Thermohaline circulation academic kids free online. Winddriven circulation, which is strongest in the surface layer of the ocean, is the more vigorous of the two and is configured as large gyres that dominate an ocean region. The dynamic influence of thermohaline circulation on wind driven circulation in the south china sea scs is studied using a simple reduced gravity model, in which the upwelling driven by mixing in the abyssal ocean is treated in terms of an upward pumping distributed at the base of the upper layer. Thermohaline circulation begins in the earths polar regions. This is the first advanced textbook to discuss both wind driven and thermohaline driven processes two important aspects of largescale ocean circulation. Thermohaline circulation driven by density and salinity differences heating and cooling at the surface upwelling and downwelling and freshwater evaporationsea ice formation cause water to move.
In contrast to the winddriven part of the ocean circulation, the thermohaline circulation is driven by density gradients and extends from the surface to the abyssal ocean. Free physical oceanography books download ebooks online. Winddriven and thermohaline processes the interaction between ocean circulation and climate change has been an. The circulation of the ocean is usually divided into two parts, a winddriven circulation that dominates in the upper few hundred meters, and a densitydriven circulation that dominates below. Wood,michaelvellinga androbertthorpe hadley centre for climate prediction and research, met o. Ocean circulation winddriven and thermohaline processes. Ocean circulation and climate the thermohaline circulation. Ocean circulation is driven and regulated by interaction with the atmosphere wind, by tidal dissipation, and by regional differences in the. Although thermohaline processes in the ocean are commonly considered separately from winddriven processes, many aspects of the ocean thermohaline and. Studies of climate frequently involve identifying a plausible forcing mechanism e. Chapter 11 the thermohaline circulation of the ocean. Hence these mechanisms amount to overlooked processes for rapid or abrupt climate changes. Thermohaline circulation thc is a part of the largescale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. It provides a concise introduction to the dynamics.
Thermohaline circulation an overview sciencedirect topics. The most dramatic seasonal change in the surface circulation of the indian. Lecture 15 ocean circulation winddriven circulation. This emphasizes the necessity to take into account both the thc. This is a true of oceanography in general of course, and the authors are from europe. This emphasizes the necessity to take into account both the thc and the wind driven circulation when considering such climate fluctuations. The latter is called the thermohaline circulation because of the role of heating, cooling, freshening, and salini. It provides a concise introduction to the dynamics and thermodynamics of oceanic general circulation. Changes in the thermohaline circulation are thought to have significant impacts on earths energy budget. A different mechanism for driving ocean currents comes from the.
Thermohaline circulation fact sheet by stefan rahmstorf. On earth, an ocean is one of the major conventional divisions of the world. Ocean circulation, and its related geophysical fluid dynamical principles, are now taught at graduate level in many earth and atmospheric science departments. The stability of the thermohaline circulation is investigated using an ocean general circulation model coupled to a simple atmospheric model.
Giant patterns of meridional overturning circulation are set up that cross the equator and connect the hemispheres together. Published online 22 july 2003 the atlantic thermohaline circulation thc plays an important role in global climate. Thermohaline circulation wikipedia republished wiki 2. As in the atmosphere, ocean circulations are driven by buoyancy effects and the flow is influenced by coriolis. They, by necessity, assumed a steady atmosphere that exerted wind stress on the ocean surface, and ignored the effects from heat and water flux. A brief treatment of thermohaline circulation follows. The dynamic influence of thermohaline circulation on winddriven circulation in the south china sea scs is studied using a simple reduced gravity model, in which the upwelling driven by. Further reading henderschott mc 1987 single layer models of the general circulation. It plays an important role in supplying heat to the polar regions, and thus in sea ice regulation. The adjective thermohaline derives from thermoreferring to temperature and haline referring to salt content, factors which together determine the density of sea water. The freshening of surface waters in high latitudes.
Thermohaline circulation thc is a part of the largescale ocean circulation that is driven by. Global ocean circulation can be divided into two major components. An efficient thermohaline circulation seems to be restricted to the upper layers in tropical and subtropical regions. The winds over the indian ocean change seasonally as a result of the differential heating of the ocean and the asian landmass. Rui xin huang ocean circulation winddriven and thermohaline. The thermohaline circulation is a term for the global densitydriven circulation of the oceans. Winds drive ocean currents in the upper 100 meters of the oceans surface. Sea water density depends on temperature and salinity, hence the name thermohaline. As in the atmosphere, ocean circulations are driven by buoyancy effects and the flow is influenced by coriolis forces and drag at the interfaces. The surrounding seawater gets saltier, increases in density and sinks. Rui xin huang the interaction between ocean circulation and climate change has been an active research frontier in earth sciences in recent years.
The best understanding of circulation concerns the wind driven ocean circulation, where notable developments were made by ekman 1905, 1923, sverdrup 1947, and stommel 1948. For an updated and more detailed version, see the following paper pdf, 3mb. A different mechanism for driving ocean currents comes. Unlike the faster winddriven circulation, which is con. As opposed to winddriven currents and tides which are due to the gravity of moon and sun, the thermohaline circulation fig. Ocean circulation thermohaline circulation request pdf. Thermohaline circulation is dependent on differences in water density, caused by differences in temperature and salinity between different bodies of water. The difference between thermohaline and wind driven circulation was distinguished in the 19thcentury, during an argument regarding ocean currents. The best understanding of circulation concerns the winddriven ocean circulation, where notable developments were made by ekman 1905, 1923, sverdrup 1947, and stommel 1948. Ocean currents national oceanic and atmospheric administration.
