Do glaciers tell a true atmospheric CO2 story?

1992, Science of The Total Environment

Abstract

Until 1985 most studies of CO2 in gas inclusions in pre-industrial ice indicated that CO 2 concentrations (up to 2450 ppm) were higher than the current atmospheric level. After 1985, lower pre-industrial CO 2 values were reported, and used as evidence for a recent man-made CO2 increase. The errors in these revised values, however, are of a similar magnitude to the apparent increase in atmospheric CO 2 level. The assumptions used in estimating lower CO 2 values in past atmospheres have been: no liquid phase in polar ice; younger age of air than of ice due to free gas exchange between deep firn and the atmosphere; and no change in composition of air inclusions. These assumptions are shown to be invalid. Liquid saline water exists in ice at low temperatures, even below-70°C; airtight ice layers are ubiquitous in Antarctic firn; and more than 20 physico-chemical processes operating in situ and in ice cores contribute to the alteration of the chemical composition of air inclusions. The permeable ice sheet with its capillary liquid network acts as a sieve which redistributes elements, isotopes, and micro-particles. Thirty-six to 100% of air recovered from old ice is contaminated by recent atmospheric air during field and laboratory operations. The value of-290 ppm, widely accepted from glacier studies for the pre-industrial atmospheric CO 2 level, apparently results from: invalid assumptions; processes in ice sheets; artifacts in ice cores; and arbitrary rejection of high readings. To date, glaciological studies are not able to provide a reliable reconstruction of either the CO 2 level in pre-industrial and ancient atmospheres or paleoclimates. Instead these studies have led to a widely accepted false dogma of man-made climatic warming. This dogma may have enormous negative impact on our common future.

Figures (17)

Concentrations of CO, in glacier ice (ppm by volume)

Concentrations of CO, in air bubbles from three Antarctic ice cores at the starting depth TABLE 2

Fig. 4. Errors of measurement of CO, in air bubbles of ice cores from Greenland and Ant- arctica (Oeschger et al., 1985) and claimed man-made increases of CO, level in recent Ant- arctic ice samples due to fossil fuel burning (A, Pearman et al., 1986; B, Raynaud and Barnola, 1985; C, Neftel et al., 1985). Solid lines indicate + 1 S.D.; broken lines indicate + 2 S.D. with the temporal differences in CO, concentrations in ice used in suppor’ of claims discussed above that the level of this gas has increased in the at mosphere due to man’s activity. This "CO, glacier signal’ was in the case o! Raynaud and Barnola (1985) 17 ppm, in the case of Neftel et al. (1985) 4¢ ppm, and in the case of Pearman et al. (1986) 13 ppm (Fig. 4). According tc Oeschger et al. (1985) the ‘errors’ (at assumed 68% probability) of singl measurements of CO, in air trapped in ice cores from Greenland and Ant arctica range between 11 and 24 ppm. At an assumed 95% probability, the ‘errors’ of measurements reach about 47 ppm (Fig. 4). Thus the claimec signals of man-made CO, increase are of the same magnitude as the range of uncertainty of measurements. In air hubbles from neishboring | 5-cm thick slices of an Antarctic ice

Fig. 5. Two sets of CO, concentrations in gas recovered from the Byrd ice core (Antarctica); redrawn from Neftel et al. (1982) (dots and bars for median and range) and Neftel et al. (1988) (shadowed areas represent the reported lo errors). Because the data have very wide variations Neftel et al. (1982) have shown the median values. Note that wide variations high readings from both upper and lower parts of the core recorded in 1982 were not presented in 1988.

samples were rich in cracks, the bubble pressure was much lower than the load pressure. This difference was due to gas release through the cracks. A similar pressure reduction was recorded in ice cores from various sites (Langway, 1958; Gow, 1968b; Gow and Wiliamson, 1975). In the Mizuho core the cracks were associated with up to an ~ 40% decrease in the gas con- tent of the ice (Nakawo and Narita, 1985). For the same Mizuho core, Narita and Nakawo (1985) reported pressure-cracked bubbles, with ’brims’ which might be caused by thermal shock and pressure release. Similar crack rings, and a fissure-like distortion of the ice structure, were observed in and around relaxed air bubbles by Shoji and Langway (1983). wT. .*4. «ff. Jl eT i kt! PE” io GY ch, Cee %y .— fi, ._4,% gf Bt gg le

Concentrations of Pb and Zn in surface snow and contaminated ice cores from East Antarctica (pg/g)

*Boutron et al. (1990). ’Boutron et al. (1987). Concentrations of SO,7", Al and Na in surface snow from Antarctica and in central parts o contaminated Vostok ice core (ng/g)

Fig. 9. Schematic illustration of processes occurring in the top 1-2 m of snow and firn strata in cold polar ice sheets (not to scale). Absorption of solar radiation at low temperature partly volatilizes and melts the snow flakes. Snow is metamorphosed to firn. The thermal gradient and gravitational compression of snow cause upward movement of gas. Some air escapes from snow and firn back to the atmosphere, and H,O vapor condenses near the wind-cooled sur- face. Depth hoar forms due to loss of material by sublimation. Meltwater seeps down and col- lects over impermeable layers.

Fig. 10. Concentrations of CO, in the Siple (Antarctica) ice core: (a) with, and (b) without assuming a 95-year younger age of air than the age of the enclosing ice. The crossed line represents the reported atmospheric CO, concentrations at Mauna Loa (Hawaii). The reported analytical uncertainty, = + 3 ppm, is larger than the size of the data points. The core was partially melted during transportation (Etheridge et al., 1988). Without assuming the age difference, the Siple and Mauna Loa curves cannot be made to overlay each other. (a) Adapted from Siegenthaler and Oeschger (1987) and Bolin et al. (1989); (b) from Fig. 3.

Composition of air in the atmosphere and in glacier ice

Fig. 11. Processes influencing the chemical and isotopic composition of air inclusions in ice. Depth is the dependent abscissa. Adapted after: Barnola et al. (1987) — CO, concentration in gas inclusions in the Vostok core and their assigned age; Gow (1971), Gow and Williamson (1975), Gow and Williamson (1976) — core volume expansion, air bubble disappearance, for- mation of secondary cavities, brittle ice, pressure in air inclusions 3 years after drilling, crystal size in the Byrd core; Vostretsov et al. (1984) — temperature in the Vostok borehole; the verti- cal arrow D indicates the total disappearance of air bubbles in the Vostok core, after Korotkevich et al. (1978); the vertical arrows C indicate the sites of highest contamination of the inner parts of the Vostok core with Pb, Zn, Al and Na from drilling fluid, after Boutron et al. (1987, 1990).