Editing Kattegat

{{short description|Sea area between Denmark and Sweden}}
{{Use dmy dates|date=March 2021}}{{Use British English|date=January 2025}}

{{Infobox body of water
| name                   = Kattegat
| other_name             = Kattegatt
| image                  = Carte Skagerrak-Kattegat2.png
| caption                = Map of the Kattegat and [[Skagerrak]]
| alt                    = Map of waters
| image_bathymetry       = 
| caption_bathymetry     = 
| depth                  = 
| max-depth              = 
| inflow                 =
| outflow                =
| catchment              =
| basin_countries        = [[Denmark]], [[Sweden]]
| length                 = 
| width                  = 
| min_width              = 
| area                   = {{convert|30000|km2|abbr=on}}
| islands                = 
| etymology              = {{lit|"cat's gate"}}
| location               = 
| pushpin_map            = Europe
| pushpin_label_position = 
| pushpin_map_alt        = Location in Europe
| pushpin_map_caption    = 
| coordinates            = {{coord|56|30|N|11|30|E|type:waterbody_scale:2500000|display=inline,title}}
| coor_pinpoint          =
| part_of                =
| type                   = 
| cities                 = 
| oceans                 = 
}}

The '''Kattegat''' ({{IPAc-en|'||k|æ|t|ə|g|æ|t}}; {{IPA|da|ˈkʰætəkæt|lang}}; {{langx|sv|Kattegatt}} {{IPA|sv|ˈkâtːɛˌɡat|}}) is a {{convert|30000|km2|abbr=on}} sea area bounded by the peninsula of [[Jutland]] in the west, the [[Danish straits]] islands of [[Denmark]] and the [[Baltic Sea]] to the south and the Swedish provinces of [[Bohuslän]], [[Västergötland]], [[Halland]] and [[Scania]] 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]] and [[North Atlantic Ocean]], though this is not the case in traditional [[Scandinavia]]n usage.

The Kattegat is a rather shallow sea and can be dangerous to navigate due to many sandy, stony reefs and the tricky shifting currents. In modern times, artificial seabed channels have been dug, many reefs have been [[dredging|dredged]] either by sand pumping or boulder clearance,<ref>[http://hojmarine.com/en/project-types/artificial-reefs/ Artificial Reefs]</ref> and a well-developed [[Lighthouse|light signaling]] network has been installed to protect the heavy international traffic on this small sea.

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

==Geography==
[[File:Gothenburg juli 2009 (ubt)-000.JPG|thumb|[[Älvsborg Castle|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 at the northernmost point of [[Skagen]] on Jutland and the southern boundary towards [[Øresund]] is at the tip of [[Kullen Lighthouse|Kullen]] Peninsula in Scania.<ref>[http://treaties.un.org/doc/Publication/UNTS/LON/Volume%20139/v139.pdf Convention No 3210]. League of Nations Treaty Series 139, 1933–1934. Retrieved 27 December 2012.</ref>

Major [[waterway]]s that drain into the Kattegat are the rivers of [[Göta älv]] at [[Gothenburg]], together with the [[Lagan River (Sweden)|Lagan]], [[Nissan (river)|Nissan]], [[Ätran (river)|Ätran]] and [[Viskan]] in the province of [[Halland]] on the Swedish side, and the Danish river of [[Gudenå]] in Jutland.

The main islands of the Kattegat are [[Samsø]], [[Læsø]] and [[Anholt (Denmark)|Anholt]]; due to their relatively dry climate, the last two are, perceived to belong to "the Danish desert belt".

A number of noteworthy coastal areas abut the Kattegat, including the [[Kullaberg Nature Reserve]] in Scania, 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 (Denmark)|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]].<ref>{{cite news|url=http://ing.dk/artikel/ingenioren-1955-byg-bro-over-samso-81947 |title=Ingeniøren 1955: Byg bro over Samsø [Build a bridge across Samsø] |newspaper=Ingeniøren|author=Rolf Ask Clausen |language=da|date=2 October 2007 |access-date=16 February 2016}}</ref><ref>{{cite web|url=http://kattegatforbindelse.dk/|title=En fast Kattegatforbindelse|website=kattegatforbindelse.dk|publisher=Kattegatkomitéen |language=da|access-date=15 May 2017}}</ref>

===Extent===
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:<ref>{{cite web |url=https://iho.int/uploads/user/pubs/standards/s-23/S-23_Ed3_1953_EN.pdf |title=Limits of Oceans and Seas |edition=3rd |year=1953 |publisher=[[International Hydrographic Organization]] |access-date=28 December 2020 |archive-url=https://web.archive.org/web/20111008191433/http://www.iho-ohi.net/iho_pubs/standard/S-23/S23_1953.pdf |archive-date=8 October 2011 }}</ref>

{{Blockquote|''On the North'': A line joining [[Skagen]] (The Skaw, northernmost point of Denmark) and Paternoster Skær ({{coord|57|54|N|11|27|E|display=inline}}) and thence northeastward through the shoals to [[Tjörn Municipality|Tjörn Island]].

