An increasing number of palaeo-climatic records have been reported to identify the Holocene climate history in the arid Xinjiang region of northwest China. However, few studies have fully considered the internal linka...An increasing number of palaeo-climatic records have been reported to identify the Holocene climate history in the arid Xinjiang region of northwest China. However, few studies have fully considered the internal linkages within the regional climate system, which may limit our understanding of the forcing mechanisms of Holocene climate change in this region. Here, we systematically consider three major issues of the moisture/precipitation, temperature and near-surface wind relevant to the Holocene climate history of Xinjiang. First, despite there still has debated for the Holocene moisture evolution in this region, more climatic reconstructions from lake sediments, loess, sand-dunes and peats support a long-term regional wetting trend. Second, temperature records from ice cores, peats and stalagmites demonstrate a long-term winter warming trend during the Holocene in middle-to high-latitudes of Asia. Third, recent studies of aeolian sedimentary sequences reveal that the near-surface winds in winter gradually weakened during the Holocene, whereas the winter mid-latitude Westerlies strengthened in the Tienshan Mountains. Based on this evidence, in the arid Xinjiang region we propose an early to middle Holocene relatively cold and dry interval, with strong near-surface winds;and a warmer, wetter interval with weaker near-surface winds in the middle to late Holocene during winter. Additionally,we develop a conceptual model to explain the pattern of Holocene climate changes in this region.From the early to the late Holocene, the increasing atmospheric COcontent and winter insolation,and the shrinking of high-latitude continental ice-sheets, resulted in increasing winter temperatures in middle to high latitudes in the Northern Hemisphere. Subsequently, the increased winter temperature strengthened the winter mid-latitude Westerlies and weakened the Siberian high-pressure system,which caused an increase in winter precipitation and a decrease in near-surface wind strength. This scenario is strongly supported by evidence from geological records, climate simulation results, and modern reanalysis data. Our hypothesis highlights the important contribution of winter temperature in driving the Holocene climatic evolution of the arid Xinjiang region, and it implies that the socio-economic development and water resources security of this region will face serious challenges presented by the increasing winter temperature in the future.展开更多
The carbon isotope ratios(δ^(13)C) of modern land plants have been widely studied,and they provide valuable information about modern and past atmospheric,ecological and climatic changes [1].According to their differe...The carbon isotope ratios(δ^(13)C) of modern land plants have been widely studied,and they provide valuable information about modern and past atmospheric,ecological and climatic changes [1].According to their different photosynthetic pathways,land plants are mostly C_(3) and C_(4) plants.The δ^(13)C values of C_(3) plants are mainly within the range of-20‰ to-34‰.展开更多
Lake level and its inferred East Asian summer monsoon(EASM)evolution in northern boundary of EASM during the Holocene are highly debated.Here,we present a 15-ka record of glycerol dialkyl glycerol tetraethers(GDGTs)in...Lake level and its inferred East Asian summer monsoon(EASM)evolution in northern boundary of EASM during the Holocene are highly debated.Here,we present a 15-ka record of glycerol dialkyl glycerol tetraethers(GDGTs)in a closed lake in northern China to address this issue.Surface and downcore sediment data demonstrate sedimentary GDGT-0 and branched GDGTs(brGDGTs)are of aquatic production.Contents of GDGT-0 and brGDGTs increase but brGDGT-based paleo-temperature proxy decreases with water depth in surface sediments along a nearshore to offshore transect.This trend is likely due to an increasingly hypoxic condition,favored by anaerobic microbes producing these GDGT-0 and brGDGTs,in bottom water.Accordingly,brGDGT-derived water temperature and pH would reflect bottom water conditions that are largely regulated by water depth of the lake.Downcore GDGT data and their derived temperature and pH consistently reveal a gradually increasing lake level from the late Pleistocene to the early Holocene,a high level during 9.5-5 ka BP and a decreasing trend afterward.The lake-level records from independent and robust proxies in this study largely agree with pollen records in the region,supporting a mid-Holocene maximum EASM precipitation.展开更多
