10:45 AM - 11:00 AM
[AOS30-01] Decadal trend of the tidally-induced stratification in Fukuoka Bay: Its potential cause and influences
Keywords:tide, estuarine circulation, air-sea interaction, Fukuoka Bay, tidal mixing
In this study, we focused on the changes in the tidally-altered stratification of Fukuoka Bay (facing to the Tsushima Strait) using archived water temperature (T) and salinity (S) observed by the Fukuoka Fisheries and Marine Technology Research Center. The T/S data observed during the summer (June - August) from 1982 to 1998 were categorized into data obtained at spring and neap tides. It is interesting that, in the 1980s (1990s), the sea surface temperature at neap tides was lower (higher) than that at the spring tides. The suggestion is that weak (strong) tidal mixing remains (destroys) the summer stratification at neap (spring) tides in 1990s, whilst this tidal mixing process did not work well in 1980s. Also of particular interest is that the salinity in the bottom layer at neap tides was higher in 1980s than that in 1990s. This suggests that Fukuoka Bay belonged to the estuarine-circulation (mixing) phase in 1980s (1990s). In conference, we will provide the analytical results of how spring/neap tide influence the T/S in the bay. Moreover, we will present the potential cause(s) of why the above phase change occurred in the Fukuoka Bay. In addition, we now attempt to uncover its influence(s) on the surrounding atmospheric condition (e.g., sea-breeze) as well as oceanic one. The response revealed in the lower-level atmosphere over the Fukuoka Bay (and neighboring land) might occur as in the Seto Inland Sea, where the fortnightly tidal cycle actually alters the air temperature and wind magnitudes over the sea via changes in the tidal mixing (Iwasaki et al., 2015).