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2 edition of Impacts of double-diffusive processes on the thermohaline circulation found in the catalog.

Impacts of double-diffusive processes on the thermohaline circulation

Jubao Zhang

Impacts of double-diffusive processes on the thermohaline circulation

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Published by Massachusetts Institute of Technology, Woods Hole Oceanographic Institution, Joint Program in Oceanography/Applied Ocean Science and Engineering in Woods Hole, Mass .
Written in English

    Subjects:
  • Thermoclines (Oceanography).,
  • Ocean circulation.

  • Edition Notes

    Statementby Jubao Zhang.
    SeriesMIT/WHOI -- 98-17., MIT/WHOI (Series) -- 98-17.
    ContributionsMassachusetts Institute of Technology., Woods Hole Oceanographic Institution.
    The Physical Object
    Pagination157 p. :
    Number of Pages157
    ID Numbers
    Open LibraryOL15537030M

    The importance of the Atlantic thermohaline circulation (THC) to climate and climate change stems from its two unique properties: its large northward heat transport and nonlinear dynamical behavior. Here we define the THC as the part of the ocean circulation which involves warm, saline surface water flowing. The important sources include (1) flow over topography, (2) convection and fronts, and (3) jet stream instability and adjustment processes. Note that mountain waves are parameterized with zero phase speed, so they can only slow the winds. A full spectrum of waves is needed to model a circulation like the quasi-biennial oscillation (QBO).


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Impacts of double-diffusive processes on the thermohaline circulation by Jubao Zhang Download PDF EPUB FB2

Impacts of Double-diffusive Processes on the Thermohaline Circulation by Jubao Zhang B. University of Science and Technology of China, Hefei, China, () M. Inst. of Atmos. Phys.Chinese Academy of Sciences, Beijing, China, () Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the.

Double-diffusive processes are studied and parameterized, and their impacts on the oceanic thermohaline circulation are investigated by single-hemisphere numerical models and scaling analysis.

Scaling analysis on the thermohaline circulation has been done under three types of Cited by: 2. Thermohaline circulation begins in the Earth's polar regions.

When ocean water in these areas gets very cold, sea ice forms. The surrounding seawater gets saltier, increases in density and sinks.

Winds drive ocean currents in the upper meters of the oceans surface. However, ocean currents also flow thousands of meters below the surface.

fecting the global thermohaline circulation. A simple. estimate (R. Schmittpersonal communication) any non-double-diffusive mixing processes, effects is associated with the.

Since collapse of the thermohaline circulation has occurred rapidly in the past, has dramatic impacts on climate, and is predicted to be a possible outcome of future greenhouse warming, it behooves us to seek a better understanding of the double-diffusive mixing processes in the ocean.

Double diffusive fluxes of heat and salt, which differ by two orders of magnitude, have a significant impact on the thermohaline circulation and oceanic heat transport. Small-scale double-diffusive structures can be coupled with large-scale circulation by strong vertical (T S) gradients and current shears created by large-scale lateral.

Export Figures View in gallery Meridional overturning streamfunction (contours) and zonal average temperature (shading) for restoring BC experiments, (a) 1H and (b) 2H, ΔT N 0. Overturning contours are 2 Sv apart; isotherms are at, and of ΔT S 30°C.

In this and all subsequent plots of overturning streamfunction, dashed, solid, and dotted contours. System that circulates water throughout the world's oceans based on density and salinity.

Moves cold, salty deep-sea water from higher to lower latitudes; creates warm, less-salty shallow current and cold, salty deep-sea current.

Transfers heat from the equator to EuropeNorth America, causing temperate climate. Thermohaline Circulation. Oceanography Ch 8 study guide by Maynard_Binaday includes 29 questions covering vocabulary, terms and more.

Quizlet flashcards, activities and games help you improve your grades. For instance, the volume-averaged diffusivities in the double-diffusive experiment are. (K ¯ T d d, K ¯ S d d) (, ) × 10 5 m 2 s.and these values are similar to the turbulent diffusivity (Equation (26)).

Figure 8 a presents the mean diapycnal velocity evaluated at various isopycnal surfaces. One such process is double-diffusive convection, which is triggered by the different molecular diffusion rates of heat and salt and utilises the potential energy stored in the unstably stratified.

