Diatom silicon isotopes as a proxy for silicic acid utilisation: a southern ocean core top calibration

摘要: Despite a growing body of work that uses diatom δ30Si to reconstruct past changes in silicic acid utilisation, few studies have focused on calibrating core top data with modern oceanographic conditions. In this study, microfiltration technique is used divide Southern Ocean silica into narrow size ranges, separating components such as radiolaria, sponge spicules and clay minerals from diatoms. Silicon isotope analysis these demonstrates inclusion small amounts non-diatom material can significantly offset the measured true δ30Si. Once correct fraction selected (generally 2–20 μm), shows strong negative correlation surface water concentration (R2 = 0.92), highly supportive qualitative use proxy for utilisation. The matches well mixed layer filtered published situ studies, suggesting little no effect either dissolution export through column, or early diagenesis, sediments Ocean. However, poor fit simple Rayleigh steady state models when single source term used. instead be described by only variations initial conditions upwelled are taken account, caveat which may introduce some error quantitative reconstructions utilisation