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| Titel |
Modeling the response of precipitation oxygen stable isotopes to the Eocene climate changes over Asia |
| VerfasserIn |
Svetlana Botsyun, Pierre Sepulchre, Yannick Donnadieu, Camille Risi, Jeremy K. Caves, Alexis Licht |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150996
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| Publikation (Nr.) |
 EGU/EGU2017-15533.pdf |
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| Zusammenfassung |
| The Himalayas and the Tibetan Plateau have become a focus of the Earth sciences because
they provide a classical example of tectonics-climate interactions. Present-day high
elevations of the Himalayas and the Tibetan Plateau is the ultimate result of the collision
between Indian and Asia plates during the Cenozoic, however, the precise uplift
history of the Himalayas and the Tibetan Plateau is still uncertain, especially for
the early Cenozoic. For the purpose of paleoelevations reconstructions, multiple
methods are available, but stable oxygen paleoaltimetry is considered to be one
of the most efficient techniques and has been widely applied in Asia. However,
paleoelevations studies using stable oxygen presume that climatic processes control
δ18O in a uniform way through time. We use climate modeling tools in order to
investigate Eocene climate and δ18O over Asia and its controlling factors. The
state-of-the-art general circulation model embedded with isotopes LMDz-iso has been
applied together with Eocene boundary conditions and varied Eocene topography of
the Himalayas and Tibet. The results of our simulations suggest that topography
change has a minor direct impact on δ18O over the Himalayas and the Tibetan
Plateau. On the contrary, Eocene δ18O in precipitation is primarily controlled by the
atmosphere circulation and global temperature changes. Based on our numerical
experiments, we show that despite persistence of large-scale atmospheric flows such
as the monsoons and westerlies, Eocene δ18O over the region is different from
those of the present-day due to global higher temperatures, southward shift to a
zone of strong convection and increased role of westerlies moisture source. We
show that the Rayleigh distillation is not applicable for the Eocene Himalayas and
conclude that the assumption about the stationarity of δ18O-elevation relationship
through geological time is inaccurate and misleading for paleoelevation estimates.
We also show that Eocene precipitation δ18O is rather insensitive to topographic
height in Asia. However, carbonate δ18O still records paleoelevation because the
fractionation between calcite and water is sensitive to temperature, which depends on
altitude. Comparison of simulated Eocene δ18O patterns with data from the carbonate
archives suggest that the Himalayas and the Tibetan Plateau did not reach high
present-day like elevations during the Eocene. Our simulations highlight the limit
of standard atmospheric distillation models when they are applied to deep time. |
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