Hydrography and Circulation in a Coastal Site of the Gulf of Finland during the Ice Season

摘要

Local hydrography and current data were recorded in the framework of the joint Finnish - Japanese experiment "Hanko 9012", which took place in Santala Bay, Baltic Sea offshore Hanko Peninsula. Santala Bay is the southernmost point of the Finnish mainland, in the mouth of the Gulf of Finland. The Bay freezes over annually. An automatic station was operating during the wintertime, covering four winters (1999-2002). Near the station, a three-dimensional electromagnetic current meter with temperature, conductivity and depth sensors was deployed. Here, data from two winters (2000-2001) are examined in order to describe the hydrography and circulation patterns of this coastal site prior to freezing, under ice cover, and after ice breakup. The time series of temperature and salinity are also compared with long term data from Tv?rminne Zoological station. In both years, one month of data records before and after the ice- season is available. This contributes to a comparison between the open water and the sea-ice season, which aids to estimate the influence of sea-ice cover on the hydrography and circulation characteristics. Under the landfast ice, a thin, stable surface layer is formed. Ice formation and melting show up in the salinity evolution in the water body, and the circulation becomes weaker during the ice season.