Thermohaline circulation an overview sciencedirect topics. It is expected that the nonlinear ocean convection processes, large scale advective thc. These, however, are superimposed on the much more sluggish circulation driven by horizontal differences in temperature and salinitynamely, the thermohaline circulation. This is the first advanced textbook to discuss both winddriven and thermohaline driven processes two important aspects of largescale ocean circulation. The thermohaline circulation is a term for the global densitydriven circulation of the oceans. On the wind driven and thermohaline circulation of the. It is likely that the processes setting the 21year time scale have oceanic origins. Detection of thermohaline structure and meridional. As a consequence the surrounding seawater gets saltier, because when sea ice forms, the salt is left behind. The thermohaline circulation of the arctic ocean and the greenland sea 289 the two loops recross the greenlandscotland ridge. The adjective thermohaline derives from thermoreferring to temperature and haline referring to salt content, factors which together determine the density of sea water. Thermohaline circulation drives a globalscale system of currents called the global conveyor belt. Wind driven circulation whole scs 3 multieddy structure northern scs 4 rossby waves. Ive seen the gulf stream mentioned as both a winddriven surface current and being part of the thermohaline circulation, which is due to density differences.
It is found that the added interaction with the wdc adds interesting new classes of. Effects of a winddriven gyre on thermohaline circulation variability claudia pasquero istituto di scienze dellatmosfera e del clima, cnr, turin, italy. The density differences are caused by changes in temperature thermo and sali. Driven by density and salinity differences heating and cooling at the surface upwelling and downwelling and freshwater evaporationsea ice formation cause water to move. 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. Ocean circulation and climate the thermohaline circulation. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The general circulation of the oceans consists primarily of the winddriven currents. The atmospheric model is so developed that it represents the wind stress and the freshwater flux more realistically than existing energy balance models. Buoyancy fluxes are the net effect of heat exchange and the freshwater exchange with the overlying atmosphere. The conveyor belt begins on the surface of the ocean near the pole in the north atlantic. Unlike the faster winddriven circulation, which is con. Pdf indian ocean circulation and climate variability researchgate.
Both winddriven chapter 10 and buoyancydriven circulations play an important role in meridional ocean heat transport. 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. Driven largely by the deepwater formation in the labrador and nordic seas, the amoc is the main mechanism for northward heat transport in the atlantic ocean. Thermohaline effects in the ocean circulation and related. Atlantic moc a major feature of the basinscale circulation in the north atlantic is the existence of the robust amoc. Variability and predictability of the ocean thermohaline. Stabilization of thermohaline circulation by winddriven.
It is because of thermohaline forcing that winddriven currents are relegated to the upper ocean in unstratified water they would extend to the bottom. The thermohaline circulation thc affects the meridional atmospheric temperature gradient and therefore the atmospheric wind and the winddriven ocean circulation. The meridional overturning circulation is associated to the abyssal circulation in the ocean. In contrast, thermohaline circulation is much slower, with a typical speed of 1 centimetre 0. Wind driven circulation drives movement in what part of the water column. Thermohaline circulation fact sheet by stefan rahmstorf. In contrast to the winddriven currents, the thc is not confined to surface. 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.
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. On the glacial and interglacial thermohaline circulation. As the seawater gets saltier, its density increases, and it. Ocean circulation, and its related geophysical fluid dynamical principles, are now taught at graduate level in many earth and atmospheric science departments. Conceptual models of the winddriven and thermohaline. The adjective thermohaline derives from thermoreferring to temperature and referring to salt content, factors which together determine the density of sea water.
In this chapter we provide a broad overview of our conceptual understanding of the winddriven circulation, the thermohaline circulation, and their transient behavior. 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. Study 22 terms thermohaline circulation flashcards quizlet. Determine and document the variability of fresh water storage and thermohaline circulation of the arctic ocean. On the glacial and interglacial thermohaline circulation and the associated transports of heat and freshwater m. The interaction between ocean circulation and climate change has been an active research frontier in earth sciences in recent years. Ocean circulation winddriven and thermohaline processes r. It provides a concise introduction to the dynamics and thermodynamics of oceanic general circulation. 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.
Huang the circulation of the oceans is a fundamental process in the movement of energy and materials around the planet. A windinduced thermohaline circulation hysteresis and. Effects of a winddriven gyre on thermohaline circulation. 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 thermohaline circulation reaches down to the seafloor and is. Eastern mediterranean,inocean processes in climate dynamics. Twoway feedback interaction between the thermohaline. South china sea circulation and thermohaline structure. The thermohaline circulation is basically an overturning of the ocean in the meridionalvertical plane. As the name suggests, the winddriven circulation is driven by. The thermohaline circulation of the arctic ocean and the. 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. Winddriven circulation an overview sciencedirect topics. This is the first advanced textbook to discuss both winddriven and thermohalinedriven processes two important aspects of largescale ocean circulation.
Winddriven and thermohaline circulations can thus be disentangled to some extent by models, which helps us understand what aspects of the circulation. 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. Thermohaline circulation deep, driven by fluxes of heat and freshwater across the sea surface. Ocean circulation what drives the ocean circulation. It is also called thermohaline circulation because is. The thermohaline circulation is not the only one leading to descent of sea water into the deep ocean. One therefore wonders what role the wind plays in the dynamics of the thc. Thermohaline and wind driven currents interact with each other, and therefore cannot be truly separated.
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. 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 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. We present an analysis of the interaction between wind. For an updated and more detailed version, see the following paper pdf, 3mb.
The winddriven circulation wdc, in turn, affects the thc by the advection of salinity anomalies into deepwater formation sites. Pdf in recent years, the indian ocean io has been discovered to have a much larger impact on. Chapter 11 the thermohaline circulation of the ocean. 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. Thus the vertical thermal structure depends on latitudinal surface temperature variations. The coupled model can reproduce the realistic deep ocean. Thermohaline circulation disruption ocean research group. In reality is not independent on the wind circulation, but a representation of it can be obtained considering buoyancy effects alone. Get an answer for what are the differences and similarities between thermohaline and surface currents. Ocean circulation winddriven circulation thermohaline circulation global ocean surface currents subtropical mid. Does the gulf stream belong to both classifications of currents. A reading of the literature on climate and the ocean suggests at least seven different, and inconsistent, definitions of the term thermohaline circulation. It is estimated that any given cubic meter of water takes about.
The effects of thermohaline circulation on winddriven. Whitehead department of physical oceanography, woods hole oceanographic institution, woods hole, massachusetts 02543 key words. Ocean circulation winddriven and thermohaline processes. In the earths polar regions ocean water gets very cold, forming sea ice. But although thermohaline circulation is not measurable, the concept is. The latter is called the thermohaline circulation because of the role of heating, cooling, freshening, and salini. As opposed to winddriven currents and tides the latter are due to the gravity of moon and sun, the thermohaline circulation often abbreviated as thc is that part of the ocean circulation which is driven by fluxes of heat and freshwater across the sea surface and subsequent interior mixing of heat and salt hence the name thermohaline. The stability of the thermohaline circulation is investigated using an ocean general circulation model coupled to a simple atmospheric model. This is the first advanced textbook to discuss both winddriven and thermohalinedriven processes two. Variability of thermohaline circulation and freshwater. Derivation is from thermofor heat and haline for salt, which together determine the density of sea water. A simplified model is used to study the possible effects of the horizontal upperocean winddriven circulation wdc on the variability of the overturning meridional circulation driven by buoyancy fluxes. In these regions the water is not forced down vertically but along constant density surfaces.