Mollusks are well known for their detailed recording of paleoenvironmental and paleoclimatic changes in their carbonate shells. In this study, we constructed 18-year blue color intensity and oxygen isotope profiles of...Mollusks are well known for their detailed recording of paleoenvironmental and paleoclimatic changes in their carbonate shells. In this study, we constructed 18-year blue color intensity and oxygen isotope profiles of a14C dated （AD 990±40） fossil giant clam,Tridacna gigas, from Shidao Island, South China Sea. Theδ18O profile of theT. gigas specimen displayed regular annual cycles and was probably controlled by seasonal variations of the climatic parameters. The blue color intensity profile showed good agreement with theδ18O series, and both had 18 clear annual cycles in accordance with the 18 visually identified annual growth bands. The annual shell growth rate determined from the blue color intensity and oxygen isotope profiles indicated that the annual shell increment of theTridacna specimen was stable after the onset of sexual ma-turity. Spectral analysis of theδ18O and blue color intensity time series suggested that the El Ni？o-Southern Oscillation （ENSO） period observed in the instrumental temperature and precipitation records of the South China Sea during the past 50 years also existed in medieval times. Our results showed that fossil giant clams could provide a good archive of historical intra-seasonal to decadal climate variations.展开更多
In the past 30 years,observational climate datasets reveal a significant a drying and warming trend over in North China.Understanding of climatic variability over North China and its driving mechanism in a long-term p...In the past 30 years,observational climate datasets reveal a significant a drying and warming trend over in North China.Understanding of climatic variability over North China and its driving mechanism in a long-term perspective is,however,limited to a few sites only,especially the lack of temperature reconstructions based on latewood density and blue intensity.In this study,we developed a 281-year latewood blue intensity chronology based on 45 cores of Picea meyeri in western North China.Based on the discovery that the warm season(May–August)mean maximum temperature is the main controlling factor affecting the change in blue light reflection intensity,we established a regression model that explained 37%of the variance during the calibration period(1950–2020),allowing to trace the mean maximum temperature up to 1760 CE.From the past 261 years,we identified seven persistent high temperature periods(1760–1773,1778–1796,1805–1814,1869–1880,1889–1934,1984–2000,2004–2020)and three persistent low temperature periods(1815–1868,1935–1963,1969–1983)in North China.Comparisons of a nearby temperature reconstructions and climate gridded data indicate that our reconstruction record a wide range of temperature variations in North China.The analysis of links between large-scale climatic variation and the temperature reconstruction showed that there is a relationship between extremes in the warm season temperature and anomalous SSTs in the equatorial eastern Pacific,and implied that the extremes in the warm season temperature in North China will be intensified under future global warming.展开更多
基金The National Basic Research Program of China(973 Program)under contract Nos 2010CB428902 and 2013CB955900the National Natural Science Foundation of China under contract No.41176042+1 种基金the West Light Foundation of The Chinese Academy of Sciences under contract No.29Y42909101the Key Programs of the Chinese Academy of Sciences under contract No.55ZZBS1304101
文摘Mollusks are well known for their detailed recording of paleoenvironmental and paleoclimatic changes in their carbonate shells. In this study, we constructed 18-year blue color intensity and oxygen isotope profiles of a14C dated （AD 990±40） fossil giant clam,Tridacna gigas, from Shidao Island, South China Sea. Theδ18O profile of theT. gigas specimen displayed regular annual cycles and was probably controlled by seasonal variations of the climatic parameters. The blue color intensity profile showed good agreement with theδ18O series, and both had 18 clear annual cycles in accordance with the 18 visually identified annual growth bands. The annual shell growth rate determined from the blue color intensity and oxygen isotope profiles indicated that the annual shell increment of theTridacna specimen was stable after the onset of sexual ma-turity. Spectral analysis of theδ18O and blue color intensity time series suggested that the El Ni？o-Southern Oscillation （ENSO） period observed in the instrumental temperature and precipitation records of the South China Sea during the past 50 years also existed in medieval times. Our results showed that fossil giant clams could provide a good archive of historical intra-seasonal to decadal climate variations.
基金National Natural Science Foundation of China,No.32061123008。
文摘In the past 30 years,observational climate datasets reveal a significant a drying and warming trend over in North China.Understanding of climatic variability over North China and its driving mechanism in a long-term perspective is,however,limited to a few sites only,especially the lack of temperature reconstructions based on latewood density and blue intensity.In this study,we developed a 281-year latewood blue intensity chronology based on 45 cores of Picea meyeri in western North China.Based on the discovery that the warm season(May–August)mean maximum temperature is the main controlling factor affecting the change in blue light reflection intensity,we established a regression model that explained 37%of the variance during the calibration period(1950–2020),allowing to trace the mean maximum temperature up to 1760 CE.From the past 261 years,we identified seven persistent high temperature periods(1760–1773,1778–1796,1805–1814,1869–1880,1889–1934,1984–2000,2004–2020)and three persistent low temperature periods(1815–1868,1935–1963,1969–1983)in North China.Comparisons of a nearby temperature reconstructions and climate gridded data indicate that our reconstruction record a wide range of temperature variations in North China.The analysis of links between large-scale climatic variation and the temperature reconstruction showed that there is a relationship between extremes in the warm season temperature and anomalous SSTs in the equatorial eastern Pacific,and implied that the extremes in the warm season temperature in North China will be intensified under future global warming.
