Ice core, analysis

LAYER-BY-LAYER ANALYSIS OF THE ICE CORE FROM BELUKHA GLACIER... 

Carbon dioxide, considered a wanning gas, comprises about 0.036 percent of the atmosphere by volume. As Figure 1 shows, carbon dioxide levels have increased as a component of the atmosphere by nearly 30 percent from the late eighteenth century to the end of the twentieth century, when the level was close to 365 parts per million by volume. Prior to the period of industrialization, carbon dioxide levels were largely stable, at about 280 parts per million, though fluctuations as low as 200 parts per million or as high as 300 parts per million have been observed through analysis of air bubbles trapped in arctic ice cores. 

Research should be conducted to understand how the oceans have operated under past climates. This would involve paleoclimatic studies including analysis of sediment and ice core records coupled with tracer-style ocean models or box models. 

Our experience to-date suggests that current measurement and analysis techniques allow the reliable detection of variations in the atmospheric C02 content of 30 percent or more. Our first measurements have been made on samples covering the last 30,000 years, a period of major climatic change which might possibly have led to a change in the atmospheric C02 content. Ice cores... 

Surface samples were collected in snow pits under ultra-clean conditions described elsewhere [13] with the exception that samples for anion analysis were collected in polystyrene cups precleaned without the use of acids. Ice core samples were cleaned to remove surface contamination using the "dry-core" procedure involving rinsing and melting of exterior surfaces with ultra-pure water [13]. Shallow-depth firn cores are permeable and the dry-core rinsing is unsuitable. Therefore an inner core of 2.5 cm diameter was taken from intervals of the 7.6 cm diameter South Pole firn core using a specially-built precleaned stainless steel corer within a -15 °C cold room. Prior to this coring, exposed ends of core sections were shaved away with precleaned stainless steel chisels. 

One way scientists have learned about the levels of carbon dioxide in the past is through the analysis of ice cores. An ice core is a tube of ice, usually drilled out of a glacier or ice sheet, that contains bubbles of air trapped inside layers of snow and ice. Each layer of snow and ice represents roughly a year. The deeper the layer, the older the ice sample. From the size and chemical content of each layer, scientists can draw conclusions about the temperatures at that point in history at that spot on the planet. At the same time, the bubbles of air preserved in each layer contain indicators of the amount of atmospheric carbon dioxide present at that time. 

Plastic containers must be washed before use. Table 28-1 shows that manganese in blood serum samples increased by a factor of 7 when stored in unwashed polyethylene containers prior to analysis. In the most demanding trace analysis of lead at 1 pg/g in polar ice cores, it was observed that polyethylene containers contributed a measurable flux of 1 fg of lead per cm2 per day even after they had been soaked in acid for 7 months.4 Steel needles are an avoidable source of metal contamination in biochemical analysis. 

Kuhlbusch, T. A. J. (1998). Black carbon in soils, sediments, and ice cores. In Environmental Analysis and Remediation, Meyers, R. A., ed., John Wiley Sons, Toronto, pp. 813-823. 

Fig. 9. The temporal variation in atmospheric CH4 as deduced from analysis of air bubbles trapped in polar ice cores (stars) and analysis of air samples (squares). After Craig and Chou (1983).

Krinner G., Genthon C., and Jouzel J. (1997) GCM analysis of local influences on ice core S signals. Geophys. Res. Lett. 24, 2825-2828. 

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