Eddy diffusivity ocean

Order-of-magnitude values for the vertical eddy diffusivity in the atmosphere and the ocean are shown in Fig. 4-15. The values for the viscous layers represent molecular diffusivities of a typical air molecule like N2. 

The inadequacy of the two-box model of the ocean led to the box-diffusion model (Oeschger et al, 1975). Instead of simulating the role of the deep sea with a well-mixed reservoir in exchange with the surface layer by first-order exchange processes, the transfer into the deep sea is maintained by vertical eddy diffusion. In... 

The deep ocean (6) is the portion of the water column from 300 m to 3300 m and is the largest ocean reservoir of dissolved P. However, since the deep ocean is devoid of light, this P is not significantly incorporated into ocean biota. Mostly, it is stored in the deep waters until it is eventually transported back into the photic zone via upwelling or eddy diffusive mixing. 

The intensified scavenging that occurs at ocean boundaries lowers the concentrations of dissolved °Th and Pa in deep waters several-fold relative to those found in open-ocean regions (Anderson et al. 1983b). Consequently, eddy diffusion and advection of deep waters from the open ocean toward ocean margins causes a net supply of dissolved Pa and °Th at a ( Taxs/ °Thxs) much greater than 0.093, and potentially as high as... 

In seawater, physical processes that transport water can also cause mass fluxes and, hence, are another means by which the salinity of seawater can be conservatively altered. The physical processes responsible for water movement within the ocean are turbulent mixing and water-mass advection. Turbulent mixing has been observed to follow Pick s first law and, hence, is also known as eddy diffusion. The rate at which solutes are transported by turbulent mixing and advection is usually much faster than that of molecular diffusion. Exceptions to this occur in locations where water motion is relatively slow, such as the pore waters of marine sediments. The effects of advection and turbulent mixing on the transport of chemicals are discussed further in Chapter 4. 

Thermohaline circulation Deep-water circulaUon caused by density differences created in the surface waters of polar regions. Cooling increases the density of the surface waters, which sink and then advect horizontally throughout the deep ocean. The water is returned to the sea surface by eddy diffusion. 

Benitez-Nelson C, Buesseler KO, Crossin G (2000) Upper ocean carbon export, horizontal transport, and vertical eddy diffusivity in the southwestern Gulf of Maine. Cont Shelf Res 20 707-736... 

Near-surface ocean nitrification at rates that are Hkely to exceed the upward eddy-diffusion of NOa from beneath the euphotic zone (e.g., Martin and Pondaven, 2006) has important implications for both the conceptual model of new vs. regenerated production (Dugdale and Goering, 1967) and for the... 

The first global CH4 budgets were compiled by Ehhalt (1974) and Ehhalt and Schmidt (1978), who used available published information to estimate emissions of CH4 to the atmosphere. They considered paddy fields, freshwater sources (lakes, swamps, and marshes), upland fields and forests, tundra, the ocean, and enteric fermentation by animals as biogenic sources. Anthropogenic sources included industrial natural gas losses and emission from coal mining, and were considered to be free. Observations of CH4 placed an upper limit on anthropogenic sources. Oxidation by the OH radical, as well as loss to the stratosphere by eddy diffusion and Hadley circulation, were presumed to be methane sinks. In spite of lack of data, this work correctly identified the major atmospheric sources and did... 

Broecker W. S., Cromwell J., and Li Y.-H. (1968) Rates of vertical eddy diffusion near the ocean floor based on measurements of the distribution of excess Rn. Earth Planet. Sci. Lett. 5, 101-105. 

The exchange of air between the northern and southern troposphere is caused to some extent by eddy diffusion in the equatorial upper troposphere, and by the seasonal displacement of the interhemispheric tropical convergence zone which lies north of the equator in July and south of the equator in January. The displacement is greatest in the region of the Indian Ocean, where the ITCZ is relocated over the Indian subcontinent in July. By tracing the transport of fission products from Chinese and French weapons tests, Telegadas (1972) has demonstrated the importance of monsoon systems for the interhemispheric air exchange in the Indian Ocean. 

The estimate for sea salt goes back to a detailed study of Eriksson (1959) of the geochemical cycles of chloride and sulfur. He calculated the rate of dry fallout of sea-salt particles from a vertical eddy diffusion model and then existing measurements of sea-salt concentrations over the ocean. This led to a global rate for dry deposition of 540 Tg/yr. Eriksson then argued that wet precipitation would remove a similar amount annually. It is now known, however, that wet precipitation is more effective than dry deposition in removing aerosol particles from the atmosphere, so that Eriksson s value must be an underestimate. The discussion in Section 10.3.5 suggests a flux rate for sea salt of about 5,000 Tg/yr. 

Ra distribution in the ocean has been modeled to derive eddy diffusivities and advection rates taking into consideration its input by diffusion from sediments, loss by radioactive decay, and dispersion... 

Recent measurements of cosmogenic (half-life, 14.3 days) and (half-life, 25.3 days) in surface ocean waters have opened up new possibilities of quantifying P-biodynamics with complementary information on eddy diffusivity in the waters, based on the cosmogenic Be (Table 3). A wealth of new P, P data have been added on the distribution of cosmogenic P and P in the surface ocean waters, and in plankton. 

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