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Journal ArticleDOI

Evolution of Asian monsoons and phased uplift of the Himalaya–Tibetan plateau since Late Miocene times

TL;DR: The results of a numerical climate-model experiment support the argument that the stages in evolution of Asian monsoons are linked to phases of Himalaya–Tibetan plateau uplift and to Northern Hemisphere glaciation.
Abstract: The climates of Asia are affected significantly by the extent and height of the Himalayan mountains and the Tibetan plateau1,2,3,4 Uplift of this region began about 50 Myr ago, and further significant increases in altitude of the Tibetan plateau are thought to have occurred about 10–8 Myr ago4,5, or more recently However, the climatic consequences of this uplift remain unclear Here we use records of aeolian sediments from China6,7 and marine sediments from the Indian8,9,10 and North Pacific oceans11 to identify three stages of evolution of Asian climates: first, enhanced aridity in the Asian interior and onset of the Indian and east Asian monsoons, about 9–8 Myr ago; next, continued intensification of the east Asian summer and winter monsoons, together with increased dust transport to the North Pacific Ocean11, about 36–26 Myr ago; and last, increased variability and possible weakening of the Indian and east Asian summer monsoons and continued strengthening of the east Asian winter monsoon since about 26 Myr ago The results of a numerical climate-model experiment, using idealized stepwise increases of mountain–plateau elevation, support the argument that the stages in evolution of Asian monsoons are linked to phases of Himalaya–Tibetan plateau uplift and to Northern Hemisphere glaciation
Citations
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Journal ArticleDOI
14 Mar 2002-Nature
TL;DR: This new evidence indicates that large source areas of aeolian dust and energetic winter monsoon winds to transport the material must have existed in the interior of Asia by the early Miocene epoch, at least 14 million years earlier than previously thought.
Abstract: The initial desertification in the Asian interior is thought to be one of the most prominent climate changes in the Northern Hemisphere during the Cenozoic era1,2,3,4. But the dating of this transition is uncertain, partly because desert sediments are usually scattered, discontinuous and difficult to date. Here we report nearly continuous aeolian deposits covering the interval from 22 to 6.2 million years ago, on the basis of palaeomagnetic measurements and fossil evidence. A total of 231 visually definable aeolian layers occur as brownish loesses interbedded with reddish soils. This new evidence indicates that large source areas of aeolian dust and energetic winter monsoon winds to transport the material must have existed in the interior of Asia by the early Miocene epoch, at least 14 million years earlier than previously thought3,5. Regional tectonic changes and ongoing global cooling are probable causes of these changes in aridity and circulation in Asia.

1,501 citations

Journal ArticleDOI
30 Apr 2010-Science
TL;DR: A synthesis of grass evolutionary biology with grassland ecosystem science will further knowledge of the evolution of traits that promote dominance in grassland systems and will provide a new context in which to evaluate the relative importance of C4 photosynthesis in transforming ecosystems across large regions of Earth.
Abstract: The evolution of grasses using C4 photosynthesis and their sudden rise to ecological dominance 3 to 8 million years ago is among the most dramatic examples of biome assembly in the geological record. A growing body of work suggests that the patterns and drivers of C4 grassland expansion were considerably more complex than originally assumed. Previous research has benefited substantially from dialog between geologists and ecologists, but current research must now integrate fully with phylogenetics. A synthesis of grass evolutionary biology with grassland ecosystem science will further our knowledge of the evolution of traits that promote dominance in grassland systems and will provide a new context in which to evaluate the relative importance of C4 photosynthesis in transforming ecosystems across large regions of Earth.

878 citations

Book
01 Jan 2002
TL;DR: The third edition of Gordon Bonan's comprehensive textbook introduces an interdisciplinary framework to understand the interaction between terrestrial ecosystems and climate change as discussed by the authors, which is suitable for advanced undergraduate and graduate students studying ecology, environmental science, atmospheric science, and geography.
Abstract: The third edition of Gordon Bonan's comprehensive textbook introduces an interdisciplinary framework to understand the interaction between terrestrial ecosystems and climate change. Ideal for advanced undergraduate and graduate students studying ecology, environmental science, atmospheric science, and geography, it reviews basic meteorological, hydrological, and ecological concepts to examine the physical, chemical, and biological processes by which terrestrial ecosystems affect and are affected by climate. This new edition has been thoroughly updated with new science and references. The scope has been expanded beyond its initial focus on energy, water, and carbon to include reactive gases and aerosols in the atmosphere. The new edition emphasizes the Earth as a system, recognizing interconnections among the planet's physical, chemical, biological, and socioeconomic components, and emphasizing global environmental sustainability. Each chapter contains chapter summaries and review questions, and with over 400 illustrations, including many in color, this textbook will once again be an essential student guide.