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program (STEP) (Grant No. 2019QZKK0602)the National Natural Science Foundation of China (Grant Nos. 41401046, 42067049)+1 种基金the Education Science and technology Innovation project of Gansu Province (2021QB-118)the Jiangxi Provincial Natural Science Foundation (Grant No. 20202BABL213035)。
文摘An increasing number of palaeo-climatic records have been reported to identify the Holocene climate history in the arid Xinjiang region of northwest China. However, few studies have fully considered the internal linkages within the regional climate system, which may limit our understanding of the forcing mechanisms of Holocene climate change in this region. Here, we systematically consider three major issues of the moisture/precipitation, temperature and near-surface wind relevant to the Holocene climate history of Xinjiang. First, despite there still has debated for the Holocene moisture evolution in this region, more climatic reconstructions from lake sediments, loess, sand-dunes and peats support a long-term regional wetting trend. Second, temperature records from ice cores, peats and stalagmites demonstrate a long-term winter warming trend during the Holocene in middle-to high-latitudes of Asia. Third, recent studies of aeolian sedimentary sequences reveal that the near-surface winds in winter gradually weakened during the Holocene, whereas the winter mid-latitude Westerlies strengthened in the Tienshan Mountains. Based on this evidence, in the arid Xinjiang region we propose an early to middle Holocene relatively cold and dry interval, with strong near-surface winds;and a warmer, wetter interval with weaker near-surface winds in the middle to late Holocene during winter. Additionally,we develop a conceptual model to explain the pattern of Holocene climate changes in this region.From the early to the late Holocene, the increasing atmospheric COcontent and winter insolation,and the shrinking of high-latitude continental ice-sheets, resulted in increasing winter temperatures in middle to high latitudes in the Northern Hemisphere. Subsequently, the increased winter temperature strengthened the winter mid-latitude Westerlies and weakened the Siberian high-pressure system,which caused an increase in winter precipitation and a decrease in near-surface wind strength. This scenario is strongly supported by evidence from geological records, climate simulation results, and modern reanalysis data. Our hypothesis highlights the important contribution of winter temperature in driving the Holocene climatic evolution of the arid Xinjiang region, and it implies that the socio-economic development and water resources security of this region will face serious challenges presented by the increasing winter temperature in the future.
基金supported by the National Natural Science Foundation of China (42001080, 42171156, and 42067049)the Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province。
文摘The carbon isotope ratios(δ^(13)C) of modern land plants have been widely studied,and they provide valuable information about modern and past atmospheric,ecological and climatic changes [1].According to their different photosynthetic pathways,land plants are mostly C_(3) and C_(4) plants.The δ^(13)C values of C_(3) plants are mainly within the range of-20‰ to-34‰.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.42171156&42003055).
文摘Lake level and its inferred East Asian summer monsoon(EASM)evolution in northern boundary of EASM during the Holocene are highly debated.Here,we present a 15-ka record of glycerol dialkyl glycerol tetraethers(GDGTs)in a closed lake in northern China to address this issue.Surface and downcore sediment data demonstrate sedimentary GDGT-0 and branched GDGTs(brGDGTs)are of aquatic production.Contents of GDGT-0 and brGDGTs increase but brGDGT-based paleo-temperature proxy decreases with water depth in surface sediments along a nearshore to offshore transect.This trend is likely due to an increasingly hypoxic condition,favored by anaerobic microbes producing these GDGT-0 and brGDGTs,in bottom water.Accordingly,brGDGT-derived water temperature and pH would reflect bottom water conditions that are largely regulated by water depth of the lake.Downcore GDGT data and their derived temperature and pH consistently reveal a gradually increasing lake level from the late Pleistocene to the early Holocene,a high level during 9.5-5 ka BP and a decreasing trend afterward.The lake-level records from independent and robust proxies in this study largely agree with pollen records in the region,supporting a mid-Holocene maximum EASM precipitation.
