current meters, for periods of a week to a month, the divergence is small compared to the vorticity, and the motion is transverse. The energy increases toward the bottom. The observed wave-numbers and frequencies fit the theoretical dispersion relationship satisfactorily. The kinetic energy of the fluctuations is much larger near the Gulf Stream than farther upslope. The vorticity is in quadrature with the upslope velocity. I conclude there is strong evidence that topographic Rossby wave mechanics are dominant below the thermocline on the continental rise north of the Gulf Stream. 相似文献
6.
Theoretically, propagating internal tides in the ocean may reflect at turning depths, where buoyancy frequencies equal tidal frequencies, before colliding with the air-sea interface or rugged bottom topography. Globally, the internal tide lower turning depths（ITLTDs） in the open ocean have been mapped; however, knowledge of the presence of ITLTDs in the South China Sea（SCS） is lacking. In this study, 2 125 high-quality temperature-salinity profiles（including 58 deep-sea hydrographic measurements... 相似文献
7.
Iris Wilke Helge Meggers Torsten Bickert 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(1):89-106
Seasonal depth stratified plankton tows, sediment traps and core tops taken from the same stations along a transect at 29°N off NW Africa are used to describe the seasonal succession, the depth habitats and the oxygen isotope ratios (δ18Oshell) of five planktic foraminiferal species. Both the δ18Oshell and shell concentration profiles show variations in seasonal depth habitats of individual species. None of the species maintain a specific habitat depth exclusively within the surface mixed layer (SML), within the thermocline, or beneath the thermocline. Globigerinoides ruber (white) and (pink) occur with moderate abundance throughout the year along the transect, with highest abundances in the winter and summer/fall season, respectively. The average δ18Oshell of G. ruber (w) from surface sediments is similar to the δ18Oshell values measured from the sediment-trap samples during winter. However, the δ18Oshell of G. ruber (w) underestimates sea surface temperature (SST) by 2 °C in winter and by 4 °C during summer/fall indicating an extension of the calcification/depth habitat into colder thermocline waters. Globigerinoides ruber (p) continues to calcify below the SML as well, particularly in summer/fall when the chlorophyll maximum is found within the thermocline. Its vertical distribution results in δ18Oshell values that underestimate SST by 2 °C. Shell fluxes of Globigerina bulloides are highest in summer/fall, where it lives and calcifies in association with the deep chlorophyll maximum found within the thermocline. Pulleniatina obliquiloculata and Globorotalia truncatulinoides, dwelling and calcifying a part of their lives in the winter SML, record winter thermocline (～180 m) and deep surface water (～350 m) temperatures, respectively. Our observations define the seasonal and vertical distribution of multiple species of foraminifera and the acquisition of their δ18Oshell. 相似文献
8.
Yu. N. Goryachkin V. A. Ivanov L. I. Ivanov I. K. Keita V. A. Plotnikov 《Physical Oceanography》1990,1(3):219-224
We have determined the energetic and spatial characteristics of baroclinic and barotropic tidal semi-diurnal fluctuations using the current temperature and velocity data collected by 12 self-contained buoy stations (SCBS) near the shelf of the Republic of Guinea at depths ranging from 50 to 1000 m. Intensive baroclinic motion was observed to prevail near the bottom within the depth range 100–1000 m. The energy of long waves largely propagated from the bottom to the surface, whereas the energy of short waves was transferred in the opposite direction.Translated by V. Puchkin. 相似文献
9.
SUN Lu ZHENG Quan''an TANG Tswen-Yung CHUANG Wen-Ssn LI Li HU Jianyu WANG Dongxiao 《海洋学报(英文版)》2012,31(2):25-32
During the South China Sea monsoon experiment (SCSMEX),three autonomous temperature line acquisition system (ATLAS) buoys with acoustic Doppler current profiler (ADCP) were moored in the South China Sea to measure temperature,salinity and current velocity.Typhoon Faith passed through about 250 km south to one of the mooring buoys located at 12 58.5 N,114 24.5 E from December 11 to 14,1998.The data analysis indicates that the typhoon winds induce a great increase in the kinetic energy at near-inertial frequencies with two maxima in the mixed layer and thermocline.The near-inertial oscillations were observed at the upper 270 m in the wake of Typhoon Faith.The oscillations were originally excited in the sea surface layer and propagated downward.The amplitudes of the oscillations decrease with depth except in the thermocline.The near-inertial oscillation signals are also remarkable in temperature and salinity fields. 相似文献
10.
