共查询到20条相似文献，搜索用时 31 毫秒
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During the past 100 years, sea-level appears to have risen by 10–15cm, probably due to the combined effects of thermal expansion of ocean-surface waters and net melting of glaciers and ice caps, associated with a small increase in global temperatures. This trend will almost certainly continue and accelerate if steadily increasing levels of carbon dioxide and other “greenhouse” gases in the atmosphere cause warming of the magnitude widely predicted by climate modellers. Rising air temperatures will cause increased melting from glaciers and ice caps, and rising sea-water temperatures will cause thermal expansion of the oceans. Moreover, warmer ocean waters could melt and weaken the many floating ice shelves that surround Antarctica, permitting increased ice discharge from glaciers that flow into them. All of these factors would cause sea-level to rise, and this paper presents and estimate of the total sea-level rise that could occur during the next century.If, as predicted by many climate models, global temperatures increase by an average of about 3°C, there is a good probability that sea-level will rise approximately 1m by the year 2100. Ultimately, such a rise would become very apparent to coastal populations, but initial change would be slow. Consequently, it is important to devise and “early warning system” for prompt detection of changes that will precede a detectable rise in sea level. These include: surface temperatures on land, oceans and ice sheets; sea-ice distribution; extent of summer melting on the polar ice sheets; areal extent and surface elevations of the ice sheets in Greenland and Antarctica. All of these parameters can be measured from space by satellites that are operating now or are planned for launch during the next few years 相似文献
3.
Dwight A. Sangrey 《Marine Georesources & Geotechnology》2013,31(1-4):45-80
Abstract The state of the art in marine geotechnology can best be defined with reference to what is known about soils on land. Differences between these two states of knowledge are the significant problems for the marine environment. Among the major problems addressed in this paper are (a) Sampling of soils, which involves much more serious disturbance than is considered acceptable on land. Disturbance results from several uniquely marine factors including total stress release and drilling mud overpressure, (b) Underconsolidation, or excess in situ pore pressure, caused by rapid rates of sedimentation, gas, leaks from an artesian pressure source, or cyclic loading. (c) Gas in sediments, which can cause an increase in the in situ pore pressure, hinders subsurface investigation, and is a major cause of sample disturbance. (d) The difficulty and necessity of in situ measurements. (e) The predominance of dynamic loading effects which can cause significant changes in soil behavior. A major difference between geotechnical engineering on land and in marine areas is the use of effective stress methods. Significant improvement in geotechnical engineering offshore can be achieved through the increased use of effective stress methods. Illustrations of these improvements are presented in this paper with particular reference to the problems of submarine slope stability. 相似文献
4.
Physical factors affecting El Niño events are subdivided into two categories. The first category includes those physical factors that have been demonstrated by modern science to have an effect on El Niño events. The second category comprises those physical factors that are only a hypothesis based on correlations that have yet to be corroborated to have affected El Niño events. This paper proposes the concept of a cause chain for an El Niño, pointing out that physical factors are linked and interdependent. The feedback effect and decrease-increase effect upon physical factors within the cause chain provide results superior to any single theory. We can only further explore the feedback effect and decrease-increase effect together with comprehensive analysis on the contributive ratio of these physical factors so as to improve the forecast accuracy of El Niño events. This represents a new way of thinking in the explanation of the cause of El Niño events. 相似文献
5.
The presence of striated myofibrils in the vacuolated cells of the pharynx of gymnolaemate bryozoans has been confirmed. The action of these musculo‐columnar cells is to cause the walls of the pharynx, which is triangular in cross‐section, to flex outward thereby sucking in food particles through the mouth. 相似文献
6.
Although it is well-known that reactions occur within estuaries to alter the flux of dissolved aluminum from rivers into the oceans, the nature and relative importance of these reactions are not well defined. In this study we show that sediment-water interactions can have a significant influence on dissolved Al distributions in estuaries. Undisturbed sediments will act as a sink for dissolved Al because of diffusion across the sediment-water interface and reaction of Al within the sediment. Resuspension of sediments will cause a release of dissolved Al into relatively Si-depleted estuarine waters.Flocculation of colloidal material may cause a net consumption of dissolved Al in estuaries. Our results indicate, however, that this process may not, in many cases, be the primary cause for curvature in Al-Cl? profiles. An alternative model, whereby Al is displaced from organic matter complexes and adsorption sites in the estuarine zone and reacts with Si and cations in solution, is consistent with the data presented in this study as well as many other studies. In this case, the extent of net Al removal in estuaries will be determined by both the amount and nature of the dissolved organic matter present. 相似文献
7.
