Aerosol Input and Snow Accumulation Rates on the Northern Greenland Ice Sheet : Reconstructed by means of Continuous Flow Analysis (CFA) of 6 shallow firn cores

• Main Author: Zens, Patrick Stephan
• Format: Bachelor Thesis
• Language: English
• Published: Uppsala universitet, Institutionen för geovetenskaper 2018
• Subjects: continuous flow analysis; Greenland; shallow firn core; aerosol; snow accumulation; glaciochemistry; kontinuerlig flödesanalys; Grönland; grunda firnkärnor; snöackumulering; glaciokemi; Physical Geography; Naturgeografi; ice core; Ice Sheet; Inlandsis
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-352970

Ice, firn and snow cores from the Greenland ice sheet offer a unique opportunity to reconstruct past climate conditions. These can be analyzed with continuous flow analysis (CFA) in order to acquire proxy information about ancient atmospheric aerosol concentrations, snow accumulation rates or temperature variations, atmospheric composition, solar activity as well as volcanism and biological activity. This project deals with high-resolution CFA applied on six shallow firn cores (A1-A6) from Northern Greenland taken during a 456 km long traverse from the deep ice core drilling sites NEEM to that called EGRIP. The practical part included CFA measurements by means of fluorescence spectroscopy for obtaining NH4+, Ca2+ and H2O2, absorption spectroscopy for H+, an ion selective electrode (ISE) for Na+ as well as insoluble dust and water electrolytic conductivity measurements. The analytical part consisted of calibrations of the measurements, the reconstruction of the depth scale of the snow/firn cores and defining annual layers using H2O2. Field density measurements and the annual layer thicknesses were used to identify annual mean snow accumulation rates. These high-resolution firn records allowed determining accurate monthly maximum and minimum aerosol concentrations in order to evaluate seasonal deposition patterns and validate the applied dating method. The reconstructed ages ranged from 17 ± 1 to 54 ± 2 years along a northwest-southeast gradient. Statistical tests resulted merely for H2O2 in correlations between the three western cores, probably explained by the dating method, which forces the annual summer maxima and winter minima of H2O2 to correlate. Trend analysis resulted in no significant changes over time except for the conductivity measurements of the two longest/oldest firn cores. This is associated with decreasing acidifying anthropogenic sulfur emissions since the 1970’s. Annual mean snow accumulation rates ranged from 0.235 ± 0.061 m w.eq.a-1 in the very west of the traverse to 0.103 ± 0.036 m w.eq.a-1 ...