The Kattegat (Danish, from Dutch, commonly used in English), or Kattegatt (Swedish) is a 30,000 km2 sea area bounded by the Jutlandic peninsula in the west, the Straits islands of Denmark to the south and the provinces of Västergötland, Scania, 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, a bay of the Baltic Sea or—as in traditional Scandinavian usage—neither of these.
Kattegat is a rather shallow sea and can be very difficult and dangerous to navigate, due to the many sandy and stony reefs and tricky currents that often shift. In modern times, artificial seabed canals have been dug, many reefs have been dredged by either sand pumping or stone fishing, and a well-developed light signaling network has been installed, to safeguard the very heavy international traffic of this small sea.
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.
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.
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.
Currently, a proposal for a bridge from Jutland to Zealand across the southern part of the Kattegat is under political consideration in Denmark: it would link the islands of Zealand and Samsø with continental Denmark.
- On the South. The limits of the Baltic Sea in the Belts and Sound:
- In the Little Belt A line joining Falshöft ( ) and Vejsnæs Nakke (Ærö: ).
According to Den Store Danske Encyklopædi and Nudansk Ordbog, the name derives from the Dutch words kat (cat) and gat (hole, gate). It derives from late medieval navigation jargon, in which captains of the Hanseatic trading fleets would compare the Danish Straits to a hole so narrow that even a cat would have difficulty squeezing its way through, on account of the many reefs and shallow waters. At one point, the passable waters were a mere 3.84 kilometers (2.39 mi) wide. The name of the Copenhagen street Kattesundet has the same etymological meaning, namely "narrow passage".
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 water route into and out of the Baltic region.
Since the Middle Ages, the Danish Royal Family has prospered from the fees it received for passage through the Øresund while Copenhagen provided shelter, trade and repair opportunities and protection from piracy.
The 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. In recent years studies and research, for instance, have given 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 repair, stop and prevent these environmentally destructive and economically damaging processes, since the first Action Plan for the Aquatic Environment in 1985, and are now busy implementing the fourth Action Plan. The action plans sum up a broad range of initiatives and include the so-called Nitrate Directives. The action plans have been viewed as a success, although the work is not finished and all goals are not completely met yet.
- Convention No 3210. League of Nations Treaty Series 139, 1933–1934. Retrieved 27 December 2012.
- "Limits of Oceans and Seas" (3rd ed.). International Hydrographic Organization. 1953. Retrieved 6 February 2010.
- Den Store Danske Encyklopædi (2004), CD-ROM edition, Copenhagen: Gyldendal, entry Kattegat.
- Nudansk Ordbog (1993), 15th edition, 2nd reprint, Copenhagen: Politikens Forlag, entry Kattegat.
- "Cattegat, The". New International Encyclopedia. 1905.
- Both the ecosystems and the Danish fishing industry has suffered greatly from the eutrophication of the Kattegat sea. (Source: Bo Barker Jørgensen and Katherine Richardson: Eutrophication in Coastal Marine Ecosystems Coastal and Estuarine Studies, American Geophysical Union 1996, ISBN 0875902669, Ch. 8)
- Implementation of the Nitrates directive in Denmark Danish Ministry of the Environment
- Action Plans for the Aquatic Environment have been a success Politiken (25th of October 2011) (Danish)