期刊
JOURNAL OF GLACIOLOGY
卷 61, 期 230, 页码 1061-1078出版社
CAMBRIDGE UNIV PRESS
DOI: 10.3189/2015JoG15J051
关键词
glacier hydrology; meltwater chemistry; subglacial precipitates and ice regelation; subglacial processes; subglacial sediments
资金
- Natural Sciences and Engineering Research Council of Canada
- Association of Canadian Universities for Northern Studies
- Garfield Weston Foundation
- Yukon Geological Survey, Simon Fraser University
- Northern Scientific Training Program
- Polar Continental Shelf Project
The subglacial chemical weathering environment is largely controlled by low temperatures and the presence of freshly comminuted minerals with a high surface area. These characteristics are believed to promote dissolution processes that give rise to low silica and high Ca2+ fluxes emanating from glacierized basins. We test an alternative hypothesis, that mineral precipitation reactions in the subglacial environment play an equally important role in controlling the water chemistry in glacierized basins. We analyze borehole and proglacial water chemistry from a subarctic polythermal glacier, complemented by mineral XRD analysis of suspended sediment, till and bedrock samples. In conjunction with a thermodynamic analysis of the water and mineral chemistry, we use reaction path modelling to study the chemical enrichment of water through the glacier system. We find that the high pH of the subglacial environment is conducive to secondary mineral precipitation, and that it is not possible to balance the water chemistry using dissolution reactions alone. We show that low silica can be explained by standard weathering reactions without having to invoke mineral-leaching reactions. Our results suggest that subglacial weathering intensity may be significantly underestimated if the production of secondary minerals is not considered.
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