Radiocarbon Fingerprinting Black Carbon Source History in the Himalayas

Black carbon (BC) is considered as an important contributor to the Himalayan glaciers melt in the past few decades. However, the long-term source apportionment of BC remains unclear. Here we present the first radiocarbon (¹⁴C)-based annual variation of BC source apportionment in an ice core spanning the period of 1959–2012 drilled from the Southeastern Tibetan Plateau, a receptor site of South Asia outflow. We find fossil fuel combustion is a major contribution (73% ± 5%), yet the biomass burning fraction (ƒ_biomass) has grown from 24% ± 4% to 30% ± 4% since 1990. Intriguingly, we further find the ƒ_biomass demonstrating a robust correlation with South Asian wildfires linked to climate oscillations. Thus, for mitigating BC impacts on Himalayan glaciers, South Asia's transition from fossil fuels to clean energy is a more efficient and urgent strategy than reducing residential biomass burning.