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Carte Skagerrak-Kattegat2.png
Map of Kattegat and Skagerrak
Europe relief laea location map.jpg
Red pog.svg
Coordinates 56°30′N11°30′E / 56.500°N 11.500°E / 56.500; 11.500 Coordinates: 56°30′N11°30′E / 56.500°N 11.500°E / 56.500; 11.500
Etymologylit.'"cat's gate"'
Basin  countries Denmark, Sweden
Surface area30,000 km2 (12,000 sq mi)

The Kattegat (Danish:  [ˈkʰætəkæt] ; Swedish : Kattegatt [ˈkâtːɛˌɡat] ) is a 30,000 km2 (12,000 sq mi) sea area bounded by the Jutlandic peninsula in the west, the Danish Straits islands of Denmark and the Baltic Sea to the south and the provinces of Västergötland, Skåne, Halland and Bohuslän in Sweden in the east. The Baltic Sea drains into the Kattegat through the Danish Straits. The sea area is a continuation of the Skagerrak and may be seen as a bay of the North Sea, but in traditional Scandinavian usage, this is not the case.


The Kattegat is a rather shallow sea and can be very difficult and dangerous to navigate because of the many sandy and stony reefs and tricky currents, which often shift. In modern times, artificial seabed channels have been dug, many reefs have been dredged by either sand pumping or stone fishing[ clarification needed ], and a well-developed light signaling network has been installed, to safeguard the very heavy international traffic of this small sea.

There are several large cities and major ports in the Kattegat, including, in descending size, Gothenburg, Aarhus, Aalborg, Halmstad and Frederikshavn.


Alvsborg at Gothenburg, a sea fortress in the Kattegat Gothenburg juli 2009 (ubt)-000.JPG
Älvsborg at Gothenburg, a sea fortress in the Kattegat

According to the definition established in a 1932 convention signed by Denmark, Norway and Sweden (registered in the League of Nations Treaty Series 1933–1934), the northern boundary between the Kattegat and Skagerrak is found at the northernmost point of Skagen on Jutland, while the southern boundary towards Øresund is found at the tip of Kullen Peninsula in Scania. [1]

Major waterways that drain into the Kattegat are the rivers of Göta älv at Gothenburg, together with the Lagan, Nissan, Ätran and Viskan in the province of Halland on the Swedish side, and the river of Gudenå in Jutland, in Denmark.

The main islands of the Kattegat are Samsø, Læsø and Anholt; the latter two are, due to their relatively dry climate, situated in what is called "the Danish desert belt".

A number of noteworthy coastal areas abut the Kattegat, including the Kullaberg Nature Reserve in Scania, Sweden, which contains a number of rare species and a scenic rocky shore, the town of Mölle, which has a picturesque harbour and views into the Kullaberg, and Skagen at the northern tip of Denmark.

Since the 1950s, a bridge project usually referred to as Kattegatbroen (The Kattegat Bridge) connecting Jutland and Zealand across the Kattegat has been considered. Since the late 2000s, the project has seen a renewed interest from several influential politicians in Denmark. The bridge is usually envisioned as connecting Hov (a village south of Odder in the Aarhus area) with Samsø and Kalundborg. [2] [3]


The International Hydrographic Organization defines the limits of the "Kattegat, Sound and Belts" (that is, the Kattegat, Øresund, Great Belt, and Little Belt) as follows: [4]

On the North: A line joining Skagen (The Skaw, northernmost point of Denmark) and Paternoster Skær ( 57°54′N11°27′E / 57.900°N 11.450°E / 57.900; 11.450 ) and thence northeastward through the shoals to Tjörn Island.

On the South: The limits of the Baltic Sea in the Belts and Sound:


According to Den Store Danske Encyklopædi and Nudansk Ordbog  [ da ], the name derives from the Dutch words katte ("cat's") and gat ("gate, passage"). It derives from late medieval navigation jargon, in which captains of the Hanseatic trading fleets would compare the Danish Straits to a passage so tight that even a cat would have difficulty squeezing its way through, owing to the many reefs and shoals. [5] [6] At one point, the passable waters were a mere 3.84 km (2.07 nmi; 4,200 yd) wide. The name of the Copenhagen street Kattesundet has a comparable etymological meaning, namely "narrow passage". [6]

An archaic name for both the Skagerrak and Kattegat was the Norwegian Sea or Jutland Sea (Knýtlinga saga mentions the name Jótlandshaf). Its ancient Latin name was Sinus Codanus. [7]


Control of the Kattegat, and access to it, have been important throughout the history of international seafaring. Until the completion of the Eider Canal in 1784, the Kattegat was the only sea route into and out of the Baltic region. [8]

Beginning in 1429 in the Middle Ages, the Danish royal family – and later the state of Denmark – prospered greatly from the Sound dues, a toll charged for passage through the Øresund, while Copenhagen provided shelter, trade and repair opportunities and protection from piracy. The dues were eventually lifted in 1857.


