Rain in China 17 percent Higher 7,000 Years Ago

Abstract: In order to produce quantitative Holocene precipitation reconstructions for particular geographical areas, explicit proxies and accurate dating controls are required. The fossilized seeds of common millet (Panicum miliaceum) are found throughout the sedimentary strata of northern China, and are highly suited to the production of accurate quantitative Holocene precipitation reconstructions: their isotopic carbon composition (δ¹³C) gives a measure of the precipitation required during the growing season, and allows these seeds to be dated.

We therefore used a robust regression function, as part of a systematic study of the δ¹³C of common millet, to produce a quantitative reconstruction of Mid Holocene summer precipitation in the Guanzhong Basin. Our results showed that summer precipitation from 7.7–3.4 ka BP was 240–477 mm, with a mean of 354 mm, i.e. ~ 50 mm or 17 {154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} higher than present levels. Maximal mean summer precipitation peaked at 414 mm, ~ 109 mm (or 36 {154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117}) higher than today, occurring during 6.4–5.5 ka BP; this is when the East Asian Summer Monsoon (EASM) was at its peak. As the δ¹³C-based precipitation record can reliably indicate EASM intensity during the Holocene, this work can provide a reliable proxy for further research into the detailed processes, and precise mechanisms, of the EASM.

Citation: Yang, Q., Li, X., Zhou, X., Zhao, K., and Sun, N.: Summer precipitation reconstructed quantitatively using a Mid Holocene δ¹³C common millet record from Guanzhong Basin, China, Clim. Past Discuss., doi:10.5194/cp-2016-87, in review, 2016.