Biogeochemical regimes in focus

摘要

The surface ocean currently absorbs about 19% of anthropogenic CO_2 emissions1. The amount of CO_2 sequestered in the ocean depends in part on the biological productivity of the surface waters. Productivity transfers CO_2 from solution into organic matter, which in turn is exported to the deeper ocean (Fig. 1). The magnitude of this biological pump can be quantified if two parameters are known: the amount of surface production and the efficiency of the transport of carbon to depth. Direct measurements of the flux of particulate carbon to depth are available2,3 but sparse. However, this flux can also be inferred from the changes in carbon, phosphorus and oxygen in subsurface layers that receive the products respired by the rain of organic matter from overlying water. As reported in Nature Geoscience, DeVries and Deutsch4 and Teng et al.~5 use such an inverse approach to show that the efficiency of carbon export is significantly greater in subtropical gyres than in more nutrient-rich ocean regions.