Ice-cores

APPLICATION OF DIFFERENT ANALYTICAL TECHNIQUES FOR Hg DETERMINATION IN ICE-CORE FROM BELUKHA... 

The very low Hg concentration levels in ice core of remote glaciers require an ultra-sensitive analytical technique as well as a contamination-free sample preparation methodology. The potential of two analytical techniques for Hg determination - cold vapour inductively coupled plasma mass spectrometry (CV ICP-SFMS) and atomic fluorescence spectrometry (AFS) with gold amalgamation was studied. 

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. 

Though measurements of solar output have been taken only for the past eighteen years, longer trend patterns can be derived from indirect data sources, such as ice cores and tree rings. Cosmic rays, which fluctuate with the sun s activity, also strike constituents of the atmosphere, creating radioactive versions of certain elements. Beiyllium, in particular, is ionized to "Be by cosmic rays. The "Be then gets incorporated into trees as they grow, and is trapped in bubbles in ice masses, as is carbon dioxide. 

Figure 1. Atmospheric methane increases over the last 300 years. Points are annual averages the concentrations before 1960 are from ice core analyses more recent data from atmospheric measurements. From Khalil and Rasmussen (40).

The estimated response time of CaCOa compensation, on the order of a few thousand years, is a serious problem because the ice core data do not show such a long delay in atmospheric CO2 changes with respect to temperature changes. Such a long delay may preclude CaCOa compensation as an important process in predicting atmospheric CO2 in the next few centuries. 

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. 

Fig. 1-2 Chemical data from the Vostok ice core. The graph of 5D can be taken as a proxy for temperature changes, as described in Chapter 18. CO2 and CH4 are greenhouse gases and vary in the same direction as temperature. Non-seasalt sulfate and methane sulfonic acid are both sulfur species existing in the particle phase, and are positively correlated with each other, but negatively with T. Major variations for all of these variables seem to correlate either positively or negatively with each other, indicating a coupled system. <5D, non-seasalt sulfate, and methane sulfonic acid data kindly provided by Dr Eric Saltzman. CO2 data are from Bamola et al. (1987) and Jouzel et al. (1993). CH4 data are from Chappellaz et al. (1990) and Jouzel et al. (1993). (ppmv = parts per million by volume ppbv = parts per billion by volime)...

Chappellaz, ]., Barnola, J. M., Raynaud, D., Korotkevich, Y. S., and Lorius, C. (1990). Atmospheric methane record over the last climatic cycle revealed by the Vostok ice core. Nature 345,127-131. 

Jouzel, J., Lorius, J. R., Petit, C. et al. (1993). Vostok ice-core - a continuous isotope temperature record over the last climatic cycle (160000 years). Nature 329,403 08. 

Fluxes of continental dust preserved in ice cores of Greenland and Antarctica suggest a 30-fold increase in dust flux during the last Glacial Maximum. Dramatic increases in new biological production in the HNLC regions may have resulted, resulting in the draw-down of atmospheric CO2 (Martin, 1990). 

Berner, W., Oeschger, H. and Stauffer, B. (1980). Information on the CO2 cycle from ice core studies. Radiocarbon 22,227-235. 

Delmas, R. J. (1993). A natural artefact in Greenland ice-core CO2 measurements. Tellus 45B, 391-396. 

Enting, I. G. (1992). The incompatibility of ice-core CO2 data with reconstructions of biotic CO2 sources, II. The influence of C02-fertilised growth. Tellus 44B, 23-32. 

Neftel, A., Oeschger, H., Schwander, J., Stauffer, B. and Zumbrunn, R. (1982). Ice core sample measurements give atmospheric CO2 content during the past 40,000 yr. Nature 295,220-223. 

Siegenthaler, U. and Oeschger, H. (1987). Biospheric CO2 emissions during the past 200 years reconstructed by deconvolution of ice core data, Tellus 39B. 

In remote ice cores, SO and NOJ concentrations have increased due to anthropogenic emissions (Mayewski et ai, 1986, 1990). This is due to the fact the precursor compounds (e.g.. 

Mayewski, P. A. et al. (1990). An ice-core record of atmospheric response to anthropogenic sulfate and nitrate. Nature 346, 554-556. 

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