Glaciochemical records for the past century from the Qiangtang Glacier No.1 ice core on the central Tibetan Plateau: Likely proxies for climate and atmospheric circulations

Abstract

Previous studies of glaciochemical records retrieved from the southern and northern sectors of the Tibetan Plateau (TP) have revealed that there are diverse patterns of climate change within this region. However, uncertainty remains regarding changes in the atmospheric environment over the central TP where the Indian monsoonal circulation and westerly winds meet. This study presents a glaciochemical record of the past 112 years from the upper part of the ice core drilled into the Qiangtang Glacier No.1 (QT-1) located in the central TP. The purpose of this study is to understand the glaciochemical controls, if any, and how these controls have been affected by both local climate parameters and atmospheric circulation patterns. An empirical orthogonal function (EOF) analysis was performed to determine the significance of any chemical components. The results show that the major soluble ions (Na+, K+, Mg2+, Ca2+, Cl−, NO3−, NH4+ and SO42−) are predominantly controlled by crustal aerosols and have high loadings on EOF1. Correlation analysis between EOF1 and the annual dust-event frequency recorded by local/regional meteorological stations suggests that the ice core chemical record provides a reasonable proxy for local/regional atmospheric dust loading. Analysis of EOF1 also demonstrates changes that are consistent with regional meteorological parameters and large-scale circulations, revealing a strong link with the glaciochemical record. The windy, cold-dry climate and/or enhanced northwesterly/westerly winds appear to be responsible for the higher atmospheric dust aerosols, leading to higher concentrations of ions. Our analysis also isolated a significant positive correlation between EOF1 and the Pacific Decadal Oscillation (PDO) index, suggesting that, as an underlying mechanism, the PDO likely influences the regional climate conditions and atmospheric circulation patterns and thereby the QT-1 ion records. Our findings may, therefore, enhance the understanding of the relationship between chemical records and climatological variations that are preserved in ice cores, improve our knowledge of changes in the composition of the atmosphere and atmospheric circulation over the central TP, and potentially facilitate reconstruction of the paleo-PDO.