HR: 0800h
AN: PP11B-0531    [Abstracts]
TI: A High-Resolution Magnetic Rrecord of Holocene Rainfall Variations from the Western Chinese Loess Plateau: Antiphase Behaviour of the African/Indian and East Asian Summer Monsoons.
AU: * Maher, B A
EM: b.maher@lancs.ac.uk
AF: Lancaster Environment Centre, Lancaster University, Lancaster, Lan LA1 4YQ, United Kingdom
AB: Using magnetic and clastic grain size proxies, we make quantitative estimates of past changes in Holocene rainfall and also identify variations in winter monsoon intensity from a very well-dated, high-resolution sequence of loess and palaeosols, west of the Chinese Loess Plateau. Dating by optically stimulated luminescence shows that dust deposition has been quasi-continuous at this site throughout the Holocene, whilst the intensity of soil development has varied throughout the sequence, apparently unrelated to changes in sedimentation rate. As reconstructed using an independently calibrated magnetic susceptibility/rainfall climofunction, rainfall in this region has varied from ~ 75 to ~ 375 mm/yr, with summer monsoon maxima centred on 10.5 ka, 6.5 ka and 3.5 ka BP. Rainfall minima occurred at the mid-Holocene (~ 5.5 ka) and also at ~ 11.75 ka, 9 ka, 2 ka and 1.2 ka BP. Winter monsoon intensity has intensified from ~ 9 ka BP onwards, varying in its phase relationships with summer monsoon intensity. After ~ 2.25 ka BP, extreme climatic instability is indicated by both climate proxies. This Holocene rainfall record correlates with other records regionally, in the Loess Plateau and South China Sea. Notably, it demonstrates an anti-phase relationship with records of summer monsoon intensity from N. Africa, the Near East and western Tibet. This mismatch suggests that internal feedbacks in the SE Asian region, especially reduction in the land/sea surface temperature gradient, have acted to counter the effects of solar forcing.
UR: http://geography.lancs.ac.uk/cemp/publications/06Maher&Hu.pdf
DE: 1512 Environmental magnetism
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 3354 Precipitation (1854)
DE: 4914 Continental climate records
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting