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Dependence of horizontal characteristic scale of chlorophyll a distribution on eddy activity at the mid-latitudes of global oceans
  • Hitoshi Kaneko,
  • Shin-ichi Ito,
  • Ken'ichi Sasaki
Hitoshi Kaneko
Mutsu Institute for Oceanography, Japan Agency for Marine-Earth Science and Technology

Corresponding Author:h_kaneko@jamstec.go.jp

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Shin-ichi Ito
Atomosphere and Ocean Reseach Institute, The University of Tokyo
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Ken'ichi Sasaki
Japan Agency for Marine-Earth Science and Technology
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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 (LD) and Rhines scale (LR). In the open ocean, the horizontal scale of Chl-a (D) decreased with increasing eddy kinetic energy (EKE), converging to πLD in the high-eddy-activity region. The ratio of zonal (Dz) to meridional (Dm) scales, RD (= Dz/Dm), 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), Dm was larger than LD, with a scale similar to πLR. In these regions, Dz values greater than Dm 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.