Organic Carbon Burial in Global Continental Margin Sediments

Continental margins, situated at the nexus of land and ocean, act as major burial hotspots for terrestrial and marine organic matter, creating a critical interface between the short-term carbon cycle and long-term geological storage. Although this burial largely regulates atmospheric CO₂, O₂ and thus climate, its magnitude and spatial distribution remain poorly constrained due to sparse observations and an extraordinary environmental variability. Here we present the first global, observation-constrained assessment of organic-carbon transfer and burial along the global continental margin, integrating observational data with spatial machine learning and three-dimensional reaction–transport modelling. We estimate a global organic-carbon transfer flux of 367 Tg C yr⁻¹ on centennial timescales, decreasing to 293 and 246 Tg C yr⁻¹ on millennial and multi-millennial scales. These results show that continental-margin sediments form one of Earth’s largest and most persistent long-term carbon sinks, exceeding lakes, reservoirs and all major vegetated coastal ecosystems combined. Burial is strongly heterogeneous, with ~70% occurring in the Northern Hemisphere and ~50% in equatorial regions, and with pronounced hotspots in tropical margins and marginal seas. These findings reduce a central uncertainty in the coastal carbon budget and thus refine global carbon cycle assessments, constrain ocean–atmosphere CO₂ exchange, and provide the first spatial framework to guide marine conservation, management, and climate policy.