Law Dome Atmospheric CO2 Data: Readme file --------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program --------------------------------------------------------------------- NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!! NAME OF DATA SET: Law Dome Atmospheric CO2 Data LAST UPDATE: 12/2001 (Original receipt by WDC Paleo) CONTRIBUTORS: D.M. Etheridge, L.P. Steele, R.L. Langenfelds and R.J. Francey Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia. J.-M. Barnola Laboratoire de Glaciologie et Géophysique de l'Environnement, Saint Martin d'Hères-Cedex, France V.I. Morgan Antarctic CRC and Australian Antarctic Division, Hobart, Tasmania, Australia IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2001-083 SUGGESTED DATA CITATION: Etheridge, D.M., et al., 2001, Law Dome Atmospheric CO2 Data, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2001-083. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Etheridge, D.M., L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M. Barnola, and V.I. Morgan. 1996. Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn. Journal of Geophysical Research 101:4115-4128. ADDITIONAL REFERENCES: Etheridge, D.M., and C.W. Wookey. 1989. Ice core drilling at a high accumulation area of Law Dome, Antarctica. In Ice Core Drilling, edited by C. Rado and D. Beaudoing, pp. 86-96. Proceedings of the Third International Workshop on Ice Core Drilling Technology, Grenoble, France, October 10-14, 1988, CNRS, Grenoble. Etheridge, D.M., G.I. Pearman, and F. de Silva. 1988. Atmospheric trace-gas variations as revealed by air trapped in an ice core from Law Dome, Antarctica. Ann. Glaciol. 10:28-33. Etheridge, D.M., G.I. Pearman, and P.J. Fraser. 1992. Changes in tropospheric methane between 1841 and 1978 from a high accumulation rate Antarctic ice core. Tellus 44B:282-294. Hamley, T.C., V.I. Morgan, R.J. Thwaites, and X.Q. Gao. 1986. An ice-core drilling site at Law Dome summit, Wilkes Land, Antarctica, Res. Note 37, Aust. Natl. Antarc. Res. Exped., Tasmania. Morgan, V.I., C.W. Wookey, J. Li, T.D. van Ommen, W. Skinner, and M.F. Fitzpatrick. 1997. Site information and initial results from deep ice drilling on Law Dome. J. Glaciol. 43:3-10. Levchenko, V. A., Francey, R. J., Etheridge, D. M., Tuniz, C., Head, J., Morgan, V. I., and Jacobsen, G., 1996. The 14C "bomb spike" determines the age spread and age of CO2 in Law Dome firm and ice. Geophysical Research Letters, 23 (23): 3345-3348. Trudinger, C. M., Enting, I. G., Etheridge, D. M., Francey, R. J., Levchenko, V. A., Steele, L. P., Raynaud, D., and Arnaud, L., 1997. Modeling air movement and bubble trapping in firn. Journal of Geophysical Research, 102 (D6): 6747-6763. Trudinger, C. M., Enting, I. G., Francey, R. J., Etheridge, D. M., and Rayner, P. J. (1999). Long-term variability in the global carbon cycle inferred from a high precision CO2 and d13C ice core record . Tellus, 51 (2): 233-248. Langenfelds, R.L., P.J. Fraser, R.J. Francey, L.P. Steele, L.W. Porter, and C.E. Allison, The Cape Grim Air Archive: The first