Sinking Diatom Assemblages as a Key Driver for Deep Carbon and Silicon Export in the Scotia Sea (Southern Ocean)

Physical and biogeochemical processes in the Southern Ocean are fundamental for modulating global climate. In this context, a process-based understanding of how Antarctic diatoms control primary production carbon export, hence global-ocean sequestration, has been identified as scientific priority. Here we use novel sediment trap observations combination with data-assimilative ocean biogeochemistry model (ECCO-Darwin) to understand environmental conditions trigger diatom ecology iron-fertilized southern Scotia Sea. We unravel role assemblage controlling sinking material escaping from euphotic zone, discuss link between changes upper-ocean composition settling exported surface 1,000 m depth March 2012 January 2013. The combined analysis situ simulation suggests that an anomalous sea-ice episode early summer 2012–2013 favored ( via restratification due melt) massive bloom Corethron pennatum rapidly sank depth. This event drove high biogenic silicon organic export ratios, while nitrogen isotopic signals matter reaching deep ocean. Our findings highlight vs. sequestration efficiency, critical factor determining stoichiometric relationship limiting nutrients Ocean.