Der kan næsten tales om en slags vandfald i havet. Den thermohaline cirkulation har stor betydning for Jordens klima. In 2013, an unexpected significant weakening of the THC led to one of the quietest Atlantic hurricane seasons observed since 1994. But these sharp boundaries are not to be imagined spatially but rather in a T-S-diagram where water masses are distinguished. Cirkulationen i oceanerne som drives af forskelle i salinitet (saltindhold) og temperatur. I det nordlige Atlanterhav, hvor vandet fryser til is, bliver saltindholdet i det vand, der ikke er frosset, endnu større, og det vil derfor synke til bunds. thermohaline Zirkulation, umfasst Meeresströmungen, die durch räumliche Unterschiede in Temperatur und Salzgehalt hervorgerufen werden. Thermohaline circulation is a 3-dimensional flow involving surface and deep ocean waters, which is driven by differences in water temperature and salinity. The process of western intensification causes the Gulf Stream to be a northward accelerating current off the east coast of North America. [1][2] The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, factors which together determine the density of sea water. Wallace Broecker, using box models, has asserted that the bulk of deep upwelling occurs in the North Pacific, using as evidence the high values of silicon found in these waters. The ocean, no longer protected by sea ice, suffers a brutal and strong cooling (see polynya). Climatic Change, 2000. 13-20. [6][7] Note that ocean currents due to tides are also significant in many places; most prominent in relatively shallow coastal areas, tidal currents can also be significant in the deep ocean. Deep waters have their own chemical signature, formed from the breakdown of particulate matter falling into them over the course of their long journey at depth. Den termohaline cirkulation er de sammenhængende havstrømme, der udgør et globalt kredsløb.Ordet er sammensat af thermo for varme og haline for havsalt.Det globale kredsløb kaldes også havenes store transportbånd. Sie entstehen durch Ein- und Abstrahlung sowie durch Austausch von Wärme und Süßwasser (Niederschlag und Verdunstung) mit der Atmosphäre, dem Meereis und … Læs Lyt Lev blandt millioner af bøger på Saxo.com. Den termohaline cirkulation er de sammenhængende havstrømme, der udgør et globalt kredsløb. The water in these circuits transport both energy (in the form of heat) and mass (dissolved solids and gases) around the globe. Sharply defined boundaries exist between water masses which form at the surface, and subsequently maintain their own identity within the ocean. Det øger saltholdigheden (saliniteten) af vandet, som derved bliver tungere, og en del af dette tungere vand synker mod bunden. The movement of surface currents pushed by the wind is fairly intuitive. Denne side blev senest ændret den 20. januar 2021 kl. 378: p. 145-149. Kaiser, N. (2008): Die Thermohaline Zirkulation-Stochastische Analyse eines dynamischen Systems , Master thesis, Simple Metadata BibTeX MPEG-21 DIDL MODS OpenURL ContextObject in Span EndNote Multiline CSV ASCII Citation EP3 XML Dublin Core HTML Citation Computer models of ocean circulation increasingly place most of the deep upwelling in the Southern Ocean,[18] associated with the strong winds in the open latitudes between South America and Antarctica. It is known as overturning. The brine progressively melts the ice just beneath it, eventually dripping out of the ice matrix and sinking. (Image source: NOAA/NCDC). Thermohaline circulation, variability, energy and moisture balance model, paleoceanography. Diese bewirken Unterschiede der Dichte und dadurch Druckgradienten. In the North Atlantic, seawater at the surface of the ocean is intensely cooled by the wind and low ambient air temperatures. Consequently, atmospheric and sea ice perturbations over the deep water production sites excite a large scale response establishing an oceanic t̀̀eleconnection'' … Wind-driven surface currents travel polewards … Deep Sea Research (1953), 6, 140-154. The thermohaline circulation is mainly driven by the formation of deep water masses in the North Atlantic and the Southern Ocean caused by differences in temperature and salinity of the water. pp. Meißner, Katrin J., 1999: Langfristige Variabilität der thermohalinen Zirkulation in einem gekoppelten Ozean-, Meereis-, Atmosphärenmodell. Define Thermohaline circulation. The global ocean conveyor belt is a constantly moving system of deep-ocean circulation driven by temperature and salinity; Stommel, H., & Arons, A. 2 . I takt med, at den varme Golfstrøm flyder mod nord, afgives varme ved fordampning. The Institute for Environmental Research & Eductation. It is part of the North Atlantic Gyre. 0 Reviews. Our goal for this website is to answer the same questions we had in the beginning of the year. The entire body of salt water that covers more than 70 percent of the earth's surface. Vergleich der thermohalinen Zirkulation in drei globalen ozeanischen Zirkulationsmodellen: Sachbericht 01.01. The Gulf Stream is also a significant potential source of renewable power generation.