Of these two seals, only the Baltic ringed seal suffers when there is not adequate ice in the Baltic Sea, as it feeds its young only while on ice. The grey seal is adapted to reproducing also with no ice in the sea. The sea ice also harbours several species of algae that live in the bottom and inside unfrozen brine pockets in the ice. The Baltic Sea flows out through the Danish straits ; however, the flow is complex.
The general circulation is anti-clockwise: northwards along its eastern boundary, and south along the western one. The difference between the outflow and the inflow comes entirely from fresh water. Additional fresh water comes from the difference of precipitation less evaporation, which is positive. An important source of salty water are infrequent inflows of North Sea water into the Baltic.
Such inflows, are important to the Baltic ecosystem because of the oxygen they transport into the Baltic deeps, used to happen regularly until the s. In recent decades they have become less frequent. The latest four occurred in , , and suggesting a new inter-inflow period of about ten years. The water level is generally far more dependent on the regional wind situation than on tidal effects. However, tidal currents occur in narrow passages in the western parts of the Baltic Sea. The significant wave height is generally much lower than that of the North Sea. Quite violent, sudden storms sweep the surface ten or more times a year, due to large transient temperature differences and a long reach of wind.
Seasonal winds also cause small changes in sea level, of the order of 0. The Baltic Sea is the world's largest inland brackish sea. The Caspian Sea is larger in water volume, but—despite its name—it is a lake rather than a sea. The Baltic Sea's salinity is much lower than that of ocean water which averages 3. The open surface waters of the Baltic Sea "proper" generally have a salinity of 0. The flow of fresh water into the sea from approximately two hundred rivers and the introduction of salt from the southwest builds up a gradient of salinity in the Baltic Sea.
The highest surface salinities, generally 0. It gradually falls further east and north, reaching the lowest in the Bothnian Bay at around 0. As salt water is denser than fresh water, the bottom of the Baltic Sea is saltier than the surface. This creates a vertical stratification of the water column, a halocline , that represents a barrier to the exchange of oxygen and nutrients, and fosters completely separate maritime environments.
Overall it follows the same southwest to east and north pattern as the surface. In contrast, the salinity of the Danish straits , which connect the Baltic Sea and Kattegat, tends to be significantly higher, but with major variations from year to year. For example, the surface and bottom salinity in the Great Belt is typically around 2. From to inflows occurred on average six to seven times per decade. Since it has been much less frequent, although a very large inflow occurred in The rating of mean discharges differs from the ranking of hydrological lengths from the most distant source to the sea and the rating of the nominal lengths.
Countries lands in the outer drainage basin :. The Baltic sea drainage basin is roughly four times the surface area of the sea itself. Most of the latter are in the Gulfs of Bothnia and Finland. The rest of the land is heavily populated. Around 22 million live in population centers of over , Geological surveys show that before the Pleistocene , instead of the Baltic Sea, there was a wide plain around a great river that paleontologists call the Eridanos. Several Pleistocene glacial episodes scooped out the river bed into the sea basin.
Instead of a true sea, the Baltic can even today also be understood as the common estuary of all rivers flowing into it. From that time the waters underwent a geologic history summarized under the names listed below. Many of the stages are named after marine animals e. The factors that determined the sea's characteristics were the submergence or emergence of the region due to the weight of ice and subsequent isostatic readjustment, and the connecting channels it found to the North Sea - Atlantic , either through the straits of Denmark or at what are now the large lakes of Sweden , and the White Sea - Arctic Sea.
The land is still emerging isostatically from its depressed state, which was caused by the weight of ice during the last glaciation. The phenomenon is known as post-glacial rebound. Consequently, the surface area and the depth of the sea are diminishing. The uplift is about eight millimetres per year on the Finnish coast of the northernmost Gulf of Bothnia. In the area, the former seabed is only gently sloping, leading to large areas of land being reclaimed in what are, geologically speaking, relatively short periods decades and centuries.
