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Encyclopedia > Sea ice
An icebreaker navigates through young (1 year old) sea ice
An icebreaker navigates through young (1 year old) sea ice
Nilas Sea Ice in arctic
Nilas Sea Ice in arctic

Sea ice is formed from ocean water that freezes. Because the oceans consist of saltwater, this occurs at about -1.8 °C (28.8 °F). From http://southport. ... From http://southport. ... Icebreaker Polarstern Track of research vessel Polarstern while breaking ice in the Southern Ocean An icebreaker is a special purpose ship or boat designed to move and navigate through ice-covered waters. ... Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution (3456 × 2304 pixel, file size: 4. ... Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution (3456 × 2304 pixel, file size: 4. ... Annual mean sea surface temperature for the World Ocean. ... Animated map exhibiting the worlds oceanic waters. ... For information on water from a sea or ocean, see sea water. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ... Fahrenheit is a temperature scale named after the German-Dutch physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ...


Sea ice may be contrasted with icebergs, which are chunks of ice shelves or glaciers that calve into the ocean. Icebergs are compacted snow and hence fresh water. Icebergs at Cape York, Greenland Iceberg at Cape York, Greenland Iceberg, Témpanos, Patagonia, Argentina. ... Ross Ice Shelf An ice shelf is a thick, floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. ... Glacial and Glaciation redirect here. ... For the village on the Isle of Wight, see Freshwater, Isle of Wight. ...

Contents

Types of sea ice

Pancake sea ice in Ross Sea
Pancake sea ice in Ross Sea

Land-fast ice or simply fast ice is sea ice that has frozen along coasts ("fastened" to them) and extends out from land into sea. Image File history File links Size of this preview: 800 × 533 pixelsFull resolution (1944 × 1296 pixel, file size: 1. ... Image File history File links Size of this preview: 800 × 533 pixelsFull resolution (1944 × 1296 pixel, file size: 1. ...


Drift ice consists of ice that float on the surface of the water, as distinguished from the fast ice, attached to coasts. When packed together in large masses, drift ice is called pack ice. Pack ice may be either freely floating or blocked by fast ice while drifting past. Drift ice consists of slabs of ice that float on the surface of the water in cold regions. ...


The most important areas of pack ice are the polar ice packs formed from seawater in the Earth's polar regions: the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean. Polar packs significantly change their size during seasonal changes of the year. Because of vast amounts of water added to or removed from the oceans and atmosphere, the behavior of polar ice packs have a significant impact of the global changes in climate, see "Polar ice packs" for details. NOAA Projected arctic changes Polar ice packs are large areas of pack ice formed from seawater in the Earths polar regions, known as polar ice caps: the Arctic ice pack (or Arctic ice cap) of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean, fringing the... Annual mean sea surface salinity for the World Ocean. ... Location of the polar regions Northern Hemisphere permafrost (permanently frozen ground) in purple. ... View of Jupiters active atmosphere, including the Great Red Spot. ... NOAA Projected arctic changes Polar ice packs are large areas of pack ice formed from seawater in the Earths polar regions, known as polar ice caps: the Arctic ice pack (or Arctic ice cap) of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean, fringing the...


An ice floe is a floating chunk of sea ice that is less than 10 kilometers (six miles) in its greatest dimension. Wider chunks of ice are called ice fields.


Formation of sea ice

Pancake ice is sea ice that has been compressed by the action of waves on frazil ice. Plates are typically 1–3 meters across
Satellite image of Scandinavia in winter. The Bothnian Bay and White Sea are covered with sea ice.
Satellite image of Scandinavia in winter. The Bothnian Bay and White Sea are covered with sea ice.

Only the top layer of water needs to cool to the freezing point. Convection of the surface layer involves the top 100–150 m, down to the pycnocline of increased density. Pancake ice. ... Pancake ice. ... Frazil ice is ice formed in turbulent supercooled water. ... Image File history File links Download high resolution version (2000x2588, 1566 KB) From http://earthobservatory. ... Image File history File links Download high resolution version (2000x2588, 1566 KB) From http://earthobservatory. ... The Baltic Sea The Bothnian Bay or Bay of Bothnia (Fin. ... Map of the White Sea Two satellite photos of the White Sea The White Sea (Russian: ) is an inlet of the Barents Sea on the North Western coast of Russia. ... A pycnocline is a layer of rapid change in water density with depth. ...

  • In calm water, the first sea ice to form on the surface is a skim of separate crystals which initially are in the form of tiny discs, floating flat on the surface and of diameter less than 2-3 mm. Each disc has its c-axis vertical and grows outwards laterally. At a certain point such a disc shape becomes unstable, and the growing isolated crystals take on a hexagonal, stellar form, with long fragile arms stretching out over the surface. These crystals also have their c-axis vertical. The dendritic arms are very fragile, and soon break off, leaving a mixture of discs and arm fragments. With any kind of turbulence in the water, these fragments break up further into random-shaped small crystals which form a suspension of increasing density in the surface water, an ice type called frazil or grease ice. In quiet conditions the frazil crystals soon freeze together to form a continuous thin sheet of young ice; in its early stages, when it is still transparent, it is called nilas. When only a few centimetres thick this is transparent (dark nilas) but as the ice grows thicker the nilas takes on a grey and finally a white appearance. Once nilas has formed, a quite different growth process occurs, in which water molecules freeze on to the bottom of the existing ice sheet, a process called congelation growth. This growth process yields first-year ice, which in a single season reaches a thickness of 1.5–2 m.
  • In rough water, fresh sea ice is formed by the cooling of the ocean as heat is lost into the atmosphere. The uppermost layer of the ocean is supercooled to slightly below the freezing point, at which time tiny ice platelets, known as frazil ice, form. As more frazil ice forms, the ice forms a mushy surface layer, known as grease ice. Frazil ice formation may also be started by snowfall, rather than supercooling.

