Abstract
Abstract. Tree-ring δ18O values are a sensitive proxy for regional physical climate, while their δ13C values are a strong predictor of local ecohydrology. Utilizing available ice-core and tree-ring δ18O records from the central Himalaya (CH), we found an increase in east–west climate heterogeneity since the 1960s. Further, δ13C records from transitional western glaciated valleys provide a robust basis for reconstructing about 3 centuries of glacier mass balance (GMB) dynamics. We reconstructed annually resolved GMB since 1743 CE based on regionally dominant tree species of diverse plant functional types. Three major phases became apparent: positive GMB up to the mid-19th century, the middle phase (1870–1960) of slightly negative but stable GMB, and an exponential ice mass loss since the 1960s. Reasons for accelerated mass loss are largely attributed to anthropogenic climate change, including concurrent alterations in atmospheric circulations (weakening of the westerlies and the Arabian Sea branch of the Indian summer monsoon). Multi-decadal isotopic and climate coherency analyses specify an eastward declining influence of the westerlies in the monsoon-dominated CH region. Besides, our study provides a long-term context for recent GMB variability, which is essential for its reliable projection and attribution.
Highlights
Glaciers in the Himalayan–Tibetan orogen are an important component of the regional hydrological cycle, and a major fraction of regional potable water is stored and provided by them
The detailed results on the analysed relationship between δ13C and compiled glacier mass balance as well as of the relationship between δ13C and available climate datasets are presented in Tables S4 and S5
We present a 273-year-long ice mass loss record from the Uttarakhand Himalaya, which is the only record of annual mass balance variability from the Himalaya so far
Summary
Glaciers in the Himalayan–Tibetan orogen are an important component of the regional hydrological cycle, and a major fraction of regional potable water is stored and provided by them. Reliable projections of future Himalayan ice mass loss require robust observations of glacier response to past and ongoing climate change. A consistent picture emerges of net ice mass loss in recent decades, which is highest in the western and central Himalaya (except the Karakoram and the Pamir Mountains) (Bolch et al, 2012; Brun et al, 2017; Dehecq et al, 2019; Maurer et al, 2019; Mölg et al, 2014; Shekhar et al, 2017; Yao et al, 2012)
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