Mesoscale eddy effects on temporal variability of surface chlorophyll a in the Kuroshio Extension
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We investigated the relationship between chlorophyll a (Chl-a) concentrations estimated from satellite observations and the activity of eddies in the Kuroshio Extension region. High (low) area-averaged Chl-a concentrations were frequently observed in the core of cyclonic (anticyclonic) eddies. Such relationships between Chl-a concentrations and eddy cores were not frequently observed in the southern part of the recirculation gyre, and advection of background meridional gradient of Chl-a by eddy-edge currents accounted for Chl-a spatial variability. Decadal-scale changes of Chl-a concentrations around the Kuroshio Extension were strongly affected by eddy activity and transport but not by large-scale near-surface isopycnal heaving. We also found that decadal changes of nutrient concentrations near the main stream could affect Chl-a concentrations in the southern part of the recirculation gyre via southward transport of eddies and mean flow.
KeywordsKuroshio Extension Decadal variability Mesoscale eddy Biological productivity Nutrient variability
S. Kouketsu, S. Itoh, T. Okunishi, and H. Kaneko were supported for this study by Grant-in-Aid for Scientific Research on Innovative Areas Grant Number 12024485. We thank the reviewers and the editor for their useful comments. We extend our appreciation to the late Dr. Toshiro Saino for his encouragement to undertake this study.
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