The "Baltic Sea anomaly" refers to interpretations of an indistinct sonar image taken by Swedish salvage divers on the floor of the northern Baltic Sea in June The treasure hunters suggested the image showed an object with unusual features of seemingly extraordinary origin. Speculation published in tabloid newspapers claimed that the object was a sunken UFO. A consensus of experts and scientists say that the image most likely shows a natural geological formation. The fauna of the Baltic Sea is a mixture of marine and freshwater species.
Among marine fishes are Atlantic cod , Atlantic herring , European hake , European plaice , European flounder , shorthorn sculpin and turbot , and examples of freshwater species include European perch , northern pike , whitefish and common roach. Freshwater species may occur at outflows of rivers or streams in all coastal sections of the Baltic Sea.
Further north the pattern is inverted. In the Bothnian Bay, roughly two-thirds of the species are freshwater. In the far north of this bay, saltwater species are almost entirely absent. Their range limit is west of Bornholm, meaning that they are absent from the vast majority of the Baltic Sea. There is a decrease in species richness from the Danish belts to the Gulf of Bothnia. The decreasing salinity along this path causes restrictions in both physiology and habitats.
However, even the most diverse sections of the Baltic Sea have far less species than the almost-full saltwater Kattegat, which is home to more than species from these groups.
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Since the Baltic Sea is so young there are only two or three known endemic species: the brown alga Fucus radicans and the flounder Platichthys solemdali. Both appear to have evolved in the Baltic basin and were only recognized as species in and respectively, having formerly been confused with more widespread relatives. A peculiar feature of the fauna is that it contains a number of glacial relict species , isolated populations of arctic species which have remained in the Baltic Sea since the last glaciation , such as the large isopod Saduria entomon , the Baltic subspecies of ringed seal , and the fourhorn sculpin.
Some of these relicts are derived from glacial lakes , such as Monoporeia affinis , which is a main element in the benthic fauna of the low-salinity Bothnian Bay. Critically endangered populations of Atlantic white-sided dolphins and harbor porpoises inhabit the sea where white-colored porpoises have been recorded,  and occasionally oceanic and out-of-range species such as minke whales ,  bottlenose dolphins ,  beluga whales ,  orcas ,  and beaked whales  visit the waters.
In recent years, very small, but with increasing rates, fin whales     and humpback whales migrate into Baltic sea including mother and calf pair. Other notable megafauna include the basking sharks. The area of the bloom extended from Germany and Poland to Finland. Researchers of the phenomenon have indicated that algal blooms have occurred every summer for decades. Fertilizer runoff from surrounding agricultural land has exacerbated the problem and led to increased eutrophication.
The more saline and therefore denser water remains on the bottom, isolating it from surface waters and the atmosphere. This leads to decreased oxygen concentrations within the zone. It is mainly bacteria that grow in it, digesting organic material and releasing hydrogen sulfide.
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Because of this large anaerobic zone, the seafloor ecology differs from that of the neighbouring Atlantic. Plans to artificially oxygenate areas of the Baltic that have experienced eutrophication have been proposed by the University of Gothenburg and Inocean AB. The proposal intends to use wind-driven pumps to inject oxygen air into waters at, or around, m below sea level. The Baltic Sea is the main trade route for export of Russian petroleum.
Many of the countries neighboring the Baltic Sea have been concerned about this, since a major oil leak in a seagoing tanker would be disastrous for the Baltic—given the slow exchange of water. The tourism industry surrounding the Baltic Sea is naturally concerned about oil pollution. Much shipbuilding is carried out in the shipyards around the Baltic Sea. For the first time ever, all the sources of pollution around an entire sea were made subject to a single convention, signed in by the then seven Baltic coastal states.
The Convention entered into force on 3 May In the light of political changes and developments in international environmental and maritime law, a new convention was signed in by all the states bordering on the Baltic Sea, and the European Community. After ratification the Convention entered into force on 17 January The Convention covers the whole of the Baltic Sea area, including inland waters and the water of the sea itself, as well as the seabed.
Measures are also taken in the whole catchment area of the Baltic Sea to reduce land-based pollution. The ratification instruments were deposited by the European Community, Germany, Latvia and Sweden in , by Estonia and Finland in , by Denmark in , by Lithuania in and by Poland and Russia in November From Wikipedia, the free encyclopedia. For other uses, see Baltic disambiguation. See also: List of rivers of the Baltic Sea. Main article: List of islands in the Baltic Sea. Main article: List of cities and towns around the Baltic Sea.