[16][17]. Nature, 1995. This photo has been graciously provided to be used in the GRID-Arendal resources library by: Riccardo Pravettoni. Thus the deep ocean—devoid of wind—was assumed to be perfectly static by early oceanographers. When we started this project in the beginning of 2012, we did not know much about the ocean and Thermohaline Circulation. 2. Diese bewirken Unterschiede der Dichte und dadurch Druckgradienten. Recent papers by Lynne Talley at the Scripps Institution of Oceanography and Bernadette Sloyan and Stephen Rintoul in Australia suggest that a significant amount of dense deep water must be transformed to light water somewhere north of the Southern Ocean. This dense water then flows into the ocean basins. [13] At about .mw-parser-output .geo-default,.mw-parser-output .geo-dms,.mw-parser-output .geo-dec{display:inline}.mw-parser-output .geo-nondefault,.mw-parser-output .geo-multi-punct{display:none}.mw-parser-output .longitude,.mw-parser-output .latitude{white-space:nowrap}40°0′N 30°0′W / 40.000°N 30.000°W / 40.000; -30.000, it splits in two, with the northern stream crossing to northern Europe and the southern stream recirculating off West Africa. This freezing point is however a function of salinity and pressure and thus −1.8 °C is not a general freezing temperature for sea water (see diagram to the right). Verursacht wird der Temperaturunterschied wiederum durch die Abhängigkeit des Umfangs … [4] Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth's oceans a global system. Jan. 20, 2021. Hence, a recent and popular name for the thermohaline circulation, emphasizing the vertical nature and pole-to-pole character of this kind of ocean circulation, is the meridional overturning circulation. Langfristige Variabilität der thermohalinen Zirkulation in einem gekoppelten Ozean-, Meereis-, Atmosphaerenmodell. This collection of currents is responsible for the large-scale exchange of water masses in the ocean, including providing oxygen to the deep ocean.The entire circulation pattern takes ~2000 years. En del af det thermohaline kredsløb, der er af stor betydning for Vesteuropas klima, er Golfstrømmen og dens forlængelse Den Nordatlantiske strøm. 13-20. thermohaline Zirkulation, umfaßt Strömungen, die durch räumliche Unterschiede in Temperatur und Salzgehalt hervorgerufen werden. At the Indian Ocean, some of the cold and salty water from the Atlantic—drawn by the flow of warmer and fresher upper ocean water from the tropical Pacific—causes a vertical exchange of dense, sinking water with lighter water above. The dense water masses formed by these processes flow downhill at the bottom of the ocean, like a stream within the surrounding less dense fluid, and fill up the basins of the polar seas. While the bulk of it upwells in the Southern Ocean, the oldest waters (with a transit time of about 1000 years)[3] upwell in the North Pacific. Rahmstorf, S., Bifurcations of the Atlantic thermohaline circulation in response to changes in the hydrological cycle. On the abyssal circulation of the world ocean. From our research we found a lot of interesting facts that we would have never known before and would now like to share with you. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, factors which together determine the density of sea water. 00:17. In the Norwegian Sea evaporative cooling is predominant, and the sinking water mass, the North Atlantic Deep Water (NADW), fills the basin and spills southwards through crevasses in the submarine sills that connect Greenland, Iceland and Great Britain which are known as the Greenland-Scotland-Ridge. The thermohaline circulation is sometimes called the ocean conveyor belt, the great ocean conveyor, or the global conveyor belt. Driven by the density gradients this sets up the main driving force behind deep ocean currents like the deep western boundary current (DWBC). Der Motor der THC ist das Absinken von kaltem und salzreichem Wasser im Nordatlantik. - 31.04.1998. 2 . [5] Moreover, temperature and salinity gradients can also lead to circulation effects that are not included in the MOC itself. [20], Downturn of AMOC (Atlantic meridional overturning circulation), has been tied to extreme regional sea level rise.