Accelerated deposition of South Asian anthropogenic emissions on southern Tibetan glaciers in the 21st century

Rapid anthropogenic emission in South Asia poses environmental challenges to the Tibetan Plateau (TP), but there remains a lack of evidence regarding how these anthropogenic emissions in South Asia have impacted the TP during the 21st century. Here we reconstruct high-resolution deposition histories of NO₃⁻ and NH₄⁺ from 1950 to 2021 using two ice cores retrieved from the Bugyai Kangri (BK) and Noijin Kangsang (NK) sites on southern TP. The ice core records showed that deposition fluxes of NO₃⁻ and NH₄⁺, derived from anthropogenic emissions, exhibited significant accelerating trends at both sites post-2000. The Positive Matrix Factorization (PMF) model and HYSPLIT backward trajectory analysis identify two distinct dominant atmospheric transport pathways originating from South Asia. Furthermore, spatial correlation analysis with high-resolution gridded emission inventories revealed significant positive correlations between the annual NO₃⁻ and NH₄⁺ deposition fluxes in ice cores and the anthropogenic NOx and NH₃ emissions from key source regions in South Asia. This study demonstrates the profound impact of anthropogenic emissions on the high-altitude cryosphere, and highlights the urgency of making regional environmental governance strategies in the context of rapid economic development in South Asia. Deposition fluxes of nitrate and ammonium on Tibetan glaciers have accelerated since 2000 due to growing anthropogenic emissions in South Asia, according to geochemical analyses of two ice cores from the southern Tibetan Plateau and back-trajectory analysis.