The micronutrient iron (Fe) is recognized as a key factor in controlling oceanic primary productivity, and subsequently impacting the carbon cycle and marine ecosystem. The high-latitude area of the North Pacific is one of the three main high-nutrient and low-chlorophyll (HNLC) regions on Earth. Also, the growth of phytoplankton is limited by the availability of Fe. Climate change, human activities and ocean acidification are expected to influence the availability and transport of Fe in the ocean. Therefore, it is of great importance to study the Fe cycle and make reliable predictions for the future.