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1.
利用Argo剖面浮标的轨迹资料研究了棉兰老岛以东中层(1000~2000 m?)深度上的中尺度环流特征. 浮标漂移深度的轨迹表明, 棉兰老岛以东的中层环流包含非常显著的中尺度信号特征. 浮标的漂移流速表明了该区域的气旋式涡旋和反气旋式涡旋在1000 m深度上的平均切向速度约为20 cm·s-1, 随着深度增加速度有所降低, 在2000 m深度上流速约为10 cm·s-1. 以上结果暗示在棉兰老岛以东区域, 依据零速度参考面的动力计算可能存在着较大误差. 涡旋的平均涡度和赤道β 平面罗斯贝数表明, 这些中尺度涡旋对于棉兰老岛以东中层环流的质量和涡度平衡起着重要的作用. 相似文献
2.
海洋反射地震通常用于调查、研究海底地质构造，勘探油气与天然气水合物资源.近期研究表明多道反射地震方法也可以对水柱的热盐细结构成像.中尺度涡与内波是重要的物理海洋现象，但是常规的物理海洋调查是在间隔若干公里的离散测站上进行的，水平分辨率较低，因此对中尺度涡的结构与内波的横向分布了解较差.本文利用在大西洋东部、南海采集的地震数据给出了低频反射地震可以对中尺度涡与内波清晰成像的新的证据.反射地震方法较传统海洋观测手段，具有明显的优势，主要体现在高的水平分辨率和短时间内对整个海水剖面进行成像方面．从地震剖面上，能够清楚地观测到中尺度涡、内波造成的反射特征变化，从而有助于改进对能量在不同尺度的海水运动之间传递过程的认识. 相似文献
3.
深海潮汐是深海混合过程的主要能量来源,对深海环流变异和沉积物搬运具有重要的调控作用.文章利用深水锚系观测系统在南海北部2100m水深处开展了近两年的高分辨率海流剖面观测,用于研究深海潮汐的季节性变化特征.通过谱分析显示,南海北部深海潮汐以全日潮为主,且在观测区域的深海中,全日潮和半日潮以垂向第一模态结构为主.斜压全日潮具有显著的季节性变化特征,夏季最强,深度平均的最大动能达86.7cm2s-2,分别是冬季的1.5倍、春秋季的2倍;而斜压半日潮没有明显的季节性变化.通过对比发现斜压全日潮的季节性变化受控于吕宋海峡附近的正压潮.另外,观测期间有三个强中尺度涡经过锚系站位,其中一个气旋式中尺度涡对深海海流影响较小,而另外两个反气旋式中尺度涡经过研究海域时可影响全水深海流,激发强亚惯性流,对深海潮汐产生边缘强化效应,并使深海斜压全日潮冬季的异相成分增强,占全日潮的85%.同时,中尺度涡对深海海水混合的增强弱化了海水层结,导致冬季的斜压全日潮流速减弱,低于夏季.南海北部深海潮汐季节性变化为研究深海盆沉积物在不同时间尺度上的分布及搬运过程提供了重要的动力机制. 相似文献
4.
利用地震海洋学方法在南海北部陆架和上陆坡区域发现了15个雾状层.这些雾状层的延伸长度从几千米到几十千米，厚度十几米到一百米，其顶界所处水深在135 m至715.5 m范围之间.雾状层在地震海洋学剖面上表现为强反射特征.不同于其他传统声学或光学方法，地震海洋学方法分辨率高，且能在短时间内对整个水体进行成像，可以记录到雾状层的时空变化特征，实现对雾状层的"四维"观测.南海北部上陆坡区域是内孤立波浅化、能量耗散集中的区域，在此过程中内孤立波会导致较大的波致流速，侵蚀海底使得表面沉积物再悬浮，进入水体，形成和维持雾状层的存在. 相似文献
5.
