[A-OS17] Chemical and Biological Oceanography

[AOS17-02] Spatio-temporal variability of subsurface Chl-a maximum in the world ocean

*Sayaka Yasunaka¹, Tsuneo Ono², Kosei Sasaoka¹, Kanako Sato¹ (1.Japan Agency for Marine-Earth Science and Technology, 2.Japan Fisheries Research and Education Agency)

Keywords:chlorophyll a, subsurface maximum, oxygen oversaturation

Chl-a concentration in ocean often retains its maximum value in subsurface layer. Using satellite retrieval of ocean surface Chl-a concentration, basin-wide spatial distribution and temporal variation of surface Chl-a has been described by many studies, while that of subsurface Chl-a has not been clarified yet. Here, we collects in-situ observation data of Chl-a concentration, and clarify the spatio-temporal variability of subsurface Chl-a concentration in the world ocean. Subsurface Chl-a maximum was stably observed in the subtropics and tropics (Figure 1). Depth of the subsurface Chl-a maximum is similar to the euphotic layer, but deeper than the euphotic layer in subtropics and shallower in tropics. Seasonal increase of oxygen below the mixed layer implied substantial biological new production. In El Niño years, subsurface Chl-a concentration in the equatorial Pacific is higher in the middle to east and lower in the west, which is opposite from surface.