Radium Inputs Into the Arctic Ocean From Rivers: A Basin-Wide Estimate

Radium isotopes have been used to trace nutrient, carbon, and trace metal fluxes inputs from ocean margins. However, these approaches require a full accounting of radium sources to the coastal ocean including rivers. Here, we aim to quantify river radium inputs into the Arctic Ocean for the first time for Ra-226 and to refine the estimates for Ra-228. Using new and existing data, we find that the estimated combined (dissolved plus desorbed) annual Ra-226 and Ra-228 fluxes to the Arctic Ocean are [7.0-9.4] x 10(14) dpm y(-1) and [15-18] x 10(14) dpm y(-1), respectively. Of these totals, 44% and 60% of the river Ra-226 and Ra-228, respectively are from suspended sediment desorption, which were estimated from laboratory incubation experiments. Using Ra isotope data from 20 major rivers around the world, we derived global annual Ra-226 and Ra-228 fluxes of [7.4-17] x 10(15) and [15-27] x 10(15) dpm y(-1), respectively. As climate change spurs rapid Arctic warming, hydrological cycles are intensifying and coastal ice cover and permafrost are diminishing. These river radium inputs to the Arctic Ocean will serve as a valuable baseline as we attempt to understand the changes that warming temperatures are having on fluxes of biogeochemically important elements to the Arctic coastal zone.

Automated summary

This study quantifies the river radium inputs into the Arctic Ocean for the first time and improves the estimates for this region. Through lab experiments and data from major rivers around the world, it is found that rivers are an important source of radium to the Arctic Ocean. Understanding river radium inputs is crucial for studying changes in biogeochemically important element fluxes as climate change and Arctic warming continue.