Archipelago Sea and Luodonjärvi Lake (Bothnian Sea)
A very different hydrographic and ecological environment from the other three OPCOM sites is this area. The Archipelago Sea is situated at the connection between the Gulf of Bothnia and the central Baltic Sea. This regional sea may be characterized as a very large deep estuary with numerous coastal lagoons. Short-term variations in circulation and associated transport/mixing processes are pre-dominantly governed by meteorological phenomena, longer term processes are dominated by thermo-haline currents in the deeper Baltic Sea, fluctuations in the fresh water inflow from the coasts, and the very rare occasions of North Sea water penetration through the Danish straits which ventilate the deep water of the Baltic Sea. Even more complicated are the interactions between the coastal lagoons (especially on the southern coastline) and the open sea, as most coastal bays are connected only by narrow channels. Tides are almost negligible in the Baltic Sea, this leads to a very high uncertainty in dynamical (and environmental) forecasting.
Very important from an ecological point of view are the large residence times of water in the Baltic once it has been transported from the rivers into the coastal waters. As most tributaries in the catchment area of the Baltic Sea are highly polluted this is especially of great concern for environmental protection. Only in some coastal areas there are already detailed measurement and monitoring activities which might enable a profound investigation as proposed for this study.
The most characterizing feature of the Archipelago Sea itself is a huge number of islands of irregular size and shape, separated by narrow passages of highly irregular depths and a few wider sea areas in between. The area is loaded by chemical, pulp and paper and other industry (also nuclear and coal power plants), by several big cities (e.g. the former capital, Turku, nowadays the third or fourth city in Finland), and through rivers by the most intensive agriculture (e.g. big piggeries) in Finland.
The increased loading is a problem in some areas near the coast where water exchange under most of the conditions is quite slow. The water exchange is very much depending on total fluctuations of the Baltic Sea and the Bothnian Sea system, on winds (or ice cover annually for a couple of months), and on the complex system of passages within the sea. Dredging of passages is frequently needed which causes further problems from the sediments contaminated from earlier loading.
OPCOM partners will especially be looking at spill combatting and sea rescue activities and the impact of environmentally relevant discharges from rivers and other effluent sources.
For further information please contact Riitta Niemelä (riitta.niemela@arges.fi) or Markku Virtanen (markku.virtanen@eia.fi).
Other OPCOM investigation areas: