Ice Core, Firn Air and Archived Air Atmospheric Methane Concentration Data --------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program --------------------------------------------------------------------- NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!! NAME OF DATA SET: Ice Core, Firn Air and Archived Air Atmospheric Methane Concentration Data LAST UPDATE: 6/2002 (Original receipt by WDC Paleo) CONTRIBUTORS: D.M. Etheridge, L.P. Steele, R.J. Francey, and R.L. Langenfelds Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia. IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2002-039 SUGGESTED DATA CITATION: Etheridge, D.M., et al., 2002, Ice Core, Firn Air and Archived Air Atmospheric Methane Concentration Data, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2002-039. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Etheridge, D. M., Steele, L. P., Francey, R. J., and Langenfelds, R. L., 1998, Atmospheric methane between 1000 A.D. and present: Evidence of anthropogenic emissions and climatic variability J. Geophys. Res. Vol. 103, No. D13, p. 15,979 (98JD00923) ADDITIONAL REFERENCES: 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. 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: Global (samples from Antarctica, Tasmania and Greenland) PERIOD OF RECORD: 1008 A.D. to 1992 A.D. LIST OF FILES: Readme_law_ch4.txt (this file), law_ch4.xls (Microsoft Excel format), law_ch4.txt (Tab-delimited ASCII text). DESCRIPTION: Ice Core methane concentration measurements from the Law Dome DE08, DE08-2, and DSS ice cores, plus Greenland Summit (EUROCORE) ice core, are listed. These data are combined with measurements of firn air from DE08-2 and archived air samples from Cape Grim, Tasmania, to calculate global annual mean methane concentrations from 1010 AD to 1992 AD, also listed. Law Dome, Antarctica 66°44'S, 112°50'E, 1390 m. Greenland Summit, 72°34'N, 37°37'E, 3200 m. Archived air samples from Cape Grim, Tasmania, Australia, 40°41'S, 144°41'E, 94 m. The methane ice core records presented here are derived from three cores obtained from Law Dome, East Antarctica from 1987 to 1993, and samples from the Eurocore and GISP2 ice cores from the Summit region, Greenland. The Law Dome sites satisfy many of the desirable characteristics of an ideal ice core site for atmospheric 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 Law Dome sites, drilling, cores, ice dating and air dating are provided in Etheridge et al. (1996), Etheridge and Wookey (1989), Morgan et al. (1997), Levchenko et al. (1996) and Trudinger et al. (1997). The air enclosed in the three ice cores from Law Dome, Antarctica has unparalleled 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). These data supersede those published earlier from the Law Dome ice core DE08 (Etheridge et al., Tellus, 1992) offering greater precision, elimination of a small and variable contamination, and more accurate dating. The methane concentrations were measured by gas chromatography and are given in the CSIRO94 CH4 scale, which is