Dead water
Encyclopedia
Dead water is the nautical term for a strange phenomenon which can occur when a layer of fresh
or brackish water
rests on top of denser salt water
, without the two layers mixing. A ship powered by direct thrust under the waterline (such as a propeller), traveling in such conditions may be hard to maneuver or can even slow down almost to a standstill. Much of the energy from the ship's propeller only results in waves and turbulence between the two layers of water, leaving a ship capable of traveling at perhaps as little as 20% of its normal speed.
The phenomenon was first described by Fridtjof Nansen
, the Norwegian Arctic explorer.
Nansen wrote the following from his ship Fram
in August 1893 in the Nordenskiöld Archipelago
near the Taymyr Peninsula
:
This phenomenon is observable where glacier
runoff flows into salt water without much mixing, such as in fjord
s.
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
or brackish water
Brackish water
Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root "brak," meaning "salty"...
rests on top of denser salt water
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...
, without the two layers mixing. A ship powered by direct thrust under the waterline (such as a propeller), traveling in such conditions may be hard to maneuver or can even slow down almost to a standstill. Much of the energy from the ship's propeller only results in waves and turbulence between the two layers of water, leaving a ship capable of traveling at perhaps as little as 20% of its normal speed.
The phenomenon was first described by Fridtjof Nansen
Fridtjof Nansen
Fridtjof Wedel-Jarlsberg Nansen was a Norwegian explorer, scientist, diplomat, humanitarian and Nobel Peace Prize laureate. In his youth a champion skier and ice skater, he led the team that made the first crossing of the Greenland interior in 1888, and won international fame after reaching a...
, the Norwegian Arctic explorer.
Nansen wrote the following from his ship Fram
Fram
Fram is a ship that was used in expeditions of the Arctic and Antarctic regions by the Norwegian explorers Fridtjof Nansen, Otto Sverdrup, Oscar Wisting, and Roald Amundsen between 1893 and 1912...
in August 1893 in the Nordenskiöld Archipelago
Nordenskiöld Archipelago
The Nordenskiöld Archipelago or Nordenskjold Archipelago is a very large and complex cluster of islands in the eastern region of the Kara Sea. Its eastern limit lies west of the Taymyr Peninsula....
near the Taymyr Peninsula
Taymyr Peninsula
The Taymyr Peninsula is a peninsula in the Far North of Russia, in the Siberian Federal District, that forms the northernmost part of mainland Eurasia and Asia...
:
- "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."
This phenomenon is observable where glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
runoff flows into salt water without much mixing, such as in fjord
Fjord
Geologically, a fjord is a long, narrow inlet with steep sides or cliffs, created in a valley carved by glacial activity.-Formation:A fjord is formed when a glacier cuts a U-shaped valley by abrasion of the surrounding bedrock. Glacial melting is accompanied by rebound of Earth's crust as the ice...
s.
See also
- IcebergIcebergAn iceberg is a large piece of ice from freshwater that has broken off from a snow-formed glacier or ice shelf and is floating in open water. It may subsequently become frozen into pack ice...
- Ice driftIce driftIce drift is movement of ice. An important type of ice drift is drift of the sea ice, i.e., of the drift ice. Unless specified otherwise, this article discusses the drift of the sea ice. The direction of the ice drift is the vector sum of the oceanic and atmospheric circulations, i.e., upper ocean...
- Internal waveInternal waveInternal waves are gravity waves that oscillate within, rather than on the surface of, a fluid medium. They are one of many types of wave motion in stratified fluids . A simple example is a wave propagating on the interface between two fluids of different densities, such as oil and water...
- Nansen's Fram expeditionNansen's Fram expeditionNansen's Fram expedition, 1893–1896, was an attempt by the Norwegian explorer Fridtjof Nansen to reach the geographical North Pole by harnessing the natural east–west current of the Arctic Ocean...
- Nordenskiöld ArchipelagoNordenskiöld ArchipelagoThe Nordenskiöld Archipelago or Nordenskjold Archipelago is a very large and complex cluster of islands in the eastern region of the Kara Sea. Its eastern limit lies west of the Taymyr Peninsula....
- Polar ice capPolar ice capA polar ice cap is a high latitude region of a planet or natural satellite that is covered in ice. There are no requirements with respect to size or composition for a body of ice to be termed a polar ice cap, nor any geological requirement for it to be over land; only that it must be a body of...
- Polar ice packsPolar ice packsPolar ice packs are large areas of pack ice formed from seawater in the Earth's polar regions, known as polar ice caps: the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean, fringing the Antarctic ice sheet. Polar packs significantly change their size during...
- PolynyaPolynyaA polynya or polynia is an area of open water surrounded by sea ice. It is now used as geographical term for an area of unfrozen sea within the ice pack. It is a loanword from , , which means a natural ice hole, and was adopted in the 19th century by polar explorers to describe navigable...
- Sea iceSea iceSea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....
- Shelf iceShelf iceShelf ice can refer to the ice that forms when a portion of a lake surface freezes. It is often then washed upon the shore. This is common within the Great Lakes.-Formation:...
- Vagn Walfrid EkmanVagn Walfrid EkmanVagn Walfrid Ekman 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 the...
- Swedish Oceanographer
External links
- Short movie demonstrating the phenomenon with a model
- Description of Dead Water
- Explanation of dead water
- New Scientist article
- 'dead water' Encyclopædia Britannica Online. 3 December 2009