Main article: Geology of the Baltic Sea. Ancylus Lake around years BP. The relic of Scandinavian Glacier in white. Much of modern Finland is former seabed or archipelago: illustrated are sea levels immediately after the last ice age. Main article: Baltic Sea anomaly.
See also: List of fish in Sweden. Further information: Baltic Sea hypoxia. Archived from the original on 2 June Retrieved 5 July Resilience and the Behavior of Large-Scale Systems. Island Press. Archived from the original on 25 February The Position of the Slavonic Languages at the present day. Oxford University Press. Le lingue baltiche in Italian. Florence: La Nuova Italia. Retrieved on 23 June Helsinki Commission.
Archived from the original PDF on 28 October Retrieved 2 July Citing Weiss, D. In Kramer, J. Stuttgart: Wittwer. Archived from the original on 15 April Retrieved 14 April Archived from the original on 21 April Retrieved 27 August International Hydrographic Organization.
Archived from the original PDF on 8 October Retrieved 6 February Archived from the original on 23 October Retrieved 11 April Retrieved 27 July A4; 25 February , p. A5; 11 June , p. Archived from the original on 27 July Snoeijs-Leijonmalm; H. Schubert; T. Radziejewska eds. Biological Oceanography of the Baltic Sea. Springer, Dordrecht. Archived from the original PDF on 6 June Nielsen; P. Dahlstrom; B. Nystrom Sea Fish. Landeshauptstadt Kiel. Retrieved on 11 October Retrieved 1 August How Stuff Works.
Live Science. Live Science, Purch. Get Real, Experts Say". Popular Mechanics. Some of this water is polluted. Additional fresh water comes from the difference of precipitation less evaporation, which is positive. An important source of salty water are infrequent inflows of North Sea water into the Baltic.
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Such inflows, important to the Baltic ecosystem because of the oxygen they transport into the Baltic deeps, once happened on average every four to five years until the s. In recent decades they have become less frequent. The latest three occurred in , and suggesting a new inter-inflow period of about ten years. The water level is generally far more dependent on the regional wind situation than on tidal effects. However, tidal currents occur in narrow passages in the western parts of the Baltic Sea. The significant wave height is generally much lower than that of the North Sea.
Violent and sudden storms often sweep the surface, due to large transient temperature differences and a long reach of wind. Seasonal winds also cause small changes in sea level, of the order of 0. The Baltic Sea's salinity is much lower than that of ocean water which averages 3. At the semienclosed bays with major freshwater inflows, such as head of Finnish Gulf with Neva mouth and head of Bothnian gulf with close mouths of Lule, Tornio and Kemi, the salinity is considerably lower. The flow of fresh water into the sea from approximately two hundred rivers and the introduction of salt from the south builds up a gradient of salinity in the Sea.
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Near the Danish straits the salinity is near that of the Kattegat, but still not fully oceanic, because the saltiest water that passes the straits is still already mixed with considerable amounts of outflow water. The salinity steadily decreases towards north and east. At the northern part of the Gulf of Bothnia the water is no longer salty and many fresh water species live in the sea.
The salinity gradient is paralleled by a temperature gradient. These two factors limit many species of animals and plants to a relatively narrow region of Baltic Sea. The most saline water is vertically stratified in the water column to the north , creating a barrier to the exchange of oxygen and nutrients, and fostering completely separate maritime environments. The land is still emerging isostatically from its subsident state, which was caused by the weight of the last glaciation. The phenomenon is known as post-glacial rebound. Consequently, the surface area and the depth of the sea are diminishing.
The uplift is about eight millimeters per year on the Finnish coast of the northernmost Gulf of Bothnia. In the area, the former seabed is only gently sloped, leading to large areas of land being reclaimed in, geologically speaking, relatively short periods decades and centuries. Later, there were fights for control over the sea with Wendish tribes dwelling on the southern shore. The Vikings also used the rivers of Russia for trade routes, finding their way eventually to the Black Sea and southern Russia. This Viking-dominated period is also referred to as Viking Age.