indistinguishable from the NOAA CMDL scale. Precision of each ice core methane measurement is about 5 ppb (1 sigma). The firn air samples were pumped from the firn layer at the DE08-2 drill site. Their effective ages range from 1993 AD for the surface to 1978 AD at a depth of 85 m. The firn air was dated by firn diffusion modelling (Trudinger et al., JGR, 1997). The archived air samples were collected several times per year during "baseline" wind conditions at the Cape Grim station since 1978 AD (Langenfelds et al., 1996). DATA: Atmospheric CH4 mixing ratios, from Law Dome (Antarctica) and Summit (Greenland) ice cores. Etheridge, D.M., L.P. Steele, R.J. Francey, and R.L. Langenfelds, Atmospheric methane between 1000 AD and present: Evidence of anthropogenic emissions and climatic variability. Journal of Geophysical Research, 103, D13, 15,979-15,993, 1998. Please see the above paper or contact David Etheridge, CSIRO, Australia with any queries. CH4 from DE08, DE08-2 and DSS ice cores (Antarctica). From Figure 2. air age (AD) CH4 (ppb) depth (m) ice age (AD) sample no. years before 2000 AD 1008 666.0 534.2 948 DSS 038 992 1048 677.8 523.4 988 DSS 040 952 1098 676.4 505.9 1038 DSS 042 902 1148 685.9 488.3 1088 DSS 043 852 1198 683.7 467.7 1138 DSS 036 802 1248 660.9 447.2 1188 DSS 039 752 1329 672.9 414.0 1269 DSS 034 671 1389 676.3 387.1 1329 DSS 024 611 1389 678.9 387.2 1329 DSS 026 611 1448 681.5 360.6 1388 DSS 022 552 1467 671.4 351.2 1407 DSS 044 533 1501 693.0 336.7 1441 DSS 023 499 1529 698.9 323.7 1469 DSS 035 471 1549 704.3 313.9 1489 DSS 018 451 1572 684.8 302.0 1512 DSS 032 428 1591 665.4 293.2 1531 DSS 021 409 1606 667.7 285.2 1546 DSS 012 394 1622 679.4 276.3 1562 DSS 045 378 1649 674.6 263.4 1589 DSS 013 351 1681 692.0 245.6 1621 DSS 020 319 1694 676.1 238.0 1634 DSS 011 306 1722 671.9 223.0 1662 DSS 019 278 1749 692.9 207.6 1689 DSS 025 251 1751 696.9 206.5 1691 DSS 014 249 1762 703.1 200.5 1702 DSS 031 238 1779 714.4 190.9 1719 DSS 017 221 1796 716.9 181.3 1736 DSS 016 204 1798 728.5 180.0 1738 DSS 015 202 1827 755.8 163.5 1767 DSS 010 173 1834 756.3 242.8 1802 DE08-2 006 166 1842 766.9 228.7 1810 DE08 222 158 1847 763.7 151.6 1787 DSS 009 153 1852 785.5 218.0 1820 DE08 200 148 1856 775.9 214.1 1824 DE08 234 144 1863 789.9 206.1 1831 DE08 232 137 1871 811.9 197.5 1839 DE08 228 129 1879 822.3 190.2 1847 DE08 255 121 1884 828.5 184.3 1852 DE08 229 116 1888 833.6 179.5 1856 DE08 252 112 1893 836.8 122.8 1833 DSS 030 107 1894 852.3 174.4 1862 DE08 241 106 1900 862.4 167.9 1868 DE08 230 100 1901 868.4 116.9 1841 DSS 007 99 1907 891.0 114.3 1847 DSS 033 93 1907 885.3 160.6 1875 DE08 253 93 1907 887.8 160.8 1875 DE08 254 93 1914 921.6 153.0 1882 DE08 239 86 1917 929.9 149.9 1885 DE08 233 83 1926 989.0 138.8 1894 DE08 231 74 1926 991.1 138.8 1894 DE08 237 74 1928 997.0 100.3 1868 DSS 008 72 1931 1006.4 99.7 1871 DSS 041 69 1934 1023.2 130.3 1902 DE08 238 66 1936 1045.2 135.7 1904 DE08-2 011 64 1938 1053.0 94.1 1878 DSS 027 62 1940 1059.9 121.9 1908 DE08 240 60 1941 1055.7 92.7 1881 DSS 037 59 1941 