Abstract
Based on stable hydrogen and oxygen isotope data (δ18O, δD) and meteorological observation data for complete hydrological annual precipitation from 2016 to 2017 in the monsoon marginal region of northern China (Fengxiang and Ningwu), the isotopic characteristics of precipitation and the sources of water vapor in these two regions combined were studied. The results showed that δ18O and δD values in the wet season (June through September) were higher than in the dry season (October to May of the following year) in Fengxiang and Ningwu. The intercept and slope of the meteoric water line in the two regions were somewhat low, revealing that the water vapor in the rainfall comes mainly from the tropical ocean. On a synoptic scale, significantly positive correlations among dry season precipitation, δ18O, and temperature manifested temperature effects, but in the wet season, the temperature effect was not significant. On a monthly scale, a relationship did not exist between the change in trend of the average value of monthly weighted δ18O in precipitation and the average temperature change value in the two regions. However, in the wet season, significantly negative relationships can be found between the average monthly weighted δ18O in precipitation and rainfall amount, which indicated a remarkable rainout effect. Further investigation revealed that continuous precipitation made the values of δ18O and δD more negative under the same source of water vapor (the rainout effect). Because the annual rainfall in the monsoon marginal region of Northern China is mainly made up of monsoon rainfall, the oxygen isotope index of geological and biological records, such as stalagmites and tree rings, which inherit meteoric water isotope information, can be used to reconstruct past rainfall changes in northern China.
Highlights
The use of stable oxygen isotopes in different geological biological carriers to reconstruct past climate changes has achieved remarkable results [1,2,3,4,5,6,7].In particular, stalagmites have attracted a lot of attention from paleoclimatological researchers becauseAtmosphere 2018, 9, 97; doi:10.3390/atmos9030097 www.mdpi.com/journal/atmosphereAtmosphere 2018, 9, 97 of its high resolution proxies and accurate dating method
In China, use of the oxygen isotope composition of stalagmites has been very successful in the Asian Monsoon Study, there are currently some disputes about its significance [8]
(2012) and Tan (2014) suggested that variations in the oxygen isotope composition of stalagmites was mainly controlled by variations in water vapor sources in the Indian and Pacific Oceans and did not reflect changes in local rainfall [9,10]
Summary
The use of stable oxygen isotopes in different geological biological carriers (such as stalagmites, tree rings, and ice cores) to reconstruct past climate changes has achieved remarkable results [1,2,3,4,5,6,7].In particular, stalagmites have attracted a lot of attention from paleoclimatological researchers becauseAtmosphere 2018, 9, 97; doi:10.3390/atmos9030097 www.mdpi.com/journal/atmosphereAtmosphere 2018, 9, 97 of its high resolution proxies and accurate dating method. In China, use of the oxygen isotope composition of stalagmites has been very successful in the Asian Monsoon Study, there are currently some disputes about its significance [8]. Maher and Thompson (2012) and Tan (2014) suggested that variations in the oxygen isotope composition of stalagmites was mainly controlled by variations in water vapor sources in the Indian and Pacific Oceans and did not reflect changes in local rainfall [9,10]. Some researchers have suggested that the oxygen isotope composition of Chinese stalagmites is controlled by changes in monsoon intensity in the upper reaches of India. Tan et al (2015) recently suggested that the indicative significance of the oxygen isotope composition of stalagmites in southern China was different at different time scales and in different regions [14]. To study the oxygen isotope characteristics and control factors of modern precipitation, one must understand the modern hydrological cycle, and explain the significance of oxygen isotope geology in the carrier, and provide a scientific basis for reconstruction of past climatic change in different areas
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