青藏高原大地构造演化——主要构造—热事件的制约及其成因探讨

尽管青藏高原具有至少5 000万年漫长的演化历史,但是我们对它的认识多是基于一些持续时间很短的构造、沉积、热和气候等事件。在前人的研究基础上,本文对发生在高原内的主要构造—热事件进行梳理,并在时空上进行对比,试图确定相对合理的动力学控制因素。在新生代早期(～50 Ma)和中新世中晚期(～10 Ma),印度板块运动速率发生两次大幅度衰减,前一事件被认为与印度与欧亚大陆碰撞有关,后一事件被认为与高原向外扩展有关,成因是高原的底部岩石圈的剥离和由此引发的均衡反弹。除此以外,在高原内还发生过两次事件,虽然它们没有反应在印度板块运动速率的变化,但是留下的痕迹遍布高原。一次是高原内部区域性挤压缩短的停止,平坦的高原面得以发育,另一次是高原周边山脉的隆升,这两次事件都发生在新生代中期(～25 Ma)。这两次构造事件呈现的"此消彼长"关系反映出高原向外的扩展,成因是否是高原岩石圈底部的剥离还是个未知数。由此可以得出结论,即:中央高原现今的构造与地貌格架定型于早期事件(～25 Ma),而高原周边造山带现今的构造和地貌格架定型于晚期事件(～10 Ma)。即使是新生代中期的扩展事件,在时间上也远远滞后于印度与欧亚大陆的碰撞时间,青藏高原新生代早期(50～35 Ma)在很大程度上仍是一段哑历史,该时期到底发生了什么？这是一个值得探索的科学问题。     

Post‐glacial vegetation reconstruction and a possible 8200 cal. yr BP event from the low arctic of continental Nunavut,Canada

Climate models suggest that the global warming during the early to mid‐Holocene may have partly resulted from the northward advance of the northern treeline and subsequent reduction of the planetary albedo. We investigated the Holocene vegetation history of low arctic continental Nunavut, Canada, from a radiocarbon‐dated sediment core from TK‐2 Lake, a small‐lake ca. 200 km north of the limit of the forest‐tundra. The pollen and loss‐on‐ignition data indicate the presence of dwarf shrub tundra in the region since the beginning of organic sedimentation at ca. 9000 cal. yr BP with dominance of Betula, especially since 8700 cal. yr BP. At 8100–7900 cal. yr BP the dominance of the shrub tundra was punctuated by a transient decline of Betula and coincident increases of Ericaceae undiff., Vaccinium‐type, and Gramineae. This suggests an abrupt disturbance of the Betula glandulosa population, approximately simultaneously with the sudden 8200 cal. yr BP event in the North Atlantic. However, in the absence of other sites studied in the area, linkage to the 8200 cal. yr BP event remains tentative. The lack of any evidence of forest‐tundra in the region constrains the northern limit of the mid‐Holocene advance of the forest‐tundra boundary in central northern Canada. Consequently, our results show that the climate models imposing a mid‐Holocene advance of the limit of the forest‐tundra to the arctic coast of Canada may have overestimated the positive climatic feedback effects that can result from the replacement of tundra by the boreal forest. Copyright © 2003 John Wiley & Sons, Ltd.     

Sensitivity of Kelani streamflow in Sri Lanka to ENSO

As part of an effort to demonstrate the use of climate predictions for water resources management, the El Niño/Southern Oscillation (ENSO) influences on stream flow in the Kelani River in Sri Lanka were investigated using correlation analysis, composite analysis and contingency tables. El Niño (warm phase of ENSO) was associated with decreased annual stream flow and La Niña (cold phase of ENSO) with increased annual flows. The annual stream flow had a negative correlation with the simultaneous ENSO index of NINO3·4 that was significant at the 95% level. This negative correlation is enhanced to a 99% level if the aggregate January to September or the April to September stream flow alone were considered. Although, there is little correlation between ENSO indices and stream flow during the October to December period, there is a high correlation between rainfall and NINO3·4 (r = 0·51, significant at the 99% level). Therefore ENSO based rainfall predictions can be used along with a hydrological model to predict the October to December stream flow. This study demonstrates the viability of using ENSO based predictors for January to September or April to September stream flow predictions in the Kelani River. The October to December stream flow may be predicted by exploiting the strong relationship between ENSO and rainfall during that period. Copyright © 2003 John Wiley & Sons, Ltd.     

The Relation between Tectonic Movement and Climatic Change

Climate and tectonics are two interactive factors in the earth's system. They are controlled by astronomical cycles. It has been unheeded for a long time that large-scale material motion caused by global climatic change is one of the powers for tectonic movement. Tectonic movement makes the distributional pattern of continent and ocean change and makes global climate type change strongly in large scale. It is a good example that the change of the sea-ice around Antarctic Continent and in the Drake Passage has the switch process for global climatic changes. Tide makes the oceanic crust of the East Pacific Ocean and the West Pacific Ocean rise or fall 60 cm oppositely. Before and after El Nino events,the oceanic level of the East Pacific Ocean and the West Pacific Ocean may rise or fall 40 cm oppositely. Because of isostasy, oceanic crust may fall or rise 13 or 20 cm. They are the reasons why El Nino events are interrelated with the earthquakes and volcanoes. This is so called seesaw phenomenon of oceanic crust.     

