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Topic: Thermohaline

  Thermohaline circulation - Wikipedia, the free encyclopedia
The thermohaline circulation is a term for the global density-driven circulation of the oceans.
Insofar as the thermohaline circulation governs the rate at which deep waters are exposed to the surface, it may also play an important role in determining the concentration of carbon dioxide in the atmosphere.
Large influxes of low density meltwater from the Greenland ice sheet is thought to have led to a disruption of deep water formation and subsidence in the extreme North Atlantic and caused the climate period in Europe known as the Younger Dryas.
en.wikipedia.org /wiki/Thermohaline_circulation   (1424 words)

 Thermohaline Circulation - Fact Sheet by Stefan Rahmstorf
As opposed to wind-driven currents and tides (which are due to the gravity of moon and sun), the thermohaline circulation (Fig.
It has been shown that in the long-term equilibrium the strength of the thermohaline circulation in models depends on the turbulent mixing coefficient [7], and that the energy required for this turbulent mixing comes to a large extent from the moon via tidal currents ([8]).
Robinson, A. and H. Stommel, The oceanic thermocline and the associated thermohaline circulation.
www.pik-potsdam.de /~stefan/thc_fact_sheet.html   (2365 words)

 The Environmental Literacy Council - The Great Ocean Conveyer Belt
In the oceans, a great current called the thermohaline circulation, which carries as much water as 100 Amazon Rivers and is a crucial factor in shaping the Earth's climate, is also driven in part by gravity.
But because of the thermohaline circulation, the French Mediterranean region is temperate, even though it lies at about the same latitude as New England.
Scientists are examining the possibility that a change in thermohaline circulation was responsible for the Little Ice Age, an unusually cold period that lasted from the 1400s to the mid-1800s.
www.enviroliteracy.org /article.php?id=545&print=1   (540 words)

 GeoSci 245: The Thermohaline Circulation
Whether or not the thermohaline circulation will be affected by by a warming climate strongly depends on the future distributions of temperature, evaporation, and precipitation over the North Atlantic.
The heat transported in the oceans is done both by the wind-driven and thermohaline circulations.
The first modern theory of the abyssal thermohaline circulation was developed in a series of papers by Stommel (1958) and Stommel and Arons (1960a,b).
geosci.uchicago.edu /%7Egidon/geosci245/thermohal/thermohaline.html   (1980 words)

 Shutdown of circulation pattern could be disastrous, researchers say
"If the thermohaline shutdown is irreversible, we would have to work much harder to get it to restart," said Michael Schlesinger, a professor of atmospheric sciences at the University of Illinois at Urbana-Champaign and a co-author of a report presented at the American Geophysical Union meeting in San Francisco.
The thermohaline circulation is driven by differences in seawater density, caused by temperature and salinity.
They found that the thermohaline circulation shut down irreversibly in the uncoupled model simulation, but reversibly in the coupled model simulation.
www.eurekalert.org /pub_releases/2004-12/uoia-soc121404.php   (604 words)

 Atlantic Thermohaline Circulation (D3)   (Site not responding. Last check: 2007-10-09)
Furthermore, as the transport of carbon by the Atlantic thermohaline circulation plays a significant role in the global carbon budget, thermohaline circulation variations may contribute to changes in the oceanic carbon transport and hence indirectly affect the atmospheric CO content.
Understanding the physics of thermohaline circulation variability, including documentation of observed penetration of the anthropogenic tracer signal into the deep ocean, has bearings on all three of the Anthropogenic Climate Change foci, in particular it is related to A1.
Schmitz, W.J., 1995: On the interbasin-scale thermohaline circulation, Rev. Geophys., 33, 151-173.
www.clivar.com /publications/other_pubs/iplan/iip/pd3.htm   (6808 words)

 Role of the Ocean Conveyor Belt as a Cause of Global Multidecadal Climate
A faster thermohaline circulation causes larger amounts of warm upper ocean mass to be advected to higher latitudes.
This inverse association between the rate of salt buildup and thermohaline strength is part of the explanation for the thermohaline's back-and-forth multi-decadal variations over many thousands of years as inferred by recent Greenland ice-core measurements.
Because there are no direct measures of thermohaline strength, it is suggested on the bottom diagram of Figure 6 that changes in the parameters which the thermohaline circulation influences be used to estimate its strength.
www.aoml.noaa.gov /phod/acvp/gray.htm   (1737 words)

