Lake Xingcuo is a small closed, hard\|water lake, situated on eastern Tibet Plateau. Stable isotope data (\{δ\{\}\+\{18\}O\} and \{δ\{\}\+\{13\}C\}) from the freshwater snail Gyraulus sibirica (Dunker) in a 34 cm lo...Lake Xingcuo is a small closed, hard\|water lake, situated on eastern Tibet Plateau. Stable isotope data (\{δ\{\}\+\{18\}O\} and \{δ\{\}\+\{13\}C\}) from the freshwater snail Gyraulus sibirica (Dunker) in a 34 cm long, radioactive isotope\|dated sediment core represent the last 200 years of Lake Xingcuo environmental history. Carbon and oxygen isotope ratios in the shells of the freshwater snail bear information on the isotopic composition of the water in which the shells were formed, which in turn characterizes the climatic conditions prevailing during the snail’s life span. Whole\|shell and incremental growth data were collected from modern and fossil shells from Lake Xingcuo. The \{δ\{\}\+\{18\}O\} values of modern shells from Lake Xingcuo are in equilibrium with those of modern waters, while \{δ\{\}\+\{13\}C\} values are indicative of snail dietary carbon and a lake with high \{δ\{\}\+\{13\}C\}\-\{TDIC\}. By calibrating \{δ\{\}\+\{18\}O\} and \{δ\{\}\+\{13\}C\} in the shell Gyraulus sibirica (Dunker) with instrument\|measured data for the period 1954-1992, we found that the \{δ\{\}\+\{18\}O\} of the snail shells is an efficient indicator to reveal air temperature in the warmer half year instead of that around the whole year, and that there is a certain positive correlation between index\{δ\{\}\+\{18\}O\} and the running average temperature in the warmer half\|year period. Climatic variability on eastern Tibet Plateau, for the last two centuries, has been successfully inferred from the\{δ\{\}\+\{18\}O\} record in freshwater snails in the sediments of Lake Xingcuo. As such, the last 200 years of palaeoclimatic record for this region can be separated into three periods representing oscillations between warming and cooling, which are confirmed by the Guliya ice record on the Tibet Plateau.展开更多
This paper presents the results of determining trace elements and δ 13C, δ 18O in Gyraulus sibirica shell continuously preserved in Xingcuo Lake sediments in the recent 50 years. By coupling these indexes and instru...This paper presents the results of determining trace elements and δ 13C, δ 18O in Gyraulus sibirica shell continuously preserved in Xingcuo Lake sediments in the recent 50 years. By coupling these indexes and instrumental meteorological data on its basin to determine the relations among them, we probed quantitatively the climatic signals recorded in Xingcuo Lake sediments. The results showed that gastropod shells in Xingcuo Lake were formed in warm seasons; that trace elements, and stable isotope in shells just recorded the climatic signals of the warm seasons instead of that of the whole year; that Mg/Ca ratio and δ 18O proxy had certain correlation with air temperature in warm seasons, when the δ 18O proxy was more sensitive; with the average ratio of them being 0.28×10 -3/℃ and the variation rate dδ 18O/dT being 1.64×10 -3/℃; that the Sr/Ca ratio and δ 13C proxy, especially Sr/Ca ratio, had close correlation; and that dSr/Ca/dP was -0.045/mm.展开更多
Seeking for an effective method to probe further the relation among Tibetan Plateau, climatic events, and natural environmental changes in the Zoige Basin, we proposed a physical model for the reconstruction of climat...Seeking for an effective method to probe further the relation among Tibetan Plateau, climatic events, and natural environmental changes in the Zoige Basin, we proposed a physical model for the reconstruction of climate and environment and a preliminary application was conducted on the 45 m (about 200 ka BP ), upper part of Core RM (310 m long) drilled in the Zoige Basin (33°57’N, 102°21’E), on the eastern Tibetan Plateau. The results showed that: a) in the Zoige region, the maximum temperature in the period equivalent to Stage 7 in the deep sea stable oxygen record was 2.7℃ higher than that at present; b) Stage 6 temperature was 4.3℃ lower than that at present; c) Stage 5 peak temperature was 5.2℃ higher than that at present; d) Stage 4 average temperature should have been 2-3℃ lower than that at present; and e) Stage 3 temperature differences within the period were more than 4℃. It was found that during Stage 6 (140-160 ka BP) the environment in the Zoige Basin was extraordinary, representing a transition period from warm dry and cold wet to warm wet and cold dry environmental conditions due to the uplift that occurred on the Tibetan Plateau at this period.展开更多