758 citations

Journal ArticleDOI
14 Jan 2010-Nature
TL;DR: In this paper, an atmospheric model is used to show that flattening of the Tibetan plateau has little effect on the monsoon, provided that the narrow orography of the Himalayas and adjacent mountain ranges is preserved.
Abstract: Heat emitted from the Tibetan plateau as dry heat and water vapour has long been assumed to be the main driver of the South Asian summer monsoon, but new work suggests that in fact it is the neighbouring mountains that are the major influence. William Boos and Zhiming Kuang use an atmospheric model to show that flattening the Tibetan plateau has little effect on the monsoon, so long as the Himalayas and surrounding mountain ranges remain. The plateau does boost rainfall locally along its southern edge, but it is the build-up of hot, moist air over India, insulated from colder, drier air by the Himalayas, that drives large-scale monsoon circulation. The elevation of the Tibetan plateau is thought to cause its surface to serve as a heat source that drives the South Asian summer monsoon, potentially coupling uplift of the plateau to climate changes on geologic timescales. Here, however, an atmospheric model is used to show that flattening of the Tibetan plateau has little effect on the monsoon, provided that the narrow orography of the Himalayas and adjacent mountain ranges is preserved. The Tibetan plateau, like any landmass, emits energy into the atmosphere in the form of dry heat and water vapour, but its mean surface elevation is more than 5 km above sea level. This elevation is widely held to cause the plateau to serve as a heat source that drives the South Asian summer monsoon, potentially coupling uplift of the plateau to climate changes on geologic timescales1,2,3,4,5. Observations of the present climate, however, do not clearly establish the Tibetan plateau as the dominant thermal forcing in the region: peak upper-tropospheric temperatures during boreal summer are located over continental India, south of the plateau. Here we show that, although Tibetan plateau heating locally enhances rainfall along its southern edge in an atmospheric model, the large-scale South Asian summer monsoon circulation is otherwise unaffected by removal of the plateau, provided that the narrow orography of the Himalayas and adjacent mountain ranges is preserved. Additional observational and model results suggest that these mountains produce a strong monsoon by insulating warm, moist air over continental India from the cold and dry extratropics. These results call for both a reinterpretation of how South Asian climate may have responded to orographic uplift, and a re-evaluation of how this climate may respond to modified land surface and radiative forcings in coming decades.

685 citations

Journal ArticleDOI
TL;DR: Geologic and geophysical data from north-central Tibet are presented, including magnetostratigraphy, sedimentology, paleocurrent measurements, and 40Ar/39Ar and fission-track studies, to show that the central plateau was elevated by 40 Ma ago.
Abstract: The surface uplift history of the Tibetan Plateau and Himalaya is among the most interesting topics in geosciences because of its effect on regional and global climate during Cenozoic time, its influence on monsoon intensity, and its reflection of the dynamics of continental plateaus. Models of plateau growth vary in time, from pre-India-Asia collision (e.g., ≈100 Ma ago) to gradual uplift after the India-Asia collision (e.g., ≈55 Ma ago) and to more recent abrupt uplift (<7 Ma ago), and vary in space, from northward stepwise growth of topography to simultaneous surface uplift across the plateau. Here, we improve that understanding by presenting geologic and geophysical data from north-central Tibet, including magnetostratigraphy, sedimentology, paleocurrent measurements, and 40Ar/39Ar and fission-track studies, to show that the central plateau was elevated by 40 Ma ago. Regions south and north of the central plateau gained elevation significantly later. During Eocene time, the northern boundary of the protoplateau was in the region of the Tanggula Shan. Elevation gain started in pre-Eocene time in the Lhasa and Qiangtang terranes and expanded throughout the Neogene toward its present southern and northern margins in the Himalaya and Qilian Shan.

