A shutdown or slowdown of the thermohaline circulation is a hypothesized effect of global warming on a major ocean circulation a 2015 study suggested that the atlantic meridional overturning circulation amoc has weakened by 1520% in 200 years. Twoway feedback interaction between the thermohaline. Driven by density and salinity differences heating and cooling at the surface upwelling and downwelling and freshwater evaporationsea ice formation cause water to move. Two types of ocean circulation define two circulation types. On the wind driven and thermohaline circulation of the baltic. Unlike the faster winddriven circulation, which is con. Lecture 15 ocean circulation winddriven circulation. The thermohaline circulation is basically an overturning of the ocean in the meridionalvertical plane. Wind driven circulation drives movement in what part of the water column. The thc is known to play an important role for the climate variability knight et al. Chu1, charles sun2, and chenwu fan1 1 naval ocean analysis and prediction laboratory department of oceanography naval postgraduate school, monterey, california. The adjective thermohaline derives from thermoreferring to temperature and referring to salt content, factors which together determine the density of sea water. What are the differences between the thermohaline current and.
Ocean circulation and climate the thermohaline circulation. The meridional overturning circulation is associated to the abyssal circulation in the ocean. The thermohaline circulation thc affects the meridional atmospheric temperature gradient and therefore the atmospheric wind and the wind driven ocean circulation. Thermohaline circulation deep, driven by fluxes of heat and freshwater across the sea surface. 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. Thermohaline circulation fact sheet by stefan rahmstorf. Ocean circulation winddriven circulation thermohaline circulation global ocean surface currents subtropical midlatitude. Download citation thermohaline ocean circulation the thermohaline. Identify the ocean response freshwater storage and thermohaline circulation to the seasonal, interannual and the apparent 1015year cycle of atmospheric circulation modes proshutinsky and johnson, 1997 in the arctic. In the north atlantic region, it is characterised by an overturning circulation, the atlantic. Ocean circulation, and its related geophysical fluid dynamical principles, are now taught at graduate level in many earth and atmospheric science departments. Thus the vertical thermal structure depends on latitudinal surface temperature variations. Whitehead department of physical oceanography, woods hole oceanographic institution, woods hole, massachusetts 02543 key words. Stabilization of thermohaline circulation by winddriven and.
Despite of the importance of this circulation many fundamental questions have not been answered satisfacto. 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. Derivation is from thermofor heat and haline for salt, which together determine the density of sea water. Both winddriven chapter 10 and buoyancydriven circulations play an impor. The winddriven circulation wdc, in turn, affects the thc by the advection of salinity anomalies into deepwater formation sites. By combining direct estimates of ocean transport using current meters and. Further reading henderschott mc 1987 single layer models of the general circulation. This upper thermohaline circulation is of minor importance compared to the wind driven circulation. In contrast to the wind driven circulation, the thermohaline circulation is of global scale.
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. Thermohaline currents slow, deep currents that affect the rast bulk of sea water beneath the pynocline. This illustrates also the difficulty of separating wind. As opposed to winddriven currents and tides which are due to the gravity of moon and sun, the thermohaline circulation fig. Wind driven surface currents such as the gulf stream head polewards from the equatorial atlantic ocean, cooling all the while and eventually sinking at high latitudes forming north atlantic. The adjective thermohaline derives from thermoreferring to temperature and haline referring to salt content, factors which together determine the density of sea water. It provides a concise introduction to the dynamics and thermodynamics of oceanic general circulation. The effects of thermohaline circulation on winddriven. This is the first advanced textbook to discuss both winddriven and thermohaline driven processes two important aspects of largescale ocean circulation. This separation of the circulation into winddriven and thermohaline com ponents is.
