Regional Moisture Source Changes Inferred from Late Holocene Stable Isotope Records

Qinghai Lake, China, is located near the northern limit of the East Asian summer monsoon (EASM) and thus is an ideal region for studies of past monsoonal changes. However, isotope records from this region reflect the combined effects of multiple climatic factors, and make climatic interpretations difficult. The authors use multi-proxy records, generated from the same sediment core from Qinghai Lake, to disentangle these multiple effects in isotope records and to infer EASM variability during the late Holocene. Records of leaf wax (C28) δD, lake carbonate δ18O and the Dunde ice core δ18O all indicate a millennial-scale depletion of mean isotopic values at ～1500--1250 years before present. Compared with independent lake temperature and salinity records, the authors suggest that this depletion of long-term mean isotopic values must have resulted from changes in moisture sources in this region. In contrast, the authors attribute high-frequency (centennial timescale) C28 δD and ice core δ18O variability dominantly to a temperature effect. The multi-proxy records provide a coherent picture in that many aspects of this regional climate (temperature, dryness, and moisture source) are strongly linked to the EASM variability.