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| Titel |
Does the North Atlantic influence the monsoon signal in Asian speleothems? |
| VerfasserIn |
Francesco S. R. Pausata, David S. Battisti, Kerim H. Nisancioglu |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250040852
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| Zusammenfassung |
| Speleothems from Indian and Chinese caves have been broadly used to infer past monsoon
strength, since the oxygen isotopic composition of the spelothems is primarily controlled by
the oxygen composition of the precipitation. However, the d18O changes recorded by the
speleothems could be due not only to a change in the strength of the monsoon but also to
other causes, such as changes in the precipitation source or the isotopic fractionation at the
source. Here we present a modelling study where we examine water isotope and moisture
source changes between a stadial climate (Last Glacial Maximum, LGM, 21 Kyr BP,
before present) and a cold abrupt event (Heinrich event 1, H1, 17 kyrs BP). Our
study aims to understand what causes the d18O change observed in the speleothems
during this period and what type of signal, whether local or large scale, the Asian
caves are recording. Simulated water isotope archives match well those recorded by
speleothems in China and India. Our study shows that water isotopes changes in Asian
speleothems are primarily linked to changes in the isotopic fractionation at the source, but
partially also to the total amount of local precipitation. The change in sea surface
temperature (SST) over the Indian Ocean is necessary in order to give an isotopic signal
at the cave’s locations. Our results show that the d18O changes recorded in the
speleothems are mainly driven by changes in the isotopic composition of monsoon
precipitation (MJJA). The Indian caves (e.g. Timta) are perfect proxies for recording the
Summer Indian Monsoon (SIM). On the other hand, Chinese caves (e.g. Hulu, Sanbao,
Dongge) records not only the East Asian Summer Monsoon (EAS), but they are also
influenced by the SIM. Our study shows a weakening of the monsoon during cold abrupt
climate changes, due to a teleconnection with the North Atlantic, cooling the Asian
continent and reducing the temperature gradient between the continent and the
ocean. |
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