Using the hydroacoustic method with a 200 kHz scientific echo sounding system,the diel vertical migration(DVM) of the sound-scattering layer(SSL) in the Yellow Sea Bottom Cold Water(YSBCW) of the southeastern Yellow Sea was studied in April(spring) and August(summer) of 2010 and 2011.For each survey,13–27 hours of acoustic data were continuously collected at a stationary station.The acoustic volume scattering strength(Sv) data were analyzed with temperature profile data.In the spring of both 2010 and 2011,the SSL clearly showed the vertical migration throughout the entire water column,moving from the surface layer at night to near the bottom during the day.Conductivity,temperature,and depth data indicated that the entire water column was well mixed with low temperature of about 8 C.However,the SSL showed different patterns in the summers of 2010 and 2011.In the summer of 2010(28 C at the surface),the SSL migrated to near the bottom during the day,but there were two SSLs above and below the thermocline at depth of 10–30 m at night.In the summer of 2011(20 C at the surface),the SSL extended throughout the entire water column at night,possibly owing to an abrupt change in sea weather conditions caused by the passage of a Typhoon Muifa over the study area.It was concluded that the DVM patterns in summer in the YSBCW area may be greatly influenced by a strengthened or weakened thermocline. 相似文献
11.
12.
黄鳍金枪鱼索饵水层影响延绳钓捕捞效率,而黄鳍金枪鱼索饵水层分布受水温垂直结构的影响,因此本文采用GAM模型分析次表层环境变量对延绳钓黄鳍金枪鱼渔获率的影响,评估黄鳍金枪鱼垂直水层分布对中西太平洋黄鳍金枪鱼延绳钓单位捕捞努力量渔获量(Catch Per Unite Effort, CPUE)的作用。模型结果表明,环境因子对热带中西太平洋延绳钓黄鳍金枪鱼渔获率空间分布影响明显。黄鳍金枪鱼延绳钓CPUE在2012年之后快速增多,高渔获率月份出现在北半球夏季,空间上在10°S,140°E附近区域。温跃层上界温度和深度、温跃层下界深度、18℃等温线深度、△8℃等温线深度及其和温跃层下界深度的深度差对延绳钓渔获率影响较大,是影响热带中西太平洋黄鳍金枪鱼延绳钓渔获率的关键环境因子。随着温跃层上界温度和深度值变大,延绳钓CPUE逐渐递增,对延绳钓CPUE影响密切的温度和深度分别为27～28℃和70～90 m。温跃层下界深度对延绳钓CPUE影响在250～280 m时最大;之后随着下界深度的变大,CPUE快速下降。18℃等温线深度对延绳钓CPUE影响呈现先震荡后递增的趋势,影响密切的区域在230 m深度上下。△8℃等温线深度与温跃层下界深度的差值对热带中西太平洋黄鳍金枪鱼延绳钓CPUE影响呈现先快速递减后缓慢增加的趋势,在深度差为70 m上下时影响最密切。研究结果揭示,在黄鳍金枪鱼活动水层受限或栖息水层和延绳钓作业深度相吻合时,延绳钓渔获率最高。依据黄鳍金枪鱼垂直活动水层调整延绳钓投钩,可以提高渔获率。因此,采用延绳钓CPUE进行渔场和资源评估时要考虑金枪鱼适宜垂直活动空间。 相似文献
13.
Direct measurements of current velocity and water temperature were undertaken at the mooring Sta. M (125°29.38' N, 31°49.70' E) on the continental shelf area in the East China Sea in June 1999 by R/V Xiangyanghong 14. The relationship between various time series of oceanic fluctuations is calculated by spectral analysis. The major results are as follows: (1) an average (u,v) of (6.9,-3.0 cm/s) at the 30 m depth is obtained during the 9-day observation, and that at the 45 m depth is (3.7,-1.1 cm/s), i. e., the mean flows are southeastward at both the 30 and 45 m depths;the currents become stronger gradually during the observation period; this may be mainly attributed to the transition of the tidal currents from neap to spring; (2)semidiurnal fluctuation is the most dominant in the current fluctuations, and rotates mainly clockwise; in the next place, there is also diurnal fluctuation;the local inertial period is close to the period of diurnal fluctuation, and an inertial motion is clockwise; thus, loca 相似文献
14.
