arm of the North Atlantic Ocean, extending northward from the latitude of southern Denmark almost to the Arctic Circle and separating the Scandinavian Peninsula from the rest of continental Europe. The largest expanse of brackish water in the world, the semienclosed and relatively shallow Baltic Sea is of great interest to scientists, while to historians it represents the economic core of the Hanseatic League, the great medieval trading group of northern European ports. The many names for the sea attest to its strategic position as a meeting place of many countries.

The large islands of Bornholm (Denmark) and Öland and Gotland (Sweden) lie in the western Baltic, while the Åland Islands (Finnish: Ahvenanmaa), farther north, rise from a narrows between Sweden and Finland and mark the entrance to the arm of the Baltic known as the Gulf of Bothnia (Bothnia, Gulf of). Just to the south of the Åland Islands, the narrow Gulf of Finland (Finland, Gulf of) stretches eastward between Finland to the north, Estonia to the south, and Russia around the eastern end, with St. Petersburg at its head. Proceeding clockwise from the west, the countries bounding the Baltic are Denmark, Sweden, Finland, Russia, Estonia, Latvia, Lithuania, Poland, and Germany.

The Baltic Sea is a shrunken remnant of the water-covered region that emerged as the melting Scandinavian ice sheet retreated toward the Arctic at the end of the Pleistocene Epoch glaciations. Some 14,000 years ago, ice covered all of northern Europe as far south as the present German-Polish coastline; by 7700 BC glacial meltwater had formed the Yoldia Sea, which stretched east from the present Skagerrak across what is now lake-strewn southern Sweden as far as the present Lake Ladoga (Ladoga, Lake), beyond the bend of the Gulf of Finland. A thousand years later, only limited areas of stagnant ice remained in northern Sweden, leaving the freshwater Ancylus Lake stretching from Arctic Sweden and Finland to the present southern Baltic. Later changes, about 4500 BC, led to a breach of the land bridge between the present Baltic and North seas and to fragmentation of the Jutland peninsula by The Sound (Sound, The) (Øresund), the Store Strait (Great Belt) (Storebælt), and the Lille Strait (Little Belt) (Lillebælt). Many of the lowland regions surrounding the sea have been rebounding slowly since the great weight of the glaciers was removed; however, in places such as Stockholm, rising sea levels have slightly exceeded the rate of land uplift. Land uplift and deposition are building up the head of the almost tideless Gulf of Bothnia.

The shallowest part of the Baltic is the continental shelf, from which rise the islands of the Danish archipelago. There the Lille Strait divides eastern Jutland from the island of Funen (Fyn), which is itself separated from Zealand (Sjælland) by the deeper Store Strait. The narrow channel of The Sound between Denmark and Sweden restricts ships to drafts up to 41 feet (12.5 metres); larger vessels call at Göteborg, Swed., which is the biggest oil port in the Baltic.

The coasts of Sweden and Finland are highly fretted and generally rocky, whereas those of the southern Baltic are flat and rather featureless. Where the crystalline rocks of the ancient rock mass of the Baltic Shield outcrop along the northern coasts, partly obscured by glacial drift and marine deposits, they are often fringed by the low, rocky islands known as a skerry guard. These are most numerous in the Saltsjön (Salt Bay) between Stockholm and the open waters of the Gulf of Bothnia and off the southwest coast of Finland. Off southeastern Sweden the narrow, elongated islands of Öland and Gotland consist of ancient limestone partly covered by sandy drift deposits. The rectangular island of Bornholm off southern Sweden was formed from a detached fragment of granite, and its high cliffs were shaped by faulting and shearing of the rock strata.

The Baltic coastline of western Germany is one of shallow fjords and bays. Kiel lies at the head of one such inlet, south of the entrance to the Kiel (Baltic–North Sea) Canal (Kiel Canal), which runs through German territorial waters. To the east is the Bay of Lübeck at the head of the Trave River estuary, where Travemünde—a ferry port for Copenhagen and Sweden—combines the functions of a seaport and tourist resort. Farther to the east, the German coast of Mecklenburg–West Pomerania is flat and low-lying. A series of long shingle bars (Nehrungen), capped by moving sand dunes, has been built up there, cutting off the distinctive shallow lagoons (lagoon) (Haffs) from the open sea. Examples are the west-east spit of Darsser-Ort, on the island of Rügen, and the link (near Świnoujście, Pol.) between the islands of Usedom (Germany) and Wolin ( Poland), which isolate Szczeciński Lagoon from the open sea. East of the Polish frontier, the port of Szczecin lies at the mouth of the Oder River. Solid rock outcrops conspicuously only on the island of Rügen, where the remarkably irregular coastline includes chalk cliffs that reach a height of about 400 feet (120 metres).