 1.1. Conveyor Belt and the Thermohaline Circulation   (Site not responding. Last check: 2007-10-09)
The Broecker [1987] and Gordon [1986] descriptions of the thermohaline circulation as a conveyor belt graphically emphasized the interconnections amongst the waters of the world's oceans.
The thermohaline circulation in the Atlantic consists of two parts: 1) northward flow of warm water (the upper limb) (some of this water contributes to the production of new deep water in the high latitudes of the North Atlantic); and 2) southward export of newly formed deep water (Figure 1) (the lower limb).
The thermohaline circulation differs from the wind-driven circulation in that the former is forced by density differences that are controlled by changes in temperature and salinity.
www.agu.org /revgeophys/fine00/node2.html   (241 words)

 NaturalSCIENCE Cover Story: A New European Ice Age?
This thermohaline circulation, or ocean overturning, is driven by comparatively small differences in sea water density, which depend on a balance between sea water cooling and salinity fluctuations arising from freshwater input (precipitation and river run-off) in the North Atlantic.
Stocker and Schmittner's study concludes that the severity of a disruption in thermohaline circulation brought on by global warming will depend on the rate of warming and, hence, on the rate of greenhouse gas emissions.
The consequences of a shut-down in the Atlantic Ocean thermohaline circulation are uncertain.
www.naturalscience.com /ns/cover/cover5.html   (673 words)

 The Day After Tomorrow: Could Abrupt Global Warming Really Happen?
Global warming is expected to increase ocean temperatures and to increase the flow of freshwater into the ocean through precipitation, run-off, and melting of glaciers.  Many climate models have projected that increased surface ocean temperatures and reduced salinity could slow the thermohaline circulation.
A few models have projected a complete shutdown of the thermohaline circulation in the case of severe global warming, but this is being debated by the scientific community.
Without the thermohaline circulation, not as much heat would be transported from the tropics to the North Atlantic region.
www.pewclimate.org /dayaftertomorrow.cfm?source=google   (1172 words)

 The role of the thermohaline circulation in abrupt climate change : Nature
The possibility of a reduced Atlantic thermohaline circulation in response to increases in greenhouse-gas concentrations has been demonstrated in a number of simulations with general circulation models of the coupled ocean−atmosphere system.
But it remains difficult to assess the likelihood of future changes in the thermohaline circulation, mainly owing to poorly constrained model parameterizations and uncertainties in the response of the climate system to greenhouse warming.
The palaeoclimate data and the model results also indicate that the stability of the thermohaline circulation depends on the mean climate state.
dx.doi.org /10.1038/415863a   (258 words)

 Abrupt Climate Change Paleo Perspective Story- Mechanisms- Thermohaline & Vegetation   (Site not responding. Last check: 2007-10-09)
Scientists have found evidence in paleoclimate records that the Younger Dryas was caused by a change in the ocean thermohaline circulation.
The thermohaline circulation is a global ocean circulation.
Often called a conveyor belt because of its northward transport at the surface, and southward return flow in the abyss in the Atlantic, the ocean thermohaline circulation system is a slow, three-dimensional pattern of flow involving the surface and deep oceans around the world.
www.ncdc.noaa.gov /paleo/abrupt/story3.html   (619 words)

 Thermohaline circulation is a density driven flow of water generated by differences in salinity or temperature.   (Site not responding. Last check: 2007-10-09)
Thermohaline circulation is a density driven flow of water generated by differences in salinity or temperature.
Water at the surface is exposed to more rapid changes in salinity through evaporation or precipitation and in temperature through cooling or heating.
Inter-ocean basin circulation and exchange between surface and deep water appears largely driven by waters of the North Atlantic. /faculty/webpages/stodd/oceanweb/oceanography/Oceanlectures02/Lecture6/sld020.htm   (161 words)

 Theoretical Climate Dynamics - 3D Ocean Circulation
The study of the oceans' low-frequency variability, however, still has to rely to a large extent on models, due to the inhomogeneity and temporal shortness of the data sets; short-term predictability on synoptic time scales, on the other hand, can be studied using data assimilation.
Basin-scale oceanic motion is dominated by wind-driven (horizontal) and thermohaline (vertical) circulations.
The figure shows two snapshots of the (zonally averaged) meridional streamfunction for an interdecadal oscillation using the box GFDL's modular-ocean model in a North Atlantic "box" geometry; the two panels show the strong (right) and weak (left) extremes of the overturning (from Chen and Ghil, 1995, 1996).
www.atmos.ucla.edu /tcd/RESEARCH/research_ocn.html   (664 words)