利用调查数据及遥感数据揭示了2013年南沙群岛海域温跃层的季节变化特征,温跃层上界深度平均值春、夏、冬季基本一致,介于45~47 m之间,秋季最大,达60 m;温跃层厚度平均值夏、秋、冬季基本一致,介于85~87 m之间,春季相对较小,为78 m。温跃层强度平均值春、夏、秋、冬季几乎一致,介于0.13~0.15℃/m之间。调查海域温跃层上界深度季节变化的形成机理为:春季西深东浅的原因是西部受净热通量较小、大风速、负的风应力旋度以及中南半岛东部外海的中尺度暖涡和反气旋环流共同作用,东部近岸海域净热通量高值、风速相对较小及风应力旋度引起的Ekman抽吸效应共同控制;夏季深度分布较均匀的原因是10°N以北风致涡动混合强但受Ekman抽吸影响,10°N以南风致涡动混合弱但风应力旋度为负值;秋季深度较其他季节平均加深15 m的原因是南沙群岛海域被暖涡占据,暖涡引起的反气旋式环流使得温跃层上界深度被海水辐聚下压;冬季正的风应力旋度产生的Ekman抽吸和冷涡引起的气旋式环流共同作用,使得温跃层上界深度较秋季平均抬升15 m。 相似文献
15.
Ｆｒｅｑｕｅｎｃｙ－ｓｅｌｅｃｔｉｖｅ ａｔｔｅｎｕａｔｉｏｎ ｏｆ ｓｏｕｎｄ ｐｒｏｐａｇａｉｏｎ ａｎｄ ｒｅｖｅｒｂｅｒａｔｉｏｎ ｉｎ ｓｈａｌｌｏｗ ｗａｔｅｒTXＦｒｅｑｕｅｎｃｙ－ｓｅｌｅｃｔｉｖｅａｔｔｅｎｕａｔｉｏｎｏｆｓｏｕｎｄｐ... 相似文献
16.
V.V. Gopalakrishna F. Durand K. Nisha M. Lengaigne T.P. Boyer J. Costa R.R. Rao M. Ravichandran S. Amrithash L. John K. Girish C. Ravichandran V. Suneel 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(6):739-754
The southeastern Arabian Sea (SEAS), located in the Indian Ocean warm pool, is a key-region of the regional climate system. It is suspected to play an important role in the dynamics of the Asian summer monsoon system. The present study reports the salient features derived from a newly harvested observational dataset consisting of repeated fortnightly XBT transects in the SEAS over the period 2002–2008. The fortnightly resolution of such a multi-year record duration is unprecedented in this part of the world ocean and provides a unique opportunity to examine the observed variability of the near-surface thermal structure over a wide spectrum, from intra-seasonal to interannual timescales. We find that most of the variability is trapped in the thermocline, taking the form of upwelling and downwelling motions of the thermal stratification. The seasonal variations are consistent with past studies and confirm the role of the monsoonal wind forcing through linear baroclinic waves (coastally-trapped Kelvin and planetary Rossby waves). Sub-seasonal variability takes the form of anomalous events lasting a few weeks to a few months and occurs at two preferred timescales: in the 30–110 day band, within the frequency domain of the Madden–Julian oscillation and in the 120–180 day band. While this sub-seasonal variability appears fairly barotropic in the offshore region, the sign of the anomaly in the upper thermocline is opposite to that in its lower part on many occasions along the coast. Our dataset also reveals relatively large interannual temperature variations of about 1 °C from 50 to 200 m depth that reflect a considerable year-to-year variability of the magnitude of both upwelling and downwelling events. This study clearly demonstrates the necessity for sustained long-term temperature measurements in the SEAS. 相似文献
17.
