A high-resolution record of Holocene rainfall variations from the western Chinese Loess Plateau: antiphase behaviour of the African/Indian and East Asian summer monsoons

Abstract

Tropical monsoons are key mechanisms for transfer of heat and moisture to higher latitudes. Here we present a high-resolution, terrestrial proxy summer monsoon record for the southeast Asian monsoon, from a rapidly accumulating Holocene loess/soil sequence in the western Chinese Loess Plateau. We use magnetic and clastic grain size proxies to make quantitative estimates of Holocene rainfall and identify variations in winter monsoon intensity. Our record reveals cyclical millennial and multimillennial rainfall changes. As with the northwest African/southwest Asian monsoon records, a short arid interval at - 12.5 to 11.5 ka BP (the Younger Dryas) and subsequent summer monsoon intensification are recorded. However, at 6 ka BP, the southeast Asian summer monsoon weakened, when the northwest African/ southwest Asian monsoons strengthened, and then, from - 5 ka BP, intensified, when northwest Africa/ southwest Asia became dry. These antiphase monsoonal relationships may reflect competition between sea surface temperature changes and solar forcing. The intensity of the southeast Asian winter monsoon 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.

The evolution of sub-monsoon systems in the Afro-Asian monsoon region during the Holocene– comparison of different transient climate model simulations

“…Although recent palaeo-studies support the global monsoon hypothesis (Cheng et al, 2012;Liu et al, 2012), there are many arguments for a rather regional behaviour and at least regional characteristics of the different monsoon systems in modern observations and palaeorecords. For the Holocene, several studies report an asynchronous rainfall trend in different parts of the Asian monsoon region Maher, 2008) and an out-ofphase evolution of the Indian and East Asian monsoon (Maher and Hu, 2006;. Some records suggest an abrupt end of the humid period in the North African monsoon area (e.g.…”

“…The timing of maximum Holocene rainfall in the Asian monsoon region strongly depends on the location (e.g. and the affecting monsoon sub-system (Maher, 2008;Maher and Hu, 2006). While moisture levels in the Indian monsoon region are highest during the early Holocene, the East Asian monsoon did not reach maximum strength before the midHolocene (Herzschuh et al, 2006;.…”

Spatial variability of Holocene changes in the annual precipitation pattern: a model-data synthesis for the Asian monsoon region

“…Fleitmann et al 2003;Wang et al 2005;Herzschuh et al 2006;Prasad and Enzel 2006) and suggest differences in the precipitation response to the insolation forcing between the Indian and East Asian monsoon region Maher and Hu 2006;Maher 2008). However, most of the proxies do not resolve seasonal signals but rather record an aggregated annual signal.…”

A Review of Recent Advances in Red-Clay Environmental Magnetism and Paleoclimate History on the Chinese Loess Plateau

“…We argue that these changes provide a more plausible explanation for the low values of χ at that time period and that the higher content of clay coats and Fe-Mn films might be caused by factors other than monsoon rainfall, such as the time of soil formation (Nie et al, 2013b). Maher and Hu (2006) have demonstrated that the magnetic enhancement of Chinese loess is mainly controlled by monsoon precipitation intensity and is not related to the time of soil formation based on age constraints from OSL dating. For this reason, we suggest that χ is a better proxy for the intensity of the EASM than field observations of soil characteristics.…”

“…For the loess-paleosol sequence, χ is the most widely accepted proxy for the EASM precipitation intensity (Liu, 1985;Evans and Heller, 1994;Maher et al, 1994;Heller and Evans, 1995;Liu et al, 1995Liu et al, , 2007Chen and An, 1999;Heslop et al, 2000;An et al, 2001;Maher and Hu, 2006). Southern sites on the CLP might be an exception to this relationship between χ and rainfall probably because a high rainfall threshold is crossed that results in the diagenetic destruction of magnetic minerals responsible for magnetic enhancement (Guo B. et al, 2001;Bloemendal and Liu, 2005).…”