As the name suggests, the winddriven circulation is. Effects of a winddriven gyre on thermohaline circulation variability claudia pasquero istituto di scienze dellatmosfera e del clima, cnr, turin, italy. Chapter 11 the thermohaline circulation of the ocean. The interaction between ocean circulation and climate change has been an active research frontier in earth sciences in recent years. What are the differences between the thermohaline current. In contrast to the wind driven part of the ocean circulation, the thermohaline circulation is driven by density gradients and extends from the surface to the abyssal ocean. In a winddriven world ocean circulation, the most prominent feature is no doubt the existence of a western boundary current, just like kuroshio in the pacific and gulf stream in the atlantic. Winds drive ocean currents in the upper 100 meters of the oceans surface. The thermohaline component of the overturning circulation operates on a mean zonal and meridional density gradient, which is partly maintained by the wind.
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. It is therefore fiendishly difficult to measure where upwelling occurs using current speeds, given all the other wind driven processes going on in the surface ocean. Determine and document the variability of fresh water storage and thermohaline circulation of the arctic ocean. The thermohaline circulation of the arctic ocean and the. On the driving processes of the atlantic meridional. These two components act simultaneously to drive the moc, the movement of seawater across basins and depths. It is that part of the ocean circulation which is driven by density differences as opposed to wind and tides. In contrast, thermohaline circulation is much slower, with a typical speed of 1 centimetre 0. 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. Thermohaline circulation thc is a part of the largescale ocean circulation that is driven by. In contrast to the winddriven currents, the thc is not confined to surface waters. The wind driven and thermohaline circulation of the baltic sea and the exchange with the north sea are investigated by using a coupled sea iceocean model of the baltic sea. The role of meridional density differences for a winddriven. The latter term was amended by the 1920s to thermohaline circulation, because water density in the ocean is.
Effects of a winddriven gyre on thermohaline circulation variability claudia pasquero istituto di scienze dellatmosfera e del clima, cnr, turin, italy eli tziperman environmental sciences, weizmann institute, rehovot, israel manuscript received 19 february 2002, in. Ocean circulation what drives the ocean circulation. Winddriven surface currents such as the gulf stream travel polewards from. An efficient thermohaline circulation seems to be restricted to the upper layers in tropical and subtropical regions. The latter is called the thermohaline circulation because of the role of heating, cooling, freshening, and salini. 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 the west. The atmospheric model is so developed that it represents the wind stress and the freshwater flux more realistically than existing energy balance models. On the wind driven and thermohaline circulation of the. In a wind driven world ocean circulation, the most prominent feature is no doubt the existence of a western boundary current, just like kuroshio in the pacific and gulf stream in the atlantic. The thermohaline circulation thc is the largescale ocean circulation associated with the transports of heat and salt wunsch,2002. Twoway feedback interaction between the thermohaline and. He thus elucidated the properties of winddriven and thermal circulation. 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. Four consecutive years, namely 1992, 1993, 1994 and 1995 including the latest major baltic inflow in january 1993 have been simulated.
Global ocean circulation can be divided into two major components. These deepocean currents are driven by differences in the waters density, which is controlled by temperature thermo and salinity haline. Buoyancy fluxes are the net effect of heat exchange and the freshwater exchange with the overlying atmosphere. There are two processes driving the circulation of the ocean. For an updated and more detailed version, see the following paper pdf, 3mb. Tidal currents winddriven currents thermohaline circulation ive seen the gulf stream mentioned as both a winddriven surface current and being part of the. Circulation of the ocean currentsocean currents the mass flow of watercurrents influence weather and climate, distribute nutrients, and scatter organisms1. 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. Tidal currents wind driven currents thermohaline circulation ive seen the gulf stream mentioned as both a wind driven surface current and being part of the. In reality is not independent on the wind circulation, but a representation of it can be obtained considering buoyancy effects alone. Decadal variability of the thermohaline ocean circulation.