In contrast, thermohaline circulation is much slower, with a typical speed of 1 centimetre 0. My only objection is that its very north atlanticcentric. The circulation shown in physical space in left can be both a horizontal e. A new, speculative, and, we hope, provocative summary of the north atlantic circulation is described, including both horizontal currents winddriven and the primarily thermohaline meridional. It therefore requires deepwater areas, of which the northern and middle atlantic have the most, for these differences or gradients to form. It is also called thermohaline circulation because is. The most dramatic seasonal change in the surface circulation of the indian ocean is the reversal of the somali current, which flows southwestwards during the northeast monsoon but is a major western boundary current.
These, however, are superimposed on the much more sluggish circulation driven by horizontal differences in temperature and salinitynamely, thermohaline circulation. This book provides a concise introduction to the dynamics and thermodynamics of the oceanic general circulation, including the thermodynamics of seawater and the energetics of the ocean circulation. Thermohaline circulation of the oceans marinespecies. Ocean circulation, and the geophysical fluid dynamical principles that underpin it, are subjects taught at graduate level in many earth science, oceanography, and atmospheric sciences departments. The effects of thermohaline circulation on winddriven. In cold regions, such as the north atlantic ocean, ocean water loses heat to the atmosphere and becomes cold and dense. Twoway feedback interaction between the thermohaline. Kuroshio, east australian current, subtropical gyre, winddriven circulation.
Nov 10, 2012 moc the meridional overturning circulation moc refers to the northsouth flow as a function of latitude and depth. The thermohaline ocean circulation a brief fact sheet by stefan rahmstorf. The meridional overturning circulation is associated to the abyssal circulation in the ocean. Thermohaline circulation driven by density and salinity differences heating and cooling at the surface upwelling and downwelling and freshwater evaporationsea ice formation cause water to move wind driven currents.
Global warming and thermohaline circulation stability by richard a. Winddriven and thermohaline processes the interaction between ocean circulation and climate change has been an active research frontier in earth sciences. Surface heat and freshwater fluxes create global density gradients that drive the thermohaline circulation part of largescale ocean circulation. Twoway feedback interaction between the thermohaline and. It was question as well weather or not these two processes happen when the wind pushes along the water or else if they are convection currents due to heating and cooling processes. As the name suggests, the winddriven circulation is. Decadal variability of the thermohaline ocean circulation. Differences in water density, resulting from the variability of water temperature thermo and salinity haline, also cause ocean currents. In a way, the thermohaline circulation can work together with winddriven circulations and create a conveyer belt that circulates all around the world. Global ocean surface currents z subtropical midlatitude ocean is dominated by subtropical gyre. However, ocean currents also flow thousands of meters below the surface. Thermohaline ocean circulation potsdam institute for climate.
The general circulation of the oceans consists primarily of. Our experiments show that the freshening can induce. The thermohaline circulation is basically an overturning of the ocean in the meridionalvertical plane. Ocean circulation and climate, volume 103 2nd edition. These two components act simultaneously to drive the moc, the movement of seawater across basins and depths. A good choice for anyone looking to get a feeling for the processes that move oceans, both winddriven and thermohaline. A new, speculative, and, we hope, provocative summary of the north atlantic circulation is described, including both horizontal currents wind driven and the primarily thermohaline meridional. Derivation is from thermofor heat and haline for salt, which together determine the density of sea water. Global warming and thermohaline circulation stability. The ocean circulation is therefore an important part of the climate system.
A good choice for anyone looking to get a feeling for the processes that move oceans, both wind driven and thermohaline. This is the first advanced textbook to discuss both winddriven and thermohalinedriven processes two important aspects of largescale ocean circulation. Effects of a winddriven gyre on thermohaline circulation. The thermohaline circulation the average depth of the ocean is 4 km but most of the life is confined to. The wind driven circulation wdc, in turn, affects the thc by the advection of salinity anomalies into deepwater formation sites. Stabilization of thermohaline circulation by winddriven. Winddriven surface currents such as the gulf stream travel polewards from the equatorial. This is difficult because the mechanisms are many and frequently small in amplitude, the response complex, and. Conceptual models of the wind driven and thermohaline circulation. Conceptual models of the winddriven and thermohaline circulation. Westwardflowing currents that travel along the equator in all ocean basins, caused by trade winds.
When ocean water in these areas gets very cold, sea ice forms. It is that part of the ocean circulation which is driven by density differences as opposed to wind and tides. Functioning of the thermohaline circulation thc the conveyor belt fig. There they are currently thought to facilitate mixing processes, especially diapycnal mixing. This is the first advanced textbook to discuss both winddriven and thermohaline driven processes two important aspects of largescale ocean circulation. This upper thermohaline circulation is of minor importance compared to the wind driven circulation. The interaction between ocean circulation and climate change has been an active research frontier in earth sciences in recent years. The thermohaline circulation thc affects the meridional atmospheric temperature gradient and therefore the atmospheric wind and the wind driven ocean circulation. The thermohaline circulation thc affects the meridional atmospheric temperature gradient and therefore the atmospheric wind and the winddriven ocean circulation. Z maintained by the subtropical high pressure system and its associated wind westerly wind at mid.
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