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

* ''In the Little Belt'': A line joining Falshöft ({{coord|54|47|N|9|57.5|E|display=inline}}) and Vejsnæs Nakke (Ærö: {{coord|54|49|N|10|26|E|display=inline}}).
* ''In the Great Belt'': A line joining Gulstav (Southernmost extremity of [[Langeland]] Island, {{coord|54|43|36|N|10|42|42|E|display=inline}}) and Kappel Kirke ({{coord|54|46|N|11|01|E|display=inline}}) on the island of [[Lolland|Laaland]].
*  ''In the Guldborg Sund'': A line joining Flinthorne-Rev ({{coord|54|38|30|N|11|49|16|E}}) and Skelby ({{coord|54|38|00|N|11|53|14|E}});
* ''In the Sound'': A line joining [[Stevns Peninsula|Stevns]] Lighthouse ({{coord|55|17|N|12|27|E|display=inline}}) and [[Falsterbo|Falsterbo Point]] ({{coord|55|23|N|12|49|E|display=inline}}).}}

==Etymology==
According to ''[[Den Store Danske Encyklopædi]]'' and ''{{ill|Nudansk Ordbog|da}}'', the name is from the [[Dutch language|Dutch]] words ''{{lang|nl|katte}}'' 'cat's' and ''{{lang|nl|gat}}'' 'gate, passage'. It derives from late [[medieval]] navigation jargon, in which captains of the [[Hanseatic League|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 [[reef]]s and shoals.<ref>''Den Store Danske Encyklopædi'' (2004), CD-ROM edition, Copenhagen: Gyldendal, entry ''Kattegat''.</ref><ref name="Nydansk">''Nudansk Ordbog'' (1993), 15th edition, 2nd reprint, Copenhagen: Politikens Forlag, entry ''Kattegat''.</ref> At one point, the passable waters were a mere {{convert|3.84|km|nmi yd|abbr=on}} wide. The name of the [[Copenhagen]] street ''[[Kattesundet]]'' has a comparable etymological meaning, namely 'narrow passage', {{literal translation|the cat's strait}}.<ref name="Nydansk"/>

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 language|Latin]] name was ''{{lang|la|Sinus Codanus}}''.<ref>{{Cite NIE|wstitle=Cattegat, The|year=1905}}</ref>

==History==
Controlling and having access to the Kattegat 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.<ref>{{Cite news|url=https://www.britannica.com/place/Kattegat|title=Kattegat {{!}} strait, Denmark-Sweden|work=Encyclopedia Britannica|access-date=2017-05-16|language=en}}</ref>

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]] sheltered and repaired ships and provided trade opportunities and protection from [[piracy]]. The dues were eventually lifted, in 1857.

== Biology ==

The [[salinity]] in the Kattegat has a pronounced two-layer structure. The upper layer's salinity is between 18‰ and 26‰, while that of the lower layer (separated by a strong [[halocline]] at around {{convert|15|m|abbr=on}}) has a salinity between 32‰ and 34‰. The lower layer consists of inflowing seawater from the Skagerrak, with a salinity on par with most other coastal seawaters, while the upper layer, consisting of inflowing seawater from the Baltic Sea, has a much lower salinity, comparable to [[brackish water]], but still a great deal higher than the rest of the Baltic. These two opposing flows transport a net surplus of {{convert|475|km3|cumi|abbr=on}} of seawater from the Baltic to the Skagerrak every year.<ref>{{cite web|url=http://www2.dmu.dk/1_viden/2_miljoe-tilstand/3_vand/4_eutrophication/hydrography.asp |title=Hydrography |author=Ærtebjerg, G., Andersen, J.H. and Schou Hansen |publisher=Danish Environmental Protection Agency and National Environmental Research Institute |website=Nutrients and Eutrophication in Danish Seawaters |date=2003 |access-date=30 January 2016}}</ref> During strong winds, the Kattegat's layers are completely mixed in places such as the [[Great Belt]], making the  overall salinity highly variable. This leads to some distinctive conditions for [[sealife]] in the area.<ref>{{cite book|url=https://books.google.com/books?id=csLKtvZNV98C&pg=PA74 |title=Physical Oceanography of the Baltic Sea|author=Matti Leppäranta and Kai Myrberg|date=2009 |publisher=Springer-Praxis |access-date=30 January 2016 |pages=72–74|isbn=9783540797036}}</ref>

