Climatological variability of air-sea CO2 fluxes induced by iron flux in the North Pacific

It is known that the ocean absorbs approximately on third of anthropogenic CO₂ in the atmosphere through air-sea gas exchanges. The ocean’s uptake of anthropogenic CO₂ plays a crucial role in mitigating the net source of CO₂ in the atmosphere. The ocean biogeochemical processes are one of the most important fields for understanding Earth’s carbon cycle to understand the global climate system. The ocean’s capacity to absorb anthropogenic CO₂ in the atmosphere is controlled by two processes: the biological carbon pump and solubility carbon pump. The biological carbon pump involves CO₂ uptake through photosynthesis, and the solubility carbon pump is influenced by water temperature. Therefore, the spatial and temporal variability of carbon sink/source in the ocean is influenced significantly by the solubility and biological carbon pumps. Especially, phytoplankton growth can induce a strong biological pump, which can have a significant impact on regional carbon cycle. The North Pacific is known as a key region where the biological carbon pump occurs effectively. In this region, seasonal variability in chlorophyll concentration peaks occurs in spring and autumn. The peaks are influenced by factors such as water temperature, vertical mixing, and atmospheric deposition. Iron supply, among various factors, can lead to spatial and temporal variations in chlorophyll concentration, thereby potentially impacting the biological carbon pump. In this study, a coupled ocean physical-biogeochemistry model was employed to investigate the climatological variability in biogeochemical environment and CO₂ flux (carbon cycle) resulting from atmospheric iron supply. The increase in chlorophyll concentration due to iron into the ocean can potentially trigger CO₂ absorption through photosynthesis.