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| Titel |
Solar Variations and Holocene East African Climate |
| VerfasserIn |
Annett Junginger, Martin H. Trauth |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055876
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| Zusammenfassung |
| The nature and causes of intensity variations of the African and Indian monsoons during the
African Humid Period (AHP, 14.8 - 5.5 kyr BP), especially their exact influence
on regional climate relative to each other, is currently intensely debated. As an
example, no consensus exists concerning the abrupt vs. gradual onset and termination
of this event, as well as the character and style of the internal climate variability
during the AHP. A potential source of dissent in the interpretation of paleo-archives
of African climate change is the ambiguous interpretation of climate proxies, the
insufficient understanding of the link between climate, geographical setting and
proxies, and dating uncertainties. Here, we present the first high-resolution 14C-dated,
reservoir-corrected, multiproxy lake-level record from the remote Suguta Valley in the
northern Kenya Rift. The presently desiccated valley was covered by a 300 m deep and 2,500
km2 large paleo-lake that was, due to its extreme catchment size of 13,000 km2
and amplifier-lake characteristic, highly sensitive to relatively moderate climate
changes, providing a high signal-to-noise ratio of the lacustrine record and shoreline
dataset extracted from the paleo-environmental inventory of the valley. This record,
spanning the time interval from 14.8 to 5 kyr BP, from a valley located between the
west-African and Indian monsoon systems, explains the onset of large lakes in East
Africa with the longitudinal shift of the Congo Air Boundary (CAB) over the East
African and Ethiopian Plateaus, as a direct consequence of the strengthening of the
Indian monsoon. This teleconnection has possibly caused abrupt humidity shifts
in East Africa during the AHP. Instead, the termination of the AHP was, despite
the precessional forced Indian monsoon weakening, relatively gradual due to an
equatorial insolation maximum. Abrupt internal lake level fluctuations up to 100 m
on centennial time-scales were related to both a general monsoon weakening and
displacement of the CAB away from the plateau regions from East Africa as a result of
small-scale solar irradiation changes. The findings of this study contribute to our
understanding of the influence and relationship between the two monsoon systems and
highlights the importance of the knowledge about the geographical, geological and
climatologically situation of the study site used for paleo-climate reconstruction. |
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