Editing Norwegian Sea (section)

=== Deep-sea currents ===
The Norwegian Sea is connected with the Greenland Sea and the Arctic Ocean by the 2,600-metre deep [[Fram Strait]].<ref name="Tyler240">[[#refTyler|Tyler, 2003]], pp. 240–260</ref> The Norwegian Sea Deep Water (NSDW) occurs at depths exceeding 2,000 metres; this homogeneous layer with a salinity of 34.91‰ experiences little exchange with the adjacent seas. Its temperature is below 0&nbsp;°C and drops to −1&nbsp;°C at the ocean floor.<ref name=b366/> Compared with the deep waters of the surrounding seas, NSDW has more nutrients but less oxygen and is relatively old.<ref name="Aken">[[#refAken|Aken, 2007]], pp. 131–138</ref>

The weak deep-water exchange with the Atlantic Ocean is due to the small depth of the relatively flat [[Greenland-Scotland Ridge]] between Scotland and Greenland, an offshoot of the [[Mid-Atlantic Ridge]]. Only four areas of the Greenland-Scotland Ridge are deeper than 500 metres: the [[Faroe-Bank Channel overflow#Faroe-Bank Channel|Faroe-Bank Channel]] (about 850 metres), some parts of the [[Iceland-Faroe Ridge]] (about 600 metres), the [[Wyville-Thomson Ridge]] (620 metres), and areas between [[Greenland]] and the [[Denmark Strait]] (850 metres) – this is much shallower than the Norwegian Sea.<ref name="Tyler"/><ref name="Aken"/> Cold deep water flows into the Atlantic through various channels: about 1.9 Sv through the Faroe Bank channel, 1.1 Sv through the Iceland-Faroe channel, and 0.1 Sv via the Wyville-Thomson Ridge.<ref name="Skreslet93">[[#refSkreslet|Skreslet & NATO, 2005]], p. 93</ref> The turbulence that occurs when the deep water falls behind the Greenland-Scotland Ridge into the deep Atlantic basin mixes the adjacent water layers and forms the [[North Atlantic Deep Water]], one of two major deep-sea currents providing the deep ocean with oxygen.<ref name="Threat">Ronald E. Hester, Roy M. Harrison ''Biodiversity Under Threat'', Royal Society of Chemistry, 2007 {{ISBN|0-85404-251-2}}, p. 96</ref>