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The history and mechanisms of dust storms in northern China remain unclear owing to the paucity of reliable long-term, high-resolution geological records. In this study, we reconstructed the dust storm history of the last ~500 years in northern China, based on sedimentary coarse fraction (>63 µm) of a well-dated core from Lake Daihai, Inner Mongolia. The high-resolution data reveal three intervals of frequent dust storms: AD 1520–1580, AD 1610–1720, and AD 1870–2000. The dust storm events in the Lake Daihai area were broadly synchronous with those inferred from other historical or geological records and generally occurred during cold intervals. Changes in the intensity of Siberian High and the westerlies modulated by temperature variations are the likely major factors controlling dust storm dynamics. An interesting feature is that although the intensities of dust storms have been systematically increased during the recent warming period, a clear decreasing trend within this period is evident. The recent increase in average dust storm intensity may be ascribed to an increase in particle supply resulting from a rapid increase in human activity, whereas the weakening trend was likely caused by decreases in average wind speed resulting from the recent global warming.

The reasons and processes that led hunter-gatherers to transition into a sedentary and agricultural way of life are a fundamental unresolved question of human history. Here we present results of excavations of two single-occupation early Neolithic sites (dated to 7.9 and 7.4 ka) and two high-resolution archaeological surveys in northeast China, which capture the earliest stages of sedentism and millet cultivation in the second oldest center of domestication in the Old World. The transition to sedentism coincided with a significant transition to wetter conditions in north China, at 8.1-7.9 ka. We suggest that these wetter conditions were an empirical precondition that facilitated the complex transitional process to sedentism and eventually millet domestication in north China. Interestingly, sedentism and plant domestication followed different trajectories. The sedentary way of life and cultural norms evolved rapidly, within a few hundred years, we find complex sedentary villages inhabiting the landscape. However, the process of plant domestication, progressed slowly over several millennia. Our earliest evidence for the beginning of the domestication process appear in the context of an already complex sedentary village (late Xinglongwa culture), a half millennia after the onset of cultivation, and even in this phase domesticated plants and animals were rare, suggesting that the transition to domesticated (sensu stricto) plants in affluent areas might have not played a substantial role in the transition to sedentary societies.

The magnitude, rate, and extent of past and future East Asian monsoon (EAM) rainfall fluctuations remain unresolved. Here, late Pleistocene–Holocene EAM rainfall intensity is reconstructed using a well-dated northeastern China closed-basin lake area record located at the modern northwestern fringe of the EAM. The EAM intensity and northern extent alternated rapidly between wet and dry periods on time scales of centuries. Lake levels were 60 m higher than present during the early andmiddle Holocene, requiring a twofold increase in annual rainfall, which, based on modern rainfall distribution, requires a ∼400 km northward expansion/migration of the EAM. The lake record is highly correlated with both northern and southern Chinese cave deposit isotope records, supporting rainfall “intensity based” interpretations of these deposits as opposed to an alternative “water vapor sourcing” interpretation. These results indicate that EAM intensity and the northward extent covary on orbital and millennial timescales. The termination of wet conditions at 5.5 ka BP (∼35 m lake drop) triggered a large cultural collapse of Early Neolithic cultures in north China, and possibly promoted the emergence of complex societies of the Late Neolithic.

The influence of recent global warming on the intensity, timing, and extent of the East Asian summer monsoon (EASM) remains not fully understood. Here we reconstruct an EASM precipitation history of the past ~ 500 years based on sedimentary multi-proxy indices from Lake Daihai, northern China. We find low EASM precipitation between ~ AD 1517 and ~ 1850, with three sharply weakened intervals, which were broadly concurrent with the Chinese dynastic and cultural transitions. The EASM intensified after ~ AD 1850, changing from cold-dry to warm-wet conditions, with greater multidecadal variability. These features match well with the coeval sea surface temperature (SST) records over the North Pacific and North Atlantic Oceans, suggesting that changes in global SSTs could have forced changes in EASM intensity and modulated regional hydroclimate on these timescales. We propose that the increased interhemispheric temperature gradients associated with the recent global warming might push northward the western Pacific Subtropical High (WPSH), the westerlies, and the monsoon front. Meanwhile, the multi-decadal warming in the North Atlantic may also strengthen the westerlies and the EASM. These multiple factors could have collectively led to higher precipitation in the converging zone of the westerlies and the WPSH since ~ AD 1850.

Sedimentary records of lipid biomarkers such as leaf wax n-alkanes are influenced by not only ecosystem turnover and physiological changes in plants but also earth surface processes integrating these signals into the sedimentary record, though the effect of these integration processes is not fully understood. To determine the depositional constraints on biomarker records in a high-altitude small catchment system, we collected both soil and stream sediments along a 1000 m altitude transect (1500–2500 m a.s.l.) in the Areguni Mountains, a subrange of the Lesser Caucasus Mountains in Armenia. We utilize a treeline at ∼ 2000 m a.s.l., which separates alpine meadow above from deciduous forest below, to assess the relative contribution of upstream biomarker transport to local vegetation input in the stream. We find that average chain length (ACL), hydrogen isotope (δD) and carbon isotope (δ13C) values of n-alkanes are significantly different in soils collected above and below the treeline. However, samples collected from the stream sediments do not integrate these signals quantitatively. As the stream drops below the treeline, the ACL, δD and δ13C values of n-alkanes preserved in streambed sediments reflect a bias toward n-alkanes sourced from trees. This suggests that either (1) there is minimal transportation of organic matter from the more open vegetation at higher elevations or (2) greater production of target biomarkers by trees and shrubs found at lower elevations results in overprinting of stream signals by local vegetation. Though these observations may preclude using n-alkanes to measure past treeline movement in these mountains, δD values of biomarkers in fluvial deposits in these settings are more likely to record local hydrological changes rather than reflect fractionation changes due to turnover in the upstream vegetation structure.

Earth’s climate can exist in many stable states that are vastly different from the modern climate state. Understanding modern and future climate requires a thorough understanding of the full range of possible climate states and the processes that trigger transitions between states. Quantitative reconstructions of past climate variables provide constrains on the magnitude, mechanisms and feedbacks involved in producing stable climate states. As such, they provide insights into past climate states unobservable today. This thesis focuses on quantifying three metrics of past climate systems: (a) quantitative rainfall amount, which provides means for assessing how the spatial distribution of rainfall changed in the past, (b) the isotopic composition of past rainwater (δP), which provides means for understand- ing how atmospheric circulation changed in the past, and (c) relative humidity, which provides estimates of evaporative processes and hydrospheric fluxes. The regions studied are in the two far reaches of the Asian continent. In eastern Asia, changes in rainfall amount and δP over the past 125 ka were studied using geomorphological evidence from a closed basin lake in Inner Mongolia, China and compound-specific δ Dwax and δ13Cwax from organic molecules in lake sediments. In western Asia, the research focused on processes that govern modern δP and modern δ Dwax and δ13Cwax in soils. In addition the hydrological regime of the Eastern Mediterranean and the Levant during the Last Glacial Maximum were studied using evidence from speleothem δ18Oc and foraminifera δ18O. These records provide empirical and quantitative information about rainfall amount, δP and relative humidity at singular locations, and as such provide the building blocks for producing coherent large-scale reconstruction of the migration of rain-belts in the past.