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| Titel |
Reconstruction of East Asian Monsoon variability 6.5ka-present using organic and inorganic geochemical proxies in the Pearl River Estuary, China |
| VerfasserIn |
David Strong, Fengling Yu, Richard Pancost, Rachel Flecker, Paul Valdes, Ian Wilkinson, John Rees, Melanie Leng, Jeremy Lloyd, Edmund Garrett |
| 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 |
250041185
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| Zusammenfassung |
| The East Asian Monsoon (EAM) is one of the most significant contributors, both
environmentally and socioeconomically, to the densely-populated East Asia region in which
over one third of the world’s population reside. Additionally, the EAM is a key system in
global atmospheric circulation. Thus, understanding past changes in the EAM is of
pivotal importance for assessing the impact of future climate change. Previous
EAM reconstructions have mainly focused on lake and cave records. However,
these records record a small, regional-scale signal of paleoprecipitation and are thus
susceptible to local responses and might not record continental-scale climate. Multiproxy
studies from marginal marine systems such as estuaries and semi-enclosed seas
have shown great potential to reconstruct past variability in the climate system,
particularly aspects of the hydrological cycle and temperature, on a continental scale.
The Pearl River was chosen for this study as it possesses a large (400,000km2)
drainage basin. The latitudinal orientation of the basin between the tropics and
subtropics (22Ë to 26Ë N), its susceptibility to both summer (humid) and winter
(dry) monsoon winds, and its location within the modern summer Inter-Tropical
Convergence Zone (ITCZ) area make the basin very sensitive to variability in the
EAM system. Here we present results for a suite of inorganic geochemical proxies
for paleosalinity (such as foraminiferal oxygen isotope ratios, δ18O) and organic
geochemical proxies for fluvial sediment flux (such as the concentration ratio of
terrestrial to marine biomarkers), testing both modern (spatial) and Holocene (temporal)
variability. The anticipated spatial variability of inorganic and organic proxies is
observed, with terrestrial signals dominating in the upper estuary but becoming weaker
towards the open sea; however, some proxies appear to record this transition with
greater fidelity than others, with the n-alcohol-based proxy being the strongest and
sterol-based proxy the weakest. Correlation to water salinity was significant in all
proxies (R2=0.51 to 0.73) and fidelity was similar to those seen in the anticipated
spatial distribution. Agreement among proxies in the temporal reconstruction is
generally strong and show significant strengthening of the monsoon (as shown by an
increase in terrigenous input) at 6.5ka, 4.5ka and 2.5ka, and weakening (as shown
by a decrease in terrigenous input) at 5.5ka and 3.5ka, with little overall trend.
This challenges aspects of previous reconstructions which show overall steady
weakening in the monsoon during the latter part of the Holocene and agrees with
aspects of a previous bulk sediment δ13C-based proxy study on the Pearl Estuary. |
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