10Be concentrations in an ice core from Akademii Nauk (Russian Arctic) for validation of the age-depth relationship: development of a sample scheme


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Diedrich.Fritzsche [ at ] awi.de

Abstract

This bachelor’s thesis aims to develop a sample scheme for the Akademii Nauk ice core from the Russian Arctic in order to reconstruct the long-term variations of the 10Be concentration. These long-term variations are assumed to vary globally simultaneous and are therefore used to synchronize different 10Be records for the purpose of dating (“wiggle matching”). This is done in order to validate an existing age-depth relationship of this ice core covering a time span of around 3 000 years. For this purpose a numerical computer model has been designed that simulates different modes of systematic sampling on high-resolution age–10Be concentration records. Two sample modes have been simulated: One mode that takes discrete, short samples and another mode that takes continuous, long samples. The model takes into account the restrictions of the Akademii Nauk ice core, for example dating uncertainties and occasional missing parts of the core. All data sets are smoothed using a 22 years running mean. This averaging smooths out most of the meteorological differences, reduces aliasing effects and still enables the reconstruction of the decadal variations. For a comparison between the original and the reconstructed curve, three complementary evaluation techniques have been applied: a mathematical neighborhood, the Pearson correlation coefficient, and the cosine similarity. The model’s results show clearly that continuous sampling performs better than taking only short samples leaving big gaps in between. This can be related to the fact that when sampling continuously no information is lost and aliasing effects are attenuated by “averaging” via melting of long samples. Regarding the sample length, the closest match of reconstructed and original curve is achieved for sample lengths of 4–8 years, with a slight preference for lengths of 8 years. Another optimum is reached for sample lengths of 22 years. The results give a clear hint that aliasing effects bias the reconstructed record. Apart from that, even when parts are missing in the ice core, a good reconstruction is still possible applying continuous sampling. For further sampling I suggest to identify a prominent part of the 10Be long-term concentration variations and fill up the gaps between the already existing data points with continuous samples within the identified part.



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Thesis (Bachelor)
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Not peer-reviewed
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Eprint ID
39003
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Albedyll, L. v. (2015): 10Be concentrations in an ice core from Akademii Nauk (Russian Arctic) for validation of the age-depth relationship: development of a sample scheme , Bachelor thesis, University of Potsdam, Institute of Earth and Environmental Science.


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