Lake-level history of Qinghai Lake on the NE Tibetan Plateau and its implications for Asian monsoon pattern - A review

The paper presents a comprehensive review on lake-level history of Qinghai Lake since marine isotope stage (MIS) 5, after re-examining the sedimentary and geomorphological nature of highstand deposits and re-evaluating the published dating results (318 luminescence ages and 17 14C ages) of shorelines, near shoreline, lacustrine, alluvial, and aeolian deposits. It is concluded that 1) Three lake shoreline sets were classified in the Qinghai Lake Basin with the corresponding elevations of 3220–3260, 3206–3215 and 3194–3205 m. 2) 14C dating on lake sediments is restricted by the upper dating limit of ∼35 thousand years (ka) BP in practice, availability of dating materials and reservoir effect, and that quartz optically stimulated luminescence (OSL) ages older than 80–60 ka may be underestimated while feldspar post-infrared infrared stimulated luminescence (pIRIR) ages could be reliable for dating these older samples. 3) Four highstands were detected by ages. The highest lake-levels at elevations of 3220–3260 m with 26–66 m above the present lake-level occurred in MIS 5, and highstands also occurred in MIS 3 (∼42–38 ka), the last deglaciation (∼16–12 ka), and the Holocene (∼6–5 ka) with similar heights at elevations of ∼3200–3209 m. During the Holocene, lake-levels were relatively low in the early Holocene (∼11–8 ka), increasing substantially after ∼8 ka and reaching the highest lake-levels (elevation of 3203.1 m) at ∼6–5 ka, then decreasing with an interruption by a highstand (elevation of 3202.4 m) at ∼1.8 ka. 4) Shoreline-based lake-level variations are consistent with major climatic proxies (e.g., δ13Corg and %thaum) of drilling cores from the lake, regional aeolian activity/pedogenesis and climate change. 5) Compared with the representative lake-levels and moisture records in the Westerlies and East Asia summer monsoon (EASM) dominances, it is suggested that lake-level variations in the southern Qilian Mountains exhibited simultaneity with changes in the intensity of EASM, while those in the northern part were synchronous with the moisture records in arid central Asia, suggesting that EASM did not extend further to the northern Qilian Mountains where the Westerlies prevailed.