Since doublediffusive processes by themselves would erode vertical gradients of temperature and salinity over time, a permanent resupply of heat and salt to the warm and salty water mass above, and a permanent thermohaline sink for the colder and fresher water mass below, are required to maintain the staircase structure.

Large-scale circulation and production of stratification: effects of wind, geometry and diffusion. Journal of Physical Oceanogra The Thermohaline Circulation (THC): Concept, Structure and Climatic Effect Concept and structure The Thermohaline Circulation (THC) is a global-scale ocean circulation driven by the.

Abstract. The effect of double-diffusive mixing on the general circulation is explored using the GFDL MOM2 model. The motivation for this comes from the known sensitivity of the thermohaline circulation to the vertical diffusivity and the earlier work of Gargett and Holloway, who studied the effects of a simple nonunity ratio between heat and salt diffusivities in a GCM.

  In this study, the thermohaline evolution of the WMT signal is analyzed in detail. Using a 1-D diffusion model sensitive to double-diffusive mixing phenomena, the contribution to the heat and salt budgets of the deep Western Mediterranean in terms of ventilation and diffusive transference from the intermediate layers above is disentangled.

Notable exceptions to this rule are problems where the non- linearity of the density dependence on temperature is significant and the so-called double diffusive processes, which depend for their functioning on the widely different molecular diffusivities for salt and heat content in.

Perseus Books, pp. Search Google Scholar Focusing on the internal oscillations of the thermohaline circulation (THC) (), testing the impact of double diffusive processes, were able to obtain oscillations in a 2 × 2 box model and stressed the sensitivity to differential mixing of temperature and salinity.

The nearly linear increase of temperature and conductivity with depth, observed after the eruption, is still prominent, except for the effects caused by double-diffusive convection below the.

Influence of thermohaline circulation on the duration and demise of peak interglacial climate in the circum-North Atlantic region.

EOS, 79 (), p. S View Record in Scopus Google Scholar. McManus, D. Oppo, J. Cullen. A million year record of millennial-scale climate variability in the North Atlantic.

can define the circulation, can its control-ling factors be sensibly discussed. A reading of the literature on climate and the ocean suggests at least seven dif-ferent, and inconsistent, definitions of the term thermohaline circulation: 1) the circulation of mass, heat, and salt; 2) the abyssal circulation; 3) the meridional overturning.

The thermohaline circulation. The main outline of the thermohaline circulation was seen in Chapter 1 (§, Figs. and ). In regions where surface water is made denser through evaporative salinification, winter cooling, salt rejection during sea-ice formation or sub-ice shelf freezing, sufficiently extreme conditions can result in.

Changes in the thermohaline circulation (THC) due to increased CO2 are important in future climate regimes. Using a coupled climate model, the Parallel Climate Model (PCM), regional responses of the THC in the North Atlantic to increased CO2 and the underlying physical processes are studied here.

The Atlantic THC shows a. Conversely, diffusive processes play a minor role in determining the bottom layer thermohaline variability. The interpretation of the experimental findings, supported by the numerical simulations, suggests that similar dynamics might be observed in other basins characterized by similar bathymetric and hydrodynamic features.

- Thermohaline circulation affects all the ocean's water - The movement of water due to different densities is thermohaline circulation - The ocean is density stratified, with the denser water at the bottom-Deep water forms in polar regions via two different processes: Antarctic Bottom Water (AABW) and North Atlantic Deep Water (NADW).

Building on the theory, it then explains the dynamics of structures resulting from double-diffusive instabilities, such as the little-understood phenomenon of thermohaline staircases.

The book. 1. Introduction [2] The Atlantic thermohaline circulation [Rahmstorf, ] is an important feature of the climate system, since it is responsible for most of the northward heat transport in the North Atlantic (up to 10 15 W) [Ganachaud and Wunsch, ].

Model experiments and paleoclimatic data suggest that changes in thermohaline circulation can have a major impact on climate. In the presence of horizontal variations in temperature and salinity along density surfaces, as is common at oceanic fronts, the small-scale double-diffusive processes can drive horizontal motions on 10m vertical scales.

