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Modern and past processes of ocean-atmosphere-climate interactions in the low-latitude western Pacific and Indian Ocean
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High-and low-latitude forcing of the East African climate since the Last Glacial Maximum
Wednesday 9th @ 1410-1430, Conference Room 1
Xiting Liu* , Ocean University of China
Presenter Email: liuxiting@gmail.com |
| High-resolution of geochemical scanner profiles have improved time resolution of sampling, which allowed us to obtain continuous sediment sequences with high temporal resolution marine records. To date, unlike the well study on the western north tropical Africa, only few studies on marine sediments off East Africa, demonstrating inland climatic conditions since the Last Glacial Maximum (LGM), have been carried out. We present X-Ray Fluorescence (XRF) Scanner measurements from a 6 m long sediment core (GeoB12624-1) on the upper slope of Tanzania to reconstruct the climatic evolution in East Africa since the Last Glacial Maximum (LGM). Log-ratios of Fe/Ca and Ti/Ca are indicative for sediment discharge of the Rufiji River, which is controlled by climatic conditions in the Rufiji catchment area. The data set records distinct precipitation peaks during the early Holocene. This corresponds a maximum in the Northern Hemisphere (NH) summer insolation and results in a transition from the arid LGM to the humid early Holocene. Our geochemical record also indicates that this climatic transition was interrupted by two severe droughts that occurred during NH cold intervals: the Heinrich stadial 1 (HS1) and the Younger Dryas (YD). Through a comparison with other nearby paleoclimatic records, we suggest that arid climatic conditions only occurred in East Africa north of 8-10゜S, whereas in southern East Africa around 15-20゜S increased humidity during the HS1 and YD prevailed. We thus conclude that these two drought events were caused by a southward migration of the Intertropical Convergence Zone (ITCZ) which was fostered by the NH cooling during the HS1 and YD. Hence, our new geochemical record clearly documents that the East African climate not only responded to low-latitude insolation forcing on sub-orbital time scales, but also, was strongly influenced by high-latitude cooling during the HS1 and YD periods. |
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