2024 Volume 80 Issue 17 Article ID: 24-17253
To assess the variability and mechanisms of nutrient transport and upper ocean primary production associated with fluctuations in the Kuroshio path off the coast of Enshu-nada Sea, numerical analyses were conducted on the nitrate flux transport processes maintaining primary production by using a three-dimensional regional ocean circulation model coupled with a nitrogen-based ecosystem model. The differences in nitrate transport were evident depending on the presence or absence of Kuroshio meandering, with upper ocean primary production being approximately 1.5 times higher during a non-meandering period compared to a meandering period. Nitrate flux budget analysis revealed that during the non-meandering period, the vertical nitrate transport within the mixed layer was amplified, primarily due to vigorous upwelling of nitrate on the northern side of the Kuroshio axis and around the Izu-Ogasawara Ridge. The nitrate supplied to the upper ocean was then transported horizontally by the counterclockwise rotating, topographically constrained standing mesoscale eddy formed between the coast and the Kuroshio, to feed the phytoplankton in Enshu-nada Sea.
