Data for "Hysteresis of phytoplankton communities over the Subpolar North Atlantic to CO2 forcing"

Marine phytoplankton play a crucial role in the ocean’s food web, marine ecosystems, and the global carbon cycle. The responses to external forcing vary across phytoplankton species, thus phytoplankton community shifts can have important implications for their roles in the Earth’s system. Here, we find that the shift towards smaller phytoplankton communities resulting from the greenhouse warming in the Sub-Polar North Atlantic (SPNA) is not easily recovered even under CO₂ removal scenarios. The persistent collapse of larger-celled diatom populations and the shift to smaller phytoplankton communities despite negative CO₂ emission was a consequence of lower surface nutrient availability followed by the slowdown of the Atlantic Meridional Overturning Circulation (AMOC). This decrease in AMOC strength and associated nutrient transport exhibits delayed recovery. The disruption in trophic dynamics induced by depleting nutrients changes the primary limiting nutrient components, contributing to the continued decrease in diatom and increase in smaller phytoplankton conversely. Consequently, the downsizing of the phytoplankton community leads to a large decrease in the ocean’s biological carbon export capacity.