seventeen years, 1978-1995, in Baseline Atmospheric Program Australia, 1994-95, edited by R.J. Francey, et al., pp. 53-70, Bur. of Meteorol. and CSIRO Div. of Atmos. Res., Melbourne, Victoria, 1996. GEOGRAPHIC REGION: Antarctica PERIOD OF RECORD: 1006 A.D. to 1978 A.D. LIST OF FILES: Readme_law_co2.txt (this file), law_co2.txt(Tab-delimited ASCII text). DESCRIPTION: Ice Core CO2 records from the Law Dome DE08, DE08-2, and DSS ice cores. Law Dome, Antarctica 66°44' S, 112°50' E, 1390 mean annual sea level (M.A.S.L.) 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). 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. Methods 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, (aa), that is younger than the age of the host ice layer (ai), from which the air is extracted. The difference (a) equals the time (Ts) for the ice layer to reach a depth (ds), where air becomes sealed in the pore space, minus the mean time (Td) for air to mix down the depth. The mean air age is thus aa = ai + a = ai + Ts - Td 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 density 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). Historical CO2 record from the Law Dome DE08, DE08-2, and DSS ice cores D.M. Etheridge L.P. Steele R.L. Langenfelds R.J. Francey Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia J.-M. Barnola Laboratoire of Glaciologie et Geophysique de l'Environnement, Saint Martin d'Heres-Cedex, France V.I. Morgan Antarctic CRC and Australian Antarctic Division, Hobart, Tasmania, Australia Ice Sample Analysis Mean Ice Depth, Ice Age, Mean Air Age, CO2 Mixing Ratio, Code Date m year A.D. year A.D. ppm DE08 205 20-Aug-92 83.10 1939 1969 323.2 DE08 235 12-Aug-93 83.98 1938 1968 323.7 DE08 225 2-Aug-93 89.15 1935 1965 319.5 DE08 226 2-Aug-93 89.00 1935 1965 318.8 DE08 203 5-Aug-92 91.95 1933 1963 318.2 DE08 212 14-Jul-93 93.00 1932 1962 318.7 DE08 213 14-Jul-93 93.15 1932 1962 317.0 DE08 214 15-Jul-93 92.68 1932 1962 319.4 DE08 215 15-Jul-93 92.84 1932 1962 317.0 DE08 201 27-Jul-92 104.44 1923 1953 311.9 DE08 208 13-Nov-92 104.61 1923 1953 311.0 DE08 236 12-Aug-93 104.29 1923 1953 312.7 DE08 227 2-Aug-93 115.66 1914 1944 309.7 DE08 243 8-Oct-93 121.80 1909 1939 311.0 DE08 240 19-Aug-93 121.90 1908 1938 310.5 DE08 238 13-Aug-93 130.27 1902 1932 307.8 DE08 231 10-Aug-93 138.79 1894 1924 304.8 DE08 237 13-Aug-93 138.79 1894 1924 304.1 DE08 233 11-Aug-93 149.86 1885 1915 301.3 DE08 239 17-Aug-93 153.00 1882 1912 300.7 DE08 253 19-Jul-95 160.70 1875 1905 296.9 DE08 254 3-Aug-95 160.90 1875 1905 298.5 DE08 230 10-Aug-93 167.86 1868 1898 294.7 DE08 241 19-Aug-93 174.39 1862 1892 294.6 DE08 252 19-Jul-95 179.50 1856 1886 293.7 DE08 229 10-Aug-93 184.31 1852 1882 291.9 DE08 255 3-Aug-95 190.30 1847 1877 288.8 DE08 228 6-Aug-93 197.54 1839 1869 287.4 DE08 232 11-Aug-93 206.09 1831 1861 286.6 DE08 234 12-Aug-93 214.10 1824 1854 284.9 DE08 200 26-Jun-92 218.02 1820 1850 285.2 DE08 222 29-Jul-93 228.74 1810 1840 283.0 Ice Sample Analysis Mean Ice Depth, Ice Age, Mean Air Age, CO2 Mixing Ratio Code Date m year