The variable and changing Southern Ocean Silicate Front: Insights from the CESM Large Ensemble

This study provides a first estimate of the spatiotemporal variability of the SF, defined using the silicate-to-nitrate (Si:N) ratio as simulated by the Community Earth System Model (CESM) Large Ensemble (1920-2100), and its response to a changing Southern Ocean.

The latitude where Si:N=1 largely coincides with regions of high gradients in silicate and the observed position of the Antarctic Polar Front (PF) and serves as an indicator of waters with adequate nutrients available for diatom growth. On seasonal to interdecadal time scales, variability in the location of the SF is largely determined by biological nutrient utilization and Southern Ocean bathymetry, respectively. From 1920 to 2100, under historical and RCP8.5 forcing, the zonally averaged SF shifts poleward by approximate to 3 degrees latitude, with no discernible shift in the position of the simulated location of the PF or the core of the Antarctic Circumpolar Current.