Stabilization of thermohaline circulation by winddriven and. Wind stress coastal ocean thermohaline circulation geostrophic velocity dynamic height these keywords were added by machine and not by the authors. On earth, an ocean is one of the major conventional divisions of the world ocean. The former process usually dominates the density and hence denser waters are produced. For an updated and more detailed version, see the following paper pdf, 3mb. A good choice for anyone looking to get a feeling for the processes that move oceans, both winddriven and thermohaline. Conceptual models of the winddriven and thermohaline. The coupled model can reproduce the realistic deep ocean circulation without any flux adjustment. The ocean circulation is therefore an important part of the climate system. Because the ocean density is a function of temperature thermo and salinity haline, this circulation is referred to as the themohaline circulation and indicates a driving mechanism. As a result, the thermohaline circulation is still poorly understood. Free physical oceanography books download ebooks online.
In cold regions, such as the north atlantic ocean, ocean water loses heat to the atmosphere and becomes cold and dense. To explain the observed thermohaline circulation, this hypothetical ocean has to be. Thermohaline effects in the ocean circulation and related simple. Conceptual models are a vital tool for understanding the processes that maintain the global ocean circulation, both in nature and in complex numerical ocean models. It provides a concise introduction to the dynamics and thermodynamics of oceanic general circulation. Thermohaline ocean processes and models thermohaline ocean processes and models whitehead, j a 19950101 00.
Term is derived from thermo heat and haline salt, which together determine the density of sea water. Ocean processes enhance decadal predictability longer timescales. As in the atmosphere, ocean circulations are driven by buoyancy effects and the flow is influenced by coriolis forces and drag at the interfaces. My only objection is that its very north atlanticcentric. The present discussion has shown that the winddriven circulation and the thermohaline circulation are major components of ocean circulation, which are ultimately driven by the surface wind stress and buoyancy fluxes. This process is experimental and the keywords may be updated as the learning algorithm improves. Students will be able to explain how warmer temperatures might affect winddriven surface cur rents, and how these effects might impact biologi cal communities of the deep ocean. In contrast to the winddriven currents, the thc is not confined to surface waters. The thermohaline circulation the average depth of the ocean is 4 km but most of the life is confined to. The thermohaline circulation of the arctic ocean and the. When ocean water in these areas gets very cold, sea ice forms. Twoway feedback interaction between the thermohaline. Ocean circulation thermohaline circulation request pdf.
Ocean circulation and climate a 21 st century perspective. In this chapter we provide a broad overview of our conceptual understanding of the winddriven circulation, the thermohaline circulation, and their transient behavior. Surface heat and freshwater fluxes create global density gradients that drive the thermohaline circulation part of largescale ocean circulation. Download book pdf largescale transport processes in oceans and atmosphere pp 163200 cite as. 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. A different mechanism for driving ocean currents comes. This is the first advanced textbook to discuss both winddriven and thermohalinedriven processes two important aspects of largescale ocean circulation.
The adjective thermohaline derives from thermoreferring to temperature and haline referring to salt content, factors which together determine the density of sea water. This is a true of oceanography in general of course, and the authors are from europe. Winddriven circulation an overview sciencedirect topics. Ocean circulation, winddriven and thermohaline processes. There are several books that deal with winddriven ocean circulation, but few, if any, cover thermohalinedriven circulation and its energetics. For example, there is evidence that interactions between the. The thermohaline circulation is the term for the global densitydriven circulation of the oceans.
Sea water density depends on temperature and salinity, hence the name thermohaline. 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. Two basic types of circulation can be distinguished, the concentration basin and the dilution basin. Thc, rather than wind driven circulation, enhances decadal climate predictability thc more likely to be governed by slower oceanic processes. Changes in the thermohaline circulation are thought to have significant impacts on earths energy budget. Stabilization of thermohaline circulation by winddriven.
Thc, rather than winddriven circulation, enhances decadal climate predictability thc more likely to be governed by slower oceanic processes. Giant patterns of meridional overturning circulation are set up that cross the equator and connect the hemispheres together. The general circulation of the oceans consists primarily of winddriven ocean currents. International geophysics ocean circulation and climate. Ocean currents national oceanic and atmospheric administration. International geophysics ocean circulation and climate a. 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. In this chapter we provide a broad overview of our conceptual understanding of the wind driven circulation, the thermohaline circulation, and their transient behavior. The atmospheric model is so developed that it represents the wind stress and the freshwater flux more realistically than existing energy balance models. While the circulation in most of the world ocean is dominated by wind driven currents, the circulation in mediterranean seas is determined by thermohaline processes.
The third process is subsurface mixing which is less dependent on surface heat and freshwater fluxes. Winddriven and thermohaline processes the interaction between ocean circulation and climate change has been an active research frontier in earth sciences. A brief treatment of thermohaline circulation follows. A numerical investigation of a nonlinear model of a winddriven ocean.