《地球物理学进展》2016,(4)
本文首次提出了一套从反射地震数据提取反射强度、反射体倾角和反射体波动振幅等属性参数的方法,并将其应用到南海西南海域.计算结果进一步表明南海西南海域在夏季主要的海洋学现象为西南季风诱发的冷流.它首先在越南东部海域自南向北流动,然后在约12°N附近开始向东弥散.海表面表现为温度低异常和海面高度低异常;水体内部则表现为以温度低异常为特征的底层冷水上涌.同时,由于地震海洋学数据具有高横向分辨率和全海洋深度成像的优点,从计算结果中还可以识别出3个视宽度为~20 km的上升流区;其上涌的视幅度约为50~150 m,且在不同的深度具有各自的特点.我们的结果可以为南海西南海域夏季上升流的精细化、定量化研究提供必不可少的数据支持;这套方法在其他海域的扩展应用也有望成为研究海水垂向分布横向变化的有力工具. 相似文献
6.
利用地震海洋学方法研究海洋内波已成为海洋地球物理学家与物理海洋学家共同关注的前沿问题.本文尝试利用当今时频分析的新手段——希尔伯特-黄变换中的经验模态分解（EMD）方法对南海东北部地震数据处理获得的垂直位移分布数据进行分解，获得了一些有新意的结果.分解结果表明，南海东北部海盆上方区域的内波包含波长约1.2、2.5、4、12.5 km的组成成分，其中波长约1.2、2.5 km的内波在200~1050 m的深度范围内上、下各层的波动基本耦合；波长约4 km与12.5 km的内波以600~700 m的水层为分界，其上、下部分的内波相位差90°，指示低波数内波能量的斜向传播.这些研究表明，EMD方法在内波运动学特征的地震海洋学研宄方面有良好的应用前景. 相似文献
7.
混合是海洋中普遍存在的一种海水运动形式,对多个海洋学分支的研究具有重要的影响.随着物理海洋学的研究重心从大尺度向中小尺度现象过渡,近年来混合问题的研究重心也逐渐转向了中小尺度现象.内波与中尺度涡都是非常重要的中小尺度物理海洋学现象,对海洋能量在不同尺度中的级联发挥着重要的作用.本文基于地震海洋学研究了海洋混合参数的提取方法,并以南海内波和地中海涡旋为例进行了计算和分析.结果显示,南海内波在200~600m深度范围内所引起的混合可达10-2.79 m2·s-1左右,比大洋的统计结果10-5 m2·s-1高出两个数量级以上.而地中海涡旋所引起的湍流混合率可达10-3.44 m2·s-1左右,与大洋统计结果相比高出1.5个数量级左右,并且地中海涡旋下边界的混合要强于上边界,这一特征与前人的研究一致,另外涡旋上边界之上以及侧边界的外侧也具有非常高的混合率. 相似文献
8.
利用地震数据反演海水的温盐分布是地震海洋学研究的一个重要方向.本文分析了采集于伊比利亚半岛西南缘海域的GOLR12低频地震数据和同步观测的XBT(eXpendable BathyThermograph)、CTD(Conductivity-Temperature-Depth)资料,将叠后约束波阻抗反演方法应用到海水温度、盐度剖面的计算当中,计算结果显示这种反演方法可以提供水平分辨率为6.25 m的温度和盐度资料,温度的精度约为0.16 ℃,可以为物理海洋学研究提供高横向分辨率的基础数据. 相似文献
9.
海洋中普遍存在的涡旋对全球海洋热、盐通量有重要贡献.一条于2000年6月在中美洲鹦鹉湾采集的地震剖面L115捕获到了一个海水次表层透镜状反射结构.透镜状反射的宽度约150 km,厚度约500 m,深度从100 m延伸到约600 m,核心深约200 m.结合和地震采集时间近同步的再分析数据中的流速和海水温度数据以及计算的Rossby数和Okubo-Weiss参数,将其解释为气旋涡,且可能是亚中尺度相干涡(SCV).由于地震剖面并未穿过涡旋核心水,涡旋顶底与核心水外层水团的双扩散作用使得剖面上的气旋涡中心表现为上下相邻的强反射双核结构.同航次采集的与L115大致正交的其他几条地震剖面也捕捉到了这个气旋涡.这些剖面整体的反射特征一致性较好,但和L115差异较大,涡旋内部普遍表现为近水平的中等强度反射.涡旋上边界为倾斜的强反射,这是气旋涡的等温线上凸引起的,这里也是亚中尺度锋面的发育区.这些地震剖面的涡旋反射特征的差异表明了该气旋涡空间结构的不对称性和时间演化特征. 相似文献
10.
湾流区涡旋对海洋垂向混合的影响 总被引：4，自引：0，他引：4
利用Argo高分辨率温盐数据和海面高度异常(SLA)数据对湾流区中尺度涡内外的混合情况进行了统计分析,结果表明,平均情况下300~540 m深度处反气旋涡内的混合率明显高于背景场,平均值量级达到4.0×10-5 m2 s-1,而涡外和气旋涡内平均混合率分别为1.6×10-5和0.8×10-5m2 s-1.反气旋涡内混合率量级在10-4 m2 s-1以上的概率达到29%,而涡外和气旋涡内情况下达到10-4 m2 s-1以上的概率仅为12%和5%.540~900 m深度上,涡内外的平均混合率量级一致.38个反气旋涡中有24个出现涡内部混合增强的现象,其中22个涡内剖面在观测时间前局地有大风过程存在或持续,混合情况与风应力有较好的对应关系,说明反气旋涡利于风生近惯性能量的下传.12个反气旋涡内剖面在540 m以下部分仍存在Thorpe尺度在5 m以上的水体翻转,甚至有3个达到了20 m以上,说明强混合现象在某些区域540 m以下的较深层仍然存在. 相似文献
11.
Karen Guihou Julien Marmain Yann Ourmières Anne Molcard Bruno Zakardjian Philippe Forget 《Ocean Dynamics》2013,63(7):793-808
The Northern current is the main circulation feature of the North-Western Mediterranean Sea. While the large-scale to mesoscale variability of the northern current (NC) is well known and widely documented for the Ligurian region, off Nice or along the Gulf of Lions shelf, few is known about the current instabilities and its associated mesoscale dynamics in the intermediate area, off Toulon. Here, we took advantage of an oceanographic cruise of opportunity, the start of a HF radar monitoring programme in the Toulon area and the availability of regular satellite sea surface temperature and chlorophyll a data, to evaluate the realism of a NEMO-based regional high-resolution model and the added value brought by HF radar. The combined analysis of a 1/64° configuration, named GLAZUR64, and of all data sets revealed the occurrence of an anticyclonic coastal trapped eddy, generated inside a NC meander and passing the Toulon area during the field campaign. We show that this anticyclonic eddy is advected downstream along the French Riviera up to the study region and disturbs the Northern current flow. This study aims to show the importance of combining observations and modelling when dealing with mesoscale processes, as well as the importance of high-resolution modelling. 相似文献
12.
Andrey G. Andreev Maxim V. Budyansky Michael Yu. Uleysky Sergey V. Prants 《Ocean Dynamics》2018,68(11):1503-1514
Large canyons incise the shelf break of the eastern Bering Sea to be preferred sites of the cross-shelf exchange. The mesoscale eddy activity is particularly strong near the shelf-break canyons. To study the mesoscale dynamics in the Navarin Canyon area of the Bering Sea, the time series of velocities derived from AVISO satellite altimetry between 1993 and 2015, drifters, Argo buoys, and ship-borne data are analyzed. We demonstrate that the strength of anticyclonic eddies along the shelf edge in spring and summer is determined by the wind stress in March–April. The increased southward wind stress in the central Bering Sea forced a supply of low-temperature and low-salinity outer shelf water to the deep basin and formation of the anticyclonic mesoscale circulation seaward of the Navarin Canyon. Enhanced northwestward advection of the Bering Slope Current water leads to increase in an ice-free area in March and April and increased bottom-layer temperature at the outer shelf. The strong (weak) northwestward advection of the eastern Bering Sea waters, determined by eastern winds in spring, creates favorable (unfavorable) conditions for the pollock abundance in the western Navarin Canyon area in summer. 相似文献
13.
