Master thesis defence by Michelle Chrabalowski – Københavns Universitet

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Master thesis defence by Michelle Chrabalowski

Continuous pH record from the Anthropogenic period of an ice core drilled in Renland, Greenland

 
ABSTRACT Chemical and physical measurements taken from ice cores can be used in order to give a record of atmospheric activity throughout history. Depending on the depth and geographical location where the ice core was drilled, the measurements can give information about Earth’s climate hundreds of thousands of years back. This information can give insight on present and future climate trends.

Continuous Flow Analysis (CFA) is a method of measuring impurities in ice cores with high resolution and low contamination. This method was used for the purposes of this thesis, in order to determine an acidity record from an ice core drilled in Renland, on the eastern coast of Greenland. The ice was transported to the Copenhagen CFA lab, where the core was melted between October 2015 and January 2016. The CFA measurements were taken simultaneously to the melting, and analyzed following completion of the CFA melting campaign. It is possible to couple measurements taken using the CFA method with measurements taken with other methods.

This thesis focuses on the acidity measurements within the upper 93.5 m of the 584 m in total of the drilled Renland core. This corresponds to the time period from 1855 A.D to 2015 A.D. The acidity is one parameter which influences the solubility of compounds in the atmosphere, as well as how various compounds will behave in relation to other components in the environment. The CFA method of measuring acidity involves the use of a spectrometer blue and red dyes in order to show concentration through an absorption method. The acidity measurement on the Renland ice core can be coupled with other components measured by the CFA in order to give a better record of atmospheric activity within the time period studied. For this reason, although the focus was on acidity, measurements of conductivity, dust, Na+, Ca+2, and NH4+ in the ice are also included, and the measurements have been compared to determine similarities and differences in seasonality, peak concentrations, and average concentration values.

It is important to measure acidity within the core because of the influence which it has on the solubility and absorption of other compounds in the atmosphere. Acidity, as can be measured in the ice core, is relevant to both human and environmental health because of the effect it has on the chemical interactions which occur in the atmosphere, especially chemical reactions involving the hydrogen ion. Although harm to human health due to acidity as seen in the ice core is not direct because the acid concentration is too dilute, adverse effects area possible through particulates which results from increased acidity, including sulfur oxides (SOx) and nitrogen oxides (NOx).

The average concentration of acidity for the Renland data corresponding to 1855 A.D and upwards was 2.09 μM H+. A 5 year smoothing was applied to the data, in order to dull the effect of short peaks from volcanoes. The average concentration of acidity for the whole data set when using a 5 year smoothing was 2.06 μM H+.  Various peaks were identified, which were matched to historic volcanic eruptions, including Hekla 1913 (Iceland), Katmai 1912 (Alaska), Krakatoa (1883) Indonesia, and others.

The most notable feature among the acidity record of the Renland core from 1855 A.D to present was the increase in acidity values from the period 1967-1975, where the average acidity ranged from 2.52 μM H+ to 6.50 μM H+ .This was compared to an average of 1.36 μM H+ prior to 1967, and 2.94 μM H+ after 1978. This increase in acidity was expected based on measurement of previous Greenland cores as well as knowledge of historical events. The increase is likely to have been caused the increase of industrial activities in the time period of the 1970’s, known as the Industrial Revolution, particularly from sources in Europe and North America. The decrease in acidity following 1978 can be attributed to the implementation of various measures to control atmospheric pollution and increased awareness of the environmental and health impacts of industrial pollution.

Supervisor: Helle A. Kjær, Centre for Ice and Climate