JpGU-AGU Joint Meeting 2017

Presentation information

[JJ] Oral

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

[A-OS30] [JJ] Ocean circulation, material cycle, and biological responsive dynamics in coastal seas

Sat. May 20, 2017 10:45 AM - 12:15 PM 303 (International Conference Hall 3F)

convener:Akihiko Morimoto(Center for Marine Environmental Studies, Ehime University), Kiyoshi Tanaka(University of Tokyo), Hideki FUKUDA(Coastal Conservation Section, International Coastal Research Center, The Atmosphere and Ocean Research Institute, The University of Tokyo), Haruko Kurihara(University of the Ryukyus), Chairperson:Akihiko Morimoto(Center for Marine Environmental Studies, Ehime University)

11:15 AM - 11:30 AM

[AOS30-03] Circulation and haline structure of a microtidal bay in the Sea of Japan influenced by the winter monsoon and the Tsushima Warm Current

*Sachihiko Itoh1, Akihide Kasai2, Aigo Takeshige, Kei Zenimoto1, Shingo Kimura1, Keita W Suzuki3, Yoichi Miyake1, Tatsuichiro Funahashi4, Yoh Yamashita3, Yoshiro Watanabe1 (1.Atmosphere and Ocean Research Institute, The University of Tokyo, 2.Graduate School of Fisheries Science, Hokkaido University, 3.Field Science Education and Research Center, Kyoto University, 4.Tokyo Metropolitan Islands Area Research and Development Center of Agriculture, Forestry and Fisheries)

Keywords:water exchange, ROFI, microtidal bay, estuarine circulation, Tsushima Warm Current, Changjiang Diluted Water

Mooring and hydrographic surveys were conducted in Tango Bay, a microtidal region of freshwater influence (ROFI) in the Sea of Japan, in order to clarify the circulation pattern in the bay and its driving forces. Monthly mean velocity records at four stations revealed an inflow and outflow at the eastern and northern openings of the bay, respectively, which indicates an anticyclonic circulation across the bay mouth. The circulation was significantly intensified in winter, in accordance with the prevailing NW wind component of the winter monsoon. The anticyclonic circulation at the bay mouth was connected to an estuarine circulation that was evident near the mouth of the Yura River at the bay head. Surface salinity just offshore of the river mouth was closely related to the Yura River discharge, whereas in lower layers the offshore water had a stronger influence on salinity. Prior to a seasonal increase in the Yura River discharge, summer salinity decreased markedly through the water column in Tango Bay, possibly reflecting intrusion of the Changjiang Diluted Water transported by the Tsushima Warm Current. In contrast with the traditional assumption that estuarine circulation is controlled mainly by river discharge and tidal forcing, the circulation in Tango Bay is strongly influenced by seasonal wind and the Tsushima Warm Current. The narrow shelf may be responsible for the strong influence of the Tsushima Warm Current on circulation and water exchange processes in Tango Bay.