670 citations

References
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Journal ArticleDOI
01 Jan 1997-Nature
TL;DR: For example, this paper found that between 8 and 6 million years ago, there was a global increase in the biomass of plants using C4 photosynthesis as indicated by changes in the carbon isotope ratios of fossil tooth enamel in Asia, Africa, North America and South America.
Abstract: Between 8 and 6 million years ago, there was a global increase in the biomass of plants using C4 photosynthesis as indicated by changes in the carbon isotope ratios of fossil tooth enamel in Asia, Africa, North America and South America. This abrupt and widespread increase in C4 biomass may be related to a decrease in atmospheric CO2 concentrations below a threshold that favoured C3-photosynthesizing plants. The change occurred earlier at lower latitudes, as the threshold for C3 photosynthesis is higher at warmer temperatures.

1,886 citations


"Evolution of Asian monsoons and pha..." refers background in this paper

  • ...2 ), inferred changes in vegetation from C 3 (forests) to C 4 (grasses) in Pakistan beginning about 8 Myr ag...

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Journal ArticleDOI
TL;DR: For example, Hou et al. as mentioned in this paper show that a small increase in the mean elevation of the Tibetan Plateau of 1000 m or more in a few million years is required by abrupt tectonic and environmental changes in Asia and the Indian Ocean.
Abstract: Convective removal of lower lithosphere beneath the Tibetan Plateau can account for a rapid increase in the mean elevation of the Tibetan Plateau of 1000 m or more in a few million years. Such uplift seems to be required by abrupt tectonic and environmental changes in Asia and the Indian Ocean in late Cenozoic time. The composition of basaltic volcanism in northern Tibet, which apparently began at about 13 Ma, implies melting of lithosphere, not asthenosphere. The most plausible mechanism for rapid heat transfer to the midlithosphere is by convective removal of deeper lithosphere and its replacement by hotter asthenosphere. The initiation of normal faulting in Tibet at about 8 (± 3) Ma suggests that the plateau underwent an appreciable increase in elevation at that time. An increase due solely to the isostatic response to crustal thickening caused by India's penetration into Eurasia should have been slow and could not have triggered normal faulting. Another process, such as removal of relatively cold, dense lower lithosphere, must have caused a supplemental uplift of the surface. Folding and faulting of the Indo-Australian plate south of India, the most prominent oceanic intraplate deformation on Earth, began between about 7.5 and 8 Ma and indicates an increased north-south compressional stress within the Indo-Australian plate. A Tibetan uplift of only 1000 m, if the result of removal of lower lithosphere, should have increased the compressional stress that the plateau applies to India and that resists India's northward movement, from an amount too small to fold oceanic lithosphere, to one sufficient to do so. The climate of the equatorial Indian Ocean and southern Asia changed at about 6–9 Ma: monsoonal winds apparently strengthened, northern Pakistan became more arid, but weathering of rock in the eastern Himalaya apparently increased. Because of its high altitude and lateral extent, the Tibetan Plateau provides a heat source at midlatitudes that should oppose classical (symmetric) Hadley circulation between the equator and temperate latitudes and that should help to drive an essentially opposite circulation characteristic of summer monsoons. For the simple case of axisymmetric heating (no dependence on longitude) of an atmosphere without dissipation, theoretical analyses by Hou, Lindzen, and Plumb show that an axisymmetric heat source displaced from the equator can drive a much stronger meridianal (monsoonlike) circulation than such a source centered on the equator, but only if heating exceeds a threshold whose level increases with the latitude of the heat source. Because heating of the atmosphere over Tibet should increase monotonically with elevation of the plateau, a modest uplift (1000–2500 m) of Tibet, already of substantial extent and height, might have been sufficient to exceed a threshold necessary for a strong monsoon. The virtual simultaneity of these phenomena suggests that uplift was rapid: approximately 1000 m to 2500 m in a few million years. Moreover, nearly simultaneously with the late Miocene strengthening of the monsoon, the calcite compensation depth in the oceans dropped, plants using the relatively efficient C4 pathway for photosynthesis evolved rapidly, and atmospheric CO2 seems to have decreased, suggesting causal relationships and positive feedbacks among these phenomena. Both a supplemental uplift of the Himalaya, the southern edge of Tibet, and a strengthened monsoon may have accelerated erosion and weathering of silicate rock in the Himalaya that, in turn, enhanced extraction of CO2 from the atmosphere. Thus these correlations offer some support for links between plateau uplift, a downdrawing of CO2 from the atmosphere, and global climate change, as proposed by Raymo, Ruddiman, and Froehlich. Mantle dynamics beneath mountain belts not only may profoundly affect tectonic processes near and far from the belts, but might also play an important role in altering regional and global climates.

