Nutrients distribution in the coastal water of East Asia relative to the Kuroshio

Nutrients in the coastal water of East Asia were surveyed from the point of contribution of the diluted water to the open water relative to the Kuroshio, the western boundary current. The Kuroshio runs along eastern Asia, sensing changes in environment in the coastal region. The nutrients-depleted water from the Kuroshio, close to the coastal water, provides heat energy and high saline water. The fresh water from the river contributes to the coastal water as diluted water and exhibits the entrainments of nutrient water into the Kuroshio. The nutrients are important parameters to monitor the interactions among the Kuroshio and inland waters. Nutrients exhibited a wide range of ratio between nitrate to phosphate, nitrate to silicate, and silicate to phosphate in East Asia as divergences from the Redfield ratios. The distribution of nutrients could also be monitored as the distribution of chlorophyll-a concentration using the ocean color sensors. Contrasts in chlorophyll-a concentration between the oligotrophic water of the Kuroshio and the trophic water of the coastal region exhibit the mixing process of two water masses. Although the chlorophyll-a concentrations estimated by the current ocean color algorithm over the coastal water are of insufficient accuracy, the distribution of chlorophyll-a concentration exhibits a variation of seasonal consumption of nutrients and response to the Kuroshio and river runoff.