Historical CO₂ records from the Law Dome
DE08, DE08-2, and DSS ice cores

Source

Period of Record

1006 A.D.-1978 A.D.

[Karl Note:  The information presented here is VERY carefully dry and politically correct.  Normally this type of data is presented in a context of the disaster awaiting the planet if "something" isn't done yesterday.  Many people have used the data on this page to "prove" many things.  I, Karl Loren, wish to draw only the simple undeniable conclusion that the percentage of carbon dioxide in the atmosphere has increased dramatically over time, with the largest rate of increase from 1830 to present time.  What you might want to conclude from this is somewhat up to you, but I suggest that the very air we breathe, despite its relatively constant percentage of oxygen, contains other components (including carbon dioxide) that could well be a major factor in health.

The actual amount of carbon dioxide shown with these very, very precise studies varies from a very stable range of about 175 PPM over a period of some 1800 years from the year 1000 to 1830.

After 1830 the amount of carbon dioxide in the atmosphere increased dramatically to where it is now, at about 320, or so, PPM.   This virtual doubling in 150 years, compared to almost no change for 1800 years may have dramatic consequences on health]

Methods

The CO₂ records presented here are derived from three ice cores obtained at Law Dome, East Antarctica from 1987 to 1993. The Law Dome site satisfies many of the desirable characteristics of an ideal ice core site for atmospheric CO₂ reconstructions including negligible melting of the ice sheet surface, low concentrations of impurities, regular stratigraphic layering undisturbed at the surface by wind or at depth by ice flow, and high snow accumulation rate. Further details on the site, drilling, and cores are provided in Etheridge et al. (1996), Etheridge and Wookey (1989), and Morgan et al (1997).

Air bubbles were extracted using the "cheese grater" technique. Ice core samples weighing 500-1500 g were prepared by selecting crack-free ice and trimming away the outer 5-20 mm. Each sample was sealed in a polyethylene bag and cooled to -80°C before being placed in the extraction flask where it was evacuated and then ground to fine chips. The released air was dried cryogenically at -100°C and collected cryogenically in electropolished stainless steel "traps", cooled to about -255°C. Further details on the extraction technique can be found in Etheridge et al. (1988 and 1992) and additional information on the ice and air sample handling are provided in Etheridge et al. (1996).

The ice core air samples, ranging from about 50 to 150 ml standard temperature and pressure (STP), were measured for CO₂ mixing ratio with a Carle 400 Series analytical gas chromatograph (GC). After separation on the GC columns, the CO₂ was catalytically converted to methane before flame ionization detection. As many as three separate analysis were made on each ice core sample. Each sample injection to the GC was bracketed by calibration gas injections. CO₂ mixing ratios were then found for each aliquot by multiplying the ratio of the sample peak area to calibration gas peak area (interpolated to the time of sample analysis) by the CO₂ mixing ratio assigned to the calibration gas. The precision of analysis of the Law Dome ice core air samples was 0.2 ppm. For greater details on the experimental techniques used on the DE08, DE08-2, and DSS ice cores, please refer to Etheridge et al. (1996).

The ice cores were dated by counting the annual layers in oxygen isotope ratio (¹⁸O in H₂O), ice electroconductivity measurements (ECM), and hydrogen peroxide (H₂O₂) concentrations. For these three parameters, each core displayed clear, well-preserved seasonal cycles allowing a dating accuracy of ±2 years at 1805 A.D. for the three cores and ±10 years at 1350 A.D. for DSS.

The enclosed air at any depth in the ice has a mean age, (a_a), that is younger than the age of the host ice layer (a_i), from which the air is extracted. The difference (a) equals the time (T_s) for the ice layer to reach a depth (d_s), where air becomes sealed in the pore space, minus the mean time (T_d) for air to mix down the depth. The mean air age is thus

a_a = a_i + a = a_i + T_s - T_d

where ages are dates A.D.

Mixing of air from the ice sheet surface to the sealing depth is primarily by molecular diffusion. The rate of air mixing by diffusion in the firn decreases as the density increases and the open porosity decreases with depth. Etheridge et al. (1996) determined the sealing depth at DE08 to be 72 m where the age of the ice is 40±1 years; at DE08-2 to be 72 m depth and 40 years; and at DSS to be 66 m depth and 68 years. For more details on dating the Law Dome ice cores and sealing densities, please refer to Etheridge et al. (1996).

 

Law Dome, Antarctica
66°44' S, 112°50' E, 1390 mean annual sea level (M.A.S.L.)

Graphical Representations

[Karl Note:  The image above, somewhat indistinct, shows a range of dates from the year 1830 to 1980!  During that period of time the amount of CO2 increased on at a dramatic rate.]

[Karl Note:  The image above, somewhat indistinct, shows a range of dates from the year 1000 to 2000!  During that period of time the amount of CO2 stayed fairly level until about 1830 when it started to rise, dramatically.]

Trends

The atmospheric CO₂ reconstructions presented here offer records of atmospheric CO₂ mixing ratios from 1006 A.D. to 1978 A.D. The air enclosed in the three ice cores from Law Dome, Antarctica has unparalled age resolution and extends into recent decades, because of the high rate of snow accumulation at the Law Dome drill sites (Etheridge et al. 1996). Etheridge et al. (1996) reported the uncertainty of the ice core CO₂ mixing ratios is 1.2 ppm. Preindustrial CO₂ mixing ratios were in the range 275-284 ppm, with the lower levels during 1550-1800 A.D., probably as a result of colder global climate (Etheridge et al. 1996). The Law Dome ice core CO₂ records show major growth in atmospheric CO₂ levels over the industrial period, except during 1935-1945 A.D. when levels stabilized or decreased slightly.

References

Graphics Digital Data

Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia

Laboratoire de Glaciologie et Géophysique de l'Environnement, Saint Martin d'Hères-Cedex, France

Antarctic CRC and Australian Antarctic Division, Hobart, Tasmania, Australia

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