 Information about Ling-Qi Zhang   (Site not responding. Last check: 2007-10-09)
Three simple models on ocean thermohaline circulation are investigated for the possibility of ocsillatory limit cycle behaviour under conditions of steady forcing.
One steady state with fast thermohaline circulation, which is driven by cooling/heating, resembles the present-day thermohaline circulation.
Stommel (1986) and Welander (1982) found that there is a thermohaline oscillation in their vertical models with turbulent mixing.
www.phys.ocean.dal.ca /people/po/Zhang_Lingqi.html   (227 words)

 NPG - Abstract
In this paper the effect of the synoptic scale variability is analyzed using a simple atmosphere-ocean coupled model.
Results show that synoptic scale frequency variability on longitudinal heating contrast between land and sea can produce a collapse of thermohaline circulation when a threshold of noise is overcome.
This result is significant because if synoptic scale variability in the next century increases due to the climatic change an increment of the probability of this collapse could be produced.
www.copernicus.org /EGU/npg/12/4/435.htm   (137 words)

 Thermohaline Circulation
The Thermohaline Circulation (THC) is the part of the large-scale global circulation which is driven by horizontal density gradients (to be distinguished from the basin gyres which are driven by the wind).
In a small number of regions of the ocean, notably the Labrador and Nordic Seas in the North Atlantic, and the Ross and Weddell Seas off Antarctica, wintertime cooling creates extremely dense waters, which sink to the ocean bottom; surface waters move poleward to replace them.
To be able to predict the climate with any confidence we therefore need to understand firstly what sets the strength of the thermohaline circulation, and secondly how it varies.
www.soc.soton.ac.uk /JRD/csp1_th3/index.php   (255 words)

 Thermohaline circulation   (Site not responding. Last check: 2007-10-09)
The thermohaline circulation is a term for the global density -driven circulation of the oceans.
However, because this thermohaline upwelling is so widespread and diffuse, its speeds arevery slow even compared to the movement of the bottom water masses.
It is therefore fiendishly difficult to measure whereupwelling occurs using current speeds, given all the other wind-driven processes going on in the surface ocean.
www.therfcc.org /thermohaline-circulation-200902.html   (728 words)

 Meeresgeologie im Internet: Thermohaline Zirkulation [www.meeresgeo-online.de]   (Site not responding. Last check: 2007-10-09)
Da diese Dichteunterschiede durch Variationen der Temperatur und Salinität bedingt sind, werden diese Strömungsmuster auch thermohalin genannt.
Sie wirken als Ausgleich dieser Druckunterschiede und stehen damit in einem Gleichgewicht mit den Ursachen dieser Dichtedifferenzen.
Thermohaline Strömungen sind im Vergleich zu windgesteuerten Strömungen langsam, aber nicht nur auf den obersten Bereich der Wassersäule beschränkt.
www.meeresgeo-online.de /inhalt/thermohalin.php?js=&sg=12   (422 words)

 Shutdown of circulation pattern could be disastrous, researchers say
Michael Schlesinger, professor of atmospheric sciences, and research specialist Natasha Andronova and colleagues have co-written a report presented at the American Geophysical Union meeting that says if global warming shuts down the thermohaline circulation in the North Atlantic Ocean, the result could be catastrophic climate change.
CHAMPAIGN, Ill. — If global warming shuts down the thermohaline circulation in the North Atlantic Ocean, the result could be catastrophic climate change.
“If the thermohaline shutdown is irreversible, we would have to work much harder to get it to restart,” said Michael Schlesinger, a professor of atmospheric sciences at the University of Illinois at Urbana-Champaign and a co-author of a report to be presented at the American Geophysical Union meeting in San Francisco, Dec. 13-17.
www.news.uiuc.edu /news/04/1213climate.html   (664 words)

