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Finland's future: Wet winters, warming Baltic, forested fells

Changes foreseen in the latest IPCC climate report raise a range of threats for Finland's natural environment.

sinileväpuuroa meressä
Eutrophication in the Baltic Sea is evident in the summer months from the proliferation of algae blooms. Image: Jaani Lampinen / Yle

A special report published this week by the UN's Intergovernmental Panel on Climate Change (IPCC) focused on the dangers posed by melting ice cover, rising sea levels, warming and changing ocean chemistry and the prospect of more extreme coastal weather events.

Earlier projections have forecast that climate change will impact Finland by bringing shorter, wetter winters to southern parts of the country. It is possible that the volume of snowfall will not decline, but the accumulation of snow will as it melts without longer periods of sub-zero temperatures.

Northern regions are warming at a faster pace than other parts of the globe, narrowing the environmental niche occupied by species such as Finland's Saimaa ringed seal and wolverines that need snow banks for dens where they birth and raise their young.

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Kuutti jäällä.
Without frozen lakes and drifting snow, Finland’s endangered Saimaa ringed seal will face extinction. Image: Yle

Warmer temperatures are also expected to lead to the spread of forests across the fells of Finnish Lapland, crowding out the indigenous plant life that now thrives there. The Arctic fox, an iconic denizen of the fells, has already become a rarity and other species may well disappear.

A rise in winter temperatures will also increase the destruction of forests. When the forest floor is not frozen, trees are more likely to be downed by the winds of winter storms. Forests are likely to be confronted by new insect pests, as well, a development already being observed in southern parts of Finland.

Warmer, less salty seawater

Changes are also being registered in the Baltic Sea. The University of Turku's research station on the island of Seili the southwestern archipelago has been monitoring the temperature and salinity of waters in the area since 1967.

Decades of data show transformations in surface waters, the topmost layer usually going down around 20 metres.

"The salinity of these sea waters has declined half a per mille, while at the same time, the temperature of surface waters has risen by around 1.5 degrees," says Associate Professor Jari Hänninen of the Biodiversity Unit of the University of Turku.

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merenmittauspoiju, Saaristomeri
An automated research station has been monitoring water quality off the coast of the island of Seili since 2006. Image: Markku Sandell / Yle

This observation is in line with forecasts of an increase of fresh water runoff into the Baltic Sea, reducing its overall salt content. At the same time, it backs projections of rising temperatures.

The Baltic climate is influenced by climatic conditions in the North Atlantic and changes happening there.

"All of the water coming into the Baltic comes from the North Atlantic," points out Hänninen.

Through evaporation, fresh water makes its way into the Baltic region as clouds. Rain from these clouds drains through river systems into the Baltic Sea.

Salt water from the North Sea enters the Baltic through the Danish straits, but the flow has diminished because of the higher rate of fresh water runoff from surrounding landmasses.

Because of mild winters, precipitation in the form of rain and melting snow is flowing into the Baltic Sea faster than in the past, raising the sea level. This in turn prevents the inflow of saltier water from the North Sea which is a largely seasonal phenomenon associated with winter storms.

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Jari Hänninen, Johannes Sahlstedt, merentutkimus, Airisto, Saaristomeri
Professor Jari Hänninen watches as student Johannes Sahlstedt retrieves a plankton sample. Image: Markku Sandell / Yle

Under these circumstances, there is no room for saltwater "pulses" to enter the main basin of the Baltic, blocking these oxygen-laden waters from flowing into the depths of the sea. This is a change that began developing in the mid-1980s.

The depths of the Baltic have suffered from hypoxia - a lack of an adequate supply of oxygen - for a long time, and no prospect of an improvement is in sight.

Overburdened by nutrients

Not only does the future of the Baltic Sea contain more fresh water, it will also contain higher concentrations of nutrients, bringing more eutrophication, overloading of the sea bottom with organic materials, and an accelerated loss of oxygen.

This will impact not only the deepest parts of the sea, but also more shallow waters, as well.

The Baltic Sea is home to a mixture of freshwater and saltwater species. As its salinity declines, saltwater species, such as the Baltic herring are coming under pressure. In contrast, freshwater species are thriving.

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Silakoita.
The average size of Baltic herring has decreased significantly since the 1980s. Image: Monica Forssell / Yle

Monitoring of plankton and Baltic herring by the University of Turku's Archipelago Research Institute has found changes in the diet of herring in these waters as larger copepods, a kind of crustacean that the fish feed on, have disappeared. As a result, herring in the area have, on average, lost a quarter of their length and up to half of their weight since the 1980s.

"Baltic herring will surely not disappear from the archipelago, but in future, most of the catch will maybe come from the south of the Baltic where salinity levels are staying higher," explains Hänninen.

Less ice

The University of Turku's Seili research station lies just north of the village of Nauvo, a boat trip of around half an hour. Jari Hänninen recalls that during the 1990's it was possible to drive by car there across the ice in the winter.

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Merenjää
With warming temperatures, there will be less winter ice cover off Finland's coasts. Image: Timo Viitanen / AOP

In recent years, the sea has frozen over no earlier than in February and thawed in March. During that short time, travel by snowmobile or small ATV has been possible, but the trip can no longer be made by car.

The lack of ice cover has and will impact the lives of residents and visitors in the archipelago, but it is not expected that sea levels will rise in the Gulf of Bothnia, even as melting glacial ice raises the levels of the earth's oceans.

The land area of Finland is still springing back from the weight of the glaciers which covered it during the last ice age. So, coastal areas are rising faster than projected sea levels. It's likely to be a different story along the south coast, however, where a study by the Finnish Meteorological Institute says the risk of flooding will grow significantly by the end of the century.

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