QingYe Wang 《中国科学:地球科学(英文版)》2017,60(9):1719-1731
The three-dimensional structure of mesoscale eddies in the western tropical Pacific(6°S–20°N, 120°E–150°E)is investigated using a high-resolution ocean model simulation. Eddy detection and eddy tracking algorithms are applied to simulated horizontal velocity vectors, and the anticyclonic and cyclonic eddies identified are composited to obtain their three-dimensional structures. The mean lifetime of all long-lived eddies is about 52 days, and their mean diameter is 147 km. Two typical characteristics of mesoscale eddies are revealed and possible dynamic explanations are analyzed. One typical characteristic is that surface eddies are generally separated from subthermocline eddies along the bifurcation latitude(~13°N) of the North Equatorial Current in the western tropical Pacific, which may be associated with different eddy energy sources and vertical eddy energy fluxes in subtropical and tropical gyres. Surface eddies have maximum swirl velocities of 8–9 cm s~(-1) and can extend to about 1500 m depth. Subthermocline eddies occur below 200 m, with their cores at about 400–600 m depth, and their maximum swirl velocities can reach 10 cm s~(-1). The other typical characteristic is that the meridional velocity component of the eddy is much larger than the zonal component. This characteristic might be due to more zonal eddy pairs(two eddies at the same latitude),which is also supported by the zonal wavelength(about 200 km) in the high-frequency meridional velocity component of the horizontal velocity. 相似文献
14.
Generation mechanisms for mesoscale eddies in the Gulf of Lions: radar observation and modeling 总被引：2，自引：2，他引：0
Amandine Schaeffer Anne Molcard Philippe Forget Philippe Fraunié Pierre Garreau 《Ocean Dynamics》2011,61(10):1587-1609
Coastal mesoscale eddies were evidenced during a high-frequency radar campaign in the Gulf of Lions (GoL), northwestern Mediterranean Sea, from June 2005 to January 2007. These anticyclonic eddies are characterized by repeated and intermittent occurrences as well as variable lifetime. This paper aims at studying the link between these new surface observations with similar structures suggested at depth by traditional acoustic Doppler current profiler measurements and investigates the eddy generation and driving mechanisms by means of an academic numerical study. The influence of the wind forcing on the GoL circulation and the eddy generation is analyzed, using a number of idealized configurations in order to investigate the interaction with river discharge, buoyancy, and bathymetric effects. The wind forcing is shown to be crucial for two different generation mechanisms: A strong northerly offshore wind (Mistral) generates a vortex column due to the bathymetric constraint of a geostrophic barotropic current, which can surface after the wind relaxes; a southerly onshore wind generates a freshwater bulge from the Rhône river discharge, which detaches from the coast and forms a well-defined surface anticyclonic eddy based on buoyancy gradients. These structures are expected to have important consequences in terms of dispersion or retention of biogeochemical material at local scales. 相似文献
15.
利用南海地区28个陆地地震台站和2个布设于太平岛和东沙岛的新增海岛地震台站2011—2016年间的连续地震背景噪声波形数据,使用互相关方法计算得到了台站间的互相关函数,并提取出Rayleigh面波群速度和相速度频散曲线.采用快速行进和子空间方法反演获得了南海及周边地区12～40s周期的Rayleigh面波群速度和相速度图像,并联合反演得到了研究区深至60km的三维S波速度结构.考虑到南海数千米厚海水层对于面波频散反演的严重影响,本文在反演模型中加入了水层,显著提高了反演结果的可靠性.成像结果表明:南海及周边地区地壳上地幔顶部S波速度结构存在显著的横向不均匀性,并与这一区域的主要构造单元具有较好的空间对应关系.在5～10km深度,莺歌海—宋红盆地区的低速异常特征可能与盆地较厚的沉积层有关.在5～15km深度,海域高速异常区与海盆空间位置具有高度一致性,推测与海盆区地壳厚度相对陆缘区明显偏薄有关.当深度从20km增加至30km,海盆区的高速特征扩展至了陆缘地区,反映了地壳厚度从海盆至陆缘逐渐增厚的趋势,与OBS(海底地震仪)深地震剖面给出的地壳精细结构结果一致.至35～60km深度,海盆的高速异常特征依然明显,且速度值随深度增加整体呈现上升的趋势,推测南海海盆区的岩石圈厚度应该大于60km. 相似文献
16.
