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The East Asian monsoon exerts a profound influence on environmental change in the East Asian region. Various factors have been hypothesized as the dominant Asian monsoon forcings, however, the forcings can change from interannual to millennial timescales. The linkages between monsoon forcings at different timescales remain unclear. To better understand the connection of the variabilities and mechanisms of the East Asian monsoon at various timescales, we present a modern analog. Various climatic data, monsoon indices, and circulation factor calculations were used to identify the variabilities and controlling factors of the modern East Asian summer and winter monsoons. Paleo-climatic proxies from a region sensitive to both summer and winter monsoons were used in concert with monsoon simulation data to reconstruct and analyze paleo-monsoon variations and mechanisms. Results showed that the weakening of the Holocene Asian summer and winter monsoons is closely linked to low-latitude summer insolation and mid-latitude winter insolation, while modern summer and winter monsoons are related to global circulation, sea surface temperature, and sea ice change. We confirm that the driving mechanism of the monsoon was dependent on timescale. [ABSTRACT FROM AUTHOR]

China is the country with the most population in the world, and its climate is extremely diverse due to tremendous differences in latitude, longitude, and altitude, ranging from tropical in the far south to subarctic in the far north and alpine in the higher elevations of the Qinghai-Tibetan Plateau. Accurate assessment of its modern climate change is conductive to addressing global warming threat. Along with the development of Past Global Changes (PAGES) research, the focus has changed from paleo-climate reconstructions to using paleo-data for assessing the present and predicting the future. Previous studies have been devoted to climate change assessment using modern climate observations and simulations. This paper presents a new assessment approach based on the mid-Holocene, which provides a naturally oriented warming that can be compared to modern human-made global warming. A variety of climatic data, including modern observations, paleo-climate records, CMIP5 (Coupled Model Intercomparison Project Phase 5) and PMIP3 (Paleoclimate Modelling Intercomparison Project 3) simulations, as well as lake level models, were applied in this synthesis. Numerical climate classification was introduced to evaluate climate change impacts to Chinese climate zones on various time scales. The results show that winter and summer seasons have different response to the naturally oriented mid-Holocene warming but human-made global warming makes the warming trend appear in all seasons. Temperate and continental dry winter climates expand dramatically during the mid-Holocene warm period; however, the future global warming could have few impacts to Chinese climate zones. Furthermore, the East Asian summer monsoon was strengthened obviously by the mid-Holocene warm climate and strong low-latitude insolation. There is no consistent trend both for the winter and summer monsoon on the background of human-made global warming. In this study, a new benchmark was established based on paleo-climate to evaluate the impacts of human-made global warming. [ABSTRACT FROM AUTHOR]

The production, transport, and deposition of dust has profound impacts and feedbacks on the regional and global environments. In parallel, the Tibet Plateau (TP) plays an important role in East Asian and global climate systems. Previous studies have shown that the dust can reach the plateau by long-distance transport from the westerlies and by short-distance transport from regional weathering. Here we present three new datasets in the Qilian Mountains of the northern TP, including two mountainous aeolian sedimentary sequences and a surface sample dataset. Proxies include grain size, magnetic susceptibility, mineral composition, total organic carbon, and total nitrogen. Data from surface samples indicate spatial gradient effects in altitude (from low to high) and latitude (from north to south), suggesting dust transport from the Gobi Desert to the plateau. The synthetic analysis of two aeolian sedimentary sequences and paleoclimate simulation data reveals that the northern TP can be a dust transport channel controlled mainly by the Asian winter monsoon and less influenced by the westerlies. [ABSTRACT FROM AUTHOR]

