First detection of glacial meltwater signature in tree‐ring δ18O: Reconstructing past major glacier runoff events at Lago Verde (Miage Glacier,Italy) |
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| Authors: | Giovanni Leonelli Manuela Pelfini Giovanna Battipaglia Matthias Saurer Rolf T W Siegwolf Paolo Cherubini |
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| Institution: | 1. Department of Earth Sciences, University of Milan, , Italy;2. Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, , 43‐81100 Caserta, Italy;3. PSI Paul Scherrer Institut, , 5232 Villigen, Switzerland;4. WSL Swiss Federal Institute for Forest, Snow and Landscape Research, , 8903 Birmensdorf, Switzerland |
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| Abstract: | With the aim of evaluating the influence of glacial meltwater signature on tree‐ring stable isotopes, we analysed δ18O and δ13C in the tree rings of Larix decidua Mill. specimens growing in the area of an ice‐contact lake (Lago Verde, at Miage Glacier, European Alps). Additionally, we analysed δ18O in the glacial meltwater of the lake and of the glacier stream and compared it with the δ18O of precipitation predicted by a spatial model. We found that tree‐ring cellulose of trees fed by glacial meltwaters (LVW site) is significantly more depleted in δ18O than at a control site LVM (?0.91‰) fed only by precipitation, thus reflecting the measured higher depletion of glacial meltwaters with respect to local precipitation. δ13C values did not show significant differences in mean values between the two sites but an anomalous correlation with summer temperature was found at the LVW site, probably due to the different responses of trees stomatal conductance. Over the 30‐year period of analysis, four years at LVW (1992, 1995, 2003 and 2009) were markedly depleted in δ18O. These years are those when the highest summer temperatures were recorded in the area (the ones during which glacier ablation usually increases and more depleted meltwaters fill the lake), with the exception of 1995 during which high water levels occurred following the year with the second highest summer temperature (1994). Overall, our analysis demonstrates that tree‐ring δ18O, driven by the glacial meltwater signature in the lake, can be used for detecting past major glacier runoff events. The proposed approach could also be used for quantifying past glacier runoff and for defining past distribution areas of glacial meltwaters in glacier forefields, thus contributing to past environmental reconstructions and to hazard assessment. |
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