The thermohaline ocean circulation a brief fact sheet by stefan rahmstorf. In contrast, thermohaline circulation is much slower, with a typical speed of 1 centimetre 0. The stability of the thermohaline circulation is investigated using an ocean general circulation model coupled to a simple atmospheric model. These, however, are superimposed on the much more sluggish circulation driven by horizontal differences in temperature and salinitynamely, thermohaline circulation. Westwardflowing currents that travel along the equator in all ocean basins, caused by trade winds.
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. This is the first advanced textbook to discuss both wind driven and thermohaline driven processes two important aspects of largescale ocean circulation. These are, in descending order by area, the pacific, atlantic, indian, southern antarctic, and arctic oceans. Conceptual models of the wind driven and thermohaline circulation. A different mechanism for driving ocean currents comes from the. Thermohaline circulation begins in the earths polar regions. The road to science my personal reflection pdf, last update. Chapter 11 the thermohaline circulation of the ocean. 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. Effects of a winddriven gyre on thermohaline circulation. While the circulation in most of the world ocean is dominated by winddriven currents, the circulation in mediterranean seas is determined by thermohaline processes. This is difficult because the mechanisms are many and frequently small in amplitude, the response complex, and. Winds drive ocean currents in the upper 100 meters of the oceans surface.
The thermohaline circulation thc affects the meridional atmospheric temperature gradient and therefore the atmospheric wind and the winddriven ocean circulation. Ocean conveyor belt the thermohaline circulation xray mag. The effects of thermohaline circulation on winddriven. Thermohaline circulation in a twolayer model with sloping. A good choice for anyone looking to get a feeling for the processes that move oceans, both wind driven and thermohaline. Buoyancy fluxes are the net effect of heat exchange and the freshwater exchange with the overlying atmosphere. Differences in water density, resulting from the variability of water temperature thermo and salinity haline, also cause ocean currents. Conceptual models of the winddriven and thermohaline circulation. As opposed to winddriven currents and tides which are due to the gravity of moon and sun, the thermohaline circulation fig. The best understanding of circulation concerns the winddriven ocean circulation, where notable developments were made by ekman 1905, 1923, sverdrup 1947, and stommel 1948. The phrases the ocean or the sea used without specification refer to.
On winddriven midlatitude convection in ocean general. Ocean circulation and climate the thermohaline circulation. Atmosphereocean dynamics by adrian gill, academic press, 1982. Winddriven surface currents such as the gulf stream. It therefore requires deepwater areas, of which the northern and middle atlantic have the most, for these differences or gradients to form. Propelled by the ocean conveyor belt as warm water from the equator is distributed around the world nearby land is affected i. Winddriven circulation is a key player in regulating the sea surface temperature and. The present discussion has shown that the wind driven circulation and the thermohaline circulation are major components of ocean circulation, which are ultimately driven by the surface wind stress and buoyancy fluxes. Ocean circulation, winddriven and thermohaline processes the chinese eddition, including corrections for typos will be published april, 2012, by high education press of china book cover pdf errata last updated on july 12012 pdf ocean garden this is a garden where i collect my most recent thought about physics of the ocean. 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. 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. They, by necessity, assumed a steady atmosphere that exerted wind stress on the ocean surface, and ignored the effects from heat and water flux.
Further reading henderschott mc 1987 single layer models of the general circulation. The interaction between ocean circulation and climate change has been an active research frontier in earth sciences in recent years. The vertical exchange of dense, sinking water with lighter water below it is known as overturning. Unlike the faster winddriven circulation, which is con. It plays an important role in supplying heat to the polar regions, and thus in sea ice regulation. Variability and predictability of the ocean thermohaline. Thermohaline circulation fact sheet by stefan rahmstorf.
Thermohaline circulation is dependent on differences in water density, caused by differences in temperature and salinity between different bodies of water. On the other hand, measurement shows that the return of deep water does not necessarily occur at the warmer part of the ocean. The surrounding seawater gets saltier, increases in density and sinks. Ocean circulation, and its related geophysical fluid dynamical principles, are now taught at graduate level in many earth and atmospheric science departments. The winddriven circulation wdc, in turn, affects the thc by the advection of salinity anomalies into deepwater formation sites. 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 mixing in the abyssal ocean is treated in terms of an upward pumping distributed at the base of the upper layer. The latter is called the thermohaline circulation because of the role of heating, cooling, freshening, and salini. Nov 10, 2012 moc the meridional overturning circulation moc refers to the northsouth flow as a function of latitude and depth. Ocean circulation by rui xin huang cambridge university press. The denser loop supplies, as a deep boundary current, part of the north atlantic deep water, while the upper loop flows around greenland into the labrador sea and baffin bay as. However, ocean currents also flow thousands of meters below the surface. Moc describing a meridional flow field, a mix of both winddriven and thermohalineflow, often integrated in eastwest direction across an ocean basin or the globe and graphically depicted as a stream function.
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