Following extended exposure to eight non-ionic compounds, the crustacean isopod Idotea balthica basteri was studied by light microscopy and histoautoradiography. Cellular modifications were found in the nervous system, the gill pleopods, the digestive system, the gonads and the moulting gland. It is suggested that these modifications may eventually cause a variation in function and may even lead to the extinction of the species. 相似文献
8.
M. S. Barash 《Oceanology》2012,52(2):238-248
At the end of the Permian, at the boundary between the Paleozoic and Mesozoic (251.0 ± 0.4 Ma), the largest mass extinction
of organisms on the Earth occurred. Up to 96% of the species of marine invertebrates and ∼70% of the terrestrial vertebrates
died off. A lot of factors were suggested and substantiated to explain this mass mortality, such as the disappearance of environmental
niches in the course of the amalgamation of the continental plates into Pangea, sea level fluctuations, anoxia, an elevated
CO2 content, H2S intoxication, volcanism, methane discharge from gas-hydrates, climate changes, impact events (collisions with large asteroids),
or combinations of many of these reasons. Some of these factors are in subordination to others, while others are independent.
Almost all of these factors developed relatively slowly and could not cause the sudden mass mortality of organisms globally.
It could have happened when large asteroids, whose craters have been discovered lately, fell to the Earth. It is suggested
that the impact events “finished off” the already suppressed biota. A simultaneous change in many of the factors responsible
for the biodiversity, including those not connected in a cause-and-effect relationship, proves the existence of a common extrater-restrial
cause that affected both the changes in the internal and external geospheres and the activation of asteroid attacks (the Sun’s
transit of spiral arms of our galaxy, the Sun’s oscillations perpendicularly to the galactic plane, etc). 相似文献
9.
本文从实测资料入手,总结A、B两类容易引起湛江（A类）和汕头（B类）超警戒水位海潮的台风,重点分析这两类台风引起超警戒水位海潮的原因,据此给予了两类海潮的预报方法。 相似文献
10.
This paper investigates the characteristics of downrush flow from breaking waves on sloping seawalls, which cause toe scour. Flow visualization techniques were employed in these experiments. The velocity and pressure of the downrush flow at the toe were analyzed. It was found that the intensity of the flow is reduced as the structure slope decreases. The empirical formula for normalized flow intensity at the structure toe is presented as a function of the relative wave run-up height. 相似文献
11.
淋巴囊肿病毒是引起多种海、淡水鱼淋巴囊肿病的病原,且不同淋巴囊肿病毒分离株间存在一定的差异。本文对25株淋巴囊肿病毒分离株mcp基因的变异特征进行分析,结果表明:分离自同一宿主的淋巴囊肿病毒mcp基因序列并非完全一致,有些同宿主分离株间存在着较少的变异,其MCP蛋白序列间的变异位点多位于不规则结构域、属于非蛋白相互作用位点;分属不同基因型淋巴囊肿病毒分离株MCP蛋白序列间的变异位点也多位于不规则结构域,变异位点为蛋白相互作用位点的比率仅占21.98%。金头鲷淋巴囊肿病毒分离株LCDV-sa是一种新的淋巴囊肿病毒基因型,此25株淋巴囊肿病毒可分为7个基因型。对淋巴囊肿病毒变异的研究,可加深对其感染机制的认识,有助于了解其传播途径,可为淋巴囊肿病的防控提供重要的理论依据。 相似文献
12.
浮式生产储油卸油船(FPSO)经历满载和卸载,油船试验和多变的波浪载荷.此时结构中较高的初始残余应力常常已被释放,很大程度上影响了此类结构疲劳强度估算准确性.应用三维弹塑性有限元方法模拟FPSO典型焊接接头的残余应力释放,并用试验数据进行验证.对结构在变幅循环载荷下的残余应力释放进行研究,得到相关的残余应力释放预报公式.从而为提高FPSO在实际载况下疲劳强度估算准确性提供有价值参考. 相似文献
13.
粉质土海岸微地貌形成及泥沙问题的工程地质分析 总被引：1，自引：0，他引：1
通过对渤海湾粉质土海岸中的黄河水下三角洲的塌陷凹坑地貌形成、埕岛海域海底电缆中断、黄骅港外航道泥沙骤淤、东营港航道开挖试验段淤积等问题进行原因分析,结合该类海岸粉质土在波浪作用下的动力特性,认为风暴期间在强烈的波浪循环荷载作用下,粉质土在趋于液状化过程中强度降低,被波浪剪切形成振荡滑动,导致运动泥沙的异常增量。因此,在研究粉质土海岸泥沙运动问题中,应注意考虑由于海底粉质土的工程地质特性而造成的泥沙侵蚀或淤积量的异常变化。 相似文献
14.
