Oceans mixing

Figure 5 Schematic illustration of the sources and sinks of DMS in the marine boundary layer of the atmosphere and the oceanic mixed layer (Taken from Bigg," with permission of Cambridge University Press)...

Gammon, R. H., Cline, J. and Wisegarver, D. (1982). Chlorofluoromethanes in the Northeast Pacific Ocean measured vertical distributions and application as transient tracers of upper ocean mixing. /. Geophys. Res. 87, 9441-9454. 

Measurements of radionuclides in seawater have been used to study a variety of processes, including ocean mixing, cycling of materials, and carbon flux (by proxy). These measurements provide information on both process rates and mechanisms. Because of the unique and well-understood source functions of these elements, models of radionuclide behavior have often led to new understanding of the behavior of other chemically similar elements in the ocean. 

The uniform isotopic composition of dissolved Mo in the oceans is readily understood in terms of the 10 -10 year Mo ocean residence time. For example, given an ocean mixing time of 10 years, and assuming that the 5 Mo contrast of different Mo isotope sources is <5%o (consistent with the range of values measured to date). Mo isotope variations between ocean basins or with depth should be <5%o/(10V10 ) = 0.05%o. Such variations are smaller than present analytical uncertainties. 

For example, the average atom of potassium spends 10 million years dissolved in the ocean before becoming incorporated into the sediments. (Potassium is in steady state, so its oceanic residence time can be computed by dividing its input rate into the total amount in seawater.) This is plenty of time for ocean mixing, which occius on time scales of a thousand years, to homogenize out any horizontal or vertical concentration gradients. 

Mean depth of oceanic mixed surface layer 75 m... 

Begemann, F. Libby, W.F. (1957) Continental water balance, ground water inventory and storage times, surface ocean mixing rates and worldwide water circulation patterns from cosmic ray and bomb tritium. Geochemica Cosmochemica Acta, 12, 277-96. 

One of the major environmental issues of our time is the impact of anthropogenically generated CO2 on the environment (see Chapter 9 for discussion). The major processes associated with fossil fuel CO2 in the oceans are the uptake of fossil fuel CO2 by the upper ocean, mixing and transport within the ocean, and reaction with calcium carbonate in sediments. In addition, biologic productivity may be influenced by increased Pc02 values- The two major reactions for uptake of CO2 by the oceans, beyond those that would occur for a chemically unreactive gas, are in a simple form ... 

The three isotopes of uranium (238U, 235U, 234U) found in nature have longer half-lives (>103 years) than the oceanic mixing time (ca. 103 years). The distribution and concentration of U in rivers, estuaries, and coastal regions are extremely variable and not well understood. More work is clearly needed to understand further the complex interactions of active and carrier phases (Fe and Mn oxides), redox transformations, direct and indirect microbial transformations, and colloidal complexation that may be involved in the nonconservative behavior of U in estuaries. 

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