MSc defence by Kasper Holst Lund

Title: "Indicators of volcanism in ice cores"

Abstract
The work done in this project has been to optimize existing continuous flow analysis (CFA) techniques used for measurements of sulphate (SO2−4 ) and acidity (H+). The optimized techniques have been tested on six short firn cores drilled during a 456 km long traverse from the NEEM drilling site to the EGRIP drilling site and on the first 350 metres of the EGRIP ice core. The measured records have been used to determine spatial variability between the cores and to investigate the volcanic signals found in the ice cores.
The sulphate technique developed by Röthlisberger et al. (2000) was optimized by exchanging the cation exchange column (CEC) to another type of CEC. This was done to try and reduce the flow problems created by the CEC. The chosen CEC was Bio-Rads Bio-ScaleTM Mini UNOsphere S Cartridge, this had no flow problems in conditions with low dust concentrations while it did show a slight drift with high dust concentrations.
The acidity technique developed by Kjær et al. (2016) was optimized by exchange the absorption cell from a 2 cm z-cell to a 1 cm cuvette, this was done to lower the risk of air bubbles getting stuck in the cell. The cuvette handled air bubble a lot better and no problems with air bubbles getting stuck was encountered. The cuvette also improved the response time from 45 seconds to 36 seconds but the sensitivity of the technique was halved due to the lower path length.
The sulphate technique was tested on three of the traverse cores but failed to produce any data due to a too high detection limit. The high detection limit is suspected to be due to old chemistry and parts in the setup. No other sulphate measurements were carried out. 
The acidity and conductivity measurements of the six traverse cores was able to clearly determine volcanic eruption across all of the core but only some of the eruptions showed up in multiple cores. The correlations found between the cores were low and no significant correlations were found in neither acidity or conductivity. Thus the spatial variation between the cores were quite high even in the big volcanic events. The low correlations are suspected to be due to post depositional effects and to errors in the dating of the cores.
The acidity and conductivity measurements of the EastGRIP core also clearly determined big events such as volcanic eruptions and wildfires. A comparison with the NEGIS core drilled very close to the EastGRIP core showed comparable peaks for most of the large events seen while the smaller features had quite some variation most likely due to post depositional effect and errors in the depth assignment. Two conductivity records were measured during the EastGRIP campaign a Bern and a Copenhagen record. A comparison shows that the correlation between the two records gets lower with time. This is most likely due to contamination from build up of particles in the line going from the Bern to the Copenhagen system. This could lead to problems with aligning the records from the different parts of the system.