Large-scale estimates of the Southern Ocean CO₂ sink do not adequately resolve the fluxes associated with Antarctic continental shelves. Using a mechanistic three-dimensional biogeochemical model of the Ross Sea, we show that Antarctic shelf waters are a strong sink for CO₂ due to high biological productivity, intense winds, high ventilation rates, and extensive winter sea ice cover. Net primary production (NPP) in these waters is ∼0.055 Pg C yr⁻¹. Some of this carbon sinks to depth, driving an influx of CO₂ of 20–50 g C m⁻² yr⁻¹. Although currently unaccounted for, the total atmospheric CO₂ sink on the Ross Sea continental shelf of 0.013 Pg C yr⁻¹ is equivalent to 27% of the most recent estimate of the CO₂ sink for the entire Southern Ocean. Given these results, these and other highly productive waters around the Antarctic continent need to be included in future budgets of anthropogenic CO₂.