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1.
本文通过测定沉积物中钍的含量,了解到在南海中部13°30′N,113°—118°E的沉积断面上,钍的分布特征是由113°E向118°E方向减少。开始时减少迅速,114°E以东减少速度非常缓慢,钍的来源可能是来自该断面的西侧。 相似文献
2.
基于2012年8月12日至9月5日中国南海海洋湍流微结构剖面仪(Turbo Map)观测资料和温盐深剖面仪(CTD)资料,对南海中南部海域上层500m以浅的混合过程进行了分析。南海次表层高温高盐的水团和中层低温低盐的水团构成的垂向温盐环境,利于在该深度范围内盐指的发育。通过盐指与湍流相关参数的计算,评估了盐指在南海上层跨越等密面混合的作用。结果表明南海中部(18°N)相对于南海南部呈现高的温度耗散率(χ)、高的混合效率(Γ)、低湍动能耗散率(ε)及低浮性雷诺数(Rε)等特征,即中部盐指信号明显强于南部。但整体海域仍然呈现出"低Γ;高Rε"的湍流特征,表明盐指对混合的贡献较小,南海中南部的上层混合还是以湍流混合为主导。另外,南海南部的混合强于中部,且呈现出整体水柱均具有较强混合的特征,其原因可能和内潮与南部相对较浅而复杂的地形相互作用有关。 相似文献
3.
基于细尺度参数化方法,利用2000—2007年的历史水文剖面资料,分析了西北太平洋海区(135°—180°E,25°—45°N)跨等密度面湍流混合的时空分布特征。结果表明,垂直平均的耗散率与地形粗糙度的空间分布基本一致,且随经度自西向东减弱。在地形粗糙的地方,耗散率达O(10–8m2/s3),而在地形平坦的地方,耗散率仅O(10–11m2/s3)。另外,上层海洋混合存在明显的季节变化,在日本近岸的海区,耗散率冬季最强而夏季最弱,与风生近惯性能量之间存在显著的正相关;在大洋内区,耗散率冬季最强而秋季最弱,与风生近惯性能量的相关关系较弱。进一步地,本文分析了风应力在不同海区对混合的影响深度,结果显示在伊豆-小笠原海脊以西,风应力的影响深度最浅为620m,而在该海脊以东最深可达1740m。 相似文献
4.
利用1992—2002年的温盐深数据与2012—2016年的Argo数据,基于细尺度参数化方法研究了吕宋海峡及周边海域(12°—30°N,115°—129°E)湍流混合的时空分布特征,并分析了地形粗糙度、内潮以及风输入的近惯性能通量对湍流混合的影响。结果表明,吕宋海峡和东海陆坡处具有强混合的特征,扩散率高达4×10~(-3) m~2/s,主要是由内潮产生导致的,其中吕宋海峡主要是M2、K1和O1内潮的贡献,而东海陆坡处主要是M_2内潮的贡献;南海北部也呈现较强的混合,且陆坡处的混合比海盆高1—2个量级;南海中央海盆和离岸的菲律宾海混合较弱,扩散率为O (10-5 m2/s)。此外,在研究区域内,湍流混合的年际变化和季节变化均不明显,且混合扩散率与风输入的近惯性能通量未表现出明显的季节相关。 相似文献
5.
用已成功地模拟了大尺度环流和黑潮的三维、斜压以及具自由海水表面的数值模式,模拟了冬季南海流场、温度场和海面高度场。所用网格为0．25°×0．25°,垂直方向分为6层;除巴土海峡和台湾海峡外,其它边界假设为封闭;巴士海峡和台湾海峡的边界值用已模拟的大尺度环流值。模拟结果基本上反映了南海冬季环流的特征。从模拟结果可知,黑潮从巴士海峡南部进入南海后,其大部分又从对21°以北返回大洋。巴士海峡西侧的气旋型环流似乎具有相对的独立性;当然,涡旋东侧在巴士海峡的N向流可能与黑潮水混合,而且从这支流中分离出－小支流继续向北,汇入到“南海暖流”中。黑潮水虽然大部分返回太平洋,但是巴士海峡西侧的气旋型环流是由巴士海峡处的黑潮诱发的,南海海底地形对南海环流的形态（特别是对“南海暖流”的形成）有很大的影响。 相似文献
6.
