Tracing permafrost input into the Laptev Sea by compound specific analyses of n-alkanoic acids

• Main Author: Kattein, Laura
• Format: Thesis
• Language: unknown
• Published: 2018
• Subjects: Arctic; Arctic Ocean; Laptev Sea; laptev; lena delta; permafrost
• Online Access: https://epic.awi.de/id/eprint/47527/; https://epic.awi.de/id/eprint/47527/1/BachelorThesisLauraKattein.pdf; https://hdl.handle.net/10013/epic.71a5b73c-1fd1-498b-bfb1-a3475aa84c37; https://hdl.handle.net/

To investigate effects of permafrost thaw on the sedimentary inventory of the Arctic Ocean, two cores recovered off the coast of the Lena delta were studied. Compound specific analyses of n-alkanoic acids were conducted to obtain information about the different sources contributing to the sediment. Stable carbon and hydrogen isotope ratios were measured using ion ratio mass spectrometry, while the radiocarbon content was determined using compound specific radiocarbon analysis. A blank and methyl correction was performed to determine the radiocarbon content at the time of deposition. Radiocarbon analyses yield generally higher ages for long-chain n-alkanoic acids, compared to short-chain ones. Two alkanoic acids (C16:0 and C28:0) used as biomarkers for marine and terrestrial input were chosen to investigate differences in the sources contributing to each core site. Hydrogen isotope ratios and radiocarbon measurements of the terrestrial biomarker suggest a topsoil permafrost dominated input of organic matter. Two binary mixing models yield similar results for the proportions of contributing sources. There was no evidence for a change of these ratios over the course of the last century. Differences in the concentration profiles of C16:0 in the two cores suggest different degradation rates in the two cores, which is supported by previously published data. Based on the stable hydrogen isotope ratios of the terrestrial biomarker, there is indication for an increased contribution of topsoil-permafrost derived organic matter from a more southern location in the catchment. A distinct influence of excess 14C produced during nuclear weapon tests is reflected in the radiocarbon content of the C16:0 samples of one core.