Atmospheric Circulation And SST Information Recorded In Tree-ring Cellulose δD And δ¹⁸O Of Abies Fargesii From The Mt. Shennongjia

It is of great theoretical and practical significance to use tree-rings stable isotope choronologies to reflect and record past climate changes.In this paper,23 cores of 18 Abies fargesii trees were collected from the Mt.Shennongjia of Hubei Province.Through a series of laboratory treatments,we finally developed annual resolution the tree-ring δ¹⁸O and 8D choronologies from 1790 to 2011 of the Abies fargesii at the Mt.Shennongjia.Then we ananlysis the correlations between tree-ring δ¹⁸O and δD choronologies and the climatic factors of the site environment,atmospheric circulation indices and SST.We further discuss that those climatic factors,circulation factors,and the SST action mechanism and influences on the δ¹⁸O and δD value of tree rings in order to provide a theoretical basis for the study of past climate change of tree ring isotope,so as to use the δ¹⁸O and δD chronologies of tree rings to reconstruct the past climate change.In order to analyze the climatic indication significance of δ¹⁸O、δD value of tree-ring in the Mt.Shennongjia,we perform correlation analysis between the δ¹⁸O and δD chronologies of tree rings and data of the approaching Badong meteorological stations,and discuss the response sensitivity of the δ¹⁸O and 8D chronologies of tree rings to the climatic factors.The response results show that the δ¹⁸O and δD chronologies of tree rings in the Mt.Shennongjia is mainly response sensitive to the June-July precipitation,the March-April temperature and the July relative humidity.The changes of the June-July precipitation,the March-April temperature and the July relative humidity are recorded to a certain extent in the δ¹⁸O and δD chronologies of tree rings.Then we can see that the δ¹⁸O and δD chronologies of tree rings and changes of climate factors in the study area have a close connection.The correlation between the δ¹⁸O and δD chronologies of tree rings and the precipitation,temperature,relative humidity and sunshine hours in the Mt.Shennongjia is lower,even it does not reach a significant level.Therefore,the response of the δ¹⁸O and δD chronologies of tree rings to precipitation,temperature,relative humidity and sunshine hours is not sensitive.In order to analyze the correlation between the δ¹⁸O and δD chronologies of tree rings and regional atmospheric circulation,we perform correlation analysis between the δ¹⁸O and δD chronologies of tree rings in the Mt.Shennongjia and regional atmospheric circulation indices.We discuss the response sensitivity of the δ¹⁸O and δD chronologies of tree rings to the Area Index of Northern Hemisphere Subtropical High（5E-360）,the Area Index of South China Sea Subtropical High（100E-120E）,the Polar Vortex Index of Pacific Ocean（Zone 2,150E-120W）,and the Southern Oscillation Index（SOI）.The results show that the δ¹⁸O chronologies of tree rings and the February-March Area Index of Northern Hemisphere Subtropical High（5E-360）,the September Area Index of South China Sea Subtropical High（100E-120E）,the January Polar Vortex Area Index of Pacific Ocean（Zone 2,150E-120W）and the January Southern Oscillation Index（SOI）have a close relationship.These indicate that the tree-ring δ¹⁸O chronology records a large scale of atmospheric circulation information.There is significant correlation between the δD chronologies of tree rings and the July Area Index ofNorthern Hemisphere Subtropical High（5E-360）,the September Area Index of South China Sea Subtropical High（100E-120E）,the August Polar Vortex Area Index of Pacific Ocean（Zone 2,150E-120W）.We also found that there is a significant positive correlation between the δ¹⁸O chronology of tree rings and the April-May SST of the South China Sea,suggesting that the April-May SST in the South China Sea has an important influence on the δ¹⁸O value of the tree ring in the Mt.Shennongjia.The relationship between the δD chronology of tree rings and the May the SST in the South China Sea,the January SST in the Bay of Bengal are a significant positive correlation.The correlation coefficient between the 8D chronology of tree rings and the January SST in the Bay of Bengal reached the reconstruction level,so as to we reconstruct the January SST in the Bay of Bengal.In order to study the variation amplitude and periodicity of the δ¹⁸O and δD chronologies of tree rings,the 5180 and δD chronologies of tree rings were analyzed by means of moving average and power spectrum.It is found that the δ¹⁸O chronology of tree rings has two distinct periods of 7.8a and 23.3a.The 7.8a period may be related to SST in the South China Sea,and the 23.3a cycle may be related to sunspot activity.The the δD chronology of tree rings also has two distinct periods,2a and 3.6a,which may be related to the El Nino phenomenon.