The Baltic Sea is a brackish sea located in Northern Europe, bordered by Sweden, Finland, Russia, Estonia, Latvia, Lithuania, Poland, Germany, and Denmark. It is known for its low salinity levels, which is a distinguishing characteristic compared to other seas. This article will discuss the reasons behind the Baltic Sea’s low salinity levels and the impact it has on the environment and human activity.
Definition of Salinity
Salinity refers to the concentration of dissolved salts, minerals, and other substances in seawater. It is typically measured in parts per thousand (ppt) or practical salinity units (PSU). The average salinity of seawater is about 35 ppt or 35 PSU. However, salinity levels can vary depending on the location, temperature, and other factors.
Factors Affecting Salinity
Various factors affect the salinity of seawater, including evaporation, precipitation, freshwater input, water inflow, and ocean currents. Evaporation increases seawater salinity by leaving behind dissolved salts and other minerals. Precipitation, on the other hand, reduces salinity by adding freshwater to the ocean. Water inflow from rivers and other sources can also affect salinity levels, especially if the water is low in dissolved salts. Ocean currents can also influence salinity by mixing water with different salinity levels.
Salinity of the Baltic Sea
The Baltic Sea is one of the least saline seas in the world, with an average salinity of about 7 to 8 ppt. This is significantly lower than the average salinity of seawater, which is about 35 ppt. The low salinity of the Baltic Sea is due to various factors, including freshwater input, water inflow, and climate change.
Reasons for Less Saline Baltic Sea
The low salinity of the Baltic Sea is primarily due to its geography and climate. The sea is shallow, with an average depth of only 55 meters, and is surrounded by land, which limits water exchange with other seas. Additionally, the Baltic Sea is located in a region with a temperate climate, which means it receives significant amounts of precipitation and freshwater input from rivers and streams.
The Role of Water Inflow
Water inflow from the North Sea and the Atlantic Ocean is another significant factor that affects the salinity of the Baltic Sea. The inflow of saltwater helps to increase the salinity levels of the Baltic Sea, but it is limited due to the geography and climate of the region. The inflow of saltwater is also affected by the amount of freshwater input, which can reduce salinity levels.
Influence of Climate Change
Climate change is also affecting the salinity levels of the Baltic Sea. Rising temperatures and changing precipitation patterns have led to an increase in freshwater input, which has further reduced salinity levels. Additionally, climate change is affecting the water inflow from the North Sea and the Atlantic Ocean, which can also impact salinity levels.
Impact of Freshwater Input
Freshwater input from rivers and streams is a significant factor that affects the salinity of the Baltic Sea. The sea receives significant amounts of freshwater from around 200 rivers and streams, including the largest inflow from the Neva River in Russia. This freshwater input reduces salinity levels and can lead to changes in the ecosystem.
Human Activities and Salinity
Human activities, such as agriculture, forestry, and industrial activities, can also impact salinity levels in the Baltic Sea. These activities can lead to increased freshwater input through runoff and pollution, which can reduce salinity levels and harm the ecosystem.
Consequences of Low Salinity
The low salinity of the Baltic Sea has significant consequences for the ecosystem, including changes in the distribution of species, reduced biodiversity, and increased susceptibility to pollution and disease. Additionally, the low salinity levels of the sea can impact human activity, including shipping and fishing.
The Baltic Sea is one of the least saline seas in the world, with an average salinity of about 7 to 8 ppt. The low salinity is due to various factors, including freshwater input, water inflow, and climate change. The consequences of low salinity levels are significant for the ecosystem and human activity in the region, making it important to monitor and manage salinity levels in the Baltic Sea.
- HELCOM. (2018). State of the Baltic Sea. Retrieved from
- Meier, H. E. M., et al. (2012). Assessment of Eutrophication in the Baltic Sea in 2011-2012: A Report from the Baltic Sea Environmental Monitoring (BSEMP) Intercalibration Exercise. Retrieved from !/menu/standard/file/Meier12BSEMP_Report_120417.pdf
- Wulff, F., et al. (2014). Climate change implications for the Baltic Sea. In: O. S. Mikkelsen, J. E. Olesen, M. J. Rasmussen, & J. H. Christensen (Eds.), Advances in Ecological Research, Volume 50 (pp. 1-58). Academic Press.