Waves and wind then act to compress these ice particles into larger plates, of several metres in diameter, called pancake ice. These float on the ocean surface, and collide with one another, forming upturned edges. In time, the pancake ice plates may themselves be rafted over one another or frozen together into a more solid ice cover, known as consolidated ice pancake ice. Such ice has a very rough appearance on top and bottom. Frazil ice is ice formed in turbulent supercooled water. ... Supercooling is the process of chilling a liquid below its freezing point, without it becoming solid. ... Snow is a type of precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. ... Pancake ice is a form of ice that is formed on water covered to some degree in slush. ...


The sea ice is largely fresh, since the ocean salt is expelled from the forming and consolidating ice by a process called brine rejection. The resulting highly saline (and hence dense) water is an important influence on the ocean overturning circulation.


Ecology

Main article: Sympagic ecology
ROV image of krill grazing under the ice.
ROV image of krill grazing under the ice.

Sea ice is part of the Earth's biosphere. Solid sea ice is permeated with channels filled with salty brine. These briny channels and the sea ice itself have its ecology, referred to as "sympagic ecology". ROV image of krill grazing under the ice. ... krill scraping icealgae in antarctica - Photo Uwe Kils and Peter Marschall GFDL higher resolution and links http://www. ... krill scraping icealgae in antarctica - Photo Uwe Kils and Peter Marschall GFDL higher resolution and links http://www. ... Remotely operated vehicles (ROV) are mobile tools used in environments too dangerous for humans. ... Families Euphausiidae Euphausia Dana, 1852 Meganyctiphanes Holt and W. M. Tattersall, 1905 Nematobrachion Calman, 1905 Nematoscelis G. O. Sars, 1883 Nyctiphanes G. O. Sars, 1883 Pseudeuphausia Hansen, 1910 Stylocheiron G. O. Sars, 1883 Tessarabrachion Hansen, 1911 Thysanoessa Brandt, 1851 Thysanopoda Latreille, 1831 Bentheuphausiidae Bentheuphausia amblyops Krill are shrimp-like marine... A false-color composite of global oceanic and terrestrial photoautotroph abundance, from September 1997 to August 2000. ...


The decline of seasonal sea ice is putting the survival of Arctic species such as ringed seals and polar bears at risk.[1][2][3] Binomial name Pusa hispida (Schreber, 1775) The Ringed Seal or Jar Seal (Pusa hispida formerly Phoca hispida) is an earless seal inhabiting the northern coasts. ... Binomial name Phipps, 1774 Polar bear range Synonyms Ursus eogroenlandicus Ursus groenlandicus Ursus jenaensis Ursus labradorensis Ursus marinus Ursus polaris Ursus spitzbergensis Ursus ungavensis Thalarctos maritimus The polar bear (Ursus maritimus) is a bear native to the Arctic. ...


References

  1. ^ Barber, D.G.; Iacozza, J. Historical analysis of sea ice conditions in M'Clintock Channel and the Gulf of Boothia, Nunavut: implications for ringed seal and polar bear habitat. Arctic 57(1) Mar. 2004, pp. 1–14.
  2. ^ Stirling, I.; Lunn, N.J.; Iacozza, J.; Elliott, C.; Obbard, M. Polar bear distribution and abundance on the southwestern Hudson Bay coast during open water season, in relation to population trends and annual ice patterns. Arctic 57(1) Mar. 2004, pp. 15–26.
  3. ^ Stirling, I.; Parkinson, C.L. Possible effects of climate warming on selected populations of polar bears (Ursus maritimus) in the Canadian Arctic. Arctic 59(3) Sept. 2006, pp. 261–75
  • Rothrock, D.A. and J. Zhang (2005). "Arctic Ocean Sea Ice Volume: What Explains Its Recent Depletion?". J. Geophys. Res. 110 (C1): C01002. 
  • How Does Arctic Sea Ice Form and Decay?. NOAA Arctic theme page. Retrieved on April 25, 2005.
  • NSIDC Sea ice. All About Sea Ice. Retrieved on October 6, 2005.
  • Konstantin Y. Vinnikov, Donald J. Cavalieri, and Claire L. Parkinson, V33, L05704, doi:10.1029/2005GL025282, 2006 [1]

See also

Severe cracks in an ice pier in use for four seasons at McMurdo Station slowed cargo operations in 1983 and proved to be a safety hazard. ... Ross Ice Shelf An ice shelf is a thick, floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. ... A polynya (pronounced pol-in-YA) is an area of open water surrounded by sea ice. ... Glacial and Glaciation redirect here. ... Ships with an Ice Class have a strengthened hull to enable them to navigate through sea ice. ...

External links


  Results from FactBites:
 
SOTC: Sea Ice (1916 words)
Sea ice is frozen seawater that floats on the ocean surface.
Grids of sea ice concentrations, as well as summaries using data from both SMMR and SSM/I depicting annual cycles of ice extent (all areas with at least 15 percent ice cover), ice covered area (the ocean area actually covered by ice), and departures from the monthly means or anomalies are available from NSIDC via ftp.
Sea ice conditions for September 2002, 2003, 2004, 2005, and 2006, derived from the NSIDC Sea Ice Index.
Antarctica: Sea ice (557 words)
Sea ice is a very effective insulator and decreases the amount of heat lost from relatively warm oceans (-1.9C) to the much colder atm (-30C).
The boundary between open sea and sea ice is usually quite sharp in summer, being defined by prevailing winds and currents pushing the sea ice fragments.
Sea ice is thicker in the Arctic because the North Pole is a frozen ocean surrounded by land, so there is no where for the ice to go and it piles up.
  More results at FactBites »

 
 

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