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Icebergs and glacial meltwater have been observed to significantly affect chlorophyll concentrations, primary production, and particle export locally, yet the quantitative influence of glacial iron on the carbon cycle of the Southern Ocean remains unknown. We analyze the impact of icebergs and glacial meltwater on the Southern Ocean carbon cycle in a global Earth System Model. We consider several simulations spanning low and high bounds of current estimates of glacial iron concentration. We find that a high glacial iron input produces the best agreement with observed iron and chlorophyll distributions. These high glacial iron input results indicate that about 30% of the Southern Ocean particle export production, that is, the flux of particulate organic matter through the 100 m depth level, is driven by glacial iron sources. This export production is associated with an uptake of 0.14 Pg carbon per year, which reduces carbon outgassing in the Southern Ocean by 30%.

Plain Language Summary Icebergs and glacial meltwater from Antarctica contain significant amounts of iron, which is important for phytoplankton growth and marine production in the iron-limited Southern Ocean. Since phytoplankton growth is connected to the carbon cycle, glacial iron sources are assumed to influence the Southern Ocean carbon cycle. However, this influence has not been quantified yet. We use a global Earth System Model to analyze the impacts of icebergs and glacial meltwater on the Southern Ocean carbon cycle. We calculate several simulations using low and high bounds of current estimates of glacial iron concentration. In our model, a high glacial iron input produces the best agreement with observed iron and chlorophyll distributions. These high glacial iron input results indicate that about 30% of the carbon export to depth is driven by glacial iron sources in the Southern Ocean, associated with a 30% reduction in carbon outgassing. Our results indicate that glacial iron plays a significant role in Southern Ocean carbon cycling and oceanic carbon uptake.