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 ²²⁶Ra and to refine the estimates for ²²⁸Ra. Using new and existing data, we find that the estimated combined (dissolved plus desorbed) annual ²²⁶Ra and ²²⁸Ra fluxes to the Arctic Ocean are [7.0–9.4] × 10¹⁴ dpm y⁻¹ and [15–18] × 10¹⁴ dpm y⁻¹, respectively. Of these totals, 44% and 60% of the river ²²⁶Ra and ²²⁸Ra, 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 ²²⁶Ra and ²²⁸Ra fluxes of [7.4–17] × 10¹⁵ and [15–27] × 10¹⁵ 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.