[A-OS12] Marine ecosystems and biogeochemical cycles: theory, observation and modeling

[AOS12-08] Dependence of horizontal characteristic scale of chlorophyll a distribution on eddy activity at the mid-latitudes of global oceans, and its long-term change

*金子 仁¹、伊藤 進一²、佐々木 建一¹ (1.海洋研究開発機構、2.東京大学大気海洋研究所)

キーワード：クロロフィル a、海洋中規模渦、ロスビー波、西岸境界、内部変形半径、ラインズスケール

Understanding of the spatial distribution of near-surface oceanic chlorophyll a (Chl-a) in relation to eddy activity is important because Chl-a is critical to biological production and carbon absorption, and its distribution is closely related to meso-scale eddies and Rossby waves. Chl-a distributions based on satellite observations from 2001 to 2018 were analyzed in association with eddy activity in mid-latitude regions of the five ocean basins (North/South Pacific, North/South Atlantic, and South Indian oceans) and related to physical eddy scales including the internal Rossby deformation radius (L_D) and Rhines scale (L_R). In the open ocean, the horizontal scale of Chl-a (D) decreased with increasing eddy kinetic energy (EKE), converging to πL_D in the high-eddy-activity region. The ratio of zonal (D_z) to meridional (D_m) scales, R_D (= D_z/D_m), converged to 1 with increasing EKE, implying isotropic uniformization with meso-scale eddies. In regions of low EKE (especially the central subtropical and eastern parts of each basin), D_m was larger than L_D, with a scale similar to πL_R. In these regions, D_z values greater than D_m were found (with scales of 500–1000 km), indicating the effects of planetary phenomena on Chl-a. In such regions the sensitivity of D to EKE tended to be higher than in western boundary regions, indicating the influence of meso-scale eddy activity on the Chl-a distribution, even with low EKE. We will also show the decadal change in the scale of D in the presentation.