An unshakable carbon budget for the Himalaya

The erosion and weathering of mountain ranges exert a key control on the long-term (105–106 yr) cycling of carbon between Earth’s surface and crust. The net carbon budget of a mountain range reflects the co-existence of multiple carbon sources and sinks, with corresponding fluxes remaining difficult to quantify. Uncertain responses of these carbon fluxes due to the stochastic nature of erosional processes further complicate the extrapolation of short-term observations to longer, climatically relevant timescales. Here, we quantify the evolution of the organic and inorganic carbon fluxes in response to the 2015 Gorkha earthquake (Mw 7.8) in the central Himalaya. We find that the Himalayan erosion acts as a net carbon sink due mainly to efficient biospheric organic carbon export. Our high-resolution time series encompassing four monsoon seasons before and after the Gorkha earthquake reveal that coseismic landslides did not significantly perturb large-scale Himalayan sediment and carbon fluxes. This muted response of the central Himalaya to a geologically frequent perturbation such as the Gorkha earthquake further suggests that our estimates are representative of at least interglacial timescales. Carbon fluxes in the central Himalaya did not change after the 2015 Gorkha earthquake and its accompanying landslides, according to observations of riverine sediment and carbon fluxes over four monsoon seasons spanning the event.