https://www.lehigh.edu/~ziy2/pubs/Chen2008QSR.pdf

Holocene moisture evolution in arid central Asia and its out-of-phase relationship with Asian monsoon history

Two atmospheric circulation systems, the mid-latitude Westerlies and the Asian summer monsoon (ASM), play key roles in northern-hemisphere climatic changes. However, the variability of the Westerlies in Asia and their relationship to the ASM remain unclear. Here, we present the longest and highest-resolution drill core from Lake Qinghai on the northeastern Tibetan Plateau (TP), which uniquely records the variability of both the Westerlies and the ASM since 32 ka, reflecting the interplay of these two systems. These records document the anti-phase relationship of the Westerlies and the ASM for both glacial-interglacial and glacial millennial timescales. During the last glaciation, the influence of the Westerlies dominated; prominent dust-rich intervals, correlated with Heinrich events, reflect intensified Westerlies linked to northern high-latitude climate. During the Holocene, the dominant ASM circulation, punctuated by weak events, indicates linkages of the ASM to orbital forcing, North Atlantic abrupt events, and perhaps solar activity changes.

/pdf/interplay-between-the-westerlies-and-asian-monsoon-recorded-5awlp9an81.pdf

Interplay between the Westerlies and Asian monsoon recorded in Lake Qinghai sediments since 32 ka

The lack of a precisely-dated, unequivocal climate proxy from northern China, where precipitation variability is traditionally considered as an East Asian summer monsoon (EASM) indicator, impedes our understanding of the behaviour and dynamics of the EASM. Here we present a well-dated, pollen-based, ~20-yr-resolution quantitative precipitation reconstruction (derived using a transfer function) from an alpine lake in North China, which provides for the first time a direct record of EASM evolution since 14.7 ka (ka = thousands of years before present, where the "present" is defined as the year AD 1950). Our record reveals a gradually intensifying monsoon from 14.7-7.0 ka, a maximum monsoon (30% higher precipitation than present) from ~7.8-5.3 ka, and a rapid decline since ~3.3 ka. These insolation-driven EASM trends were punctuated by two millennial-scale weakening events which occurred synchronously to the cold Younger Dryas and at ~9.5-8.5 ka, and by two centennial-scale intervals of enhanced (weakened) monsoon during the Medieval Warm Period (Little Ice Age). Our precipitation reconstruction, consistent with temperature changes but quite different from the prevailing view of EASM evolution, points to strong internal feedback processes driving the EASM, and may aid our understanding of future monsoon behaviour under ongoing anthropogenic climate change.

/pdf/east-asian-summer-monsoon-precipitation-variability-since-1qsvcpqx5u.pdf

East Asian summer monsoon precipitation variability since the last deglaciation

Asian monsoon oscillations in the northeastern Qinghai–Tibet Plateau since the late glacial as interpreted from visible reflectance of Qinghai Lake sediments

Palaeoclimatic changes in the Qinghai Lake area during the last 18,000 years

Evolution of Chaka Salt Lake in NW China in response to climatic change during the Latest Pleistocene-Holocene

/pdf/the-grainsize-of-the-core-qh-2000-in-qinghai-lake-and-its-1yn00mepqz.pdf

The Grainsize of the Core QH-2000 in Qinghai Lake and Its Implication for Paleoclimate and Paleoenvironment

Lake Kusai lies in the Hoh Xil area, northern Tibetan Plateau. Based on the analyses of Total Organic Carbon content (TOC), Total Nitrogen content (TN) and Grain Size of sediments from Core KS-2006, this paper mainly analyzed the moisture variability in this area during the past 4000 years. The results showed that the moisture evolution of this area in the past 4000 years experienced the stages as follow: dry periods: 3900-3590 cal aBP, 3320-2630cal aBP, 1720-1420cal aBP and 1100-840cal aBP; humid periods: 3590-3320cal aBP, 2630-1720cal aBP, 1420-1100cal aBP and after 840cal aBP. Our results were generally consistent with the climatic changes inferred from the Oxygen Isotope, Dongge Cave, which indicates that the climate in northern Tibetan Plateau was also controlled by the Asian Monsoon. Additionally, Medieval Warm Period and Little Ice Age were well recorded in Lake Kusai as well.

/pdf/a-4000-year-moisture-evolution-recorded-by-sediments-of-lake-27sub9vcke.pdf

A 4000-year moisture evolution recorded by sediments of Lake Kusai in the Hoh Xil area, northern Tibetan Plateau

The three characteristic areas of western China – the Tibetan Plateau, the Loess Plateau and the lowland desert areas – show a vegetation evolution of strong temporal and spatial variability during the Marine Isotope Stages (MIS) 3 and 2. Most of these vegetation changes can be related to regional climate variability recorded in various climate archives. Most areas of western China are covered by steppes and forest steppes during the MIS 3. The optimal climate conditions for vegetation growth (warm and wet) occurred at the later MIS 3 around 40 ka causing the expansion of forests on the Tibetan Plateau and the Loess Plateau beyond their present-day limits. Due to the generally dry and cold climate around the time of the Last Glacial Maximum (LGM) (~21 ka), western China was mostly covered by deserts and semi-deserts during this period. The late glacial vegetation is characterized by several changes on millennial time scale: the vegetation optimum during the Bolling/Allerod period (~15–13 ka) yielded a large-scale forest expansion, a deterioration of the vegetation condition occurred during the Younger Dryas event around 12 ka. The transition towards a warmer and wetter climate at the beginning of the Holocene is evidently indicated in most vegetation records showing especially the spreading of broad-leaved trees on the Loess Plateau and at the margins of the Tibetan Plateau.

Liu Xingqi

Papers

Palaeoclimatic changes in the Qinghai Lake area during the last 18,000 years

Evolution of Chaka Salt Lake in NW China in response to climatic change during the Latest Pleistocene-Holocene

The Grainsize of the Core QH-2000 in Qinghai Lake and Its Implication for Paleoclimate and Paleoenvironment

A 4000-year moisture evolution recorded by sediments of Lake Kusai in the Hoh Xil area, northern Tibetan Plateau

Vegetation evolution in arid China during Marine Isotope Stages 3 and 2 (~65–11 ka)