[21]. The term MOC is more accurate and well defined, as it is difficult to separate the part of the circulation which is driven by temperature and salinity alone as opposed to other factors such as the wind and tidal forces. für Polar- und Meeresforschung, 1998. AABW formed in the Weddell Sea will mainly fill the Atlantic and Indian Basins, whereas the AABW formed in the Ross Sea will flow towards the Pacific Ocean. (1960). Diese als Golfstrom bekannte Meeresströmung The density of ocean water is not globally homogeneous, but varies significantly and discretely. In the Pacific Ocean, the rest of the cold and salty water from the Atlantic undergoes haline forcing, and becomes warmer and fresher more quickly. Kiejtési kalauz: Ismerd meg, hogyan ejtik ezt:thermohaline circulation angol nyelven, anyanyelvi kiejtéssel! Das bedeutet: Er wird durch Temperatur- und Salzkonzentrationsunterschiede innerhalb der Weltmeere hervorgerufen, welche beide für die unterschiedliche Dichte des Wassers verantwortlich sind. Den thermohaline cirkulation har stor betydning for Jordens klima.Ud over forskellen i saltindhold og i temperatur drives kredsløbet også af vinde … – I. Stationary planetary flow patterns on a sphere. n. 1. Alfred-Wegener-Inst. Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. Böning, Claus W. (1995) Die thermohaline Zirkulation des Atlantischen Ozeans in wirbelauflösenden Modellen Deutsche Hydrographische Zeitschrift, Suppl. adjective of, or relating to a combination of temperature and salinity Böning, Claus W. (1995) Die thermohaline Zirkulation des Atlantischen Ozeans in wirbelauflösenden Modellen. However, because this thermohaline upwelling is so widespread and diffuse, its speeds are very slow even compared to the movement of the bottom water masses. This is also known as 'haline forcing' (net high latitude freshwater gain and low latitude evaporation). Its presence has led to the development of strong cyclones of all types, both within the atmosphere and within the ocean. Vandet omkring isen bliver saltere, fordi saltet udelades under fryseprocessen. How to create a webinar that resonates with remote audiences In general, ocean water velocities range from fractions of centimeters per second (in the depth of the oceans) to sometimes more than 1 m/s in surface currents like the Gulf Stream and Kuroshio. Wind moving over the water also produces a great deal of evaporation, leading to a decrease in temperature, called evaporative cooling related to latent heat. Det nedsynkende vand bliver derved til en del af den Nordatlantiske Dybhavsstrøm. This process is known as brine rejection. Abbr. Analyses of ocean observations and model simulations suggest that there have been considerable changes in the thermohaline circulation (THC) during the last century. thermohaline circulation angol fordítása. The out-flowing undersea of cold and salty water makes the sea level of the Atlantic slightly lower than the Pacific and salinity or halinity of water at the Atlantic higher than the Pacific. Note that, unlike fresh water, seawater does not have a density maximum at 4 °C but gets denser as it cools all the way to its freezing point of approximately −1.8 °C. Other investigators have not found such clear evidence. Drivkraften bag strømmen er til dels forskelle i densiteten af vand i oceanerne, skabt af forskelle i temperatur og salinitet, dette kaldes den termohaline cirkulation. The EU-funded 'Thermohaline Overturning - At risk?' As such, the state of the circulation has a large impact on the climate of the Earth. Oc. However, modern instrumentation shows that current velocities in deep water masses can be significant (although much less than surface speeds). I filmen "The Day After Tomorrow" begynder en istid meget pludseligt som følge af klimaforandringer, der fører til et nedbrud i oceancirkulationen, det der også kaldes den termohaline cirkulation. B. Thermohaline definition is - involving or dependent upon the conjoint effect of temperature and salinity. Den atlantiske termohaline cirkulation benævnes også på engelsk med forkortelsen AMOC (Atlantic meridional overturning circulation). Wasser ist umso schwerer, je salziger oder je kälter es ist – die gleiche Wasserdichte kann also durch verschiedene Kombinationen der Wassereigenschaften zustande kommen. A part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes, Atmospheric, oceanographic, cryospheric, and climate models. Hello Select your address Best Sellers Today's Deals New Releases Electronics Books Customer Service Gift Ideas Home Computers Gift Cards Sell pp. Der Antrieb für diesen umfangreichen Massen- und Wärmeaustausch ist thermohaliner Natur. Thermohaline sirkulation. United Nations Environment Programme / GRID-Arendal, 2006. On occasion, it is used to refer to the meridional overturning circulation (often abbreviated as MOC). Although there has been recent debate, there is consensus that the climate of Western Europe and Northern Europe is warmer than it would otherwise be due to the North Atlantic drift,[14][15] one of the branches from the tail of the Gulf Stream. This motion is called convection, it orders the stratification by gravitation. Tætheden af vandet afhænger af temperatur og saltholdighed. This warmer, fresher water from the Pacific flows up through the South Atlantic to Greenland, where it cools off and undergoes evaporative cooling and sinks to the ocean floor, providing a continuous thermohaline circulation.