In the Kattegat, the salinity has a pronounced two-layer structure. The upper layer has a salinity between 18‰ and 26‰ and the lower layer – separated by a strong halocline at around 15 m (49 ft) – has a salinity between 32‰ and 34‰. The lower layer consists of inflowing seawater from the Skagerrak, with a salinity on level with most other coastal seawaters, while the upper layer consists of inflowing seawater from the Baltic Sea and has a much lower salinity, comparable to brackish water, but still a great deal higher than the rest of the Baltic sea. These two opposing flows transport a net surplus of 475 km3 (114 cu mi) seawater from the Baltic to the Skagerrak every year. [9] During stronger winds, the layers in the Kattegat are completely mixed in some places, such as the Great Belt, so the overall salinity is highly variable in this small sea. This sets some unique conditions for the sealife here. [10]

Cold seeps, locally known as bubbling reefs (Danish : boblerev), are found in the northern Kattegat. Unlike cold seeps in most other places (including the North Sea and Skagerrak), the Kattegat bubbling reefs are at relatively shallow depths, generally between 0 and 30 m (0–100 ft) below the surface. [11] [12] The seeps rely on methane deposited during the Eemian period and during calm weather the bubbles can sometimes be seen on the water surface. [12] Carbonate cementation and lithification form slaps or pillars up to 4 m (13 ft) tall, and support a rich biodiversity. [11] [12] Because of their unique status, the Kattegat bubbling reefs receive a level of protection and are recognized as a Natura 2000 habitat (type 1180) by the European Union (EU). [13]

Ecological collapse

Kattegat was one of the first marine dead zones to be noted in the 1970s, when scientists began studying how intensive industrial activities affected the natural world. [14] [15] Since then, studies and research has provided much insight into processes like eutrophication, and how to deal with it. Denmark and the EU have initiated costly and far-reaching domestic projects in order to stop, repair and prevent these environmentally destructive and economically damaging processes [16] since the first Action Plan for the Aquatic Environment in 1985, and are now busy implementing the fourth Action Plan. The action plans sums up a broad range of initiatives and includes the so-called Nitrate Directives. [17] The action plans have generally been viewed as a success, although the work is not finished and all goals are not completely met yet. [18]

Protections and regulation

Grenen in Denmark is important for bird migrations and is a protected area. Vista de Greenen.JPG
Grenen in Denmark is important for bird migrations and is a protected area.
Bjarekusten Nature Reserve with Hovs Hallar in Sweden. Hovs hallar.JPG
Bjärekusten Nature Reserve with Hovs Hallar in Sweden.

Due to the very heavy sea traffic and many large coastal settlements, the Kattegat has been designated as a Sulphur Emission Control Area as part of the Baltic Sea since 2006. As from 1 January 2016 the benchmark for sulphur in fuels was lowered to 0.1%. [19]

Several larger areas of the Kattegat are designated as Natura 2000 and under various bird protections such as the Ramsar Convention. The remaining larger shallow reefs are among the protections, as they are important spawning and feeding grounds for fish and marine mammals and they support a thriving but threatened biodiversity. Protected areas includes:

Denmark [20]

Sweden [21]

See also

Related Research Articles

Baltic Sea Sea in Northern Europe

The Baltic Sea is an arm of the Atlantic Ocean, enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain.

Geography of Denmark Geographical features of Denmark

Denmark is a Nordic country located in Northern Europe. It consists of the Jutland Peninsula and several islands in the Baltic Sea, referred to as the Danish Archipelago. Denmark is located southwest of Sweden and due south of Norway and is bordered by the German state Schleswig-Holstein to the south, on Denmark's only land border, 68 kilometres long.

Transport in Denmark

Transport in Denmark is developed and modern. The motorway network covers 1,111 km while the railway network totals 2,667 km of operational track. The Great Belt Fixed Link connecting the islands of Zealand and Funen and the New Little Belt Bridge connecting Funen and Jutland greatly improved the traffic flow across the country on both motorways and rail. The two largest airports of Copenhagen and Billund provide a variety of domestic and international connections, while ferries provide services to the Faroe Islands, Greenland, Iceland, Germany, Sweden, and Norway, as well as domestic routes servicing most Danish islands.

