[A-OS09] 海洋混合学：物質循環・気候・生態系の維持と長周期変動の解明

[AOS09-P13] 黒潮栄養塩ストリームの構造とインパクト

*小松 幸生^1,2、廣江 豊³ (1.東京大学大学院新領域創成科学研究科、2.東京大学大気海洋研究所、3.水産研究・教育機構西海区水産研究所)

キーワード：黒潮栄養塩ストリーム、黒潮親潮移行領域、等密度面輸送

Recently the Kuroshio has drawn attention as an important supply route of nutrients in the western North Pacific. However, it is unknown whether nutrient concentrations are enhanced along the jet on isopycnal surfaces, as is the case for the “nutrient stream” along the Gulf Stream. We aim to ascertain the structure of nutrient concentration enhancement along the Kuroshio jet and to estimate the impact of nutrient transport downstream to the Kuroshio-Oyashio interfrontal zone (KOIZ), which is a highly productive region and a major global fishing ground. Recent multiple- transects and retrospective analyses of historic hydrographic data have revealed that the along-jet maximum nitrate concentration appears only in spring on the isopycnal surface 25<σ_θ<26 in the downstream region of the Kuroshio. The Kuroshio nutrient stream contributes significantly to productivity in the euphotic layer along its downstream trajectory, in conjunction with enhanced vertical turbulence. Analysis of the budget of epipycnal nitrate transport across transects that enclosed the KOIZ suggests that the Kuroshio nutrient stream has a non-negligible potential to significantly impact high productivity in the KOIZ.