A.D. year A.D. ppm DE08-2 008 9-Dec-93 81.11 1948 1978 335.2 DE08-2 012 15-Dec-93 81.30 1948 1978 332.0 DE08-2 003 17-Aug-93 85.05 1945 1975 331.2 DE08-2 002 6-Aug-93 87.96 1943 1973 328.1 DE08-2 005 24-Aug-93 90.55 1941 1971 324.1 DE08-2 015 3-Aug-95 91.69 1940.2 1970 325.2 DE08-2 016 3-Aug-95 92.30 1939.7 1970 324.7 DE08-2 009 15-Dec-93 120.27 1918 1948 309.9 DE08-2 007 9-Dec-93 128.79 1910 1940 310.5 DE08-2 011 15-Dec-93 135.82 1904 1934 309.2 DE08-2 006 9-Dec-93 242.81 1802 1832 284.5 Ice Sample Analysis Mean Ice Depth, Ice Age, Mean Air Age, CO2 Mixing Ratio, Code Date m year A.D. year A.D. ppm DSS 004 13-Nov-92 78.02 1901 1959 315.7 DSS 001 20-Aug-92 81.82 1896 1954 313.6 DSS 002 21-Aug-92 81.82 1896 1954 314.7 DSS 003 21-Aug-92 81.82 1896 1954 314.1 DSS 029 24-Nov-93 86.19 1890 1948 311.4 DSS 037 7-Jun-95 92.86 1881 1939 309.2 DSS 027 18-Nov-93 94.13 1878 1936 307.9 DSS 041 15-Jun-95 99.82 1871 1929 305.2 DSS 008 13-Aug-93 100.32 1868 1926 305.0 DSS 033 2-Jun-95 114.45 1847 1905 299.0 DSS 007 11-Aug-93 116.89 1841 1899 296.5 DSS 030 24-Nov-93 122.82 1833 1891 294.7 DSS 009 20-Aug-93 151.56 1787 1845 286.1 DSS 010 20-Aug-93 163.51 1767 1825 285.1 DSS 015 8-Oct-93 179.97 1738 1796 283.7 DSS 016 14-Oct-93 181.34 1736 1794 281.6 DSS 017 14-Oct-93 190.88 1719 1777 279.5 DSS 031 2-Jun-95 200.64 1702 1760 276.7 DSS 014 23-Aug-93 206.50 1691 1749 277.2 DSS 025 10-Nov-93 207.58 1689 1747 276.9 DSS 019 21-Oct-93 223.01 1662 1720 277.5 DSS 011 20-Aug-93 238.00 1634 1692 276.5 DSS 020 21-Oct-93 245.63 1621 1679 275.9 DSS 013 23-Aug-93 263.35 1589 1647 277.2 DSS 012 23-Aug-93 285.20 1546 1604 274.3 DSS 021 28-Oct-93 293.20 1531 1589 278.7 DSS 032 2-Jun-95 302.14 1512 1570 281.9 DSS 018 21-Oct-93 313.93 1489 1547 282.8 DSS 035 7-Jun-95 323.84 1469 1527 283.2 DSS 023 10-Nov-93 336.73 1441 1499 282.4 DSS 044 30-Jun-95 351.30 1407 1465 279.6 DSS 022 28-Oct-93 360.64 1388 1446 281.7 DSS 024 10-Nov-93 387.13 1329 1387 280.0 DSS 026 18-Nov-93 387.20 1329 1387 280.4 DSS 034 5-Jun-95 414.22 1269 1327 283.4 DSS 039 14-Jun-95 447.34 1188 1246 281.7 DSS 036 9-Jun-95 467.85 1138 1196 283.9 DSS 043 30-Jun-95 488.46 1088 1146 283.8 DSS 042 15-Jun-95 506.03 1038 1096 282.4 DSS 040 14-Jun-95 523.56 988 1046 280.3 DSS 038 12-Jun-95 534.27 948 1006 279.4 Mean Air Age, CO2, 20 Year Smoothed, year A.D. ppm 1832 284.3 1833 284.1 1834 284.0 1835 283.8 1836 283.7 1837 283.5 1838 283.4 1839 283.4 1840 283.4 1841 283.4 1842 283.5 1843 283.6 1844 283.7 1845 283.9 1846 284.1 1847 284.2 1848 284.4 1849 284.6 1850 284.7 1851 284.9 1852 285.0 1853 285.1 1854 285.3 1855 285.4 1856 285.6 1857 285.7 1858 285.9 1859 286.1 1860 286.2 1861 286.4 1862 286.5 1863 286.6 1864 286.8 1865 286.9 1866 287.0 1867 287.1 1868 287.2 1869 287.4 1870 287.5 1871 287.7 1872 287.9 1873 288.1 1874 288.4 1875 288.7 1876 289.0 1877 289.4 1878 289.8 1879 290.2 1880 290.7 1881 291.2 1882 291.7 1883 292.1 1884 292.6 1885 293.0 1886 293.3 1887 293.6 1888 293.8 1889 294.0 1890 294.2 1891 294.3 1892 294.5 1893 294.6 1894 294.7 1895 294.8 1896 294.9 1897 295.0 1898 295.2 1899 