Zige Tangco is a meromictic saline lake located on the central Tibetan Plateau.Two parallel cores(ZGTC A-1 and ZGTC A-2)were collected from the lake at a water depth of 25 m during summer 2006.The chronology of core A...Zige Tangco is a meromictic saline lake located on the central Tibetan Plateau.Two parallel cores(ZGTC A-1 and ZGTC A-2)were collected from the lake at a water depth of 25 m during summer 2006.The chronology of core A-1 was reconstructed based on the Constant Initial Concentration(CIC)model of 210Pb and three accelerator mass spectrometry(AMS)ages from the chitin fragments.The hard water effect calibration of the sediment ^(14)C age showed that the reservoir effect ranged from 1655 yr at 1950 AD to 1540 yr at 1610 AD.The hydrological variation in Zige Tangco during the past 800 yr was reconstructed using multi-proxies,including organic and carbonate content,stable isotopes of fine-grained carbonate minerals(<38.5μm)and grain-size distribution of the lake sediments.Our results show that there were strong fluctuations in the lake level between 1200 and 1820 AD,and at least three dry periods were recorded between 1235 and 1315 AD,1410 and 1580 AD,and 1660 and 1720 AD characterized by high carbonate content,abrupt positive shifts of stable isotopes,and high sand content.The low-lake-level periods during the Little Ice Age(LIA)in Zige Tangco correspond to the lower δ^(18)O values in the Guliya ice core and the lower precipitation reconstructed from tree rings in Delingha.This demonstrated that the summer monsoon on the central Tibetan Plateau weakened during the dry and cold periods,whereas the winter monsoon strengthened.Relatively wetter periods or higher lake levels in Zige Tangco occurred at 1580-1650 AD and 1820-1900 AD.Negative shifts in stable isotopes were related to increased lake levels between 1800 and 1820 AD.Our results also showed that the summer monsoon precipitation on the central Tibetan Plateau was mainly controlled by solar activity during the past 800 yr.展开更多
Widespread lakes on the Tibetan Plateau(TP)are valuable archives for investigating climate and environment changes, which could provide essential information on the mechanisms of past climate changes on the TP and the...Widespread lakes on the Tibetan Plateau(TP)are valuable archives for investigating climate and environment changes, which could provide essential information on the mechanisms of past climate changes on the TP and their interaction with the global climate systems.However, there is a lack of in-depth investigation of modern limnological processes in the Tibetan lakes, which hampers the understanding of paleolimnological records and lake ecosystem succession. In this study, we performed continuous temperature monitoring at two lakes, Bangong Co, a freshwater lake in the western TP, and Dagze Co, a brackish lake in the central TP, in order to characterize the patterns of seasonal temperature variability, stratification,and mixing. Temperature data for an entire hydrological year demonstrate that Bangong Co is a dimictic lake and that Dagze Co is a meromictic lake. The higher salinity in the deep water at Dagze Co prevents the lake from overturning completely, and this finding is supported by simulations using a physical limnological model Lake Analyzer. Continuous lake water temperature monitoring provides fundamental data for classifying Tibetan lakes, as well as the hydrological basis for understanding their paleolimnological records and ecosystem succession.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41971097).
文摘Zige Tangco is a meromictic saline lake located on the central Tibetan Plateau.Two parallel cores(ZGTC A-1 and ZGTC A-2)were collected from the lake at a water depth of 25 m during summer 2006.The chronology of core A-1 was reconstructed based on the Constant Initial Concentration(CIC)model of 210Pb and three accelerator mass spectrometry(AMS)ages from the chitin fragments.The hard water effect calibration of the sediment ^(14)C age showed that the reservoir effect ranged from 1655 yr at 1950 AD to 1540 yr at 1610 AD.The hydrological variation in Zige Tangco during the past 800 yr was reconstructed using multi-proxies,including organic and carbonate content,stable isotopes of fine-grained carbonate minerals(<38.5μm)and grain-size distribution of the lake sediments.Our results show that there were strong fluctuations in the lake level between 1200 and 1820 AD,and at least three dry periods were recorded between 1235 and 1315 AD,1410 and 1580 AD,and 1660 and 1720 AD characterized by high carbonate content,abrupt positive shifts of stable isotopes,and high sand content.The low-lake-level periods during the Little Ice Age(LIA)in Zige Tangco correspond to the lower δ^(18)O values in the Guliya ice core and the lower precipitation reconstructed from tree rings in Delingha.This demonstrated that the summer monsoon on the central Tibetan Plateau weakened during the dry and cold periods,whereas the winter monsoon strengthened.Relatively wetter periods or higher lake levels in Zige Tangco occurred at 1580-1650 AD and 1820-1900 AD.Negative shifts in stable isotopes were related to increased lake levels between 1800 and 1820 AD.Our results also showed that the summer monsoon precipitation on the central Tibetan Plateau was mainly controlled by solar activity during the past 800 yr.
基金supported by the National Natural Science Foundation of China (41072120, 41321061)
文摘Widespread lakes on the Tibetan Plateau(TP)are valuable archives for investigating climate and environment changes, which could provide essential information on the mechanisms of past climate changes on the TP and their interaction with the global climate systems.However, there is a lack of in-depth investigation of modern limnological processes in the Tibetan lakes, which hampers the understanding of paleolimnological records and lake ecosystem succession. In this study, we performed continuous temperature monitoring at two lakes, Bangong Co, a freshwater lake in the western TP, and Dagze Co, a brackish lake in the central TP, in order to characterize the patterns of seasonal temperature variability, stratification,and mixing. Temperature data for an entire hydrological year demonstrate that Bangong Co is a dimictic lake and that Dagze Co is a meromictic lake. The higher salinity in the deep water at Dagze Co prevents the lake from overturning completely, and this finding is supported by simulations using a physical limnological model Lake Analyzer. Continuous lake water temperature monitoring provides fundamental data for classifying Tibetan lakes, as well as the hydrological basis for understanding their paleolimnological records and ecosystem succession.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program (2019QZKK0206)the National Natural Science Foundation of China (41701041, 41975125, and 41988101)。