 ASTTEX: Agulhas-South Atlantic Thermohaline Transport Experiment
Mass and thermohaline fluxes and their connection to global climate are still the subject of controversy.
An additional element of uncertainty is added by the extreme variability in size, strength and thermohaline signature of individual Agulhas eddies, which are dissimilar enough that some were at one time ascribed an origin in the Brazil Current (e.g., Smythe-Wright et al., [1996]).
A similar technique, ETTA (Enhanced Thermohaline Transport Analysis) was developed by Dr. Byrne in her doctoral thesis and uses historic hydrography and altimetric sea surface height in concert with acoustic travel time to distinguish thermohaline anomalies in the water column.
gyre.umeoce.maine.edu /ASTTEX   (666 words)

 Simulation of the Bohai Sea Circulation and Thermohaline Structure Using COHERENS Model - Storming Media
Abstract: The goals of this work are to simulate the Bohai Sea circulation and thermohaline structure and to Investigate the physical mechanisms using the Coupled Hydrodynamical-Ecological Model for Regional and Shelf Seas (COHERENS) with realistic bottom topography and coastal geometry.
The thermohaline structure is vertically stratified during the summer monsoon.
The experiments show that the surface wind effect is the major forcing to drive the surface currents and the thermohaline structure, the thermohaline flux is the important driving force for the thermal structure, and the tidal mixing is responsible for the deep layer characteristics.
www.stormingmedia.us /13/1335/A133504.html   (269 words)

 IUGG 2003 Scientific Program   (Site not responding. Last check: 2007-10-09)
The later motivates a critical revision of existing theories for thedynamic/topographic control and relative contributions to CIW formation ofdifferent regions of the Black Sea.
The correlation between thermohaline andtracer fields, the latter including Chlorofluorocarbon (CFC) concentrationsmeasured during the1988 R/V Knorr cruise, is also analyzed.
Part of the studyaddresses the control of the fresh water balance on the vertical penetrationpatterns, including the present day thermohaline conveyor belt, as well asextreme cases which might have existed in the ancient Black Sea.
www.olympus.net /IAPSO/abstracts03/P02/04/016652-1.html   (239 words)

 Climate Timeline Tool: About CTL
Driven by the sun's heat absorbed by tropical oceans and impacted by variations in salt content in the water, the Thermohaline Circulation or THC is a powerful force on the world's climate system.
As heat from the tropics is carried by the Gulf Stream into the North Atlantic where it is vented into the atmosphere, a deep convection of ocean waters is caused by surface cooling, with the flow of water then sinking to depths and then upwelling back to the surface at lower latitudes.
As we examine in Climate Science 10,000, scientists are looking at how influxes of freshwater into the North Atlantic can impact the THC.
www.ngdc.noaa.gov /paleo/ctl/thc.html   (256 words)

 IfM Kiel: Sonderforschungsbereich 460: Overview   (Site not responding. Last check: 2007-10-09)
The main goal of SFB 460 is to investigate fluctuations of water mass formation and transport processes in the subpolar North Atlantic (Fig.
Approximately two thirds of the net transport of North Atlantic Deep Water originate in this area, either through entrainment of near-bottom overflow water masses from the Iceland Basin and Norwegian Sea, or as a result of deep wintertime convection processes in the Labrador Sea and ultimately Irminger Sea.
Despite significant international efforts in modeling and observing this region, the relevant thermohaline processes and circulation patterns of this area remain insufficiently understood.
www.ifm.uni-kiel.de /allgemein/research/projects/sfb460/sfb460-e.htm   (877 words)

 Thermohaline circulation   (Site not responding. Last check: 2007-10-09)
The major water masses in the deep ocean are differentiated by their temperature and salinity.
These properties determine their relative densities, which in turn drive deep thermohaline circulation of the oceans.
Modified from figure courtesy of Dr. Steve Hovan, Indiana University of Pennsylvania.
seis.natsci.csulb.edu /rbehl/NADW.htm   (79 words)

 La circulation thermohaline en Antarctique   (Site not responding. Last check: 2007-10-09)
Le moteur de la circulation thermohaline est la variation de densité des eaux, induite par des changements de température et de salinité.
Mais cette convection thermohaline antarctique est moins intense et efficace que son équivalent Nord Atlantique.
C'est parce qu'il y a circulation thermohaline, et plong√©e d'eau, que le Gulf Stream remonte vers le nord pour remplacer l'eau qui plonge, et réciproquement.
www.ens-lyon.fr /Planet-Terre/Infosciences/Climats/Ocean/Articles/thermohal-Antar.htm   (1912 words)

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