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| Titel |
Tropical African Rainbelt dynamics since the Last Glacial Maximum |
| VerfasserIn |
James Collins, Stefan Mulitza, Enno Schefuß, David Heslop, Matthias Prange, Matthias Zabel, Rik Tjallingii, Trond Dokken, Enqing Huang, Andreas Mackensen |
| 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 |
250036307
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| Zusammenfassung |
| The tropical rainbelt delivers nearly all of the rainfall between 20°N and 20°S in Africa and
so is a vital part of the African climate system. On millennial timescales, rainfall fluctuations
in Africa are commonly attributed to a latitudinal migration in the position of the rainbelt.
However, this mechanism is not consistent with new proxy data, which suggest synchronous
wet and dry conditions in both hemispheres. As such, we tested the migration hypothesis
by reconstructing the dynamics of the rainbelt for extreme climate states of the
past. Proxies utilised for this purpose were estimates of weathering intensity based
on major element composition of sediments derived from terrigenous soils and
estimates of vegetation type based on δ13C of plant-wax n-alkanes. Samples were
taken from a large-scale latitudinal transect of 8 marine sediment cores located
offshore tropical western Africa, covering the entire seasonal range of the tropical
rainbelt.
We find that, contrary to the prevailing hypothesis, the rainbelt was not located in a more
southerly position relative to modern-day during Heinrich Stadial 1 and the Last
Glacial Maximum but instead was contracted latitudinally in both hemispheres. A
contraction rather than a southward shift may have been linked to the extension of
Antarctic sea ice or to the cool glacial atmosphere during Heinrich Stadial 1 and the
Last Glacial Maximum. During Heinrich Stadial 1, the rainbelt was shifted slightly
southwards relative to the Last Glacial Maximum, which was likely associated with an
enhanced inter-hemispheric SST gradient, although nonetheless, the rainbelt was
compressed relative to modern-day conditions. These results suggest that glacial boundary
conditions had a much larger influence on African rainfall distribution than ocean
circulation. |
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