Ocean processes into a model for the global overturning. View notes lecture 15 from oceanograp 1005 at louisiana state university. Functioning of the thermohaline circulation thc the conveyor belt fig. Variability of thermohaline circulation and freshwater. Study 22 terms thermohaline circulation flashcards quizlet. Ocean currents, global warming learn with flashcards, games, and more for free. Surface currents wind driven movements of water at or near the oceans surface2. In these regions the water is not forced down vertically but along constant density surfaces. Sea water density depends on temperature and salinity, hence the name thermohaline. It is organized in basinscale coherent current systems, which are globally connected through the southern ocean see e. Moves cold, salty deepsea water from higher to lower latitudes. The stability of the thermohaline circulation is investigated using an ocean general circulation model coupled to a simple atmospheric model.
Jan 29, 2015 the thermohaline current also called the global conveyor belt is a large scale ocean circulation system that is fueled by density differences between layers of water. Thermohaline circulation in a twolayer model with sloping. System that circulates water throughout the worlds oceans based on density and salinity. Figure 17 shows time mean juneseptember maps of total wind power combining geostrophic. The density differences are caused by changes in temperature thermo and sali. Thermohaline and wind driven currents interact with each other, and therefore cannot be truly separated. Winddriven surface currents such as the gulf stream. 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. The circulation of a global ocean model has been presented in temperature salinity coordinates for the first time. Winddriven circulation an overview sciencedirect topics. Variability and predictability of the ocean thermohaline circulation jochem marotzke max planck institute for meteorology mpim centre for marine and atmospheric sciences zmaw bundesstrasse 53, 20146 hamburg, germany with contributions by johanna baehr, felix landerer, johann jungclaus, maria paz chidichimo mpim, stuart cunningham, joel. The thermohaline circulation is a term for the global densitydriven circulation of the oceans. Thermohaline circulation of the oceans coastal wiki.
Nov 10, 2012 ocean circulation what drives the ocean circulation. Upwelling ecosystems are among the most productive in the world ocean, contributing 10% of the worlds primary productivity and 20% of the worlds fisheries catch. Variability and predictability of the ocean thermohaline. When depth to the picolene is shallow that means cold bottom h20 comes to the surface this is called upwelling. The thermohaline circulation of the arctic ocean and the greenland sea 289 the two loops recross the greenlandscotland ridge. This is the first advanced textbook to discuss both wind driven and thermohaline driven processes two important aspects of largescale ocean circulation. 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. However, ocean currents also flow thousands of meters below the surface. Therefore, merged hybrid approaches are required, using sets of coastal. 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.
In contrast to the quasihorizontal winddriven gyres, which are constrained to limited ranges of latitude and depth, the thermohalinedriven overturning cells are global in scale. The thermohaline current also called the global conveyor belt is a large scale ocean circulation system that is fueled by density differences between layers of water. Kuroshio, east australian current, subtropical gyre, winddriven circulation. The process of western intensification causes the gulf stream to be a. Because the ocean density is a function of temperature thermo and salinity haline, this circulation is referred to as the.
Learn vocabulary, terms, and more with flashcards, games, and other study tools. Stabilization of thermohaline circulation by winddriven. The thermohaline circulation is not the only one leading to descent of sea water into the deep ocean. It carries a substantial amount of heat and saline waters poleward, thereby altering the atmospheric circulation and sea ice. Thermohaline circulation disruption ocean research group. Detection of thermohaline structure and meridional. On the glacial and interglacial thermohaline circulation. The wind driven circulation wdc, in turn, affects the thc by the advection of salinity anomalies into deepwater formation sites. This is the first advanced textbook to discuss both winddriven and thermohalinedriven processes two important aspects of largescale ocean circulation. It is also called thermohaline circulation because is. The thermohaline circulation is a part of the largescale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. In contrast to the winddriven circulation, the thermohaline circulation is of global scale. The thermohaline circulation thc affects the meridional atmospheric temperature gradient and therefore the atmospheric wind and the winddriven ocean circulation. The resulting ths distills the ocean circulation into three distinct cells.
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