Evaluation of the ability of the Chinese stalagmite δsup18/supO to record the variation in atmospheric circulation during the second half of the 20th century

摘要

The Chinese stalagmite δ18O (δ18O_cs) hasprovoked debate worldwide over the past few years due to its lack ofquantitative calibration, leading us to questions of whetherδ18O_cs records a local or large-scale signal and whetherδ18O_cs records the signal of a single remote water vapor source ormultiple water vapor sources. In this study, we observe all of theδ18O_cs trends within the instrumental period to verify whetherthey possess a common trend, which could be used as a basis to determinewhether the trends reflect the large-scale signal together or whether eachtrend reflects the local signal. The results show that most of theδ18O_cs experienced a linear increase from 1960 to 1994, which mayindicate that the δ18O_cs could record a trend occurringin large-scale atmosphere circulations. We then quantitatively describe theproportion of water vapor transport (WVT) from different source regions.Using the NCEP/NCAR (National Centers for Environmental Protection/National Centerfor Atmospheric Research) reanalysis data from 1960 to 1994, the ratios of theintensities of three WVTs from the Bay of Bengal, the South China Sea, andthe western North Pacific during the summer are calculated. We define R_SCS/BOBas the ratio of the WVT intensities from the South China Sea to those fromthe Bay of Bengal, R_WNP/BOB as the ratio of the WVT intensities from thewestern North Pacific to those from the Bay of Bengal, and R_WNP/SCS asthe ratio of the WVT intensities from the western North Pacific to thosefrom the South China Sea. The significant decadal increase occurs in thetime series of R_WNP/BOB and R_WNP/SCS, most likely resulting from thestrengthening of the WVT from the western North Pacific in the late 1970sdue to the western Pacific subtropical high that extended westward. Furtheranalysis indicates that when the equatorial central and eastern Pacific isin the El Ni?o phase, the sea surface temperature (SST) in the tropicalIndian Ocean, the Bay of Bengal, and the South China Sea is high, and the SSTat the middle latitudes in the North Pacific is low, then theR_WNP/BOB and R_WNP/SCS values tend to be high. After the late 1970s,the equatorial central and eastern Pacific have often been in the ElNi?o phase. Therefore, we confirm that the δ18O_csprimarily records the variation in atmospheric circulation during the secondhalf of the 20th century.