Temperature Estimates Oxygen

The seasonal variations of 5 0 and 5D values of snow at the South Pole in Fig. 17.23 imply that the isotope 

The surface temperatures and 5 0 values of the snow at the South Pole during 1964/65 are positively correlated and approximate to line A in Fig. 17.24  

A more serious restriction is that isotope fractionation is not governed by the temperature at the surface where the snow accumulated, but by the temperature 

Equations 17.5 (line A) and 17.6 (line B) can be used to estimate the temperature of condensation in the atmosphere and the temperature of deposition of the surface from the values of snow deposited at the South Pole and, perhaps, elsewhere in the interior of the East Antarctic ice sheet. For example, if the measured value of snow is -50.0%o, equation 17.5 (line A) yields t = -42°C and equation 17.6 (line B) indicates t = -31°C. The estimated surface temperature (t ) is probably a more appropriate descriptor of the climate at South Pole, whereas the condensation temperature (t ) is more relevant to the meteorological process of snow formation at the South Pole. 

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Particle Temperature Overshoot. The temperature of the burning char particles will run hotter than that of the bed by amounts that depend upon particle size, reactivity, bed temperature. It is determined in part by the heat released at the particle surface due to reaction and in part to the additional heat released by carbon monoxide oxidation near the particle surface (54-58). Measurements for 1.8 to 3.2 millimeter size coke particles burning in a fluidized band of sand at 1173 K increased from the bed temperature at low oxygen concentrations to values 150 to 200 K above the bed temperature for oxygen concentrations approaching that of air (72). Estimation of this temperature rise is important for purposes of evaluating the NO/C reaction and also for prediction of the burnout times of fines. 

The process we have followed is identical with the one we used previously for the uranium/oxygen (U/0) system (1-2) and is summarized by the procedure that is shown in Figure 1 Thermodynamic functions for the gas-phase molecules were obtained previously ( ) from experimental spectroscopic data and estimates of molecular parameters. The functions for the condensed phase have been calculated from an assessment of the available data, including the heat capacity as a function of temperature ( ). The oxygen potential is found from extension into the liquid phase of a model that was derived for the solid phase. Thus, we have all the information needed to apply the procedure outlined in Figure 1. 

Niimberg D., Muller A., and Schneider R. R. (2000) Paleo-sea surface temperature calculations in the equatorial east Atlantic from Mg/Ca ratios in planktic foraminifera a comparison to sea surface temperature estimates from 31, oxygen isotopes, and foraminiferal transfer function. Paleoceanography 15(1), 124—134. 

It is clear from the results of this study that, for barnacles at least, there is no potential for using the 8 0 value of shell carbonate as a predictor of elevation within living range in the intertidal zone, and hence oxygen-isotopes will be of no use as a proxy for refining estimates of palaeo sea-level. Indeed, the consistency in the 8 0 composition between specimens of varying size and position on the shoreface implies that palaeo-temperature estimates could be derived fi om fossil barnacles if an independent estimate of salinity were available. 

The organization of this paper will be to discuss the assumptions of thermometry, processes of isotope exchange, and approaches for recovering temperature estimates of identifiable geological events. This is followed by applications of oxygen and carbon isotope thermometry to metamorphic and igneous rocks. While many careful studies have been published since 1947, emphasis will be placed on studies that have benefited from technical, experimental, and theoretical advances of the past decade. 

However, these data have been generated at a time, when accurate methods to estimate oxygen in alkali metals have not been available. In a very recent study, oxygen saturation concentrations in the temperature range 70 to 200 °C have been measured in purified potassium applying the distillation method The results best fit Eq. (3). 

The resulting temperature estimates in column (1) range from 613°C to 1126°C. Omitting the lowest and the highest values yields a mean of 872 112°C (let) The oxygen-isotope fractionation factors reported by Chiba et al. (1989) for feldspar-pyroxene are Albite-Diopside = 1.81, Anorthite-Diopside = 0.76. For labradorite (An = 60%, Ab = 40%) the numerical value of A is ... 

According to the results obtained by Schumpe et al. 15) the anions always have positive Hi values, while the Hi values for cations are negative. These authors concluded that equation (31) together with their ionic specific constants for salting-out oxygen at 25 (data are tabulated in their article), could be applied to estimate oxygen solubilities in mixed electrolyte solutions in the temperature range of 10 to 40 C. Moreover,... 

Recently, Emerson et al. (1999) have confirmed with careful specific-heat measurements previous findings of Nakazawa and Ishikawa (1989) and Moler et al. (1997) that in the overdoped regime a sharp increase of the Debye temperature takes place. This is shown in fig. 78. In their estimated oxygen content scale the abrupt increase of the Debye temperature takes place at x 6.98. In view of the fact that the oxygen determination was indirect, it seems reasonable to assume that this effect is related to the displacive martensitic transformation (x=6.95, determined directly, with high accuracy, sect. 3.1.3) and the series of structural phenomena which accompany it in the overdoped region the abrupt decrease of the unit-cell volume (fig. 25e), the decrease of the h-axis, the decrease of the orthorhombicity (figs. 25b,c) and the minimum of the c-axis (Rusiecki et al. 1990) (fig. 28a). 

In a similar vein, mean seawater temperatures can be estimated from the ratio of 0 to 0 in limestone. The latter rock is composed of calcium carbonate, laid down from shells of countless small sea creatures as they die and fall to the bottom of the ocean. The ratio of the oxygen isotopes locked up as carbon dioxide varies with the temperature of sea water. Any organisms building shells will fix the ratio in the calcium carbonate of their shells. As the limestone deposits form, the layers represent a chronological description of the mean sea temperature. To assess mean sea temperatures from thousands or millions of years ago, it is necessary only to measure accurately the ratio and use a precalibrated graph that relates temperatures to isotope ratios in sea water. 

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