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91.
A variance spectrum of climatic variability is presented that spans all time scales of variability from about one hour (10−4 years) to the age of the Earth (4 × 109 years). An interpretive overview of the spectrum is offered in which a distinction is made between sources of variability that arise through stochastic mechanisms internal to the climatic system (atmosphere-ocean-cryosphere) and those that arise through forcing of the system from the outside. All identifiable mechanisms, both internal and external, are briefly defined and clarified as to their essential nature. It is concluded that most features of the spectrum of climatic variability can be given tentatively reasonable interpretations, whereas some features (in particular the quasi-biennial oscillation and the neoglacial cycle of the Holocene) remain fundamentally unexplained. The overall spectrum suggests the existence of a modest degree of deterministic forms of climatic change, but sufficient nonsystematic variability to place significant constraints both on the extent to which climate can be predicted, and on the extent to which significant events in the paleoclimatic record can ever manage to be assigned specific causes. 相似文献
92.
93.
Plastic pellets on New Zealand beaches 总被引:1,自引:0,他引:1
Murray R Gregory 《Marine pollution bulletin》1977,8(4):82-84
Small plastic pellets, of the kinds commonly being recorded as contaminants on beaches, and in coastal as well as oceanic waters adjoining industrialized regions of the Northern Hemisphere are also widely distributed on the beaches of New Zealand. 相似文献
94.
旋转多基线数字近景摄影测量 总被引:5,自引:0,他引:5
提出了一种全新的数字近景摄影测量方法——旋转多基线数字近景摄影测量。该方法通过应用旋转摄影增大了摄影视场角,应用"多基线"的摄影方式增大了摄影交会角,提高了交会精度,并且解决了近景摄影测量中大交会角影像难以实现自动匹配的困难。同时,该方法将传统的区域网空中三角测量应用于近景摄影测量,用于影像外方位元素的解算,在提高精度的同时减少了外业工作量,提高了生产效率。 相似文献
95.
John W. Murray 《Marine Geology》1976,22(2):103-119
On any area of continental shelf the foraminiferal assemblage in the bottom sediment is likely to be composed of an indigenous benthic component and an allochthonous planktonic component sedimented from the water column above. Planktonic forminiferids are essentially oceanic and it seems clear that their presence in shelf sediments is often due to transport from an oceanic source. Evidence from the Celtic Sea, northwestern Gulf of Mexico, Persian Gulf and Andaman Sea shows that with passage away from the ocean there is a reduction in the planktonic—benthic ratio in the bottom sediment, a progressive decrease in size of the planktonic tests and a reduction in diversity of the planktonic assemblage. Thus a study of the relationships between the planktonic and benthic foraminiferids in these areas gives a measure of proximity to or isolation from the ocean. It is suggested that these relationships are useful tools in the interpretation of palaeoecology and in the reconstruction of former patterns of water circulation. 相似文献
96.
采用生态学单因子梯度试验方法,进行了白脊藤壶金星幼体的室内培养以及附着基、温度、盐度、幼体密度和幼体低温保存时间等因子分别对白脊藤壶金星幼体附着的影响的研究,结果表明,在培养水体为水温25℃、盐度30的膜滤海水,幼体培养密度为1只/ml,饵料为牟氏角毛藻,投饵量为(0.75-5)×10 5 cells/ml的培养条件下,白脊藤壶无节幼体在培养4天后即大部分顺利发育至金星幼体阶段,实现了白脊藤壶金星幼体在实验室内的大量培养.另一方面,实验结果还表明,在白脊藤壶金星幼体附着抑制实验中,玻璃培养皿和聚苯乙烯六孔板都可采用作为附着基,温度、盐度、幼体密度及幼体低温保存时间的适宜范围分别为20-35℃、15-45、1-20只/ml和0-8天.本研究结果揭示了白脊藤壶可作为筛选天然海洋防污产物的模型生物,并确定了其基础实验条件的适宜范围. 相似文献
97.
Aurora C. Elmore Robert C. Thunell Richard Styles David Black Richard W. Murray Nahysa Martinez Yrene Astor 《Journal of South American Earth Sciences》2009,27(2-3):197-210
The varved sediments that accumulate in the Cariaco Basin provide a detailed archive of the region’s climatic history, including a record of the quantity of fluvial and wind-transported material. In this study, we examine the sedimentological characteristics (clay mineralogy and grain size) of both surface sediments and sinking lithogenic material collected from sediment trap samples over a three-year period from 1997 to 2000. Data from biweekly sediment trap samples show a tri-modal particle size distribution, with prominent peaks at 2, 22 and 80 μm, indicating sediment contributions from both eolian and fluvial sources. The clay mineralogy of the water column samples collected from 1997 to 1999 also shows distinctive characteristics of eolian and fluvial material. An examination of surface sediment samples from the Cariaco Basin indicates that the Unare River is the main source of riverine sediments to the eastern sub-basin. By combining these sedimentological proxies, we estimate that ~10% of the terrigenous material delivered to the Cariaco Basin is eolian, while ~90% is fluvial. This represents an annual dust accumulation rate of ~0.59 mg/cm2/yr. Since aerosols are closely linked to climate variability, the ability to quantify paleo-dust fluxes using sedimentological characteristics will be a useful tool for future paleoclimate studies looking at sub-Saharan aridity and latitudinal migration of the Intertropical Convergence Zone. 相似文献
98.
99.
盐城海岸带湿地景观格局变化研究 总被引:3,自引:0,他引:3
利用4个时相的陆地卫星遥感影像及相关资料,在遥感和地理信息系统技术支持下,对盐城国家级自然保护区的核心区和缓冲区进行了景观格局分析。结果表明,从1988~2002年,淤泥质滩涂面积增长了13.33%;分形维数从1.0991上升到1.1166,蔓延度指数从76.4426下降到53.1142,表明研究区形状趋于规则,人为干扰程度增大,景观有破碎有上升的趋势,该边缘生境异质性在逐步增强;人类对滩涂的影响增加,逐渐成为影响该生态系统的主要力量。 相似文献
100.