Post-Depositional Physical and Chemical Changes in Snowpacks: the Impact of Metamorphic Intensity
Abstract
The concentrations of soluble impurities in ice cores have the potential to yield extremely detailed information about past atmospheric composition and biogeochemical cycles. However, post depositional modifications of snow composition alter this chemical signal in a manner that is not well understood. In particular, snow metamorphism causes dramatic modifications of snow physics and chemistry that lead to the release of some chemicals to the atmosphere in amounts that we are not able to quantify. To address this question, we are studying the physical and chemical evolution of the Arctic snowpack in Fairbanks, Alaska, under conditions of very strong temperature gradients that induce rapid changes. To investigate the possible range of the magnitude of the transformations, we are coupling our investigation of the snowpack with a similar snowpack subjected to very low temperature gradients by allowing air circulation under it. We have accomplished this by placing three large (2 by 4 meter) tables a meter above the ground surface prior to the onset of winter. The comparison of time series of major ions, aldehydes, stable isotopes of water, snow specific surface area, snow permeability, and of the morphology of snow crystals in both snowpacks shows that the magnitude of the temperature gradient is crucial in determining the physical and chemical evolution of the snowpack. Our results are used to discuss how variations in temperature gradients caused by climate change may have altered the chemical signal archived in ice cores, and we suggest possible ways to correct post-deposition modifications.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSM.C34A..01T
- Keywords:
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- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0322 Constituent sources and sinks;
- 1863 Snow and ice (1827);
- 3344 Paleoclimatology