海流对于海洋渔业、海洋表层初级生产力分布、海洋物质输运等理化生现象有着重要影响。文章利用海洋再分析流场资料,简要分析印度洋海区和南海海区(20°S—30°N,30°E—130°E)的流场年平均以及季节变化特点,得出以下结论:1南海海区流场的季节变化显著,受到季风、黑潮和地形的共同影响作用,在东北季风期间存在沿粤东沿岸至海南岛南侧转向沿越南沿岸的一支流系,该流系的强度变化影响爪哇海等南海南侧海区流场变化。2苏拉威西岛东侧和加里曼丹岛西侧流系有明显的季节变化,在流动强盛的时期这两支流系均是偏南向流动;从爪哇海流出的海流常年存在,夏季附近流速最大,最大流速分布在1.0m/s。3赤道印度洋海区和非洲东岸的沿岸流存在明显的季节变化,上层海区流动的低流速区存在流向切变;沿岸流最大流速在5-9月出现,可达1.8m/s以上,而赤道流系则在11月,可达0.8m/s以上。 相似文献
7.
利用2019年7月在长江口科学考察实验研究夏季航段(NORC2019-03-02)中获得的MSS90L湍流剖面仪的直接观测数据,本文计算并分析了该断面的湍动能耗散率ε和垂向湍扩散系数KZ的分布情况。湍动能耗散率的大小为1.72×10?10～2.95×10?5 W/kg;垂向湍扩散系数的大小为3.24×10?7～4.55×10?2 m2/s。湍动能耗散率和垂向湍扩散系数的分布相似,均为上层最强,底层次之,中层最弱。上层由于风应力的作用,使得湍动能耗散率和垂向湍扩散系数较大;温跃层处层化较强,抑制了湍动能的耗散和垂向上的湍混合。盐度锋面的次级环流会促使低盐水团脱离,锋面引起的垂向环流会加强海洋的湍混合。低盐水团与外界的能量交换较少,湍动能耗散率较弱。长江口海区存在明显的上升流和下降流,它们是由锋面的次级环流产生的;上升流和下降流的存在促进湍动能的耗散与湍混合。 相似文献
8.
利用1993~2017年海表面高度异常数据集,分析研究了西北太平洋季节内变化(20~120d)的整体分布特征,结果表明空间上季节内信号在20°N附近海域(16°~24°N)最强,时间上在6~8月达到一年中的最大值。在吕宋海峡东侧(123.875°E,20.125°N)季节内信号周期(70d)和传播速度(10.7~12.7cm/s)均大于吕宋海峡西侧(119.625°E, 20.125°N)(60 d, 6.5~7.8cm/s)。在大洋内部(123°~140°E, 18°~24°N)存在准90d的周期信号,传播速度约10.3cm/s。传播路径受黑潮的影响发生改变,由沿纬度西传转向向西北方向传播。第一斜压Rossby波理论对海表面高度季节内变化的周期和传播速度具有很好的解释性。 相似文献
9.
珠江河口底边界层湍流特征量研究 总被引：3，自引：0，他引：3
通过高频流速仪ADV和脉冲相干声学多普勒剖面仪PC-ADP对珠江河口崖门底边界层进行了三个测次潮内(25 h)顶点连续观测,利用观测数据计算分析了潮流底边界层内的湍流特征量及其时空变化.结果表明:1)对于半日潮流占优的河口,各湍流特征量均具有明显的四分之一周日的变化规律;2)湍流强度、床底应力和摩阻流速在潮内的平均值以位于河口湾的测点所测值最大,依次向上游递减,而湍动能耗散率则沿河口湾至上游逐渐增大;3)三个测次边界层内涡动粘滞系数的平均值分别为2.42×10 -3 m 2/s、2.20×10 -4m 2/s和6.16×10 -4 m 2/s,拖曳系数的均值为7.89×10 -3、1.63×10 -3和1.99×10 -2,两者潮内的变化均非常显著,相差可达一到两个数量级;4)在充分混合的潮流底边界层内,湍动能生成与耗散基本处于局部平衡状态,三个测次湍动能耗散率均值在8.89×10 -5 W/kg～7.43×10 -6 W/kg之间. 相似文献
10.
利用Argo浮标资料分析横跨吕宋海峡20.5°N断面的水文特征 总被引：2，自引：0，他引：2
基于Argo浮标资料,分析了一条横跨南海北部、吕宋海峡和西太平洋（20.5°N,114°~130°E）断面的海水温度、盐度的分布特征.其结果表明：Argo剖面资料得到的2008年秋季20.5°N断面海水的温度、盐度分布态势与气候态秋季的分布基本一致,主要差异在于南海次表层水的盐度极大值和西太平洋次表层水的盐度极大值,2008年秋季二者均比气候态秋季的低0.1左右.通过动力计算（选取1 200 m为速度零面）表明：Argo浮标剖面资料与融合的卫星高度计产品得到的20.5°N,117.5°~124.5°E断面的表层地转流北分量的分布比较吻合;吕宋海峡中部（20°~21°N）的黑潮主轴大致位于121.5°E附近,其东边界可达123°E,而西边界仅限于121°E以西,其可能原因是该季节黑潮的左侧存在着一个气旋式环流,阻碍了黑潮西进;黑潮在20.5°N断面的体积流量为27×106m3/s左右,最大流速约为55 cm/s,出现在70 m层左右. 相似文献
11.
