Marine geologic nitrous oxide vents mobilized by drilling: Hidden climate risk from continental shelf strata

Marine sediments, historically regarded as negligible nitrous oxide (N ₂ O) sources despite harboring Earth's largest reactive nitrogen reservoirs, undergo greenhouse gas activation when penetrated through industrial drilling. Quantitative analysis of well head gases from over 400 offshore drilling sites in China’s Bohai Sea and more than 1200 onshore sites (Sichuan, Xinjiang, Inner Mongolia, Shaanxi, Liaoning, and Gansu provinces) revealed unprecedented N ₂ O accumulation in deep marine strata. The N ₂ O concentrations reached 1.42 vol%, exceeding those in overlying water columns by orders of magnitude. Exclusive offshore prevalence, depth gradient dependency, and source-diagnostic decoupling from thermogenic alkanes confirm sedimentary denitrification as the origin. Our findings establish offshore drilling operations as major climate forcing vectors through geologic N ₂ O mobilization, demanding urgent integration of these emissions into Intergovernmental Panel on Climate Change marine greenhouse gas budgets.