Large contribution of pteropods to shallow CaCO₃ export

The literature on the relative contributions of pelagic calcifying taxa to the global ocean export of CaCO₃ is divided. Studies based on deep sediment trap data tend to argue that either foraminifers or coccolithophores, both calcite producers, dominate export. However, the compilations of biomass observations for pteropods, coccolithophores, and foraminifers instead show that pteropods dominate the global ocean calcifier biomass and therefore likely also carbonate export. Here we present a new global ocean biogeochemical model that explicitly represents these three groups of pelagic calcifiers. We synthesize databases of the physiology of the three groups to parameterize the model and then tune the unconstrained parameters to reproduce the observations of calcifier biomass and CaCO₃ export. The model can reproduce both these observational databases; however, substantial dissolution of aragonite above the aragonite saturation horizon is required to do so. We estimate a contribution of pteropods to shallow (100 m) export of CaCO₃ of at least 33% and to pelagic calcification of up to 89%. The high production‐high dissolution configuration that shows closest agreement with all the observations has a CaCO₃ production of 4.7 Pg C/year but CaCO₃ export at 100 m of only 0.6 Pg C/year.