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| Titel |
Evolution of the Indian Summer Monsoon eastern branch and terrestrial vegetation since the Last Glacial |
| VerfasserIn |
Astrid Contreras-Rosales, Tim Jennerjahn, Thejna Tharammal, Andreas Lückge, Vera Meyer, Andre Paul, Enno Schefuß |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088606
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| Publikation (Nr.) |
 EGU/EGU2014-2728.pdf |
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| Zusammenfassung |
| The Indian summer monsoon (ISM) is one of the major climatic phenomena on the planet
and supports the living of over a billion people. Thus, understanding its natural driving forces
and ecological consequences are a matter of first importance. We provide a continuous record
of the ISM precipitation and continental vegetation over the Ganges-Brahmaputra-Meghna
lower catchment and the Indo-Burman ranges for the last 18,000 years (18 ka), based on
terrestrial biomarkers of a sediment core from the northern Bay of Bengal (NBoB).
Compound-specific stable isotope analysis of hydrogen (δD) and carbon (δ13C) on plant
wax-derived n-alkanes was conducted to reconstruct changes in precipitation and
vegetation composition, respectively. The results are compared to results from an
isotope-enabled general atmospheric circulation model (IsoCAM) for selected time-slices
(pre-industrial, mid-Holocene and Heinrich Stadial 1 [HS1]). Our findings indicate
that changes in the δD of precipitation and plant waxes around the NBoB were
mainly driven by the amount effect, and strongly influenced by summer monsoon
precipitation. Model results also support the hypothesis of a constant moisture source (i.e.
the NBoB) throughout the study period. Qualitative precipitation changes inferred
from our alkane δD record suggest that, overall, the Holocene (last 10 ka) was
moister than the late glacial (18-10 ka BP). Precipitation was strongest during the
early Holocene (8.6–8.4 ka BP), whereas the most arid conditions were recorded
during the HS1 (16.9–15.4 ka BP). These changes are comparable in timing and
magnitude to those detected in other ISM records from central and western Asia
[1, 2, 3, 4], suggesting simultaneous variability of the western (Arabian Sea) and
eastern (Bay of Bengal) ISM branches. Downcore n-alkane δD anomalies were used
to evaluate past changes in the precipitation isotopic signature and the observed
anomalies were similar to those obtained from the IsoCAM model. Quantitative
estimations of summer precipitation amount by the IsoCAM model predict, relative to the
pre-industrial period, 20% more rain during the mid-Holocene and 20% less during
HS1, respectively. Vegetation changes deduced from the n-alkane δ13C record
indicate a shift from C4-plant dominated ecosystems during the Late Glacial to
mixed C3/C4-plant vegetation during the Holocene. Comparison of the δD and δ13C
records suggests that vegetation composition is strongly linked to precipitation
variability.
References
Berkelhammer et al. 2013, Geoph. Monog Series.
Fleitmann et al. 2007, Quaternary Sci. Rev.; Quaternary Sci. Rev.
Shakun et al. 2007, Earth Planet. Sci. Lett.
Sinha et al. 2005, Geology. |
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