声波从海底沉积层上的反射     

唐应吾  笪良龙 《中国海洋大学学报(自然科学版)》1998,(3)

假设海底为一液态层复盖一孔隙弹性固体半空间,用声阻抗的概念,导出了其上的声反射系数的唯象公式。再将松散的沙（泥）质沉积物中的声阻抗的表式用于液态层,建立了反射系数与沙（泥）质沉积物的具体参数的联系。文末对高声频情况下的海底上的声反射系数进行了简化。并对几个特例作了数值计算。  相似文献   

Spatial distribution of primary production off Sanriku, northwestern Pacific, during spring estimated by Ocean Color and Temperature Scanner (OCTS)   总被引：2，自引：0，他引：2  

Joji Ishizaka 《Journal of Oceanography》1998,54(5):553-564

An algorithm to estimate primary production by chlorophylla and sea surface temperature from satellite was evaluated with primary production data from the Ocean Color and Temperature Scanner (OCTS) Sanriku field campaign. The algorithm was applied to the data of OCTS on the Advanced Earth Observing Satellite (ADEOS) off Sanriku, North Pacific, on April 26, 1997. The wavelength-, time-, and depth-resolved model reasonably estimated the chlorophyll-specific primary production of each depth and water column integrated primary production. Although the model parameters were adjusted with the photosynthesis-irradiance curves obtained in the region, the resultant primary production was not significantly different from the global model of Antoine and Morel (1996). This is probably because there is considerable variability in the physiological parameters in this limited area, off Sanriku, and in the limited time, spring. Estimated integrated primary production was well correlated with chlorophylla but not with temperature. This indicates that the temperature dependence of the primary production was less than the variability caused by chlorophylla concentration.  相似文献   

Temporal variations of surface oceanic and atmospheric CO2 fugacity and total dissolved inorganic carbon in the northwestern North Pacific     

Tomonori Watai  Masaaki Kikuchi  Takakiyo Nakazawa 《Journal of Oceanography》1998,54(4):323-336

In order to examine temporal variations of the surface oceanic and atmospheric fCO₂ and the DIC concentration, we analyzed air and seawater samples collected during the period May 1992–June 1996 in the northwestern North Pacific, about 30 km off the coast of the main island of Japan. The atmospheric CO₂ concentration has increased secularly at a rate of 1.9 ppmv yr⁻¹, and it showed a clear seasonal cycle with a maximum in spring and a minimum late in summer, produced mainly by seasonally-dependent terrestrial biospheric activities. DIC also showed a prominent seasonal cycle in the surface ocean; the minimum and maximum values of the cycle appeared in early fall and in early spring, respectively, due primarily to the seasonally-dependent activities of marine biota and partly to the vertical mixing of seawater and the coastal upwelling. The oceanic fCO₂ values were almost always lower than those of the atmospheric fCO₂, suggesting that this area of the ocean acts as a sink for atmospheric CO₂. Values varied seasonally, mainly reflecting seasonal changes of SST and DIC, with a secular increase at a rate of 3.7 μatm yr⁻¹. The average values of the annual net CO₂ flux between the ocean and the atmosphere calculated by using the different bulk equations ranged between −0.8 and −1.7 mol m⁻²yr⁻¹, and its magnitude was enhanced and reduced late in spring and mid-summer, respectively, due mainly to the seasonally varying oceanic fCO₂.  相似文献   

赤道海洋波动弱非线性动力学系统浅析   总被引：2，自引：0，他引：2  

王凡  吴德星  冯士笮  侍茂崇 《海洋科学》1998,22(3):40-42

通过对连续层化条件下赤道海洋波动及相关环流特征尺度和物理量的尺度分析,全面分析了赤道海洋波动及其相关环流所属动力学系统的性质。分析结果表明,该系统为以参数ε为表征的弱非线性动力学系统,在此基础上建立了适合描述赤道波非线性效应的动力学模型。  相似文献   

把海洋经济作为“1号工程”全力抓好     

滕宝玉 《海岸工程》1998,17(2):59-62

荣成市确立了把海洋经济作为“1号工程”全力抓好的经济发展思路,决心继续保持全国第一渔业大县的位次。为此,提出了三条措施：①对海洋经济的地位和作用还要再认识;②要有建设国内外一流大企业的雄心壮志;③要找准今后海洋经济大发展的“起重杠杆”。  相似文献   

Eustatic and hydrodynamic controls on the architecture of a deep shelf sand bank (Celtic Sea)   总被引：3，自引：0，他引：3  