[[Cold seep]]s, known locally as ''bubbling reefs'' ({{langx|da|boblerev}}), can be found in the northern Kattegat. Unlike those in most other places (including the North Sea and Skagerrak), the Kattegat's cold seeps are at relatively shallow depths, generally from {{convert|0|to(-)|30|m|ft|abbr=on|-2}} below the surface.<ref name=Jensen1992>{{cite journal|author1=Jensen |author2=Aagaard |author3=Burke |author4=Dando |author5=Jørgensen |author6=Kuijpers |author7=Laier |author8=O'Hara |author9=Schmaljohann | year=1992 | title="Bubbling reefs" in the Kattegat: Submarine landscapes of carbonate-cemented rocks support a diverse ecosystem at methane seeps | journal=Marine Ecology Progress Series | volume=83 | pages=103–112 | doi=10.3354/meps083103|bibcode=1992MEPS...83..103J |doi-access=free }}</ref><ref name=HelcomCS>{{cite web|url=http://helcom.fi/Red%20List%20of%20biotopes%20habitats%20and%20biotope%20complexe/HELCOM%20Red%20List%201180%20Submarine%20structures%20made%20by%20leaking%20gases.pdf | title=Red List – Submarine structures made by leaking gases | publisher=[[HELCOM]] | year=2013 | access-date=16 June 2017}}</ref> The seeps rely on methane deposited during the [[Eemian]] period and during calm weather the bubbles can sometimes be seen on the surface of the water.<ref name=HelcomCS/> Carbonate [[Cementation (geology)|cementation]] and [[lithification]] form slaps or pillars up to {{convert|4|m|ft|abbr=on}} tall and support a rich [[biodiversity]].<ref name=Jensen1992/><ref name=HelcomCS/> Due to their distinct properties, the Kattegat bubbling reefs are under protection and are recognised by the [[European Union]] (EU) as a [[Natura 2000]] habitat (type 1180).<ref>{{cite web| title=Proposed measures for fisheries management in Natura 2000-sites in the Danish territorial area of the Kattegat and Samsø Belt | url=https://naturerhverv.dk/fileadmin/user_upload/NaturErhverv/Filer/Fiskeri/Natura_2000_hav/Rev/Forslag_til_fiskeriregulering_Kattegat.pdf | series=Meeting at the AgriFish Agency, Copenhagen | publisher=[[Minister for Food, Agriculture and Fisheries (Denmark)]] | date=20 March 2012 | access-date=16 June 2017}}</ref>

===Ecological collapse===
The Kattegat, characterised by widespread [[oceanic anoxic event|anoxia]],<ref name="DruonEtAl2004">{{cite journal |last1=Druon |first1=Jean-Noël |last2=Schrimpf |first2=Wolfram |last3=Dobricic |first3=Srdjan |last4=Stips |first4=Adolf |date=19 May 2004 |title=Comparative assessment of large-scale marine eutrophication: North Sea area and Adriatic Sea as case studies |url=https://www.int-res.com/articles/meps2004/272/m272p001.pdf |journal=Marine Ecology Progress Series |volume=272 |pages=1–23 |doi=10.3354/meps272001 |bibcode=2004MEPS..272....1D |access-date=10 August 2023}}</ref> was one of the first marine [[dead zone (ecology)|dead zone]]s to be noted in the 1970s, when scientists began to study the effects of heavy industry on the natural world.<ref>{{cite web|url=http://www.unep.org/Documents.Multilingual/Default.asp?DocumentID=486&ArticleID=5393&l=en|title=Further Rise in Number of Marine 'Dead Zones'|publisher=[[UNEP]]|date=19 October 2006|access-date=30 January 2016|archive-date=4 October 2009|archive-url=http://arquivo.pt/wayback/20091004170617/http%3A//www.unep.org/Documents.Multilingual/Default.asp?DocumentID%3D486%26ArticleID%3D5393%26l%3Den|url-status=dead}}</ref><ref>{{cite book|url=https://books.google.com/books?id=9fEKAAAAQBAJ&pg=PA4 |title=Introduction to Marine Biology |author=Karleskint, Turner and Small |publisher=Brooks/Cole |page=4|date=2013 |edition=4|isbn=978-1285402222 }}</ref> Since then,  research has leant much insight into processes like [[eutrophication]], and how to deal with it. Since the first Action Plan for the Aquatic Environment in 1985, Denmark and the EU have begun costly, far-reaching domestic projects  to stop, repair and prevent these environmentally destructive and economically damaging processes<ref>{{Cite book |doi=10.1029/CE052p0155|chapter = Benthic macrofauna and demersal fish|title = Eutrophication in Coastal Marine Ecosystems| volume=52| pages=155–178|series = Coastal and Estuarine Studies|year = 1996|last1 = Hagerman|first1 = Lars| last2=Josefson| first2=Alf B.| last3=Jensen| first3=Jørgen N.| isbn=978-0-87590-266-1}}</ref> 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.<ref>[http://www.mst.dk/English/Agriculture/nitrates_directive/implementation_in_denmark/ Implementation of the Nitrates directive in Denmark] {{Webarchive|url=https://web.archive.org/web/20131203112345/http://www.mst.dk/English/Agriculture/nitrates_directive/implementation_in_denmark/ |date=3 December 2013 }} Danish Ministry of the Environment</ref> The action plans have generally been viewed as a success, although the work is not finished and not all goals have been met yet.<ref>{{cite web|url=http://politiken.dk/debat/analyse/ECE1422611/vandmiljoeplaner-har-vaeret-en-succes/|title=Action Plans for the Aquatic Environment have been a success|newspaper=Politiken|author1=Jesper H. Andersen |author2=Jacob Carstensen |date=25 October 2011|language=da|access-date=24 November 2014}}</ref>

