Japan Geoscience Union Meeting 2019

Presentation information

[E] Poster

A (Atmospheric and Hydrospheric Sciences ) » A-OS Ocean Sciences & Ocean Environment

[A-OS09] Ocean Mixing Processes: Impact on Biogeochemistry, Climate and Ecosystem

Sun. May 26, 2019 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Ichiro Yasuda(Atmosphere and Ocean Research Institute, The University of Tokyo), Toshiyuki Hibiya(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Jun Nishioka(Hokkaido University, Institute of low temperature sciences), Shin-ichi Ito(Atmosphere and Ocean Research Institute, The University of Tokyo)

[AOS09-P13] Structure and impact of the Kuroshio nutrient stream

*Kosei Komatsu1,2, Yutaka Hiroe3 (1.Graduate School of Frontier Sciences, The University of Tokyo, 2.Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan, 3.Seikai National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Nagasaki, Japan)

Keywords:Kuroshio nutrient stream, Kuroshio-Oyashio interfrontal zone, epipycnal transport

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<σθ<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.