Indian summer monsoon and winter Total Solar Irradiance signals in the tree‐ring δ18O from foothills of High Asia, northern Pakistan

Abstract

AbstractA tree‐ring stable oxygen isotope (δ18O) chronology was developed for the past 171 years by four Abies pindrow trees growing in southwest foothills of High Asia, northern Pakistan, which is correlated with observed and modelled δ18O of precipitation in Islamabad over the instrumental period. The averaged tree‐ring δ18O chronology is significantly negative correlated with local (r = −.651, p < .001, n = 38) and regional (r = −.664, p < .001, n = 65) summer precipitation variations. Analysis of vertically integrated water vapour flux and surface wind field suggests that the sampling site is located at the northern limit of the Indian summer monsoon (ISM). Our tree‐ring δ18O series is significantly (p < .001, n = 143) negatively correlated with observed Homogenous India rainfall, All Indian rainfall, Core‐Monsoon India rainfall and Northwest India rainfall. This is the first detected ISM signal from tree‐ring δ18O over northern Pakistan. Several ISM‐related paleoclimate proxies, including three stalagmites δ18O series (Sahiya cave, Jhumar cave and Qunf cave) and a tree‐ring δ18O series (Manali), show consistent variability and a correlation coefficient of .566 (p < .001, n = 165) with our tree‐ring δ18O, suggesting that a combination of multiple proxies may be potentially useful to understand the full perspective of ISM before instrumental era. In addition, we found that the satellite‐observed winter Total Solar Irradiance exerts influence on the tree‐ring δ18O variation (r = .643, p < .001, n = 38), which may be linked to runoff of the Indus River and ISM precipitation.