These intrusive instabilities arise because of the buoyancy flux convergences due to the mixing by salt fingers and. Schematic of the generalized Sakai and Peltier model. Salinity in each box diffuses between boxes and a larger background box or bath. The thermohaline circulation is modeled by a unidirectional (possibly nonlinear) transport of salinity from box 1 to box 2 to box 3 superimposed onto the diffusive exchange.

In oceans, about 44 regions display double-diffusive process (You, ). In certain regions, e. the North Atlantic, the double-diffusive mixing is several times stronger than the turbulence. The thermohaline circulation 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.

The term thus refers to a driving mechanism. Important features of the thermohaline circulation are deep water formation. Zhang, J.Impacts of double-diffusive processes on the thermohaline circulation. thesis, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, pp.

Zhang, J.R W. Schmitt, and R X. Huang, The relative influence of diapycnal mixing and hydrologic forcing on the stability of the. ows of the thermohaline circulation in single hemispheric models and to assess their linear stability. In this paper, we consider ows which are forced by a merid-ional temperature gradient in a single hemispheric idealized basin (Greatbatch and Zhang, ); the model is described in section 2.

Within this model, we show that. Freshwater imbalances in the deep convection regions of the polar and subpolar regions of the North Atlantic result in alternating multiple equilibrium states of the global thermohaline vertical circulation - the conveyor belt [53]. On the other hand, large scale modeling relies heavily on the parametrization of subgrid processes.

View raw image; Potential temperature and salinity sampled at 2-db intervals at Oden 91 station 17 (88°N, 85°E) in Amundsen Basin, after Anderson et al.

Approximate depth ranges having background gradients in the diffusive convective, salt fingering, and double-diffusively stable regimes are indicated, based on a subjective removal of the effects of intrusions from the.

The thermohaline circulation is a very slow moving current that can be difficult to distinguish from general ocean circulation. Therefore, it is difficult to measure or simulate. This version of the visualization combines the Earth look of the original thermohaline visualization with the new thermohaline flow field generated for the Science On.

myr and will drive a thermohaline circulation having the following characteristics: high salinity shelf water (at øC), formed by winter sea-ice production in the open Ross Sea, flows along the seabed toward the tidal mixing fronts below the ice shelf; and meltwater (at øC), produced in the well.

Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo-referring to temperature and -haline referring to salt content, factors which together determine the density of sea water.

Wind-driven surface currents (such as the Gulf Stream. Most of Earths water is stored in the ocean. Although 40 percent of Earths population lives within, or near coastal regions- the ocean impacts people everywhere.

Without the ocean, our planet would be uninhabitable. This animation helps to convey the importance of Earths oceanic processes as one component of Earths interrelated systems. Collapse and rapid resumption of atlantic meridional circulation linked to deglacial climate changes.

Nature, (), April [4] Michael Vellinga and RichardA Wood. Impacts of thermohaline circulation shutdown in the twenty­first century. Abrupt variations of the past climate may well be linked to different pattern of the ther- mohaline circulation (THC). The sensitivity of the THC to atmospheric and oceanic factors is therefore of interest.

Effects on the THC of both Atlantic-to-Pacific moisture transport and Bering Strait's throughflow are studied using a frictional-geostrophic, three-dimensional, coarse res- olution ocean. In the north Atlantic, the thermohaline circulation consists of warm surface water flowing northward and cold deepwater flowing southward, resulting in a net poleward transport of heat.

The surface water sinks in highly restricted sinking regions located in high latitudes. Source: ACIA Glossary.Title: Thermohaline Circulation Author: e Last modified by: Hrsb Created Date: 12/15/ PM Document presentation format: On-screen Show – A free PowerPoint PPT presentation (displayed as a Flash slide show) on - id: 5bf74c-NTQ1Y.Abstract.

The North Atlantic is a peculiarly convective ocean. The convective renewal of intermediate and deep waters in the Labrador Sea and Greenland/Iceland Sea both contribute significantly to the production and export of North Atlantic Deep Water, thus helping to drive the global thermohaline circulation, while the formation and spreading of degree water at shallow-to-intermediate.