Estimating ocean net primary productivity from daily cycles of carbon biomass measured by profiling floats

Abstract

Abstract The dependence of net primary productivity (NPP), a central metric in ecology and biogeochemistry, on sunlight drives daily cycles in carbon biomass in the ocean's euphotic zone. In this study, we infer NPP from the daily cycle of biomass. These estimates were extracted from bio‐optical measurements collected by an array of robotic profilers distributed across temperate and polar regions of the southern hemisphere. We estimate NPP in the region south of 30°S as ~11.4 Pg C yr −1 , and south of 50°S (the Southern Ocean) as ~4.6 Pg C yr −1 . We obtain comparable estimates when complementary daily cycles of oxygen are used instead (11.7 and 3.5 Pg C yr −1 ). This approach will be valuable for providing the basin‐scale, ground‐truthed information necessary to assess changes in subsurface primary productivity related to climate.