Japan Geoscience Union Meeting 2023

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[E] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-CG Complex & General

[A-CG30] Extratropical oceans and atmosphere

Sun. May 21, 2023 10:45 AM - 12:00 PM 201A (International Conference Hall, Makuhari Messe)

convener:Shion Sekizawa(Research Center for Advanced Science and Technology, University of Tokyo), Shota Katsura(Atmosphere and Ocean Research Institute, The University of Tokyo), Yuta Ando(Kyushu University), Shoichiro Kido(JAMSTEC Application Lab), Chairperson:Shota Katsura(Scripps Institution of Oceanography, University of California, San Diego), Shion Sekizawa(Research Center for Advanced Science and Technology, University of Tokyo)


11:00 AM - 11:15 AM

[ACG30-02] Mode water-seasonal pycnocline system in mid-latitude oceans

★Invited Papers

*Toshio Suga1 (1.Graduate School of Science, Tohoku University)

Keywords:ocean circulation, atmosphere-ocean interaction, potential vorticity, heat content, nutrient transport, buoyancy flux

Mode waters are water masses that originate in deep winter mixed layers and are characterized by vertical homogeneity of water properties. The term "mode" refers to a statistical mode. The name "mode water" is derived from the fact that the temperature and salinity of this water mass is the mode in the volume distribution by regional temperature and salinity class, i.e., it occupies a large regional volume. The vertical homogeneity of the density of the mode water leads to the property of vertical minima of potential vorticity. Because of the conservation of potential vorticity, mode water has been used as a tracer of ocean circulation. On the other hand, the formation of mode water is the result of local atmosphere-ocean interaction with large heat release from the ocean to the atmosphere, which is stored as anomalies in temperature, salinity, and thickness and spread over a wide area. This has also drawn attention to the role of mode water in regional to basin-scale atmosphere-ocean interaction. In addition, interest has been focused on the storage and transport of oxygen, carbon dioxide, and nutrients taken up by mode water during its formation and its role in the material cycle and ecosystem. When treating mode water as a tracer of circulation or as a "memory" of winter mixed layer temperature, it is natural to focus on the potential vorticity minimum, a core of mode water itself. On the other hand, in order to consider the role of mode water in large-scale atmosphere-ocean interaction, material circulation, and ecosystem, it seems useful to look at the mode water as a "mode water-seasonal pycnocline system" that is integrated with the overlying seasonal pycnocline, rather than just the mode water itself. From the above perspectives, a review of modal water studies mainly in the North Pacific will be presented and the merits of considering this system will be discussed.