Holocene high resolution cold events recorded by d13C of soil organic matter from

a climate sensitive zone in the Chinese loess plateau: A hint of La Nina?

Zheng-Hua Li1, 3, Claudia I. Mora1, Sue Wang2

1) Department of Geological Sciences, University of Tennessee, Knoxville, TN 37996, USA

2) School of Geosciences, University of Wollongong, NSW 2522, Australia

3) State Key Laboratory of Loess and Quaternary Geology, CAS, Xi'an, 710054, China

A high resolution record of δ¹³C of soil organic matter (SOM) over the last ~40kaBP was measured in a loess-paleosol sequence within the desert transitional zone of the Chinese loess plateau near Zhenbeitai. The data reveal cold events, characterized by an increased fraction of C3 vegetation, include the Younger Dryas and ~8.2ka event, as well as a middle Holocene cooling episode. The cold events and cooling episode correlate well with atmospheric CH₄ concentrations recovered from ice cores in GISP2 and Taylor Dome, but do not correspond to δ¹⁸O of ice core in GISP. The SOM carbon isotope record is possibly related to low latitude climate, controlled by conditions in the Pacific Ocean, which delivers water vapor to this area. Modern ENSO and its counterpart La Nina result in hot/dry conditions over Northern China during an ENSO episode and cool/wet conditions during La Nina. Recent studies suggest long-term ENSO-like paleoclimate cycles are recorded in geological archives. Thus, millenial scale variations in δ¹³C of SOM in the loess-desert transition zone, which responds to changes in the principal water vapor supply (Pacific Ocean) and temperature, may reflect wet/cooling cycles related to long-term La Nina-like episodes.