Master thesis defense by Lisa Lolk Hauge – Københavns Universitet

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Master thesis defense by Lisa Lolk Hauge

Title: “A portable firn core melter for Greenland snow accumulation studies”. 

Abstract: Ice, firn and snow cores from the Greenland Ice Sheet (GrIS) contain infor- mation on past climates from deposition and densification of aerosols in the ice matrix. These climatic records can be analyzed with the Continuous flow analysis (CFA) technique where the ice core is melted continuously and the meltwater stream analysed for impurity content and other climate proxies. Rothlisberger2000 Certain chemical impurities show seasonal cycles which make them a great tool for dating the ice core and for estimating the ac- cumulation rate at the respective core drill site. Knowing the accumulation rate is necessary to calculate surface mass balance models of the GrIS that are used to etimate sea level rise. This generates a need for fast, high resolu- tion measurements of accumulation from multiple drill sites on the ice sheet, and this thesis proves that these measurements can be performed by the Lightweight In-Situ Analysis (LISA) Box: A small portable firn core melter with an incorporated CFA system for analysing impurities. The LISA Box is designed to produce fast results from snow and firn cores to resolve annual layers and measures conductivity, hydrogen peroxide and calcium that are largely proxies for acidity, anthropogenic emmissions and continental dust, respectively. These proxies measured by the Box are chosen for their clear annual signal and their practical, simple setup in the CFA system; both in regard to chemistry (fewer mixing coils, etc.) and mechanical (instrument detection stability). The Box was constructed and tested in the field at the EGRIP camp in July 2017 and features a novel firn melt head (MH) that measures full firn cores of a 4-inch diameter. Percolation in the MH was apparent, and revised designs of the MH for light snow cores and dense firn cores are also presented in this work. A set of of five 1m long snow cores were measured for conductivity and from these data annual layer thicknesses are found to be 23.9 ± 5cm. The depth co-registration was made discretely and had to be linearly interpolated. No density profile was obtained from the sample site, thus an average density from Schaller2016 was used to obtain the mean annual accumulation rate, giving 8.63 ± 1.87cm in ice equivalent. The Box its objectives of being practical, portable and prolific, which is clear from the quality of the data with sub-annual resolution in a remote location that was collected by non-scientists. It has great potential for further devel- opment for use in accumulation studies, but also outreach and teaching are possibilities.