Abstract
An oxygen isotope record of a stalagmite from Huanglong Cave in the eastern Qinghai-Tibet Plateau dated with 230Th and 210Pb methods provides variations of the Asian monsoon with an average resolution of 1 year over the past 50 years. This study shows that the δ 18O of dripwater in the cave represents the annual mean δ 18O of local meteoric precipitation and the stalagmites were deposited in isotopic equilibrium. A comparison of the stalagmite δ 18O record with instrumentally meteorological data indicates that shifts of the δ 18O are largely controlled by the amount effect of meteoric precipitation conveyed through the southwest monsoon (the Indian monsoon) and less affected by temperature. Therefore, the variations of δ 18O record reflect the changes in monsoon precipitation on inter-annual time scales under the influence of the southwest monsoon. Like many other stalagmite δ 18O records in the Asian monsoon regions, the δ 18O record of the stalagmite from Huanglong Cave also reveals a gradually enriched trend during the past 50 years, i.e. relatively enriched in 18O. This trend may indicate the decline of the Asian monsoon intensity which is consistent with the decrease of monsoon indices. The weakening of the modern Asian monsoon well matched with the temperature changes in stratosphere, which may illustrate that the weakening of the monsoon mainly results from the lowering of solar radiation.
Highlights
Modern stalagmite oxygen isotopic composition and its implications of climatic change from a high-elevation cave in the eastern Qinghai-Tibet Plateau over the past 50 years
This study shows that the δ18O of dripwater in the cave represents the annual mean δ18O of local meteoric precipitation and the stalagmites were deposited in isotopic equilibrium
Based on the research of modern carbonate-water oxygen isotope system and the instrumental observation data, this paper probes into the stalagmite oxygen isotopic composition and its implications from a high-elevation cave―Huanglong Cave in the eastern Qinghai-Tibet Plateau, and discusses the relationship between monsoon precipitation and upper stratospheric temperature changes over the past 50 years, which would help us improve understanding the variations of the Asian monsoon and the future climate
Summary
Modern stalagmite oxygen isotopic composition and its implications of climatic change from a high-elevation cave in the eastern Qinghai-Tibet Plateau over the past 50 years. Burns et al.[12] discussed the relation between the stalagmite δ18O records and instrumental monsoon precipitation in southern Oman on inter-decadal scales, much research work is still needed on modern stalagmite depositing process and the changes of oxygen isotope composition in responses to the climate change on short time scales. Based on the research of modern carbonate-water oxygen isotope system and the instrumental observation data, this paper probes into the stalagmite oxygen isotopic composition and its implications from a high-elevation cave―Huanglong Cave in the eastern Qinghai-Tibet Plateau, and discusses the relationship between monsoon precipitation and upper stratospheric temperature changes over the past 50 years, which would help us improve understanding the variations of the Asian monsoon and the future climate
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