Starting in the eleventh century, the southern and eastern shores of the Baltic were settled by Germans and to a lesser extent by Dutch, Danes and Scots in the course of the Ostsiedlung. Lands next to the sea's eastern shore were among the last in Europe to be converted to Christianity in the Northern Crusades: Finland in the twelfth century by the Swedes, and what are now Estonia and Latvia in the early thirteenth century by the Danes and the Germans Livonian Brothers of the Sword. The Teutonic Knights gained control over parts of the southern and eastern shore of the Baltic Sea, where they set up their monastic state while fighting the Poles, the Danes, the Swedes , the Russians of ancient Novgorod, and the Lithuanians last Europeans to convert to Christianity.
In the thirteenth to seventeenth centuries, the strongest economic force in Northern Europe became the Hanseatic League , which used the Baltic Sea to establish trade routes between its member cities. In the sixteenth and early seventeenth centuries, Polish-Lithuanian Commonwealth , Denmark and Sweden fought wars for dominion. Eventually, it was the Swedish Empire that virtually encompassed the Baltic Sea.
In the eighteenth century, Russia and Prussia became the leading powers over the sea. Russia's Peter the Great saw the strategic importance of the Baltic and decided to found his new capital, Saint Petersburg at the mouth of the Neva river at the east end of the Gulf of Finland. Trading developed not just within the Baltic region but also with the North Sea region, especially eastern England and the Netherlands.
After the unification of Germany in , the whole southern coast became German.
Baltic States and North Sea countries join forces in BANOS CSA | Flanders Marine Institute
In the frigid waters of January , the Baltic Sea became a mass grave for drowned people on torpedoed refugee ships. As of , the sinking of the Wilhelm Gustloff  remains the worst maritime disaster, killing an estimated people, mostly women and children, and about wounded German soldiers. In , a Russian group of scientists found over five thousand airplane wrecks, sunken warships, and other materiel mainly from the Second World War, lying at the bottom of the sea. After , the German population was expelled from all areas east of the Oder-Neisse line, making room for Polish and Russian settlers.
Poland gained a vast stretch of the southern shore, Russia gained another access to the Baltic with the Kaliningrad oblast. The Baltic states on the eastern shore were again incorporated in the Soviet Union , Poland and East Germany became communist states. The sea then was a border between opposing military blocs: in the case of military conflict, in parallel with a Soviet offensive toward the Atlantic Ocean , communist Poland's fleet was prepared to invade the Danish isles. This border status also impacted trade and travel, and came to an end only after the collapse of the communist regimes in Eastern and Central Europe in the late s.
While being a major route for navigation, the sea also provides amber , especially from its southern shores. The bordering countries have traditionally provided lumber, wood tar , flax, hemp, and furs. Sweden had from early medieval times also a flourishing mining industry, especially on iron ore and silver.
Poland had and still has extensive salt mines. All this has provided for rich trading since the Roman times. In the s, environmental scientists in the Baltic region began to note negative effects of large-scale industrial development and chemical runoffs from agriculture. Effluence from pulp mills was especially damaging with high nitrogen release from nitrates in papermaking. Concern over threats to the region's plant and animal life enabled cooperation between the region's countries.
Beaches were no longer safe for swimming. Cooperation over environmental issues led to the signing by Baltic countries of the Helsinki Convention on the Protection of the Marine Environment of the Baltic Sea Area. Although the agreement was signed in , due to political wrangling and consensus building, it was enacted on May 3, Political changes and developments in environmental and maritime law caused a new convention to be signed in All the states bordering on the Baltic Sea, and the European Community joined in the agreement.
The Convention covers the entire Baltic Sea region, including all the inland waters, the Baltic Sea's water and its seabed. Measures were also taken in the whole catchment area of the Baltic Sea to reduce land-based pollution. This was one of the first international attempts to control land-based sources of pollution in a shared marine environment. Determination of its effectiveness continues to develop, with emphasis upon sustained development. The governing body of the Convention is the Helsinki Commission.
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