Ocean Iron Fertilization (OIF) has been proposed as a potential carbon dioxide removal (CDR) strategy by alleviating iron limitation, enhancing phytoplankton growth, and strengthening the biological carbon pump. However, the regional responses of different marine ecosystems and the long-term carbon sequestration potential of OIF under future climate change remain poorly understood. This study employs an Earth System Model to investigate the impacts of OIF under the SSP5-8.5 scenario using realistic surface iron flux perturbations. Iron fertilization experiments are conducted in three representative marine ecosystems: the equatorial upwelling region, the subtropical oligotrophic gyre, and the subarctic North Pacific. The study focuses on the responses of net primary productivity, export production, air–sea CO₂ flux, and carbon sequestration efficiency to iron fertilization. In addition, the roles of nutrient redistribution, phytoplankton community shifts, and climate change in regulating the effectiveness of OIF are evaluated. This study is expected to improve our understanding of the regional responses of the biological pump to iron fertilization and provide a scientific basis for assessing the long-term carbon sequestration potential of OIF under future climate change.