The importance of continental margins in the global carbon cycle

Approximately half of the world's net annual photosynthesis occurs in the oceans (∼48 Pg C y −1 ). Areas bordering continents (bottom <2000 m) support 10–15% of this production. We used satellite data to compute annual global net primary production (1998–2001), and derived the global particulate organic carbon (POC) flux settling below the permanent thermocline and to the seafloor using an empirical model of POC remineralization. Approximately 0.68 Pg C y −1 sink below the thermocline on continental margins, compared to 1.01 Pg C y −1 in the deep ocean. Over 0.62 Pg C y −1 settles to the seafloor on margins, compared to 0.31 Pg C y −1 to deep ocean sediments. At least 0.06 Pg C y −1 may be buried in sediments on margins. Therefore, margins may be responsible for >40% of the carbon sequestration in the ocean. These regions must be accounted for in realistic models of the global carbon cycle and its linkages to climate change.