The effective age of bubbles in polar ice
| ISSN: |
1420-9136
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| Keywords: |
Firn closure ; atmospheric composition ; bubble trapping
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| Source: |
Springer Online Journal Archives 1860-2000
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| Topics: |
Geosciences
Physics
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| Notes: |
Abstract A mathematical description of the trapping of air bubbles in polar ice is analysed in order to assist in the interpretation of measurements of anthropogenic constituents which have recently increased on time scales comparable to the firn closure time. The effective age of a layer of ice is defined in terms of the time at which the atmospheric concentration of a constitutent was equal to the mean concentration for bubbles found in that layer. Under the assumption of uniform snow deposition at a particular site, the effective age is found to be the same for all constituents that vary linearly throughout the trapping period for a layer. Using a trapping distribution based on theoretical and observational studies, the corrections for non-linearity are found to be small for typical anthropogenic constituents. This property makes it possible to use smoothly increasing tracers such as the chlorofluorcarbons to determine the effective age empirically, even though, it is an extremely poorly-conditioned problem to determine the entire trapping time distribution function by inversion of tracer concentrations.
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| Type of Medium: |
Electronic Resource
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| URL: |