A long-term mean turbulent mixing in the depth range of 200–1000 m produced by breaking of internal waves across the middle and low latitudes (40°S–40°N) of the Pacific between 160°W and 140°W is examined by applying fine-scale parameterization depending on strain variance to 8-year (2005–2012) Argo float data. Results show that elevated turbulent dissipation rate (ε) is related to significant topographic regions, along the equator, and on the northern side of 20°N spanning to 24°N throughout the depth range. Two patterns of latitudinal variations of ε and the corresponding diffusivity (Kρ) for different depth ranges are confirmed: One is for 200–450 m with significant larger ε and Kρ, and the maximum values are obtained between 4°N and 6°N, where eddy kinetic energy also reaches its maximum; The other is for 350–1000 m with smaller ε and Kρ, and the maximum values are obtained near the equator, and between 18°S and 12°S in the southern hemisphere, 20°N and 22°N in the northern hemisphere. Most elevated turbulent dissipation in the depth range of 350–1000 m relates to rough bottom roughness (correlation coefficient?=?0.63), excluding the equatorial area. In the temporal mean field, energy flux from surface wind stress to inertial motions is not significant enough to account for the relatively intensified turbulent mixing in the upper layer. 相似文献
12.
Turbulent mixing in the central equatorial Pacific has been quantitatively evaluated by analyzing data from microstructure measurements and conductivity temperature depth profiler (CTD) observations in a meridionally and vertically large region. The result that strong turbulent mixing with dissipation rate ε (>O(10?7) W kg?1), continuing from sea-surface mixed layer to low Richardson number region below, in the area within 1° of the equator, shows that turbulent mixing has a close relationship to shear instability. ε > O(10?7) W kg?1 and turbulent diffusivity K ρ > O(10?3) m2 s?1 were obtained from near-surface to 85 db at stations even southwardly beyond 3°S, where it is already far from the southern boundary (~2°S) of the Equatorial Undercurrent. Turbulence-induced heat flux and salinity flux were calculated, and both had their maxima in the equatorial upwelling region, though the former was downward and the latter was upward. Accordingly, vertical velocity in the upwelling region was estimated to be similar to the results derived by other methods. These fluxes and the vertical velocity suggest the critical importance of turbulent mixing in maintaining the well-mixed upper layer. Secondly, in the intermediate region (>500 db), turbulent eddies were investigated by applying Thorpe’s method to the CTD data. A large number of overturns were detected, with spatial-averaged K ρ (700–1,000 db) being 3.3 × 10?6 m2 s?1, and the corresponding K ρ-max reaching to O(10?4) m2 s?1 in the north (3°–13°N). The results suggest that, in the intermediate region, considerable turbulent mixing occurs and moderates the properties of the water masses. 相似文献
13.