Jean-Yves Reynaud  Bernadette Tessier  Jean-Noël Proust  Robert Dalrymple  Tania Marsset  Marc De Batist  Jean-François Bourillet  & Gilles Lericolais 《Sedimentology》1999,46(4):703-721

The architecture of a tidal sand bank in the south-eastern Celtic Sea was examined using very high-resolution seismic surveys. The bank comprises four depositional units. The lowest unit 1 is characterized by gently dipping (1–8°) strata that strike parallel to the length of the bank. Unit 1 is erosionally overlain by unit 2, which forms the bulk of the bank. This unit consists of stacked sets of downcurrent-dipping (7–12°) master bedding formed by climbing, sinuous-crested tidal dunes that are up to 20 m high. These deposits are locally incised by an anastomosed channel network (unit 3) that may represent a buried swatchway system. The upper part of the bank comprises wave-related deposits that are mainly preserved on the bank flanks (unit 4). The outer bank surface is erosional. The bank is believed to have formed during the last post-glacial sea-level rise. The facies evolution from unit 1 to unit 3 indicates an upward increase in tidal energy, mainly characterized by the thickening of dune cross-bed sets in unit 2. The majority of bank growth is inferred to have occurred in water depths of the order of 60 m. This evolution was controlled by relative sea-level rise, which is likely to have caused an episode of tidal resonance with associated strong tidal currents that were responsible for the incision of the deep, cross-cutting channels of unit 3. The transition to wave-dominated sedimentation in unit 4 is related to the decay of resonance with continued sea-level rise.  相似文献   

Fractal analysis of bathymetry and gravity profiles across the Chagos-Laccadive Ridge and the Carlsberg Ridge in the Indian Ocean     

B. Ashalatha  R. N. Singh 《Journal of Earth System Science》1999,108(2):81-85

Gravity and bathymetry data have been extensively used to infer the thermo-mechanical evolution of different segments of the oceanic lithosphere. It is now understood that magmatic fluid processes involved in the accretion of oceanic crust are spatially complex and episodic. The nature of these processes which are in general nonlinear, can be described using fractal analysis of marine geophysical data. Fractal analysis has been carried out for gravity and bathymetry profiles over the aseismic Chagos-Laccadive Ridge and the spreading Carlsberg Ridge. The Iterated Function Systems (IFS) have been used to generate synthetic profiles of known dimension (D) and these are compared with the observed profiles. The D for the data sets are in the range of 1–1.5. The D for gravity profiles is less than those of bathymetry and the D for gravity and bathymetry over spreading ridge is higher than the aseismic ridge. The low fractal dimension indicates that the processes generating them are of low dimensional dynamical systems.  相似文献   

深海橄榄岩研究进展   总被引：2，自引：0，他引：2  

王金荣  郭原生 《地球科学进展》1999,14(6):566-570

很久以来,深海橄榄岩一直被认为是洋中脊下地幔熔融残留体,但最近深海橄榄岩实际矿物组分研究和全岩化学成分重建的结果表明,深海橄榄岩是洋脊下地幔熔融残留体和过量橄榄石的混合物。深海橄榄岩的成因是洋脊下上隆地幔降压熔融作用和熔体上升通过地幔最上部的热边界层时发生冷却、结晶出橄榄石的联合作用的结果。地幔熔融程度越高,深海橄榄岩越亏损,则含有越多的过量橄榄石。为此,只要把深海橄榄岩中过量的橄榄石剔除后,其实际矿物组分就能有效地反映洋脊下地幔熔融作用和熔融萃取过程。  相似文献   

洋脊三联点研究进展     

吴树仁  陈庆宣  谭成轩 《地质科技情报》1999,18(1):13-18

概述了８０年代后期以来洋脊三联点构造研究方面的某些新资料和新成果,综合分析了全球洋脊三联点构造的主要类型和基本特征;重点论述ＲＲＲ型和ＲＲＦ型洋脊三联点轨变结构特性、几何形态、运动状态和构造演化过程,并以具有微板块的三联点结构演化过程分析为例,简要讨论洋脊三联点构造研究的全球构造意义 。  相似文献   

一种模拟三维海流运动的差分方法     

黄平 《热带海洋学报》1999,18(1):31

提出了一种模拟三维海流运动的隐式差分方法,井给出其计算步骤。通过对该差分方法的稳定性分析可以发现,它的时间步长取值有较大的灵活性。该方法被用于崖门海域的海流模拟。实例计算表明,该差分方法计算过程稳定,计算结果合理,能较好地反映出三维海流运动的特征。  相似文献