Winter water exchange should benefit the Baltic Sea
The Baltic Sea's water level has dropped significantly since the start of the year as high-pressure systems and easterly winds have pushed seawater into the North Sea. In the long term, however, this is expected to have a positive effect as oxygen-rich water flowing back from the North Sea will significantly improve the Baltic Sea's ecosystem.
Water has effectively been pushed out of the Baltic Sea after a month of persistent easterly winds drove large volumes of water into the North Sea. According to German scientists, the Baltic has not seen such low water levels in 140 years.
"This time, Estonia did not break any records. Estonian records occur when there is very little ice and very strong easterly winds combined with high pressure. Estonia's record has been one meter and 20 centimeters below the long-term average," said academician Tarmo Soomere.
The standing Estonian record dates back to 1959 when strong easterly winds of up to 20 meters per second blew for several days over the Väinameri. This winter's lowest level, however, was measured only recently.
"On February 13, the water level around the Väinameri fell 75 centimeters below average. At the moment, it has risen and is 35–40 centimeters below average, but in the coming days it will start to fall again, remaining around 50–55 centimeters below average. At this point, no record is in sight," said Environment Agency forecaster Kertu Sild.
According to Ilja Maljutenko, a senior researcher in marine physics at Tallinn University of Technology, salinity measurements taken in the Danish straits indicate that the sea is gradually beginning to return.
"The drop in water levels began in January and lasted until early February and the subsequent recovery will not happen instantly. We are dealing with very large water masses — comparable to the volume of ten Lake Peipuses — that need to flow back," Maljutenko said.
The return of such massive volumes will take time and the senior researcher said water levels in the Baltic Sea could recover by early March. However, rising water levels mean that Estonia's ice roads are unlikely to last much longer.
"Winter's backbone has probably been broken. It is no longer freezing as hard and the roads are unlikely to remain drivable for much longer," Maljutenko noted.
This winter's water exchange will nevertheless benefit the Baltic Sea. "A large influx of oxygen-rich water will come to us from the North Sea, which makes life on the Baltic Sea floor possible in the first place," Soomere said.
The benefits of the water exchange will not be immediate, but Soomere said that within a few years there will be more fish in the Baltic than before. However, not enough saline water will reach the sea to allow cod to once again live in the Baltic.
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Editor: Marcus Turovski, Marko Tooming