《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(5):631-656
Full-depth conductivity-temperature-depth-oxygen profiler (CTDO2) data at low latitudes in the western North Pacific in winter 1999 were analyzed with water-mass analysis and geostrophic calculations. The result shows that the deep circulation carrying the Lower Circumpolar Water (LCPW) bifurcates into eastern and western branch currents after entering the Central Pacific Basin. LCPW colder than 0.98°C is carried by the eastern branch current, while warmer LCPW is carried mainly by the western branch current. The eastern branch current flows northward in the Central Pacific Basin, supplying water above 0.94°C through narrow gaps into an isolated deep valley in the Melanesian Basin, and then passes the Mid-Pacific Seamounts between 162°10′E and 170°10′E at 18°20′N, not only through the Wake Island Passage but also through the western passages. Except near bottom, dissolved oxygen of LCPW decreases greatly in the northern Central Pacific Basin, probably by mixing with the North Pacific Deep Water (NPDW). The western branch current flows northwestward over the lower Solomon Rise in the Melanesian Basin and proceeds westward between 10°40′N and 12°20′N at 150°E in the East Mariana Basin with volume transport of 4.1 Sv (1 Sv=106 m3 s−1). The current turns north, west of 150°E, and bifurcates around 14°N, south of the Magellan Seamounts, where dissolved oxygen decreases sharply by mixing with NPDW. Half of the current turns east, crosses 150°E at 14–15°N, and proceeds northward primarily between 152°E and 156°E at 18°20′N toward the Northwest Pacific Basin (2.1 Sv). The other half flows northward west of 150°E and passes 18°20′N just east of the Mariana Trench (2.2 Sv). It is reversed by a block of topography, proceeds southward along the Mariana Trench, then detours around the south end of the trench, and proceeds eastward along the Caroline Seamounts to the Solomon Rise, partly flowing into the West Mariana and East Caroline Basins. A deep western boundary current at 2000–3000 m depth above LCPW (10.0 Sv) closes to the coast than the deep circulation. The major part of it (8.5 Sv) turns cyclonic around the upper Solomon Rise from the Melanesian Basin and proceeds along the southern boundary of the East Caroline Basin. Nearly half of it proceeds northward in the western East Caroline Basin, joins the current from the east, then passes the northern channel, and mostly enters the West Caroline Basin (4.6 Sv), while another half enters this basin from the southern side (>3.8 Sv). The remaining western boundary current (1.5 Sv) flows over the middle and lower Solomon Rise, proceeds westward, then is divided by the Caroline Seamounts into southern (0.9 Sv) and northern (0.5 Sv) branches. The southern branch current joins that from the south in the East Caroline Basin, as noted above. The northern branch current proceeds along the Caroline Seamounts and enters the West Mariana Basin. 相似文献
14.
In the present study, we report N_2 fixation rate(~(15)N isotope tracer assay) and the diazotroph community structure(using the molecular method) in the western tropical North Pacific Ocean(WTNP)(13°–20°N, 120°–160°E). Our independent evidence on the basis of both in situ N_2 fixation activity and diazotroph community structure showed the dominance of unicellular N_2 fixation over majority of the WTNP surface waters during the sampling periods.Moreover, a shift in the diazotrophic composition from unicellular cyanobacteria group B-dominated to Trichodesmium spp.-dominated toward the western boundary current(Kuroshio) was also observed in 2013. We hypothesize that nutrient availability may have played a major role in regulating the biogeography of N_2 fixation.In surface waters, volumetric N_2 fixation rate(calculated by nitrogen) ranged between 0.6 and 2.6 nmol/(L·d) and averaged(1.2±0.5) nmol/(L·d), with 10 μm size fraction contributed predominantly(88%±6%) to the total rate between 135°E and 160°E. Depth-integrated N_2 fixation rate over the upper 200 m ranged between 150 μmol/(m~2·d)and 480 μmol/(m~2·d)(average(225±105) μmol/(m~2·d). N_2 fixation can account for 6.2%±3.7% of the depthintegrated primary production, suggesting that N_2 fixation is a significant N source sustaining new and export production in the WTNP. The role of N_2 fixation in biogeochemical cycling in this climate change-vulnerable region calls for further investigations. 相似文献
15.
Kojiro Ando Masaki Kawabe Daigo Yanagimoto Shinzou Fujio 《Journal of Oceanography》2013,69(2):159-174
To clarify the global deep-water circulation in the northwest Pacific, we conducted current observations with seven moorings at 40°N east of Japan from May 2007 to October 2008, together with hydrographic observations. By analyzing the data, while taking into consideration that the deep circulation has a northward component in this region and carries low-silica, high-dissolved-oxygen water, we clarified that the deep circulation flows within the region between 144°30′ and 146°10′E at 40°N on and east of the eastern slope of the Japan Trench with marked variability; the deep circulation flows partly on the eastern slope of the trench and mainly to the east during P1 (10 May–24 November 2007), is confined to the eastern slope of the trench during P2 (25 November 2007–20 May 2008), and flows on and to the immediate east of the eastern slope of the trench during P3 (21 May–15 October 2008). Previous studies have identified two branches of the deep circulation at lower latitudes in the western North Pacific; one flows off the western trenches and the other detours near the Shatsky Rise. It was thus concluded that the eastern branch flows westward at 38°N and then northward to the east of the trench, finally joining the western branch around 40°N during P1 and P3, whereas the eastern branch passes westward south of 38°N, joins the western branch around 38°N, and flows northward on the eastern slope of the trench during P2. 相似文献
16.
A. P. Nedashkovsky 《Oceanology》2012,52(4):467-477
The variability of the phosphates, silicates, alkalinity, oxygen, CO2 pressure, salinity, and temperature in the surface mixed layer (SML), as well as the variations of its thickness along the drift passage of the North Pole 35 station, are considered. The station drifted over the Nansen Basin mainly eastwards from ??105 to ??30° E. The surveys were performed from October of 2007 till June of 2008 at three-day intervals. The SML parameters are mainly determined by the advection and mixing with the underlying waters. The analysis of the hydrochemical variability shows that the surface waters at the eastern and western areas of the drift are of different origins. The waters of the eastern area were subjected to the impact of riverine runoff. These waters were spread westwards. The fraction of riverine waters in the eastern area amounts to 3%. In the western area of the drift, presumably transformed Atlantic waters were observed, which spread eastwards from the Fram Strait. The drift path of the station crosses the boundary of the water masses near 85° N and 45° E. 相似文献
17.
A general pattern for turbulent mixing in the upper layer of the South China Sea (SCS) is presented based on TurboMAP measurements in April and May 2010. The turbulence level decreased significantly overall from north to south, and weakened from east to west in the northern SCS. The average dissipation rate north of 18°N reaches 1.69 × 10?8 W/kg, approximately six times larger than that south of 18°N. The mean mixing efficiency in the SCS is 0.2, with a maximum of 0.31 near the Luzon Strait. At one repeatedly occupied station located in the central deep basin, the dissipation rate varies diurnally in the mixed layer and pycnocline due to diurnal heating and cooling by solar radiation and local barotropic tide, respectively. 相似文献
18.
利用2016年夏季长江河口现场水文特性与湍流微结构观测资料, 分析了长江河口水体温盐结构、层化发育、湍流与混合特征。结果表明: 1)夏季长江河口水体密度层化结构明显, 根据各层水体密度梯度差异, 可将水体分为底部混合层和上层密度跃层, 两部分的密度层化界限与浮力频率等值线lg N 2 = - 4.0接近。2)底部混合层湍动能耗散率大, 层化结构弱, 水体分层稳定性弱; 上层密度跃层湍动能耗散小, 层化结构强, 水体分层稳定性强, 这有利于河口内波的发育与传播。3)在密度层化的作用下, 水体的湍动能耗散率、湍动能剪切生成及浮力通量的能量关系在一定范围内符合湍动能局部能量平衡方程。不同层之间的湍流弗劳德数Frt和湍流雷诺数Ret在Frt-Ret平面上呈现明显的分区, 与经典的分层剪切流理论基本吻合。 相似文献
19.
Oceanic current data in the warm pool region of the western equatorial Pacific measured by upward-looking moored Acoustic
Doppler Current Profilers at two equatorial sites (147°E and 154°E) and two off-equatorial sites (2°N and 2°S, 156°E) during
TOGA/COARE Intensive Observing Period (IOP) from November 1992 to February 1993 are used to examine short-term variabilities
in the upper layer above 160–240 m. In time series of the zonal and meridional currents in many layers, spectral peaks are
found at periods around 2 days and 4 days in addition to high energies in a period range longer than 10 days. The signal with
the period of about 2 days has significantly high energies at all sites, and its magnitude is higher for the meridional current
than for the zonal one. This signal is especially active in the first half of IOP from November to December in 1992. In this
period, the quasi-2-day signal in the current field is coherent between northern (2°N) and southern (2°S) stations, but it
has no evident relationship with that in the surface wind field around the stations. The quasi-4-day signal with the period
of about 4 days has highest energies in layers above 160 m at the southern station, and is coherent between northern and southern
stations. Besides, the signal at the station of 2°S has a significantly high coherence with that in the wind at the southern
station, suggesting that it is a local phenomenon. 相似文献
20.
We present a comparison of the Global Ocean Data Assimilation System (GODAS) five-day ocean analyses against in situ daily data from Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) moorings at locations 90°E, 12°N; 90°E, 8°N; 90°E, 0°N and 90°E, 1.5°S in the equatorial Indian Ocean and the Bay of Bengal during 2002–2008. We find that the GODAS temperature analysis does not adequately capture a prominent signal of Indian Ocean dipole mode of 2006 seen in the mooring data, particularly at 90°E 0°N and 90°E 1.5°S in the eastern India Ocean. The analysis, using simple statistics such as bias and root-mean-square deviation, indicates that standard GODAS temperature has definite biases and significant differences with observations on both subseasonal and seasonal scales. Subsurface salinity has serious deficiencies as well, but this may not be surprising considering the poorly constrained fresh water forcing, and possible model deficiencies in subsurface vertical mixing. GODAS reanalysis needs improvement to make it more useful for study of climate variability and for creating ocean initial conditions for prediction. 相似文献