Significance Organic particles that sink to the deep ocean release carbon dioxide in waters that remain out of contact with the atmosphere on long timescales. This paper reconstructs particle flux profiles from large-scale ocean nutrient distributions, revealing systematic regional variations that have proved difficult to detect from direct observations alone. We show that the “transfer efficiency” of organic matter to depth is greatest in high-latitude regions and lowest in the subtropics, and is well explained by variations in phytoplankton community structure. These results suggest a greater sensitivity of atmospheric CO ₂ to high-latitude carbon export, and predict reduced ocean carbon storage as subtropical communities expand in response to climate warming.