[11]. The main cause of the inactivity was caused by a continuation of the spring pattern across the Atlantic basin. - Freshening of high latitude surface water can change the large scale oceanic transport of heat and salt. ), https://da.wikipedia.org/w/index.php?title=Den_termohaline_cirkulation&oldid=10584145, Commons-kategori på Wikidata er ens med lokalt link, Sider med Webarchive-skabelon som henviser til Wayback Machine, Wikipedia artikler med LCCN autoritetsdata-ID, Wikipedia artikler med GND autoritetsdata-ID, Creative Commons Navngivelse/Del på samme vilkår 3.0. This high-latitude cooling and the low-latitude heating drives the movement of the deep water in a polar southward flow. Atlantic meridional overturning circulation, one of the quietest Atlantic hurricane seasons observed since 1994, "The concept of the thermohaline circulation", "Characterizing transport between the surface mixed layer and the ocean interior with a forward and adjoint global ocean transport model", The Thermohaline Circulation - The Great Ocean Conveyor Belt, "RAPID: monitoring the Atlantic Meridional Overturning Circulation at 26.5N since 2004", "Satellites Record Weakening North Atlantic Current Impact", Gulf Stream's Tidal Energy Could Provide Up to a Third of Florida's Power, "Closure of the meridional overturning circulation through Southern Ocean upwelling", "Estimates of Meridional Atmosphere and Ocean Heat Transports", 10.1175/1520-0442(2001)014<3433:EOMAAO>2.0.CO;2, "Extreme sea level rise event linked to AMOC downturn", http://arquivo.pt/wayback/20141126093524/http%3A//www.eu%2Dthor.eu/, Deep-ocean Assessment and Reporting of Tsunamis, North West Shelf Operational Oceanographic System, Jason-2 (Ocean Surface Topography Mission), https://en.wikipedia.org/w/index.php?title=Thermohaline_circulation&oldid=998100178, Short description is different from Wikidata, Wikipedia articles needing clarification from October 2017, Creative Commons Attribution-ShareAlike License, This page was last edited on 3 January 2021, at 20:36. I polare områder bliver havvand meget koldt, og is dannes. The deep water flows through the Antarctic Ocean Basin around South Africa where it is split into two routes: one into the Indian Ocean and one past Australia into the Pacific. Wind-driven surface currents (such as the Gulf Stream) travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes (forming North Atlantic Deep Water). Formation and movement of the deep water masses at the North Atlantic Ocean, creates sinking water masses that fill the basin and flow very slowly into the deep abyssal plains of the Atlantic. In the deep ocean, the predominant driving force is differences in density, caused by salinity and temperature variations (increasing salinity and lowering the temperature of a fluid both increase its density). The dense water masses that sink into the deep basins are formed in quite specific areas of the North Atlantic and the Southern Ocean. This is known as "stable stratification" as opposed to unstable stratification (see Brunt-Väisälä frequency)[clarification needed] where denser waters are located over less dense waters (see convection or deep convection needed for water mass formation). Just as river valleys direct streams and rivers on the continents, the bottom topography constrains the deep and bottom water masses. Ustabilt hav kan skabe pludselige klimaændringer. The Gulf Stream influences the climate of the east coast of North America from Florida to Newfoundland, and the west coast of Europe. English: This map shows the pattern of thermohaline circulation also known as "meridional overturning circulation". Flow from the Arctic Ocean Basin into the Pacific, however, is blocked by the narrow shallows of the Bering Strait. When dense water masses are first formed, they are not stably stratified, so they seek to locate themselves in the correct vertical position according to their density. The aim was to assess the strength of THC, and to provide an early warning system for large-scale changes affecting the European climate. To maintain a balance, water must be rising elsewhere.

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