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941.
Sachiko Oguma Tsuneo Ono Akira Kusaka Hiromi Kasai Yasuhiro Kawasaki Tomonori Azumaya 《Journal of Oceanography》2008,64(4):525-539
In this study we used two stable isotopes, δ13C and δ18O, for water mass classification in the coastal region off eastern Hokkaido. δ13C* values, which were corrected for the biological effect, and δ
18O values up to 300 m depth suggested that the isotopic character of the onshore and offshore water in the southern Okhotsk
Sea, the Nemuro Strait and the western North Pacific could be explained by the mixing of three source waters: the Oyashio
water (OYW), Soya Warm Current water (SWCW) and East Sakhalin Current water (ESCW). In summer, δ
13C*-δ
18O plots indicated mixing between SWCW from the southern Okhotsk Sea and OYW in the Pacific coast of southeastern Hokkaido,
while temperature-salinity plots of the onshore water showed minimal difference from the offshore OYW. In winter, on the other
hand, the mixed water of ESCW and OYW (or SWCW) appeared in the Pacific coastal region, distributed as cold, low salinity
onshore water. Finally, we estimated mixing ratios of OYW, SWCW and ESCW in the coastal region of western North Pacific using
their mean values of δ
13C* and δ
18O as endmembers. These results suggest seasonal and yearly changes of water mass combination en route from the southern Okhotsk
Sea to the western North Pacific. 相似文献
942.
943.
加蓬G4-188区块是一个新的海外勘探区块,在钻井过程中遇到了井壁垮塌、气侵、井斜控制困难等诸多难题,影响了钻井施工的速度。针对这些难题,实施了解决G4-188区块钻井施工难点的各项技术措施,为G4-188区块后续钻井施工提供了有益的技术支持。 相似文献
944.
根据低渗油田和特低渗油田的特点,研制出PVDF管式超滤膜,开展室内基础研究,并在江苏台兴油田进行中试和大规模的现场试验。经过处理后,水质标准达到油田回注水A1标准(SY/T5329-1994),满足了低渗油田和特低渗油田的注水要求。 相似文献
945.
946.
947.
Hirokazu Ozaki Hajime Obata Mikio Naganobu Toshitaka Gamo 《Journal of Oceanography》2009,65(2):235-244
We measured potential temperature, salinity, and dissolved oxygen profiles from the surface to the bottom at two locations
in the north Ross Sea (65.2°S, 174.2°E and 67.2°S, 172.7°W) in December 2004. Comparison of our data with previous results
from the same region reveals an increase in potential temperature and decreases in salinity and dissolved oxygen concentration
in the bottom layer (deeper than 3000 m) over the past four decades. The changes were significantly different from the analytical
precisions. Detailed investigation of the temperature, salinity, dissolved oxygen and σ
3 value distributions and the bottom water flow in the north Ross Sea suggests a long-term change in water mass mixing balance.
That is to say, it is speculated that the influence of cool, saline, high-oxygen bottom water (high-salinity Ross Sea Bottom
Water) formed in the southwestern Ross Sea has possibly been decreased, while the influences of relatively warmer and fresher
bottom water (low-salinity Ross Sea Bottom Water) and the Adélie Land Bottom Water coming from the Australia-Antarctic Basin
have increased. The possible impact of global warming on ocean circulation needs much more investigation. 相似文献
948.
The Changjiang (Yangtze) Estuary is located in the East China Sea shelf with shallow water. Affected by the tide mixing and the runoff of the Changjiang River and the Qiantang River, the turbidity is very high. Generally, the water-leaving radiance is high in the turbid water because of the large particle scattering. Based on the in-situ data and ocean color remote sensing data of SeaWiFS, it was found that there was a black water region with the normalized water-leaving radiances less than 0.5 mW/(cm2·μm2·... 相似文献
949.
The overall effects of trawling on benthic habitats and their assemblages are dependent on the distribution and intensity of trawl effort. The benthic habitats of the Spencer Gulf prawn trawling grounds are subjected to known variable levels of trawling disturbance recorded from fisher's logbooks. These habitats have not been quantitatively investigated. The aim of the study was firstly to characterise the macro-faunal and -floral assemblages and secondly, to comparatively assess trawl impact by testing the null hypothesis of no differences between five sites exposed to different intensity of trawl effort. The distribution and abundance of benthic macro-fauna and -flora were studied at two sampling resolutions by using beam trawl sampling (10,000 m2) and underwater stereophotography (4.5 m2) at five sites with different levels of trawl disturbance (effort). The results showed that the Spencer Gulf prawn trawling grounds are characterised by sandy sediments with a low content of silt and clay, with the exception of one site with very fine gravel. Biomass, abundance and cover of macro-fauna and -flora were generally low throughout, but with large differences among sites. Biomass, abundance and cover were found to be negatively correlated to both trawl hours from 1994–1998 and during the period of study. ANOSIM and SIMPER analyses using biomass, abundance and percentage cover as variables showed significant differences between sites with eight species or taxonomic groups contributing more than 10% to the observed similarity within sites. The two northern sites were dominated by sponges and the bearded mussel, Trichomya hirsutus, and the southern hammer oyster, Malleus meridianus. Other species that contributed to the similarity within sites were the ascidian, Polycarpa viridis, mobile epifauna (the blue swimmer crab, Portunus pelagicus, and the western king prawn, Penaeus (Melicertus) latisulcatus) and demersal fish species (Degens leatherjacket, Thamnaconus degeni, and the Melbourne silver belly, Parequula melbournensis). Simpson's Index of Diversity (1 − λ) and species richness in the beam trawl samples were fairly even across all sites, but a significant effect of site was found in the stereophotographic transect samples. It was concluded that prawn trawling has a strong influence on the structure of the benthic habitats of the Spencer Gulf prawn fishing grounds highlighted by the magnitude of change and the strength of the gradient of effects. Confounding factors linked to the biophysical attributes of the sites are believed to be minor. 相似文献
950.
This study describes a new convenient and robust system developed to measure benthic boundary layer properties, with emphasis placed on the determination of bed shear stress and roughness height distribution within estuarine systems by using velocity measurements. This system consisted of a remotely operated motorised traverser that allowed a single ADV to collect data between 0 and 1 m above the bed. As a case study, we applied the proposed traversing system to investigate bottom boundary layer (BBL) hydraulic properties within Coombabah Creek, Queensland, Australia. Four commonly-employed techniques: (1) Log-Profile (LP); (2) Reynolds stress (RS); (3) Turbulent Kinetic Energy (TKE); and (4) Inertial Dissipation (ID) used to estimate bed shear stresses from velocity measurements were compared. Bed shear stresses estimated with these four methods agreed reasonably well; of these, the LP method was found to be most useful and reliable. Additionally, the LP method permits the calculation of roughness height, which the other three methods do not. An average value of bed shear stress of 0.46 N/m2, roughness height of 4.3 mm, and drag coefficient of 0.0054 were observed within Coombabah Creek. Results are consistent with that reported for several other silty bed estuaries. 相似文献