Changes in the vegetation and climate of the westerly-dominated areas in Central Asia during the Holocene were interpreted using pollen-assemblages and charcoal data from a 300-cm-long sediment core of the Sayram Lake...Changes in the vegetation and climate of the westerly-dominated areas in Central Asia during the Holocene were interpreted using pollen-assemblages and charcoal data from a 300-cm-long sediment core of the Sayram Lake,northern Xinjiang.Accele-rator Mass Spectrometry(AMS) radiocarbon dating methods were applied to bulk organic matter of the samples.Artemisia spp./Chenopodiaceae ratios and results from principal component analysis were used to infer that the lake basin was dominated by desert vegetation before ca.9.6 cal.ka BP,which suggests a warm and dry climate in the early Holocene.Desert steppe/steppe expanded during 9.6-5.5 cal.ka BP,indicating a remarkable increase both in the precipitation and temperature during the mid-Holocene.Desert vegetation dominated between 6.5 and 5.5 cal.ka BP,marking an extreme warmer and drier interval.The steppe/meadow steppe recovered,and temperatures decreased from 5.5 cal.ka BP in the late Holocene,as indicated by the increased abundance of Artemisia and the development of meadows.Holocene temperatures and moisture variations in the Sayram Lake areas were similar to those of adjacent areas.This consistency implies that solar radiation was the main driving factor for regional temperature changes,and that the effect of temperature variations was significant on regional changes in humidity.The evolution of climate and environment in the Sayram Lake areas,which were characterized as dry in the early Holocene and relatively humid in the middle-late Holocene,are clearly different from those in monsoonal areas.Dry conditions in the early Holocene in the Sayram Lake areas were closely related to decreased water vapor advection.These conditions were a result of reduced westerly wind speeds and less evaporation upstream,which in turn were caused by seasonal changes in solar radiation superimposed by strong evaporation following warming and drying local climate.展开更多
One of the Holocene abrupt events around 4200 years ago,lasting for~200 years,is thought to have caused cultural disruptions,yet terrestrial climatic status right after the cold/dry event remains poorly defined and is...One of the Holocene abrupt events around 4200 years ago,lasting for~200 years,is thought to have caused cultural disruptions,yet terrestrial climatic status right after the cold/dry event remains poorly defined and is often presumed that a generally cool condition prevailed during the Bronze Age(~4000-2200 years ago).Here we report an alkenone-based summer temperature record over the past~12,000 years,in addition to two updated alkenone records,from Northwest China,providing new insights into the climatic status right after the event.Our results indicate that exceptional terrestrial warmth,up to~6°C,occurred around 4200-2800 years ago during the Bronze Age,superimposed on the long-term Holocene cooling trend.The exceptional warmth in Northwest China,together with other climate anomalies elsewhere,suggests an unusual large-scale climatic reorganization at 4200-2800 years ago when solar activity remained high,with important implications to the climate background for cultural developments during the Bronze Age.展开更多
基金supported by National Natural Science Foundation of China(Grant No.40802084)International Science&Technology Cooperation Program of China(Grant No.2011DFA21240)the CAS/SAFEA International Partnership Program for Creative Research Teams(Grant No.KZZDEW-TZ-08)
文摘Changes in the vegetation and climate of the westerly-dominated areas in Central Asia during the Holocene were interpreted using pollen-assemblages and charcoal data from a 300-cm-long sediment core of the Sayram Lake,northern Xinjiang.Accele-rator Mass Spectrometry(AMS) radiocarbon dating methods were applied to bulk organic matter of the samples.Artemisia spp./Chenopodiaceae ratios and results from principal component analysis were used to infer that the lake basin was dominated by desert vegetation before ca.9.6 cal.ka BP,which suggests a warm and dry climate in the early Holocene.Desert steppe/steppe expanded during 9.6-5.5 cal.ka BP,indicating a remarkable increase both in the precipitation and temperature during the mid-Holocene.Desert vegetation dominated between 6.5 and 5.5 cal.ka BP,marking an extreme warmer and drier interval.The steppe/meadow steppe recovered,and temperatures decreased from 5.5 cal.ka BP in the late Holocene,as indicated by the increased abundance of Artemisia and the development of meadows.Holocene temperatures and moisture variations in the Sayram Lake areas were similar to those of adjacent areas.This consistency implies that solar radiation was the main driving factor for regional temperature changes,and that the effect of temperature variations was significant on regional changes in humidity.The evolution of climate and environment in the Sayram Lake areas,which were characterized as dry in the early Holocene and relatively humid in the middle-late Holocene,are clearly different from those in monsoonal areas.Dry conditions in the early Holocene in the Sayram Lake areas were closely related to decreased water vapor advection.These conditions were a result of reduced westerly wind speeds and less evaporation upstream,which in turn were caused by seasonal changes in solar radiation superimposed by strong evaporation following warming and drying local climate.
基金financially supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDB40000000)the National Natural Science Foundation of China(41672349,40802084)Hong Kong Research Grants Council(17325516)。
文摘One of the Holocene abrupt events around 4200 years ago,lasting for~200 years,is thought to have caused cultural disruptions,yet terrestrial climatic status right after the cold/dry event remains poorly defined and is often presumed that a generally cool condition prevailed during the Bronze Age(~4000-2200 years ago).Here we report an alkenone-based summer temperature record over the past~12,000 years,in addition to two updated alkenone records,from Northwest China,providing new insights into the climatic status right after the event.Our results indicate that exceptional terrestrial warmth,up to~6°C,occurred around 4200-2800 years ago during the Bronze Age,superimposed on the long-term Holocene cooling trend.The exceptional warmth in Northwest China,together with other climate anomalies elsewhere,suggests an unusual large-scale climatic reorganization at 4200-2800 years ago when solar activity remained high,with important implications to the climate background for cultural developments during the Bronze Age.
