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| Titel |
Changes in East Asian summer monsoon precipitation during the Holocene deduced from a freshwater flux reconstruction of the Changjiang (Yangtze River) based on the oxygen isotope mass balance in the northern East China Sea |
| VerfasserIn |
Y. Kubota, R. Tada, K. Kimoto |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 2 ; Nr. 11, no. 2 (2015-02-17), S.265-281 |
| Datensatznummer |
250117168
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| Publikation (Nr.) |
 copernicus.org/cp-11-265-2015.pdf |
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| Zusammenfassung |
| The δ18O of seawater (δ18Ow), an indirect
indicator of sea surface salinity (SSS), in the northern East China Sea
(ECS) is reconstructed for the Holocene using paired analyses of Mg / Ca ratio and δ18O of planktic foraminiferal tests. According to modern observation,
interannual variations in SSS during summer in the northern ECS are mainly
controlled by the Changjiang (Yangtze River) discharge, which reflects
summer rainfall in its drainage basin. Thus, changes in the summer SSS in
the northern ECS are interpreted as reflecting variations in the East Asian
summer monsoon (EASM) precipitation in the Changjiang Basin. This
interpretation is confirmed by a strong relationship between the SSS in the
northern ECS and the Changjiang discharge during the wet season (May–October)
based on instrumental salinity records from 1951 to 2000. However, it is
difficult to estimate absolute salinity values in the past with high
accuracy, because the past salinity–δ18Ow regression
slope, end member salinity, and δ18Ow values are not well
understood. Here, we conduct δ18Ow mass-balance calculation to estimate the
freshwater contribution to the surface water of the northern ECS during the last 7 kyr by assuming a
simple mixing between two end members – the seawater and the Changjiang freshwater. The result indicates
that there has been no gradual decreasing secular trend in the Changjiang
freshwater flux from the middle Holocene to the present day, suggesting that
summer insolation in the Northern Hemisphere does not regulate the EASM
precipitation in the Changjiang Basin. Instead, internal feedback appears to
have been more important during the Holocene. The absence of a decreasing
trend in regional summer precipitation over the Changjiang Basin since the
middle Holocene is contradictory to Chinese speleothems' δ18O
records, suggesting that it is not possible to explain orbital changes in
Chinese speleothems' δ18O during the Holocene by changes in
summer precipitation, but that such changes are related to other factors
such as changes in the moisture source. |
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