Water Transport through the Åland Sea / Перемещение воды в Аландском море

• Published in: Ambio special report 1977-01 (5), p.117-125
• Main Authors: Ehlin, U., Ambjörn, C., Элин, У., Амбьёрн, С.
• Format: Article
• Language: English
• Subjects: Buoys; Hydrochemical, Hydrographical and Meteorological Characteristics / Гидрохимические, гидрографические и метеорологические характеристики; Hydrology; Isotherms; Meteorology; Ocean currents; Sea transportation; Sea water; Seas; Surface layers
• ISSN: 0301-0325

The aim of this paper is to give information about a present investigation of the transport of water and nutrients through the Åland Sea and to give some examples of the preliminary results. The investigation is carried out in co-operation with the Marine Research Institute in Finland which is responsible mainly for the chemical work. The Swedish Meteorological and Hydrological Institute is concentrating on the current pattern and the water transports. During June to December 1973 and 1974, 12 recording current meters with temperature sensors were placed at 4 stations in a section between Sweden and Åland in the sill area Understen-Märket. The instruments, placed at 8, 40 and 70-80 m depth, have worked fairly well and the data return is 75-90% of expected. A recording temperature meter placed outside Understen has collected data from 11 different levels during the same time periods. The observations are so far evaluated only for certain periods. The results show that in the horizontal the currents in the surface layer have the same principal direction over the whole section during about 20% of the time. The surface currents on the western side are more often going towards the south rather than the north and are stronger in this dominant direction. In the eastern part the southerly currents are still predominant but not to such an extent as on the western side. In deeper layers the northerly current is dominant on the western side and almost as frequent as the southerly on the eastern side. The currents are often of the same direction through the whole vertical and no pronounced two-layer current system has been observed. The typical time periods for the transports towards north or south seem also to differ along the section. They are about 1-3 days on the western side and only about 1 day on the eastern. The size of the transport calculated as a daily mean value is up to 10 km³/day both to the north and to the south in the summer. Calculations based on water level recordings show that water transports to or from the Gulf of Bothnia coupled to volume variations are of the size of 5-10 km³/day during summer and up to 40 km³/day during late autumn (1973). During 1975-76 the field observations with recording instruments will be restricted to current and temperature measurements at only one station but they will instead be extended over the whole winter period. In addition, occasional measurements of temperature, salinity and nutrients will also be carried out.