Nanda Kishore Reddy Busireddy Krishna K. Osuri Sanikommu Sivareddy Ramasamy Venkatesan 《Ocean Dynamics》2018,68(11):1431-1441
The Bay of Bengal (BoB) is a distinct oceanic region for mesoscale oceanic eddies. The sea level anomaly from the Archiving, Validation, and Interpretation of Satellite Oceanographic (AVISO) help to identify an unusual anti-cyclonic eddy (ACE) over head BoB during May–July 2014. Two Indian moored buoys (BD08 and BD09) located over this region aided to study the subsurface thermohaline structures of the ACE. Compared to no-eddy environment, the temperature and salinity showed an increment of ~?3–4 °C and ~?1–2 PSU, respectively, during the ACE life period. The temperature and depth of the isothermal layer at genesis (peak) stages are increased to ~?30 °C (~?30.7 °C) and ~?20 m (30 m) when compared with no-eddy conditions (28.2 °C and 10 m). The thermocline depth is deepened to 75 m at the peak stage, while it is 50 m in no-eddy condition. A temperature difference of 3 °C between no-eddy and peak stages of ACE is observed up to 50 m. The ocean heat content (OHC) at BD08 (BD09) during genesis and peak stages has increased by ~?72% (~?50%) and ~?247% (~?181%), respectively, when compared with no-eddy conditions. Moreover, the MOHC also shows a similar increment of ~?125% (~?123%) and ~?258% (~?284%), respectively. A noticeable influence is seen in turbulent fluxes and lower atmospheric variables during eddy life. This study highlights the capability of moored buoys in understanding the subsurface thermohaline features of the eddies over northern BoB. 相似文献
17.
Sergey V. Prants Andrey G. Andreev Michael Yu. Uleysky Maxim V. Budyansky 《Ocean Dynamics》2014,64(6):771-780
Using Lagrangian methods, we analyze a 20-year-long estimate of water flux through the Kamchatka Strait in the northern North Pacific based on AVISO velocity field. It sheds new light on the flux pattern and its variability on annual and monthly time scales. Strong seasonality in surface outflow through the strait could be explained by temporal changes in the wind stress over the northern and western Bering Sea slopes. Interannual changes in a surface outflow through the Kamchatka Strait correlate significantly with the Near Strait inflow and Bering Strait outflow. Enhanced westward surface flow of the Alaskan Stream across the 174°E section in the northern North Pacific is accompanied by an increased inflow into the Bering Sea through the Near Strait. In summer, the surface flow pattern in the Kamchatka Strait is determined by the passage of anticyclonic and cyclonic mesoscale eddies. The wind stress over the Bering basin in winter–spring is responsible for eddy generation in the region. 相似文献
18.
为了探明南海北部海陆过渡带的深部地壳结构,我们在香港外海域进行了一次海陆地震联洲的实验,利用固定地震台网远距离接收海上气枪信号,接收距离远达200多km,并利用此次实验的测线1剖面模拟得到了海陆过渡带的深部地壳速度结构.速度结构模型表明:研究区海陆过渡带的地壳结构非均匀性较明显,由陆至海沉积层有一个突然增厚的特点;莫霍面深度约为26～29 km,上地壳P波速度约为5.5～6.4 km/s,下地壳P波速度为6.5～6.9 km/s.在担杆列岛往海方向有一个低速破碎带,其上地壳P波速度为5.2～6.1 km/s,下地壳P波速度为6.2～6.4 km/s,结合野外地质调查的结果,推测它可能为滨海断裂带.在担杆列岛往陆方向香港和深圳之间的研究区域,莫霍面有较大起伏,可能与此处发育的海丰断裂有关. 相似文献
19.
20.
Mesoscale circulation along the Sakhalin Island eastern coast 总被引：1，自引：1，他引：0
Sergey V. Prants Andrey G. Andreev Michael Yu. Uleysky Maxim V. Budyansky 《Ocean Dynamics》2017,67(3-4):345-356
The seasonal and interannual variability of mesoscale circulation along the eastern coast of the Sakhalin Island in the Okhotsk Sea is investigated using the AVISO velocity field and oceanographic data for the period from 1993 to 2016. It is found that mesoscale cyclones with the horizontal dimension of about 100 km occur there predominantly during summer, whereas anticyclones occur predominantly during fall and winter. The cyclones are generated due to a coastal upwelling forced by northward winds and the positive wind stress curl along the Sakhalin coast. The anticyclones are formed due to an inflow of low-salinity Amur River waters from the Sakhalin Gulf intensified by southward winds and the negative wind stress curl in the cold season. The mesoscale cyclones support the high biological productivity at the eastern Sakhalin shelf in July– August. 相似文献