Research groups such as Hokkaido University, the University of Tokyo, and Nagasaki University have succeeded in clarifying the nutritional material circulation image of the North Pacific Ocean, which is the end point of the "ocean conveyor belt."
The western North Pacific, facing Japan, is estimated to generate 6% of the total marine fishery resources, even though it accounts for only 26% of the total ocean area.The mechanism that creates the abundance of the western North Pacific involves the nutrients that determine the growth of phytoplankton and the supply and process of iron, which is a micronutrient.Until now, the North Pacific Ocean has been vaguely regarded as the exit of the ocean conveyor belt (global scale ocean circulation), and has been considered as a sea area where nutrients accumulated in deep sea water are brought to the surface layer.However, scientific knowledge was lacking in understanding the mechanism by which nutrients circulate and are linked to biological production.
In this study, we observed and sailed the Sea of Okhotsk and the Bering Sea, which are located on the edge of the North Pacific Ocean called the "Marginal Sea," and constructed a dataset that captures the entire picture of the North Pacific Ocean.Analysis of this data showed that high concentrations of nutrients were accumulated in the middle-rise waters extending over the North Pacific Ocean, and that there was a strong vertical mixture on the edge of the marginal sea.It was found that when this vertical mixture mixes the sea, nutrients are transferred from the middle layer water to the surface layer, and high nutrient concentration is maintained in the surface layer of the North Pacific Ocean.It was also found that the western North Pacific Ocean was further fertilized by the mixture of nutrients derived from the middle layer water formed in the Bering Sea and iron flowing out from the Sea of Okhotsk.
This achievement, which elucidated the nutrient cycle system in which the middle layer water spreading in the North Pacific carries nutrients, mixes in the marginal sea and springs up to the surface layer, understands the changes in the carbon cycle and nutrient cycle in the ocean due to future climate change. It is considered to be an indispensable finding for this.
