The ocean’s gravity-driven carbon flux from serendipitous particle traps

Adam Christopher Stoer , Bin Wang, Katja Fennel

Particles sinking into the ocean’s interior are a food source for deep-sea ecosystems and sequester carbon from the atmosphere. Yet, measurements of the sinking flux are sparse, leaving substantial uncertainties in its magnitude and variability. We demonstrate how a fleet of Argo floats has serendipitously measured the sinking flux for the last decade because particles settled onto the floats while adrift deep below the surface and were resuspended during ascent. With these new-found particle “traps”, we estimate a global sinking flux of 790 TgC yr⁻¹ (95% C.I. 470–1,120 TgC yr⁻¹) at 1,000 m depth, where carbon is sequestered on timescales of centuries. This set of unanticipated flux observations offers a new way to investigate the biological carbon pump at the relevant scales and frequencies. Such observations will be valuable for addressing how the sinking particle flux responds to climate change and potential initiatives aimed at sequestering atmospheric carbon.