Øresund The strait between Denmark and Sweden

Øresund or Öresund, commonly known in English as the Sound, is a strait which forms the Danish–Swedish border, separating Zealand (Denmark) from Scania (Sweden). The strait has a length of 118 kilometres (73 mi); its width varies from 4 kilometres (2.5 mi) to 28 kilometres (17 mi). It is 4 kilometres (2.5 mi) wide at its narrowest point between Helsingør in Denmark and Helsingborg in Sweden.

Skagerrak Sea between Denmark, Norway and Sweden

The Skagerrak is a strait running between the Jutland peninsula of Denmark, the southeast coast of Norway and the west coast of Sweden, connecting the North Sea and the Kattegat sea area through the Danish Straits to the Baltic Sea.

Great Belt Strait in Denmark linking the Baltic Sea to the Kattegat strait and the Atlantic Ocean

The Great Belt is a strait between the major islands of Zealand (Sjælland) and Funen (Fyn) in Denmark. It is one of the three Danish Straits.

Little Belt Strait in Denmark linking the Baltic Sea to the Kattegat strait and the Atlantic Ocean

The Little Belt is a strait between the island of Funen and the Jutland Peninsula in Denmark. It is one of the three Danish Straits that drain and connect the Baltic Sea to the Kattegat strait, which drains west to the North Sea and Atlantic Ocean.

European route E20 Road in trans-European E-road network

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Grenen is a long sandbar spit at Skagen Odde, north of the town of Skagen.

Danish straits Three channels in Denmark connecting the Baltic Sea to the North Sea

The Danish straits are the straits connecting the Baltic Sea to the North Sea through the Kattegat and Skagerrak. Historically, the Danish straits were internal waterways of Denmark; however, following territorial losses, Øresund and Fehmarn Belt are now shared with Sweden and Germany, while the Great Belt and the Little Belt have remained Danish territorial waters. The Copenhagen Convention of 1857 made all the Danish straits open to commercial shipping. The straits have generally been regarded as an international waterway.

Amager Strandpark Seaside park in Copenhagen

Amager Strandpark is a seaside public park in Copenhagen, Denmark. It is located on the island of Amager and includes an artificial island and offers a total of 4.6 km (2.9 mi) of beaches. From the beach, the Middelgrunden wind farm can be seen on the horizon.

Jutland Peninsula in Europe

Jutland, known anciently as the Cimbric or Cimbrian Peninsula, is a peninsula of Northern Europe that forms the continental portion of Denmark and part of northern Germany. The names are derived from the Jutes and the Cimbri, respectively.

Skagen Odde Nature Centre

The Skagen Odde Nature Centre, on the northern tip of Denmark's Jutland, is a museum devoted to the effects of sand, water, wind and light. It was designed in 1989 by Jørn Utzon, the celebrated architect behind the Sydney Opera House. Under the leadership of his son Jan, the centre was completed in 2000.

Johns Rock is a rock in Denmark's territorial waters in the Kattegat bay of the North Sea, near the island of Læsø.

A graded shoreline is a stage in the cycle of coastal development characterised by a flat and straight coastline. It is formed under the influence of wind and water from the original bays, islands, peninsulas and promontories. Sand and gravel is carried away and dumped at other locations depending on the direction and strength of sea currents. Typical of graded shorelines are the formation of dunes, wide sandy beaches and sometimes a lagoon or a spit. Where two graded shorelines meet, a headland may form with a sandy reef in the sea beyond it. Parallel to the graded shoreline sandbanks may form as a result of sediments transported away from the shore.

Skagen Odde

Skagen Odde, also Skagens Odde, sometimes known in English as the Scaw Spit or The Skaw, is a sandy peninsula which stretches some 30 km (19 mi) northeast and comprise the northmost area of Vendsyssel in Jutland, Denmark.

Ålbæk Bugt Bay off the coast of Denmark

Albæk Bugt is a shallow bay, some 20 m (66 ft) deep, off the northeast coast of Skagen Odde in the north of Jutland, Denmark. It stretches from Skagen in the north to Hirsholmene to the south. On the Kattegat side of Vendsyssel, it is frequently used as an anchorage for vessels seeking shelter from the west wind in the Skagerrak.

Skagens Vippefyr

Skagen's Vippefyr is a navigational light mechanism located in Skagen in the far north of Jutland. The original vippefyr, the first of its kind, was built in 1627. A faithful copy now stands on the same site. It replaced an earlier parrot light (papegøjefyr) and served until 1747 when the White Lighthouse was brought into operation.

Bay of Aarhus

The Bay of Aarhus, or Aarhus Bay, is a Danish waterway by Aarhus in eastern Jutland.

Køge Bay Bay near Køge, Denmark

Køge Bay is an approximately 500 square kilometres (190 sq mi) shallow Danish bay in the southern part of Øresund, between Greater Copenhagen area in the North and Stevns Klint in the South, and as a part of Zealand.


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