Background: Closed basins occupy 21% of the world's land area and can substantially affect global carbon budgets. Conventional understanding suggests that the terminal areas of closed basins collect water and carbon from throughout the entire basin, and changes in lake organic carbon sinks are indicative of basin-wide organic carbon storages. However, this hypothesis lacks regional and global validation. Here, we first validate the depositional process of organic carbon in a typical closed-basin region of northwest China using organic geochemical proxies of both soil and lake sediments. Then we estimate the organic carbon sinks and human impacts in extant closed-basin lakes since the Last Glacial Maximum (LGM). Results: Results show that 80.56 Pg organic carbon is stored in extant closed-basin lakes mainly found in the northern mid-latitudes. Carbon accumulation rates vary from 17.54 g C m−2 yr−1 during modern times, 6.36 g C m−2 yr−1 during the mid-Holocene and 2.25 g C m−2 yr−1 during the LGM. Then, we evaluated the influence by human activities during the late Holocene (in the past three thousand years). The ratio of human impacts on lake organic carbon storage in above closed basins is estimated to be 22.79%, and human-induced soil organic carbon emissions in the past three thousand years amounted to 207 Pg. Conclusions: While the magnitude of carbon storage is not comparable to those in peatland, vegetation and soil, lake organic carbon sinks from closed basins are significant to long-term terrestrial carbon budget and contain information of climate change and human impact from the whole basins. These observations improve our understanding of carbon sinks in closed basins at various time scales, and provide a basis for the future mitigation policies to global climate change. [ABSTRACT FROM AUTHOR]

The fluctuation of a single lake level is a comprehensive reflection of water balance within the basin, while the regional consistent fluctuations of lake level can indicate the change of regional effective moisture. Previous researches were mainly focused on reconstructing effective moisture by multiproxy analyses of lake sediments. We carried out a series of experiments, including a transient climate evolution model, a lake energy balance model and a lake water balance model to simulate continuous Holocene effective moisture change represented by variability of virtual lake level in East and Central Asia. The virtual lake level, area, water depth and salinity are not equivalent to actual values, but we estimated relative changes of the regional effective moisture. We also explored the driving mechanisms of effective moisture change in different geographical regions. Our results indicated that gradually falling effective moisture during the Holocene in northern China was due to the combined effects of high lake evaporation caused by longwave and shortwave radiation, and low precipitation caused by reductions of summer solar insolation. A decline in effective moisture through the Holocene in the Tibetan Plateau and southern Central Asia resulted from decreased precipitation because of the weakening of the Asian summer monsoon. Increased precipitation induced by the strengthening of the westerly circulation contributed to the effective moisture rise during the Holocene in northern Central Asia. [ABSTRACT FROM AUTHOR]

Terrestrial ecosystems have received considerable attention as a significant sink for organic carbon at regional to global scales. Previous studies were focused on assessment and quantification of carbon sinks for one ecotype, and few have worked on the interconnection of terrestrial sinks. In this paper, we synthesized the data from China's second national soil survey and direct measurements from 54 lakes. Meanwhile, we investigated the controlling factors of carbon accumulation dynamics in soils and lakes. Results showed varied spatial distribution of soil and lake organic carbon in different regions, and three storage modes were found. The storage mode of watershed collection was observed in the region of the Qinghai-Tibetan Plateau, while the northeast China and Yunnan-Guizhou Plateau revealed another storage mode of autochthonous deposition, and the mode of human activities affection was represented by the East Plain and Mongolia-Xinjiang Plateau. The spatial difference throughout China was regulated by various climate patterns, geological conditions and anthropogenic interference. Our results provide insights into carbon storage modes in various regions, and also inform strategies for enhancing global carbon sequestration and future mitigation policies towards global climate change. • Climate, topography and human activity regulate regional soil and lake carbon storage. • Three carbon storage modes based on relationship between soil and lake carbon. • Suggestions to enhance carbon sequestration through soil and lake management. [ABSTRACT FROM AUTHOR]