1,753 citations

Journal ArticleDOI
02 May 1997-Science
TL;DR: This model predicts east-west extension on the high plateau without convective removal of Tibetan lithosphere and without eastward movement of the crust east of the plateau.
Abstract: Field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern Tibetan plateau since about 4 million years ago. Instead, central eastern Tibet has been nearly stationary relative to southeastern China, southeastern Tibet has rotated clockwise without major crustal shortening, and the crust along portions of the eastern plateau margin has been extended. Modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle. This model also predicts east-west extension on the high plateau without convective removal of Tibetan lithosphere and without eastward movement of the crust east of the plateau.

1,331 citations

Journal ArticleDOI
01 May 1995-Nature
TL;DR: The authors examined grain-size data from Chinese loess and intercalated accretionary palaeosols of last-glacial age for evidence of similar climate signals remote from the North Atlantic region.
Abstract: EPISODES of massive iceberg release (Heinrich events)1-3 into the North Atlantic Ocean during the last glaciation were associated with recurring episodes of unusually cold North Atlantic surface water (Bond cycles)4 and cold air temperatures over Greenland (Dansgaard-Oeschger events)5,6. Four of the youngest of these cold events have also been reported in climate records from sites outside the North Atlantic region7, but until now the entire suite has been identified only in North Atlantic marine sediments, Greenland ice-core records and, tentatively, in French lake sediments8. Here we examine grain-size data from Chinese loess and intercalated accretionary palaeosols of last-glacial age for evidence of similar climate signals remote from the North Atlantic region. We see grain-size maxima with ages that match those of the last six Heinrich events, which we interpret as an indication of the changing strength of the East Asian winter monsoon, which largely controls the transport and deposition of central Asian aeolian dust. Thus it seems that these Heinrich events have left their signature in the Chinese loess record. This is consistent with simulations of the glacial climate9, which imply that the climates of the North Atlantic and China were linked by the effect of westerly winds.

1,171 citations


"Evolution of Asian monsoons and pha..." refers background in this paper

  • ...1 ), and in an area that is very sensitive to variations in the east Asian summer and winter monsoon...

    [...]

Journal ArticleDOI
TL;DR: In this article, a thin viscous sheet model for deformation of continental lithosphere subjected to an indenting boundary condition yield distributions of crustal thickness, of stress and strain rate, and of latitudinal displacements that may be compared with observations in the India-Asia collision zone.
Abstract: Numerical experiments on a thin viscous sheet model for deformation of continental lithosphere subjected to an indenting boundary condition yield distributions of crustal thickness, of stress and strain rate, and of latitudinal displacements that may be compared with observations in the India-Asia collision zone. A simple indenting boundary condition applied to initially laterally homogeneous sheets obeying a power law rheology produces results that are in broad agreement with the observations, provided that the power law exponent is three or greater and the sheet can support vertically integrated stress differences of 2×1013 (±5 × 1012) N m−1 in regions in front of the indenter. Under these conditions, the calculated deformation shows accommodation of convergence primarily by crustal thickening, to produce a plateau in front of the indenter. Palaeomagnetic data from India and Tibet, and the observed distribution of topography, suggest that much of the post-Eocene convergence of India with Asia has been taken up by deformation within Asia that involved crustal thickening. The principal difference between calculation and observation is the absence from the calculated strain rate fields of east-west extension of the plateau in front of the indenting boundary. The calculations show that once such a plateau is formed, the buoyancy force associated with the crustal thickness contrast inhibits further thickening and the plateau strains at less than half the rate of its immediate surroundings. Seismically determined regional strain rates exhibit a similar distribution, with the Tibetan plateau straining at about one quarter the rate of the Tien Shan and Ningxia-Gansu regions. Calculated principal compressive stress orientations and regional strain rates agree with the seismically determined quantities in the Mongolia-Baikal, Tien Shan, Tibet, and Ningxia-Gansu regions of Asia, to within the uncertainty of the latter. The vertically integrated stresses that are calculated for the viscous sheet are comparable with those that can be supported by a Theologically stratified continental lithosphere obeying laboratory-determined flow laws. We suggest that the thin viscous sheet model, described in this paper and its companion, gives a simple and physically plausible description of the observed deformation in central Asia; in this description the predominant mechanism of accommodation of continental convergence is diffuse crustal thickening, with shear on vertical planes playing a subsidiary role once large crustal thickness contrasts have been established.

993 citations


"Evolution of Asian monsoons and pha..." refers background in this paper

  • ...Moreover, models of plateau formation suggest continued development of the plateau towards the north and eas...

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