Model exploration of the processes governing iron scavenging and the strength of the hydrothermal vent iron source

Abstract:

New parameterizations of iron scavenging and hydrothermal vent sources have been explored using the Community Earth System Model – Biogeochemical Elemental Cycling Model (CESM-BEC). Implementation of different iron scavenging schemes help to better elucidate dominant removal processes controlling dissolved iron concentrations in the ocean. Inclusion of hydrothermal vent sources allows for a more comprehensive understanding of deep sea iron cycling. Scientific literature suggests that iron binding ligands are an important component of iron cycling in that they reduce iron losses to particle scavenging, and thus increase iron lifetime in the ocean. In this work, we explore three iron scavenging schemes: implicit ligands, explicit ligands at a fixed concentration, and dynamic explicit ligands. Dynamic explicit representation of iron-binding ligands has been included in the CESM-BEC to better understand the control ligands exert on dissolved iron concentrations. This scavenging scheme includes explicit ligands sources and sinks and dynamic cycling with iron. Ligand sources include remineralization of POC, DOC, and refractory DOC, with some reuse of ligands by phytoplankton. Ligand sinks include biological uptake, ligand degradation and particle scavenging. Hydrothermal vents have been shown to be an important source for the deep-sea iron budget. In this work, we use new data from GEOTRACES campaigns that sampled along hydrothermal ridges to better constrain the hydrothermal iron source in the model.