Strong Tides in 1964 and 1982

The differential rotation between solid and fluid caused by tidal force can explain a 1500 to 1800-year cycle of the climate change. Strong tide increases the vertical and horizontal mixing of water in ocean by drawing the cold Pacific water from the depths to the surface (or by making the warm water flow from the West Pacific to the East as well as from the North to the South). It cools or warms the atmosphere above and makes La Nina or El Nino occur in the whole world. Astronomical data have shown that strong tide is often associated with El Nino events. Volcanic activities at submarine are also controlled by strong tide. Volcanic activities can also draw warm water from the depths to the surface in the Pacific and volcanic ash can keep out sunlight, which is the most important external forcing factor for El Nino. If volcanic ash reaches into the stratosphere, finer aerosols will spread throughout the globe during a few months and will float in it for one to three years to weaken the sun's direct radiation to the areas. It is one of the factors to postpone EI Nino just like the process of solar eclipse.     

DRY-WET EVOLUTION IN GUANGDONG PROVINCE DURING LAST 500 YEARS

1 INTRODUCTIONThe global warming change has already become one ofthe focuses that many scientists pay attention to, and theprecipitation change of China is also one part of thequestionsunder the whole world changes today. Accord-ing to the actual material analysis, the climate in Chinahad a warm-dry tendency in a wide spread range duringthe past one hundred years (ZHAO, 1993), and it couldnot draw a verdict as for future tendency at present. Fol-lowing the thought of Prof. HUANG Bing…     

The Latest Research Progress on El Ninod

1　ＭａｔｈｅｍａｔｉｃＭｏｄｅｌｏｆＴｉｄａｌＶｉｂｒａｔｉｏｎＳｕｐｐｏｓｅｔｈａｔ 3ｓｅｍｉ -ａｘｅｓｏｆａｅｌｌｉｐｓｏｉｄａｒｅａ ,ｂａｎｄｃ (ａ >ｂ >ｃ) ,ｌａｔｉｔｕｄｅｉｓθ ,ｌｏｎｇｉｔｕｄｅｉｓψ(ｃｈａｎｇｉｎｇｆｒｏｍ 0°ｔｏ 90°) ,     

The Latest Research Progress on El Nino

Cold water in the deep Pacific can be drawn up to the surface (or west warm water drifts eastwards) because strong tide increases the mixing of seawater both in vertical and horizontal. In this way greenhouse effect is decreased or in-creased by means of absorbing (or releasing) CO2. Therefore, La Nina cold event (or El Nino warm event) may occur, which is caused by wanning - up or cooling - down air above the ocean. Volcanic action at sea bottom is also controlled by strong tide.     

BOOK REVIEWS

Book Reviewed in this article: Hillslope Processes. Binghamton Symposia in Geomorphology International Series: 16. Athol D. Abrahams , ed. The Atlas of Central America and the Caribbean. The Diagram Group . The Cultural Atlas of Islam. Isma'il R. al Faruqi and Lois Lamaya'al Faruqi . Atlas of Israel Contemporary Africa: Development, Culture and the State. Morag Bell . Fundamentals of Physical Geography. David Briggs and Peter Smithson . The Bicentennial Census: New Directions for Methodology in 1990. Constance F. Citro and Michael L. Cohen , eds . World Patterns of Modern Urban Change: Essays in Honor of Chauncy D. Harris. Michael P. Conzen , ed . New Directions for Agriculture and Agricultural Research: Neglected Dimensions and Emerging Alternatives. Kenneth A. Dahlberg , ed . Water Resources Atlas of Florida. E.A. Fernald and D.J. Patton , eds . Landscape Ecology. R.T.T. Forman and M. Godron . The Myth of the North American City: Continentalism Challenged. Michael Goldberg and John Mercer . The Permafrost Environment. Stuart A. Harris . Climate and Circulation of the Tropics. Stefan Hastenrath . The Island of South Georgia. Robert Headland . The Making of Urban Europe, 1000-1950. Paul M. Hohenberg and Lynn Hollen Lees . Bombay in Transition: The Growth and Social Ecology of a Colonial City, 1889–1980. Meera Kosambi . Plant Closings; Public or Private Choices? Richard B. McKenzie , ed . Malaysia: Tradition, Modernity and Islam. R.S. Milne and Diane K. Mauzy . Technology on the Frontier: Mining in Old Ontario. Dianne Newell . The Maritime Political Boundaries of the World. J.R.V. Prescott . Tall Office Buildings in the United States. James W. Pygman and Richard Kateley (Real Estate Research Corporation). Technology, Regions, and Policy. John Rees , ed . The United States and the Regional Organization of Asia and the Pacific: 1965-1985. W.W. Rostow . Renewable Energy: Progress, Prospects. Stephen W. Sawyer Wisconsin Foundations. Gwen Schultz . Dwelling, Place and Environment: Towards a Phenomenology of Person and World. David Seamon and Robert Mugerauer , eds . Power and Place: Canadian Urban Development in the North American Context. Gilbert A. Stelter and Alan F.J. Artibise , eds . Small Firms in Regional Economic Development: Britain, Ireland and the United States. D. J. Storey , ed . Mathematical Methods in Human Geography and Planning. A. G. Wilson and R. J. Bennett . El Niño North: Niño Effects on the Eastern Subarctic Pacific Ocean. W. S. Wooster and D. L. Fluharty , eds . The Soviet Iron and Steel Industry. Craig ZumBrunnen and Jeffrey Osleeb .     

SCR Distribution Function in the Radial IMF Approximation

The transport of cosmic rays in the interplanetary medium is considered in terms of the kinetic equation describing the energetic particle scattering by magnetic irregularities and their focusing by the regular interplanetary magnetic field. The analytical expression for solar cosmic ray distribution function in the approximation of radial regular magnetic field is obtained and the evolution of energetic particle angular distribution is analyzed. The obtained results can be used for the analysis of ground-level enhancements of cosmic ray intensity.