## Doctoral Dissertations

Spring 1996

Dissertation

Earth Sciences

#### Degree Name

Doctor of Philosophy

Paul Mayewski

#### Abstract

The Greenland ice sheet preserves high resolution records of environmental and climate change spanning seasons to hundreds and thousands of years. In this study, we utilize major chemical species measurements of surface snowpit samples and ice cores collected at GISP2, 20D, Mount Logan, and Sentik Glacier to investigate major chemical species spatial distribution, temporal variations, and possible sources for the major chemical species in these ice cores.

A two-sided t-distribution test (a = 0.05) was applied for the study of major chemical species spatial distribution over a portion of central Greenland. The results suggest that concentrations of major chemical species in snow do not vary significantly over the central Greenland. The relationship between chemical concentration and snow accumulation rate was investigated using the snowpits and ice core samples. Chemical concentrations do not vary with snow accumulation rate over the Greenland ice sheet We further suggest that it is improper to study the relationship between chemical concentration and snow accumulation rate by using data collected from different geographic sites.

Of all the chemical series studied, only NO$\sb3\sp-$ concentration data are normally distributed. NO$\sb3\sp-$ concentration in snow is affected by post-depositional exchange with the atmosphere. The persistent summer maxima in NO$\sb3\sp-$ observed in Greenland snow is believed mainly due to NO$\rm\sb{x}$ released from peroxyacetyl nitrate (PAN) by thermal decomposition in the presence of higher OH concentrations in summer.

A nearly complete depletion of NO$\sb3\sp-$ (94%) and depletion of Cl$\sp-$ (63%) correlates with the largest volcanic eruption horizon in the GISP2 core. It is suggested that such depletion is due to the large amounts of SO$\sb4\sp{2-}$ disturbing atmospheric photochemistry and extremely acidic condition in ice layer.

The 110,000 year long major chemical species fluctuations in the GISP2 ice core demonstrate that chemical concentrations are inversely correlated with $\delta\sp{18}$O during last glacial period, suggesting that chemical concentration increases while temperature decreases, and vice versa. During the Holocene the atmosphere was acidic, during interstadials the atmosphere was a neutral or alkalescent, and during stadials the atmosphere was alkaline. Changes in major chemical composition and ratios also indicate that source regions differed during these periods.

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