Complex principal component analysis of mass balance changes on the Qinghai–Tibetan Plateau

Abstract. Climatic time series for Qinghai–Tibetan Plateau locations are rare. Although glacier shrinkage is well described, the relationship between mass balance and climatic variation is less clear. We studied the effect of climate changes on mass balance by analyzing the complex principal components of mass changes during 2003–2015 using Gravity Recovery and Climate Experiment satellite data. Mass change in the eastern Himalayas, Karakoram, Pamirs, and northwestern India was most sensitive to variation in the first principal component, which explained 54 % of the change. Correlation analysis showed that the first principal component is related to the Indian monsoon and the correlation coefficient is 0.83. Mass change on the eastern Qinghai plateau, eastern Himalayas–Qiangtang Plateau–Pamirs area and northwestern India was most sensitive to variation of the second major factor, which explained 16 % of the variation. The second major component is associated with El Niño; the correlation coefficient was 0.30 and this exceeded the 95 % confidence interval of 0.17. Mass change on the western and northwestern Qinghai–Tibetan Plateau was most sensitive to the variation of its third major component, responsible for 6 % of mass balance change. The third component may be associated with climate change from the westerlies and La Niña. The third component and El Niño have similar signals of 6.5 year periods and opposite phases. We conclude that El Niño now has the second largest effect on mass balance change of this region, which differs from the traditional view that the westerlies are the second largest factor.