Stephanie K. Moore Nathan J. Mantua Jan A. Newton Mitsuhiro Kawase Mark J. Warner Jonathan P. Kellogg 《Estuarine, Coastal and Shelf Science》2008,80(4):545-554
Temporal and spatial patterns of variability in Puget Sound's oceanographic properties are determined using continuous vertical profile data from two long-term monitoring programs; monthly observations at 16 stations from 1993 to 2002, and biannual observations at 40 stations from 1998 to 2003. Climatological monthly means of temperature, salinity, and density reveal strong seasonal patterns. Water temperatures are generally warmest (coolest) in September (February), with stations in shallow finger inlets away from mixing zones displaying the largest temperature ranges. Salinities and densities are strongly influenced by freshwater inflows from major rivers during winter and spring from precipitation and snowmelt, respectively, and variations are greatest in the surface waters and at stations closest to river mouths. Vertical density gradients are primarily determined by salinity variations in the surface layer, with stations closest to river mouths most frequently displaying the largest buoyancy frequencies at depths of approximately 4–6 m. Strong tidal stirring and reflux over sills at the entrance to Puget Sound generally removes vertical stratification. Mean summer and winter values of oceanographic properties reveal patterns of spatial connectivity in Puget Sound's three main basins; Whidbey Basin, Hood Canal, and Main Basin. Surface waters that are warmed in the summer are vertically mixed over the sill at Admiralty Inlet and advected at depth into Whidbey Basin and Hood Canal. Cooler and fresher surface waters cap these warmer waters during winter, producing temperature inversions. 相似文献
18.
应用WOA13季节平均数据和BELLHOP模型,在季节、声源频率等因素确定的情况下,分10 m表面声源和250 m水下声源,分析北大西洋冬季东、西部海区的声波导情况。在给出不同海区位置的声速场和声波导具体信息的基础上,研究其规律:最小声速值和声道轴深度由直布罗陀海峡向外递减扩散,表层声速值和声速梯度由南向北递减,声跃层存在于低纬度海区,混合层在低纬度通常在100 m以内,在高纬度增加至100 m以上。10 m深度表面声源的汇聚区反转深度随纬度增加逐渐减少,西部海区深于东部海区;西部海区的汇聚区跨度大于东部海区,东西部跨度最大值出现在25°N和15°N,传播损失基本一致。250 m水下声源的汇聚区反转深度浅于10 m深度表面声源时,同样是西部海区大于东部海区,汇聚区跨度呈低-高-低规律,东西部跨度最大值出现在35°N和25°N;东部海区25°N以南、西部海区15°N以南,不同接收深度上的传播损失差异较大,以北差异较小。同时简要叙述了声影区对目标探测的影响。 相似文献
19.
千岛湖水温垂直分层的空间分布及其影响因素 总被引：1，自引：0，他引：1
湖泊热力分层及热力循环深刻影响深水湖泊生态系统。随着全球气候变暖,湖泊热力过程会发生显著变化。作为深水水库型湖泊,千岛湖的热力过程与水环境的变化紧密相连,为了分析千岛湖水体水温、湖泊热力分层参数(温跃层深度、厚度和强度)的分布,探讨温跃层深度与水温、水体透明度以及水深之间的关系,本文根据2014年7月份与2015年5月份对千岛湖全湖60个采样点的水体理化指标的垂向分布调查数据,计算得到千岛湖热力分层参数,进而分析其时空分布特征及主要影响因素。结果表明,千岛湖水体水温垂直分布呈现正温分布,春夏季全湖范围内均存在不同程度的温度分层现象,温跃层深度、厚度和强度均从上游河口向下游敞水区逐步增大,这种空间变化的趋势在7月份比5月份更显著。水温、透明度和水深是影响温跃层深度的主要因素。夏季湖泊热力分层稳定期温跃层深度与表层水温(0—2m)存在显著负相关关系,与透明度和水深存在正相关关系。 相似文献
20.
《African Journal of Marine Science》2013,35(1):55-62
The density of red crab Geryon maritae between 18°00′ and 18°30′S and in depths of 350-1 000 m was quantitatively examined by photography. This area, estimated to be approximately 92 000 ha, is part of the commercial crab ground off South West Africa. The biomass of red crab, up to 55,5 kg·ha?1, is one of the highest recorded off the African coast for the species. Density of red crab was highest in depths exceeding 600 m, the greatest density (350,2 crabs·ha?1) being recorded in the 600-699 m depth zone. Another crab, Bathynectes piperitus, was also photographed in the shallower depths of the survey area (300-500 m), and some density estimates for this species at those depths are presented. 相似文献