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East Asian Precipitation δ 18 O Relationship With Various Monsoon Indices
Author(s) -
Wang Yingzhao,
Hu Chaoyong,
Ruan Jiaoyang,
Johnson Kathleen R.
Publication year - 2020
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2019jd032282
Subject(s) - speleothem , climatology , monsoon , precipitation , east asian monsoon , environmental science , atmospheric sciences , walker circulation , atmospheric circulation , el niño southern oscillation , geology , geography , cave , meteorology , archaeology
Chinese speleothem oxygen isotope (δ 18 O) variations have been widely interpreted as recording the evolution of the Asian Monsoon. However, calibration of δ 18 O to monsoon intensity has not yet been carried out in a quantitative way. To understand the climatic significance of δ 18 O, we measured monthly precipitation δ 18 O data at Heshang Cave, China, where speleothem δ 18 O records were previously obtained. We examined the influence of local climate and large‐scale atmospheric circulation on the δ 18 O by correlating to local meteorological data and various monsoon indices. We find neither a significant amount effect nor temperature effect, and therefore suggest that local climate is not the primary driver of δ 18 O variability. On seasonal timescales, monthly δ 18 O is significantly correlated to all monsoon indices, especially the Indian Monsoon (IM) and Western North Pacific Monsoon (WNPM) indices, proving δ 18 O responds dominantly to the tropical monsoon circulation. On interannual timescales, there are significant negative correlations between annual δ 18 O and the WNPM and IM monsoon indices defined by zonal winds, reflecting the impact of the El Niño‐Southern Oscillation on δ 18 O. Similar correlations between δ 18 O and precipitation amount in these monsoon regions lend further support to this finding. As the driving force of seasonal and interannual monsoon changes can be compared to variations on orbital and suborbital scales, respectively, we argue that speleothem δ 18 O in southern China is influenced by both external forcing and internal variability. Solar radiation plays an indispensable role on the orbital and seasonal scale δ 18 O variations, whereas ocean–atmosphere interactions are dominant on suborbital timescales.