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| Titel |
The contribution of grain boundary melting to the water budget of polycrystalline ice |
| VerfasserIn |
Erik Thomson, John S. Wettlaufer, Larry A. Wilen |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055478
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| Zusammenfassung |
| Even well below the melting temperature many environmentally important impurities remain
dissolved in liquid solutions above their eutectics. Such impurities are found in
atmospheric particles and are eventually layered into glaciers and ice sheets as snow is
compressed into ice. Thus, even at cold temperatures reservoirs of chemically reactive
aqueous solutions exist in the cryosphere. The faster diffusion in such unfrozen liquids
results in an effective bulk diffusion proportional to the phase fraction of liquid,
Deff = ÏlDl , which affects the redistribution of chemical, isotopic, and insoluble impurity
constituents within polycrystalline ice. Grain boundaries in ice are nanoscopic compared
with the veins and nodes known to contain bulk liquid water well below melting.
However, grain boundaries dominate the ice surface area and therefore may contribute
substantially to the available liquid at sub-freezing temperatures. Using measured
equilibrium thicknesses of impurity rich ice grain boundaries we calculate their
contribution to the liquid budget of polycrystalline ice for environmentally relevant grain
sizes. Our results demonstrate that near the colligative melting temperature the
volume fraction of liquid at grain boundaries can be significant and may dominate the
equilibrium phase fraction. This finding may have far reaching effects relating to
ice core timelines, glacial mechanics, and chemical reservoirs in frozen clouds. |
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