Master thesis defense by Nicholas Emiliano Robles – Københavns Universitet

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Master thesis defense by Nicholas Emiliano Robles

Title: "Spatial and Temporal Analysis of Greenland Shallow Snow Cores and HIRHAM5 Data"

ABSTRACT

Tiny gas bubbles filled with past climate atmospheres are trapped within the various layers of the Greenland ice sheet. The continuous flow analysis was used to measure eleven shallow snow cores from a section of the Windsled traverse in May and June 2017 from Windsled to EGRIP. Through fluorescence and absorption techniques H2O2, NH4+, Ca2+, H+, and Na+ were measured along with conductivity and dust. An age scale was created using H2O2 peaks as summer and troughs as winter. Weather variables: precipitation, snow fall, temperature, water evaporation, wind speeds, and wind direction were calculated through the HIRHAM5 model. Then DERMA model back trajectories were used to compare Summit and EGRIP aerosol sourcing.

A spatial and temporal analysis of the snow core data was conducted during two time periods: 2012/13 – 2016 and 2014 & 2016. H2O2 showed a clear temporal and spatial signals with peaks occurring in the summer and troughs during winter during both time periods. Many of the other proxies did not exhibit normal temporal and spatial concentrations because of various errors including contamination and biases from the transition from MQ to sample. However, through the use of exponential smoothing Ca2+ did show maximums during spring. Outliers are evaluated and where the seasonal variability does not match is discussed. Through the use of HIRHAM5 data another spatial and temporal analysis was conducted on this data, which showed much more promising results. The analysis was conducted during two time periods: 2012-2016 and 1980-2017. There were clear temporal patterns including peaks in precipitation and snowfall occurring in early fall. Surface wind speeds are higher during winter periods and slower during summer periods. Spatially, there is an increase in concentration from north to south with few results finding constant concentrations across the locations.

The snow core and HIRHAM5 data were then compared to find any specific patterns. Because much of the snow core data was contaminated conclusions were made based on the expected spatially and temporally. Ca2+ and dust are heavily impacted from strong winds, NH4+ is impacted through various chemical processes, precipitation, and wind patterns, and much of the acidity and conductivity is impacted through the arctic haze phenomenon occurring in winter and early spring and volcanic events. This section of the traverse is highly important and needs to be studied more. The low accumulation and shallow cores have presented various challenges. There needs to more investigation into this region in order to continue the scientific knowledge of the NEGIS region. Conclusively, it is unfortunate about the contamination, however, the results in this report produce a spatial and temporal statistical analysis from 2012 – 2016 and compares the results with HIRHAM5 and DERMA model outputs.

Keywords: continuous flow analysis, shallow snow cores, glaciochemistry, NEGIS, HIRHAM5, DERM