New Study Sheds Light on 'Dead Water' Phenomenon
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New study sheds light on 'dead water' phenomenon -- Sott.net:
Norwegian mariners called it dodvann - dead water. They'd known for centuries that patches of seawater in narrow fjords could mysteriously sap a ship's speed, drastically slowing it or stopping it altogether. In his 1897 book, Farthest North, explorer Fridtjof Nansen wrote of his encounter with dead water north of Siberia in 1893: "We could hardly get on at all for the dead-water, and we swept the whole sea along with us." Dead water, Nansen noted, occurred "where a layer of fresh water rests upon the salt water of the sea," as happens in northern fjords when snow and ice from mountains melt into the ocean.[Emphasis from original article - Ed]
Nansen's report of dead water was investigated by scientists at the time, including the Swedish oceanographer Vagn Walfrid Ekman. In 1904, Ekman published research that showed dead water was caused by hidden waves in a dense subsurface layer of salt water that slowed the forward motion of a ship. Today's speedy ships easily overcome these submerged waves, and for most mariners dead water is now largely forgotten.
But more than 100 years later, scientists are still exploring the phenomenon, and a new investigation has uncovered more details about its underlying mechanics.
Journal Reference:
Johan Fourdrinoy, Julien Dambrine, Madalina Petcu, et al. The dual nature of the dead-water phenomenology: Nansen versus Ekman wave-making drags [$], Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.1922584117)
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