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

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

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geology (hsv//eng)

Nyckelord

particle scavenging

submarine groundwater discharge

siliceous algae

global ocean

submarine groundwater discharge

radium isotopes

biogenic silica

thorium isotopes

antarctic ocean

nutrient fluxes

coastal waters

residence time

mixing zones

river water

Geology

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