Seasonal signals of trace elements and stable isotopes in snow and firn at Kohnen station, Antarctica

• Main Author: Weinhart, Alexander
• Format: Thesis
• Language: unknown
• Published: - 2016
• Subjects: Antarc*; Antarctica; Dronning Maud Land; EPICA
• Online Access: https://epic.awi.de/id/eprint/42214/; https://epic.awi.de/id/eprint/42214/1/MasterThesis.pdf; https://hdl.handle.net/10013/epic.48942; https://hdl.handle.net/10013/epic.48942.d001

Ice cores provide several environmental archives that give us insights into the history of the climate of the earth. Stable water isotopes can be used for long term temperature trends during Holocene and young Pleistocene while trace elements indicate seasonal patterns on short term and glacials on long term scales. Nevertheless, syn- and postdepositional processes influence the originally deposited signal of those proxies. As there is lack of continuous data-based annual accumulation distribution in Antarctica, it is still not clear, how single species are deposited in snow and how the signal can be interpreted. Especially the temporal variability of deposition dependent on seasonal accumulation is a fact that needs to be unterstood. Therefore, in this master thesis we try to explain, how the deposition of proxies is coupled with accumulation and show implications for an interpretation of distinct proxy signals. For this purpose, snow profiles with a length of 50 cm were taken at four different locations, which are along a path of 40 m. The main site was sampled 41 times within a period of 53 days, while the other three locations were used as reference for spatial variance. With that setup, especially the temporal resolution was in the focus of interest. The liner were cut into distinct samples of 1 cm (0-30 cm depth) and 2 cm (30-50 cm depth) and analyzed on several trace elements (Na+, Cl-, NO3 -, SO42-, Ca2+, Mg2+ and MSA) using a Dionex IC 2100 ion chromatograph. δ18O and δ2H measurements were conducted using cavity ring-down spectroscopy (CRDS) and an Picarro analyzer. Study area is the EPICA drill site Kohnen (75°0‘ S; 0°4‘ E) in Dronning Maud Land, Antarctica with an accumulation rate of 64 mm w.e. per year and upward tendency towards higher values. We performed a time-depth-correlation taking recent ablation stake measurements into account and plotted the isotopic and aerosol record on the basis of an estimated accumulation distribution. We used a value of 0.5 cm a-1 snow per winter month which is, ...