Dead water is the nautical term for a phenomenon which can occur when there is strong vertical density stratification due to salinity or temperature or both. It is common where a layer of fresh or brackish water rests on top of denser salt water , without the two layers mixing. The phenomenon is frequently, but not exclusively, observed in fjords where glacier runoff flows into salt water without much mixing. The phenomenon is a result of energy producing internal waves that have an effect on the vessel. The effect can also be found at density boundaries between sub surface layers.
11-821: [REDACTED] Look up dead water in Wiktionary, the free dictionary. Deadwater(s) or Dead water may refer to: Places [ edit ] Deadwater, Hampshire , village in England Deadwater, Northumberland , village in England Deadwater railway station , a closed railway station Deadwaters, South Lanarkshire , a village in Scotland; See List of places in South Lanarkshire Deadwater Ait , island in
22-482: A constant abnormally slow progress. The second, Ekman type, causes speed oscillations. The Ekman type may be temporary and become Nansen type as the vessel escapes the particular regime causing the oscillating speed. An interesting historical possibility is that the effect caused Cleopatra's ships difficulties and loss at the Battle of Actium in 31 BC in which legend attributes the loss to remora (suckerfish) attaching to
33-544: A standstill and "stick". An increase in speed by a few knots can overcome the effect. Experiments have shown the effect can be even more pronounced in the case of submersibles encountering such stratification at depth. The phenomenon, long considered sailor's yarns, was first described for science by Fridtjof Nansen , the Norwegian Arctic explorer. Nansen wrote the following from his ship Fram in August 1893 in
44-403: Is different from Wikidata All article disambiguation pages All disambiguation pages dead water In the better known surface phenomenon a ship traveling in a fresh water layer with a depth approximately equal to the vessel's draft will expend energy creating and maintaining internal waves between the layers. The vessel may be hard to maneuver or can even slow down almost to
55-796: The Nordenskiöld Archipelago near the Taymyr Peninsula : When caught in dead water Fram appeared to be held back, as if by some mysterious force, and she did not always answer the helm. In calm weather, with a light cargo, Fram was capable of 6 to 7 knots. When in dead water she was unable to make 1.5 knots. We made loops in our course, turned sometimes right around, tried all sorts of antics to get clear of it, but to very little purpose. Nansen's experience led him to request physicist and meteorologist Vilhelm Bjerknes to study it scientifically. Bjerknes had his student, Vagn Walfrid Ekman , investigate. Ekman, who later described
66-501: The expedition of the Fram , Fridtjof Nansen had observed that icebergs tend to drift not in the direction of the prevailing wind but at an angle of 20°-40° to the right. Bjerknes invited Ekman, still a student, to investigate the problem. Later, in 1905, Ekman published his theory of the Ekman spiral which explains the phenomenon in terms of the balance between frictional effects in
77-708: The ocean and the Coriolis force , which arises from moving objects in a rotating environment, like planetary rotation . On completing his doctorate in Uppsala in 1902, Ekman joined the International Laboratory for Oceanographic Research , Oslo where he worked for seven years, not only extending his theoretical work but also developing experimental techniques and instruments such as the Ekman current meter and Ekman water bottle . From 1910 to 1939 he continued his theoretical and experimental work at
88-478: The River Thames near Windsor, Berkshire, England Other uses [ edit ] Deadwater (film) , horror film Deadwater (topography) , part of an estuary through which there is little to no water flow Dead water , nautical term when a layer of fresh water rests on top of denser salt water, without mixing dead water caused by low oxygen levels in aquatic environments Topics referred to by
99-522: The effect now bearing his name as the Ekman spiral , demonstrated the effect of internal waves as being the cause of dead water. A modern study by the Université de Poitiers entities CNRS' Institut Pprime and the Laboratoire de Mathématiques et Applications revealed that the effect is due to internal waves moving the vessel back and forth. Two types occur. The first as observed by Nansen causes
110-599: The hulls. This fluid dynamics –related article is a stub . You can help Misplaced Pages by expanding it . Vagn Walfrid Ekman Vagn Walfrid Ekman (3 May 1874 – 9 March 1954) was a Swedish oceanographer . Born in Stockholm to Fredrik Laurentz Ekman , himself an oceanographer, he became committed to oceanography while studying physics at the University of Uppsala and, in particular, on hearing Vilhelm Bjerknes lecture on fluid dynamics . During
121-453: The same term [REDACTED] This disambiguation page lists articles associated with the title Deadwater . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Deadwater&oldid=979731679 " Categories : Disambiguation pages Place name disambiguation pages Hidden categories: Short description
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