Climate change modes between East Asia and southwestern North America are interlinked; however, little research has been done in comparing the underlying mechanisms between time scales. Here we present a comprehensive study using modern observations, paleoclimate records, and PMIP3/CMIP5 simulations to investigate the multi-timescale wet/dry changes in East Asia and southwestern North America and its relationship in climate change modes since the Last Glacial Maximum. Results show that wet/dry conditions in the monsoon and non-monsoon regions of East Asia and southwestern North America all have reverse changes at different timescales. On the millennial-scale the two continents are linked through the factors of insolation, greenhouse gas concentrations, El Niño-Southern Oscillation, and the northern hemisphere ice sheet. On the modern interannual and interdecadal scales the two climate systems are interlinked through the atmosphere-ocean interaction and precipitation and temperature patterns of both continents. This study provides a new perspective for the linkage study between different continents on a long-term scale, as well as a new recognition to global monsoon system. • Investigates the multi-timescale wet/dry changes in EA and SWNA. • Wet/dry conditions in the monsoon and non-monsoon regions of EA and SWNA all have reverse changes. • Modern wet/dry changes are closely affected by precipitation and temperature, as well as SST. • Wet/dry changes at the millennial timescale are closely related to AMOC and ENSO. • Provides a new perspective for the linkage study between different continents on a long-term scale. [ABSTRACT FROM AUTHOR]

The ocean plays a crucial role in the global and regional climate. Many regional monsoon climates are interlinked by ocean currents and sea surface temperature (SST). The climate link between the East Asian and North American continent has been proposed and verified by many studies. A widely accepted hypothesis is that the precipitation of the monsoon marginal zone is strongly affected by the monsoon intensity. However, our rigorous test does not support a causal relation between precipitation in the monsoon marginal zone and summer monsoon intensity. Here we present systematic analysis with modern observation and simulation datasets, the Holocene paleoclimatic records and simulations from the East Asian summer monsoon (EASM) and North American summer monsoon (NASM) marginal zone to verify the relation between precipitation in the monsoon marginal zone and the ocean. Our results suggest that precipitation of the EASM and NASM marginal zone is affected by the Pacific SST and the El Niño-Southern Oscillation (ENSO) rather than the monsoon intensity. In particular, the impacts of SST lead to synchronous variations in the EASM and NASM marginal zone. With the global warming and increasing ENSO events, precipitation in the monsoon marginal zone, which locates in semi-arid regions, would reduce, resulting in an expansion of the semi-arid region. • Precipitation in the monsoon marginal zone will reduce with global warming, resulting in an expansion of semi-arid regions. • The wet-dry conditions in the EASM and NASM marginal zone are negatively correlated with SST at the millennial scale. • The transmission effect of SST links the EASM and NASM marginal zone synchronously. • Precipitation in the monsoon marginal zone is projected to reduce with global warming and more frequent ENSO events, resulting in an expansion of the semi-arid region. [ABSTRACT FROM AUTHOR]

• Carbonate δ 18 O from surface sediments is affected both by precipitation and temperature. • Organic carbon isotope (δ 13 C org) from surface sediments reflects the vegetation growth status. • The eolian sedimentary sequence reconstructs the climate change in the northern QTP since the LGM. • There is a close relationship between climate mode in the northern QTP and the westerly jet stream. • Climates in the northern QTP and high-altitude regions of mid-latitudes will be wetter in the future. Climate change from the northern Qinghai-Tibet Plateau (QTP) is affected by the combined effects of the Asian summer monsoon and the westerlies. However, changes in monsoon vapor transport and the westerly jet stream, as well as their effect to climate change mode there, are not clear at different time scales. Here we present composite research using paleoclimate reconstructions and ensemble simulations since the Last Glacial Maximum (LGM) on the basis of an eolian sedimentary sequence in the northern QTP. Results from 317 surface sediment samples show that pedogenic carbonate δ 18 O is affected both by precipitation and temperature, and organic carbon isotope (δ 13 C org) reflects the vegetation growth status in areas where precipitation is greater than 290 mm. Proxies from the sedimentary sequence and the Paleoclimate Modeling Intercomparison Project 3 (PMIP3) simulations show a close relationship between climate change mode in the northern QTP and the westerly jet stream whose movement is triggered by warm or cold conditions in the high-latitude regions. That is, when the climate is in cold/glacial period the westerly jet stream strengthens and moves southward, and the mountains become wetter. This climate change mode can be validated by records from mountains of North America and Africa. According to the CMIP5 simulations, the westerly jet stream will strengthen in the future, and climate in the northern QTP and the high-altitude region of the mid-latitudes will become wetter with global warming. [ABSTRACT FROM AUTHOR]