Atmosphere-ocean interface

Romero, O.E., Dupont, L., Wyputta, U., Jahns, S., and Wefer, G (2003) Temporal variability of fluxes of eolian-transported freshwater diatoms, phytoliths, and pollen grains off Cape Blanc as reflection of land-atmosphere-ocean interface in northwest Africa. J. Geophys. Res. 108, 3153. 

Circulation in the near-surface ocean is driven by fiiction of wind on the atmosphere-ocean interface, whereas in deeper waters it is mostly density-driven. Unequal heating of the Earth s surface creates... 

The role of the World Ocean in the global cycle of C02 is mainly manifested through the process of its exchange at the atmosphere-ocean boundary. The intensity of ocean-atmosphere gas exchange is determined by the dynamic and diffusive behavior of the turbulent layers of water and air near the interface. Here numerous physical schemes appear which reflect the situations of wave formation, their collapse, and the... 

Loss of radon in the ocean occurs typically through radioactive decay (producing four short-lived daughters before decaying to °Pb) or loss to the atmosphere at the air-sea interface. Loss of radon owing to turbulence or diffusion at the air-sea interface leads to a depletion of radon with respect to "Ra, allowing for studies on gas exchange at this interface. ... 

The magnitude and direction of the net flux density, F, of any gaseous species across an air-water interface is positive if the flux is directed from the atmosphere to the ocean. F is related to the difference in concentration (Ac), in the two phases by the relation... 

The conclusions of Hurt s study of year-by-year oxygen isotope ratios in 72 years of S. gigantea are thus supportive of the conclusions of the CIAP study [49] that solar variations influence the abundances of many kinds of chemical species in the stratosphere, and therefore influence the.amount of solar energy they absorb and re-radiate to earth, and therefore influence the surface temperature of the earth and especially the surface temperatures of the oceans. It is the surface temperature of the oceans which produces the phenomena we have discussed the isotope ratio variations in rain and hence in tree rings, the isotope ratio variations in the Greenland ice cap, in the organic carbon and uranium concentrations in sea cores, and furthermore variations of the sea surface temperature produces variations in the carbon-14 to carbon-12 ratio fractionation at the sea air interface and hence in the carbon-14 content of atmospheric carbon dioxide and hence in the carbon-14 content of tree rings. 

C is introduced into the oceans mainly through the exchange of 14C02 at the air-sea interface. 14C once produced in the atmosphere gets quickly oxidized to 14C02 and enters the exchangeable carbon system. 

Air-Sea interface The boundary between the surface ocean and atmosphere. 

At the air-water interface, water molecules are constantly evaporating and condensing in a closed container. In an open container, water molecules at the surface will desorb and diffuse into the gas phase. It is therefore important to determine the effect of a monomolecular film of amphiphiles at the interface. The measurement of the evaporation of water through monolayer films was found to be of considerable interest in the study of methods for controlling evaporation from great lakes. Many important atmospheric reactions involve interfacial interactions of gas molecules (oxygen and different pollutants) with aqueous droplets of clouds and fog as well as ocean surfaces. The presence of monolayer films would thus have an appreciable effect on such mass transfer reactions. 

Carbon dioxide mainly exits the oceans at the interface with the atmosphere. Warm surface waters easily release carbon dioxide into the atmosphere. When warm waters rise to the surface, mainly near the equator, carbon dioxide is transferred from the water to the air. Because of this, the sea is a source of carbon for the carbon cycle as well as a carbon sink. 

Figure 7.1. View of Earth from Apollo 17 showing the African continent, the Southern Ocean and portions of the Atlantic and Indian Oceans, Antarctica, and extensive cloud cover. It emphasizes interfaces between continents and oceans (solid-liquid), continents and atmosphere (solids and gases), and oceans and atmosphere (liquids and gases). From NASA (http //visibleearth.nasa.gov/view-rec.php id = 12907).

The size of the interface between atmosphere and hydrosphere is immense (see Appendix E) 71% of the earth s surface (361 x 106 km2) is covered by water. In addition, the atmosphere contains about 13 x 1015 kg of water vapor. Expressed as liquid volume, this amounts to 13 x 1012 m3 or 2.5 cm per m2 of earth surface. This is a small volume compared to the total ocean volume of 1.37 x 1018 m3, but it is important in terms of the additional interfacial area between water and air. Although most of the water in the atmosphere is present as water vapor, roughly 50% of the earth s surface is covered by clouds which contain between 0.1 and 1 g of liquid water per cubic meter of air. The water is present in droplets with a typical diameter of 20 pm. Thus, clouds supply an air-water interface area of the order of 0.1 m2 per cubic meter of air (Seinfeld, 1986). For a cloud cover 500 m thick this would yield an air-water contact zone of 50 m2 per m2 of earth surface. 

In the seventies, the growing interest in global geochemical cycles and in the fate of man-made pollutants in the environment triggered numerous studies of air-water exchange in natural systems, especially between the ocean and the atmosphere. In micrometeorology the study of heat and momentum transfer at water surfaces led to the development of detailed models of the structure of turbulence and momentum transfer close to the interface. The best-known outcome of these efforts, Deacon s (1977) boundary layer model, is similar to Whitman s film model. Yet, Deacon replaced the step-like drop in diffusivity (see Fig. 19.8a) by a continuous profile as shown in Fig. 19.8 b. As a result the transfer velocity loses the simple form of Eq. 19-4. Since the turbulence structure close to the interface also depends on the viscosity of the fluid, the model becomes more complex but also more powerful (see below). 

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