Oceans stratosphere

Bromine compounds are found ia the atmosphere ia small amounts the sea is a primary source. Rainfall over the Pacific and Indian Oceans has been found to contain 60—80 f-lg/L of bromine (46). Approximately 10 parts per trillion (v/v) of bromine is found ia the stratosphere (47). 

Susan Solomon and James Anderson showed that CFCs produce chlorine atoms and chlorine oxide under the conditions of the ozone layer and identified the CFCs emanating from everyday objects, such as cans of hair spray, refrigerators, and air conditioners, as the primary culprits in the destruction of stratospheric ozone. The CFC molecules are not very polar, and so they do not dissolve in rain or the oceans. Instead, they rise to the stratosphere, where they are exposed to ultraviolet radiation from the Sun. They readily dissociate in the presence of this radiation and form chlorine atoms, which destroy ozone by various mechanisms, one of which is... 

COS destruction in the stratosphere calculated with a model uptake of COS in the oceans and hydrolysis may imply an atmospheric lifetime of only a few years and a source of a few tens of billions (10 °) of moles per year. 

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. 

Ultraviolet radiation (UVR) is a natural fraction of the solar radiation, and therefore has always influenced life in aquatic ecosystems. The development of oxygenic photosynthesis 2.5-2 J billion years ago (Holland 1984) led to drastic chemical changes in the Earth s oceans and atmosphere. The gradual increase in photosyn-thetically produced oxygen over millions of years was accompanied by a strong enrichment of it in the atmosphere, which ultimately acted as precursor for the ozone (03) layer in the stratosphere. 

Thiemens MH, Heidenreich JE (1983) The mass independent fractionation of oxygen - A novel isotope effect and its cosmochemical implications. Science 219 1073-1075 Thiemens MH, Jackson T, Zipf EC, Erdman PW, van Egmond C (1995) Carbon dioxide and oxygen isotope anomalies in the mesophere and stratosphere. Science 270 969-972 Thode HG, Monster J (1964) The sulfur isotope abundances in evaporites and in ancient oceans. In Vinogradov AP (ed) Proc Geochem Conf Commemorating the Centenary of V I Vernadsku s Birth, vol 2, 630 p... 

While there are a variety of other chlorinated organics such as methylchloroform (CH3CC13) that are emitted, these have relatively short tropospheric lifetimes because they have an abstractable hydrogen atom (e.g., see WMO, 1995). For example, while the stratospheric lifetime of methylchloroform is estimated to be 34 7 years (Volk et al., 1997), its overall atmospheric lifetime is only 5-6 years, primarily due to the removal by OH in the troposphere (toii 6.6 years), with a much smaller contribution from uptake by the ocean (roi i an 85 years) (WMO, 1995). 

These data also demonstrate the impact of bromine chemistry on the stratosphere (see Chapter 12.D). The initial ODP for methyl bromide is 15, due primarily to the large a factor associated with bromine chemistry. However, since it is removed by reaction with OH in the troposphere as well as by other processes such as hydrolysis in the oceans and uptake by soils and foliage (see Chapter 12.D), it has a short atmospheric lifetime of 1.3 years and hence the ODP decreases rapidly with time, toward a long-term steady-state value. 

In addition, there is an obseived correlation between total column ozone and the El Nino Southern Oscillation (ENSO) in the tropical troposphere, with decreases in total ozone in middle and sometimes polar latitudes following the ENSO by several months the period associated with the ENSO is 43 months (Zerefos et al., 1992). While the association between the ENSO and ozone is not well understood, it has been proposed that the warming of the troposphere in the tropics over the Pacific Ocean causes increases in the upper troposphere air temperatures and tropopause height and an upwelling in the lower stratosphere. If sufficiently large, this could have more widespread impact than just in the tropics (e.g., see Zerefos et al., 1992 and Kalicharran et al., 1993). 

Atom for atom, bromine is even more efficient at destroying ozone than is chlorine. There has therefore been much concern that releases of volatile bromine compounds such as methyl bromide may contribute disporpor-tionately to thinning of the stratospheric ozone layer. Whereas there is no longer any doubt over the role of human activity in stratospheric pollution by CFCs, which are exclusively anthropogenic, attempts to assess the importance of human activity in pollution by methyl bromide have been confused by large natural releases of CH3Br from oceans and forest fires. Besides, unlike the case of CFCs released into the environment, a major fraction of the methyl bromide injected into soils to kill pests is destroyed in the ground. 

Figure 1-1 An ozone hole forms each year in the stratosphere over the South Pole at the beginning of spring in October. The graph compares ozone pressure in August, when there is no hole, with the pressure in October, when the hole is deepest. Less severe ozone loss is observed at the North Pole. [Data from National Oceanic and Atmospheric Administration.]...

Frederick, J.E., R.P. Cebula, and D.F. Heath (1986) Instrument characterization for the detection of long term changes in stratospheric ozone an analysis of the SBUV/2 radiometer. Journal cf Atmospheric and Oceanic Technology 3 472-480. 

The study of the low atmosphere (including land and ocean exchanges with or through the atmosphere) which is the supply of most material found in the stratosphere. 

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