Kinetics of Conversion of Air Bubbles to Air-Hydrate Crystals in Antarctic Ice
The depth-dependence of bubble concentration at pressures above the transition to the air hydrate phase and the optical scattering length due to bubbles in deep ice at the South Pole are modeled using diffusion-growth data from the laboratory, taking into account the dependence of age and temperatur...
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| Format: | Text |
| Language: | English |
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2008
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.256.3576 http://arxiv.org/pdf/astro-ph/9501073v2.pdf |
| Summary: | The depth-dependence of bubble concentration at pressures above the transition to the air hydrate phase and the optical scattering length due to bubbles in deep ice at the South Pole are modeled using diffusion-growth data from the laboratory, taking into account the dependence of age and temperature on depth in the ice. The model fits the available data on bubbles in cores from Vostok and Byrd and on scattering length in deep ice at the South Pole. It explains why bubbles and air hydrate crystals co-exist in deep ice over a range of depths as great as 800 m and predicts that at depths below ∼ 1400 m the AMANDA neutrino observatory at the South Pole will operate unimpaired by light scattering from bubbles. 1 Ancient air is known to be trapped in polar ice at depths below the layer of firn (i.e., porous) ice. Early investigations showed that the air was trapped in bubbles which decreased in size and concentration with increasing depth. To account for the disappearance of bubbles at great depth, Miller (1) predicted that the bubbles would convert into a clathrate hydrate phase at depths corresponding to a pressure greater than that for formation of that phase. He showed that the phase consists of a cubic crystal structure in which O2 and N2 molecules from air are trapped in clathrate cages. If O2 and N2 occur in atmospheric proportions |
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