295.5 1900 295.8 1901 296.1 1902 296.5 1903 296.8 1904 297.2 1905 297.6 1906 298.1 1907 298.5 1908 298.9 1909 299.3 1910 299.7 1911 300.1 1912 300.4 1913 300.8 1914 301.1 1915 301.4 1916 301.7 1917 302.1 1918 302.4 1919 302.7 1920 303.0 1921 303.4 1922 303.8 1923 304.1 1924 304.5 1925 305.0 1926 305.4 1927 305.8 1928 306.3 1929 306.8 1930 307.2 1931 307.7 1932 308.2 1933 308.6 1934 309.0 1935 309.4 1936 309.8 1937 310.0 1938 310.2 1939 310.3 1940 310.4 1941 310.4 1942 310.3 1943 310.2 1944 310.1 1945 310.1 1946 310.1 1947 310.2 1948 310.3 1949 310.5 1950 310.7 1951 311.1 1952 311.5 1953 311.9 1954 312.4 1955 313.0 1956 313.6 1957 314.2 1958 314.9 1959 315.6 1960 316.3 1961 317.0 1962 317.7 1963 318.4 1964 319.2 1965 320.0 1966 320.8 1967 321.8 1968 322.8 1969 323.8 1970 324.8 1971 325.8 1972 326.9 1973 328.0 1974 329.2 1975 330.3 1976 331.5 1977 332.6 1978 333.7 Mean Air Age, CO2, 75 Year Smoothed, year A.D. ppm 1010 279.5 1015 279.6 1020 279.7 1025 279.8 1030 279.9 1035 280.0 1040 280.2 1045 280.3 1050 280.5 1055 280.7 1060 280.9 1065 281.1 1070 281.3 1075 281.5 1080 281.7 1085 281.9 1090 282.1 1095 282.3 1100 282.5 1105 282.7 1110 282.9 1115 283.0 1120 283.2 1125 283.3 1130 283.5 1135 283.6 1140 283.7 1145 283.8 1150 283.9 1155 284.0 1160 284.0 1165 284.1 1170 284.1 1175 284.1 1180 284.0 1185 284.0 1190 283.9 1195 283.8 1200 283.6 1205 283.4 1210 283.2 1215 283.0 1220 282.8 1225 282.5 1230 282.3 1235 282.2 1240 282.0 1245 281.9 1250 281.9 1255 281.9 1260 282.0 1265 282.1 1270 282.2 1275 282.3 1280 282.5 1285 282.6 1290 282.8 1295 282.9 1300 283.0 1305 283.1 1310 283.2 1315 283.3 1320 283.3 1325 283.2 1330 283.1 1335 282.9 1340 282.7 1345 282.4 1350 282.1 1355 281.8 1360 281.5 1365 281.2 1370 281.0 1375 280.7 1380 280.5 1385 280.4 1390 280.3 1395 280.3 1400 280.3 1405 280.4 1410 280.5 1415 280.6 1420 280.7 1425 280.8 1430 280.9 1435 280.9 1440 280.9 1445 280.9 1450 280.8 1455 280.7 1460 280.6 1465 280.6 1470 280.6 1475 280.8 1480 281.0 1485 281.3 1490 281.6 1495 281.9 1500 282.2 1505 282.5 1510 282.7 1515 282.9 1520 283.1 1525 283.2 1530 283.2 1535 283.2 1540 283.1 1545 283.0 1550 282.8 1555 282.6 1560 282.2 1565 281.8 1570 281.2 1575 280.5 1580 279.7 1585 278.8 1590 278.0 1595 277.1 1600 276.4 1605 275.8 1610 275.5 1615 275.3 1620 275.3 1625 275.4 1630 275.6 1635 275.9 1640 276.1 1645 276.3 1650 276.4 1655 276.5 1660 276.5 1665 276.5 1670 276.4 1675 276.4 1680 276.4 1685 276.4 1690 276.5 1695 276.6 1700 276.7 1705 276.8 1710 276.9 1715 277.0 1720 277.0 1725 277.0 1730 277.0 1735 276.9 1740 276.9 1745 276.9 1750 277.0 1755 277.2 1760 277.6 1765 278.0 1770 278.6 1775 279.3 1780 280.1 1785 280.8 1790 281.6 1795 282.3 1800 282.9 1805 283.4 1810 283.8 1815 284.0 1820 284.2 1825 284.3 1830 284.4 1835 284.5 1840 284.6 1845 284.8 1850 285.2 1855 285.7 1860 286.3 1865 287.2 1870 288.2 1875 289.4 1880 290.8 1885 292.3 1890 293.7 1895 295.2 1900 296.7 1905 298.2 1910 299.9 1915 301.5 1920 303.2 1925 304.9 1930 306.5 1935 308.0 1940 309.3 1945 310.5 1950 312.0 1955 314.1 1960 316.9 1965 320.5 1970 324.7 1975 329.4