East of Szczecin the coast of Pomerania (Pomorze) is generally flat and featureless, with sand dunes and spits bounding brackish lagoons. The Vistula River drains into the Baltic through a number of distributaries; the historic city of Gdańsk lies on the most westerly of these, the Motława. To the east, spectacular lagoon and shingle bar features have developed. Sand dunes, covering an elongated shingle spit, almost enclose the brackish Wiślany (Frisches) Lagoon, at the northeastern end of which lies Königsberg, the historic German outpost founded by the Teutonic Knights. Once the chief city and port of East Prussia, it is now the Russian port of Kaliningrad. Northward, the cliff coast is noted for its amber, a fossilized resin that formed a valued item of medieval trade throughout the Baltic and as far afield as Venice, which was reached by the “Amber Route” via Kraków (Pol.) and Vienna. At the northern end of the triangular inlet of the Curonian Lagoon, at the mouth of the Neman River, lies Klaipėda, Lith., the most northeasterly city of Germanic origin in the Baltic. Cutting off the lagoon from the Baltic is another shingle spit (the Curonian Spit), some 60 miles (100 km) long, capped by low fixed dunes and fringed by high moving dunes of white sand.

The Baltic Sea is no longer the major highway of trade (international trade) that it was in the Middle Ages, when it flourished as the main means of communication between the ports (Lübeck, Rostock, Visby, and Gdańsk) of the Hanseatic League. The German Hansa merchants traded mainly in fish, notably salted herring and stockfish (dried cod from Norway and Iceland), and also in softwood timber for shipbuilding, hemp for ropes, flax for sailcloth, and grain. Forest products included honey and furs, notably from Russia and Finland, as well as Stockholm tar and amber, the latter being a semiprecious commodity. Overfishing of herring, the opening up of trade to the Americas and the Caribbean following the European Age of Discovery (mid-15th to mid-16th century), and the increase in the size of sailing ships led to the decline of the Hanseatic League. Copenhagen, however, continued to prosper on the profits from tolls exacted from passing shipping, until tolls were abolished in 1857.

The construction of the Kiel Canal in the late 19th century and the development of railways and highways in the 20th century began to change the nature of trade and transport across the Baltic Sea. World War II also brought political and economic change to the region, and traditional trading patterns were amended accordingly. In the 21st century the number of ocean vessels sailing around Jutland is only a fraction of that of earlier decades. Instead, there has been an increase in Baltic Sea crossings by large roll-on, roll-off ferries and fast hovercraft, hydrofoils, and catamarans. There are many such linkages, the busiest being between Helsingør, Den., and Helsingborg, Swed.

Bulk cargoes of oil and coal still come by all water routes into the Baltic, and many exports of minerals, timber, and wood products move in the opposite direction by sea around Jutland. These traditional exports represent a diminishing value in overall trade. The greatest values are in consumer goods, most of which are carried in containers by integrated land and sea transport to markets and to and from the North Sea ports of Hamburg, Ger., and Rotterdam, Neth. This has led to increased interest in building a bridge between Denmark and Sweden. Shipbuilding has declined in Sweden but has continued in Poland and Finland (especially for ice-strengthened vessels); marine engines are produced in Denmark. Generally, however, light engineering, high-quality furniture production, and motor-vehicle manufacturing have replaced many of these maritime-based industries.

Ed.

Aarno Voipio (ed.), The Baltic Sea (1981), is an informative overview of the area. Boris Winterhalter (ed.), The Baltic Sea (1988), is a set of colloquium papers on the Baltic's geology; and Ole Bagge and Otto Rechlin, Baltic Sea Fishery Resources (1989), is a collection of the proceedings from a symposium. A special issue of Ambio, vol. 9, no. 3–4 (1980), is devoted to the Baltic. Gunnar Alexandersson, The Baltic Straits (1982), discusses The Sound, Kattegat, and Skagerrak. General references include Ing-Marie Gren, R. Kerry Turner, and Fredrik Wulff, Managing a Sea: The Ecological Economics of the Baltic (2000). References on the environmental status and condition of the Baltic that include overviews of deliberations and studies are the Baltic Marine Environment Protection Commission, The Third Baltic Sea Pollution Load Compilation (PLC 3) (1998), The Baltic Sea Joint Comprehensive Environment Action Programme: Recommendations for Updating and Strengthening (1998), Third Periodic Assessment of the State of the Marine Environment of the Baltic Sea, 1989–1993, 2 vol. (1996), and Activities Overview (annual). A dissertation completed at the Swedish University of Agricultural Sciences characterizes an economic approach to the reduction of nutrient pollution in the Baltic: Katarina Elofsson, Cost Effective Reductions in the Agricultural Load of Nitrogen to the Baltic Sea (1997). A review of the international agreements relating to marine pollution control in the Baltic and other regional seas can be found in James M. Broadus et al., Comparative Assessment of Regional International Programs to Control Land-Based Marine Pollution: The Baltic, North Sea, and Mediterranean (1993).Alastair Dougal Couper Ed.