Procedures For Removing Surface Contaminants From Deep Ice Cores

The surfaces of the deep ice cores from Greenland and Antarctica were contaminated during drilling at concentration levels several orders of magnitude greater than those found in the uncontaminated ice. Several procedures for removing these contaminants were studied. Ultrasonic vibration followed by self-cleaning in meltwater was found to be the most effective procedure for removal of surface contamination. (Author).

Over 100 samples taken at about 15-m intervals in the portion of the Camp Century ice core between 70- and 1360-m depths were analyzed for their Na(+), K(+), Ca(2+) and Mg(2+) contents by atomic absorption spectroscopy. Based on independent stable isotope analyses these maxima occurred over the last third of the Wisconsin glaciation.

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"This report documents most of the ice cores so far collected on a world-wide basis, as well as providing information on literature sources and on the currents status of research activities which may affect the types of data that can be archived."--Foreword.

Concentrations of sodium, potassium, magnesium, calcium, silicon, aluminum, lead and sulfate were measured in surface snow and in individual annual accumulation layers from a 373-m-deep ice core from Dye 3, Greenland (65 deg 12 min N, 43 deg 47 min W), covering the time period from 1232 to 1971 A.D. Average background (pre-1840) concentrations in micrograms/liter were determined. Observed concentrations of sodium, potassium, magnesium, calcium, silicon and aluminum can be adequately explained by relative abundances of these elements in seawater and terrestrial dust. Late 19th century annual ice layers contain twice as much sulfate as pre-1840 deposits, reflecting the increased use of fossil fuels in the Northern Hemisphere. Lead concentrations in post-1955 snow deposits are more than an order of magnitude greater than pre-1840 baseline concentrations and are attributed to smelting and the increased use of lead alkyls in gasoline.