== Protections and regulation ==
[[File:Vista de Greenen.JPG|thumb|Grenen in Denmark is important for bird migrations and is a protected area.]]
[[File:Hovs hallar.JPG|thumb|Bjärekusten Nature Reserve with Hovs Hallar in Sweden.]]
Due to its 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%.<ref>{{cite web |url=http://readmt.com/analysis/article/2014/08/12/new-environmental-requirements-may-lead-to-distortion-of-competition/ |title=New sulphur regulations may lead to distortion of competition in the shipping industry |publisher=MT Online |date=12 August 2014 |access-date=19 January 2016 |archive-date=26 January 2016 |archive-url=https://web.archive.org/web/20160126111730/http://readmt.com/analysis/article/2014/08/12/new-environmental-requirements-may-lead-to-distortion-of-competition/ |url-status=dead }}</ref>

Several large areas of the Kattegat are designated under Natura 2000 and 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  support a thriving but threatened [[biodiversity]]. Protected areas include:

'''Denmark'''<ref>{{cite web |url=http://naturstyrelsen.dk/naturbeskyttelse/natura-2000/ |title=Natura 2000 |publisher=Danish Nature Agency |language=da |access-date=19 January 2016 |archive-url=https://web.archive.org/web/20160210024351/http://naturstyrelsen.dk/naturbeskyttelse/natura-2000/ |archive-date=10 February 2016 |url-status=dead }}</ref>
* [[Grenen]]
* The Bay of Aalborg, comprising a {{convert|1774|km2|abbr=on}} shallow sea area.
* [[Beach meadow]]s on [[Læsø]] and the stony [[reef]]s south of the island.
* [[Anholt (Denmark)|Anholt]] and the sea north of the island.

'''Sweden'''<ref>{{cite web |url=http://www.naturvardsverket.se/natura2000# |title=Natura 2000 |publisher=Swedish Environmental Protection Agency |language=sv |access-date=19 January 2016 |archive-date=26 January 2016 |archive-url=https://web.archive.org/web/20160126085841/http://www.naturvardsverket.se/natura2000 |url-status=dead }}</ref>
* The [[Nordre älv]] [[estuary]] north of Gothenburg. An important spot for migratory birds and fish.
* The [[Vrångö]] archipelago (Swedish: ''Vrångöskärgården''), part of the [[Archipelago of Gothenburg]]. An important reproduction area for seabirds and seals.
* [[Kungsbacka Fjord]]. A shallow water fjord between Gothenburg and [[Varberg]], including important [[salt marsh]]es. 
* [[Hovs Hallar]] 
* [[Kullaberg Nature Reserve]]

== Gallery ==
<gallery>
Anholt Havmøllepark.jpg|There are several offshore [[windfarm]]s in the Kattegat.
Bianca Rambow (North of Funen).2.ajb.jpg|Some of the world's busiest shipping lanes pass through the Kattegat.
Fladen Light.PNG|The larger shallow sand and stony reefs have been equipped with light signaling in modern times. 
Kungälv Municipality from the air.jpg|There are several small archipelagos near the mainland in the Swedish part of the Kattegat.
Barakullen.jpg|The Swedish coasts in the Kattegat are rocky shores, like this one in Kullaberg, or sandy or gravel beaches.
Grenå Strand.JPG|All the Danish coasts in the Kattegat are sandy or gravel beaches with no exposed [[bedrock]].
</gallery>

==See also==
* [[Øresund Bridge]]

== References ==
{{Reflist}}

==External links==
{{Commons category|Kattegat}}
* {{Cite Americana|wstitle=Cattegat |short=x}}
* {{Cite Collier's|wstitle=Cattegat |short=x}}

{{Authority control}}

[[Category:Kattegat| ]]
[[Category:Denmark–Sweden border]]
[[Category:International straits]]
[[Category:Straits of Denmark]]
[[Category:Straits of Sweden]]
[[Category:Straits of the Baltic Sea]]
[[Category:Landforms of Västra Götaland County]]
[[Category:Landforms of Skåne County]]
[[Category:Landforms of Halland County]]