文摘Lake Xingcuo is a small closed, hard\|water lake, situated on eastern Tibet Plateau. Stable isotope data (\{δ\{\}\+\{18\}O\} and \{δ\{\}\+\{13\}C\}) from the freshwater snail Gyraulus sibirica (Dunker) in a 34 cm long, radioactive isotope\|dated sediment core represent the last 200 years of Lake Xingcuo environmental history. Carbon and oxygen isotope ratios in the shells of the freshwater snail bear information on the isotopic composition of the water in which the shells were formed, which in turn characterizes the climatic conditions prevailing during the snail’s life span. Whole\|shell and incremental growth data were collected from modern and fossil shells from Lake Xingcuo. The \{δ\{\}\+\{18\}O\} values of modern shells from Lake Xingcuo are in equilibrium with those of modern waters, while \{δ\{\}\+\{13\}C\} values are indicative of snail dietary carbon and a lake with high \{δ\{\}\+\{13\}C\}\-\{TDIC\}. By calibrating \{δ\{\}\+\{18\}O\} and \{δ\{\}\+\{13\}C\} in the shell Gyraulus sibirica (Dunker) with instrument\|measured data for the period 1954-1992, we found that the \{δ\{\}\+\{18\}O\} of the snail shells is an efficient indicator to reveal air temperature in the warmer half year instead of that around the whole year, and that there is a certain positive correlation between index\{δ\{\}\+\{18\}O\} and the running average temperature in the warmer half\|year period. Climatic variability on eastern Tibet Plateau, for the last two centuries, has been successfully inferred from the\{δ\{\}\+\{18\}O\} record in freshwater snails in the sediments of Lake Xingcuo. As such, the last 200 years of palaeoclimatic record for this region can be separated into three periods representing oscillations between warming and cooling, which are confirmed by the Guliya ice record on the Tibet Plateau.
文摘This paper presents the results of determining trace elements and δ 13C, δ 18O in Gyraulus sibirica shell continuously preserved in Xingcuo Lake sediments in the recent 50 years. By coupling these indexes and instrumental meteorological data on its basin to determine the relations among them, we probed quantitatively the climatic signals recorded in Xingcuo Lake sediments. The results showed that gastropod shells in Xingcuo Lake were formed in warm seasons; that trace elements, and stable isotope in shells just recorded the climatic signals of the warm seasons instead of that of the whole year; that Mg/Ca ratio and δ 18O proxy had certain correlation with air temperature in warm seasons, when the δ 18O proxy was more sensitive; with the average ratio of them being 0.28×10 -3/℃ and the variation rate dδ 18O/dT being 1.64×10 -3/℃; that the Sr/Ca ratio and δ 13C proxy, especially Sr/Ca ratio, had close correlation; and that dSr/Ca/dP was -0.045/mm.
文摘Seeking for an effective method to probe further the relation among Tibetan Plateau, climatic events, and natural environmental changes in the Zoige Basin, we proposed a physical model for the reconstruction of climate and environment and a preliminary application was conducted on the 45 m (about 200 ka BP ), upper part of Core RM (310 m long) drilled in the Zoige Basin (33°57’N, 102°21’E), on the eastern Tibetan Plateau. The results showed that: a) in the Zoige region, the maximum temperature in the period equivalent to Stage 7 in the deep sea stable oxygen record was 2.7℃ higher than that at present; b) Stage 6 temperature was 4.3℃ lower than that at present; c) Stage 5 peak temperature was 5.2℃ higher than that at present; d) Stage 4 average temperature should have been 2-3℃ lower than that at present; and e) Stage 3 temperature differences within the period were more than 4℃. It was found that during Stage 6 (140-160 ka BP) the environment in the Zoige Basin was extraordinary, representing a transition period from warm dry and cold wet to warm wet and cold dry environmental conditions due to the uplift that occurred on the Tibetan Plateau at this period.
