Indian summer monsoon and winter Total Solar Irradiance signals in the tree‐ring δ 18 O from foothills of High Asia, northern Pakistan

Abstract

A tree‐ring stable oxygen isotope (δ 18 O) 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 δ 18 O of precipitation in Islamabad over the instrumental period. The averaged tree‐ring δ 18 O chronology is significantly negative correlated with local ( r = −.651, p n = 38) and regional ( r = −.664, p 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 δ 18 O series is significantly ( p 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 δ 18 O over northern Pakistan. Several ISM‐related paleoclimate proxies, including three stalagmites δ 18 O series (Sahiya cave, Jhumar cave and Qunf cave) and a tree‐ring δ 18 O series (Manali), show consistent variability and a correlation coefficient of .566 ( p n = 165) with our tree‐ring δ 18 O, 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 δ 18 O variation ( r = .643, p n = 38), which may be linked to runoff of the Indus River and ISM precipitation.

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