Radiocarbon dating of alpine ice cores with the dissolved organic carbon (DOC) fraction
High-alpine glaciers are valuable archives of past climatic and environmental conditions. The interpretation of the preserved signal requires a precise chronology. Radiocarbon (14C) dating of the water-insoluble organic carbon (WIOC) fraction has become an important dating tool to constrain the age...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
| Published: |
2020
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/tc-2020-234 https://tc.copernicus.org/preprints/tc-2020-234/ |
| Summary: | High-alpine glaciers are valuable archives of past climatic and environmental conditions. The interpretation of the preserved signal requires a precise chronology. Radiocarbon (14C) dating of the water-insoluble organic carbon (WIOC) fraction has become an important dating tool to constrain the age of ice cores from mid-latitude and low-latitude glaciers. However, in some cases this method is restricted by the low WIOC concentration in the ice. In this work, we report first 14C dating results using the dissolved organic carbon (DOC) fraction, which is present at concentrations of at least a factor of two higher than the WIOC fraction. We evaluated this new approach by comparison to the established WIO14C dating based on parallel ice core sample sections from four different Eurasian glaciers covering an age range of several hundred to around 20’000 years. 14C dating of the two fractions yielded comparable ages with WIO14C revealing a slight, barely significant, systematic offset towards older ages. Our data suggests this to be caused by incompletely removed carbonate from mineral dust (14C depleted) contributing to the WIOC fraction. While in the DOC extraction procedure inorganic carbon is monitored to ensure complete removal, the average removal efficiency for WIOC samples was here estimated to be ~96%. We did not find any indication of in-situ production systematically contributing to DO14C as suggested in a previous study. By using the DOC instead of the WIOC fraction for 14C dating, the required ice mass can be reduced to typically ~250 g, yielding a precision of ±200 years or even better if sample sizes typically required for WIO14C dating are used. This study shows the potential of pushing radiocarbon dating of ice forward even to remote and Polar Regions, where the carbon content in the ice is particularly low, when applying the DOC fraction for 14C dating. |
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