Lateral Particle Supply as a Key Vector in the Oceanic Carbon Cycle

Abstract

The export of particulate organic carbon (POC) from surface waters to the ocean interior via the biological carbon pump is largely envisioned as a vertical process. However, several lines of evidence suggest that lateral supply of aged organic matter hosted on lithogenic particles derived from sediment resuspension may also be a significant process. Despite its potential importance, lateral POC supply has not been systematically examined on a global scale. Here, we assess the contribution of resuspended sediment to sinking particulate matter in the ocean using literature data of sediment trap studies. Proportions and absolute fluxes of lithogenic material at 158 sites and available radiocarbon contents are compiled to develop a global‐scale assessment. We find that lithogenic material accounts for 25 ± 20% of sinking particulate matter, comprising a mean flux of 67 mg m−2d−1. Lithogenic material flux generally decreased with increasing distance from the coast and with increasing height above the seafloor. The Δ14C values of POC exhibited a linear relationship with a wt/wt ratio of lithogenic material to POC. Loadings of aged POC to lithogenic material obtained from this relationship were similar to or higher than POC content of the surface sediment in the vicinity. Based on this relationship, and the global mean of lithogenic material content of sinking particulate matter, we calculate that aged POC from sediment resuspension comprises 0.2–0.7% of sinking particles and 4–11% of sinking POC intercepted by sediment traps. (©2020. American Geophysical Union)