Closing the Global Marine ²²⁶ Ra Budget Reveals the Biological Pump as a Dominant Removal Flux in the Upper Ocean

Radium isotopes are powerful proxies in oceanography and hydrology. mass balance models, including assessments of submarine groundwater discharge (SGD), often overlook particle scavenging (PS) as a pathway for dissolved radium removal from the world ocean. Here, we build global ocean 226Ra model reevaluate potential importance PS. We find that PS is major sink upper ocean, removing about 96% total input various sources. Aside vertical exchange with lower SGD largest source into The biological pump transfers particles to deep resulting but overlooked impact on marine budget. Our findings suggest models should consider systems high siliceous algae production export fluxes long water residence times prevent underestimation large-scale fluxes.