You Yage
YuZhi Associated Professor Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou
. Professor Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou 《中国海洋工程》1995,(4)
In this paper, the extreme wave loads on an on-shore wave power device are investigated. First, boundary element method is applied to solve the three dimensional potential problem based on the small amplitude wave assumption. Then the motion of the Oscillating Water Column (OWC) inside the device and its laods on the device are calculated in time domain. Several protective techniques often applied are simulated by changing the constraint of the upper end of the chamber of the device. Numerical results are used to judge the effectiveness of these techniques. The investigation shows that damping can not effectively restrain the motion of OWC when the period of incident wave is long, which may cause dangerous loads on the structure. The shut chamber can effectively restrain the motion of OWC, but alternatively cause high pressure in the chamber. A Contracting opening with a Taper (CT) can exhaust a great amount of kinetic energy of OWC, and significantly decrease the loads. It is a promising protective tec 相似文献
15.
Shallow depressions (pockmarks) in recent sediments of the western Baltic Sea were investigated as the possible surface expression
of a deeper-seated hydrocarbon reservoir or a submarine freshwater discharge. Hydrocarbon gases extracted from the recent
sediments associated with pockmarks had molecular and isotopic compositions different from those in the deeper Schwedeneck
field. Salinities in the vicinity of the pockmarks decreased from brackish Baltic seawater to freshwater conditions with depth.
Freshwater outflow from underlying glacial sediment aquifers is the likely cause of these pockmarks. 相似文献
16.
海底铁锰结核纹层和柱状构造成因的探讨 总被引：5，自引：0，他引：5
铁锰结核的内部构造反映了其生长环境,也反映了生长机制,由于微生物生态演替造成的氧化和还原条件的交替,产生了具有不同矿物和化学成分的纹层和柱状构造。 相似文献
17.
Two processes are generally explained as causes of temporal changes in the stoichiometric silicon/nitrogen (Si/N) ratios of
sinking particles and of nutrient consumption in the surface water during the spring diatom bloom: (1) physiological changes
of diatom under the stress of photosynthesis of diatom and (2) differences of regeneration between silicon and nitrogen. We
investigated which process plays an important role in these changes using a one-dimensional ecosystem model that explicitly
represents diatom and the other non-silicious phytoplankton. The model was applied to station A7 (41°30′ N, 145°30′ E) in
the western North Pacific, where diatom regularly blooms in spring. Model simulations show that the Si/N ratios of the flux
exported by the sinking particles at 100 m depth and of nutrient consumptions in the upper 100 m surface water have their
maxima at the end of the spring diatom bloom, the values and timings of which are significantly different from each other.
Analyses of the model results show that the differences of regeneration between silicon and nitrogen mainly cause the temporal
changes of the Si/N ratios. On the other hand, the physiological changes of diatoms under stress can hardly cause these temporal
changes, because the effect of the change in the diatom's uptake ratio of silicon to nitrogen is cancelled by that in its
sinking rate. 相似文献
18.
本文研究了L-多巴、多巴胺、肾上腺素、去甲肾上腺素等儿茶酚胺类物质对魁蚶幼虫的变态诱导作用。结果显示:10-4mol/L的L-多巴有较为显著的诱导能力，而各浓度组多巴胺都不能诱导幼虫变态,且高浓度L-多巴和多巴胺对幼虫有毒害效应。10-4-10-6mol/L的肾上腺素和去甲肾上腺素都能表现出诱导作用并且对幼虫无害,为应用于魁蚶的苗种生产提供了可能。 相似文献
19.
海南岛风暴潮灾害承灾体初步分析 总被引：1，自引：0，他引：1
本文分析海南岛沿岸易受风暴潮灾害侵袭的区域,归纳了8类承灾体及承灾体所处高程与所淹水深的关系,以0518号台风引发的风暴潮灾害调查结果进行统计和比较,得出承灾能力最弱的系统因素是海水养殖业的结论。 相似文献
20.
Foundations of offshore structures are designed to withstand a combination of static and cyclic loads due to ocean waves. Wave action on offshore structures can cause a significant amount of cyclic horizontal and vertical forces to be transmitted to the soil through the foundation. In all these cases, these cyclic loads are considered to be superimposed over the initial sustained static stress due to the self-weight of structures. This study considers various factors that influence the development of deformation and pore water pressure in a typical cemented marine clay. These results show that the sustained static shear stress significantly influences the strength and deformation behavior of marine clay under cyclic loading. Up to a certain range of sustained static stress, there is an improvement in strength during cyclic loading and the cyclic strains are greatly reduced. 相似文献