1062.2 121.8 1909 DE08 243 59 1942 1069.1 128.8 1910 DE08-2 007 58 1944 1082.5 90.5 1884 DSS 052 56 1946 1081.8 115.7 1914 DE08 227 54 1950 1103.7 86.2 1890 DSS 029 50 1950 1102.9 120.2 1918 DE08-2 009 50 1955 1143.5 104.3 1923 DE08 236 45 1955 1140.0 104.4 1923 DE08 201 45 1955 1145.3 104.6 1923 DE08 208 45 1956 1164.3 81.8 1896 DSS 001 44 1956 1171.8 81.8 1896 DSS 003 44 1956 1183.8 81.8 1896 DSS 002 44 1957 1179.5 81.4 1897 DSS 047 43 1957 1186.4 81.4 1897 DSS 048 43 1961 1218.5 78.0 1901 DSS 004 39 1964 1258.7 92.7 1932 DE08 214 36 1964 1248.6 92.8 1932 DE08 215 36 1964 1273.3 93.0 1932 DE08 212 36 1964 1260.6 93.2 1932 DE08 213 36 1965 1261.3 92.0 1933 DE08 203 35 1967 1285.2 89.0 1935 DE08 226 33 1967 1278.4 89.2 1935 DE08 225 33 1967 1288.5 74.0 1907 DSS 049 33 1970 1351.7 84.0 1938 DE08 235 30 1971 1357.2 83.1 1939 DE08 205 29 1972 1380.3 92.2 1940 DE08-2 016 28 1972 1379.9 91.6 1940 DE08-2 015 28 1973 1385.8 90.6 1941 DE08-2 005 27 1974 1421.5 70.4 1914 DSS 050 26 1975 1420.4 88.0 1943 DE08-2 002 25 1977 1458.1 85.1 1945 DE08-2 003 23 1980 1479.7 81.1 1948 DE08-2 008 20 1980 1479.3 81.2 1948 DE08-2 012 20 Greenland Ice Core Results. From Figure 3. air age (AD) CH4 (ppb) depth (m) ice age (AD) sample no. years before 2000 AD 1075 701.2 272.1 871 Eurocore 495 925 1121 720.7 261.2 917 Eurocore 475 879 1165 743.1 252.3 971 Eurocore 459 835 1209 734.4 242.9 1015 Eurocore 442 791 1281 706.4 227.9 1080 Eurocore 415 719 1376 710.1 208.9 1177 Eurocore 353 624 1464 706.3 188.4 1262 Eurocore 343 536 1512 732.0 178.4 1308 Eurocore 325 488 1556 750.2 168.7 1351 Eurocore 307 444 1648 712.6 148.9 1442 Eurocore 271 352 1733 724.2 129.1 1527 Eurocore 235 267 1775 759.6 119.2 1572 Eurocore 217 225 1797 761.8 118.7 1602 GISP2 203 1800 766.8 118.0 1605 GISP2 200 1807 774.0 116.6 1612 GISP2 193 1842 808.8 104.1 1639 Eurocore 190 158 1885 875.3 94.2 1681 Eurocore 172 115 CH4 in firn air samples from DE08-2. From Figures 1 and 5. air age AD) CH4 (ppb) depth (m) 1993.1 1652.5 0 7 1993.1 1654.1 0 7 1991.4 1656.3 10 9 1991.4 1659.0 10 9 1991.0 1655.3 15 9 1990.5 1650.5 20 9 1989.6 1639.4 30 10 1989.6 1641.8 30 10 1988.7 1625.0 40 11 1988.7 1626.5 40 11 1987.2 1607.8 55 13 1987.2 1608.6 55 13 1986.7 1603.0 60 13 1986.1 1601.5 65 14 1985.5 1589.6 70 15 1985.5 1593.2 70 15 1984.2 1562.6 75 16 1984.2 1563.9 75 16 1981.5 1497.3 80 19 1981.5 1498.7 80 19 1978.2 1460.9 85 22 CH4 in archive tanks from Cape Grim Station, Tasmania, deseasonalised. From Figure 5. year (AD) CH4 (ppb) 1978.3 1468.3 22 1979.1 1490.9 21 1980.7 1507.7 19 1984.4 1572.9 16 1986.1 1594.6 14 1986.1 1593.2 14 1986.9 1603.5 13 1987.0 1603.5 13 1987.0 1602.3 13 1987.2 1608.5 13 1987.4 1617.2 13 1988.5 1620.9 12 1989.4 1635.0 11 1989.9 1636.3 10 1990.3 1641.7 10 1990.4 1641.5 10 1990.9 1646.6 9 1990.9 1645.7 9 1990.9 1645.5 9 1990.9 1646.2 9 1990.9 1645.4 9 1990.9 1644.2 9 1990.9 1645.6 9 1990.9 1645.1 9 1991.0 1645.2 9 1991.5 1658.7 9 1991.5 1655.5 9 1992.0 1665.8 8 1992.1 1665.9 8 1992.2 1665.8 8 1992.3 1667.1 8 1992.7 1667.9 7 1992.7 1667.1 7 1993.2 1666.7 7 1993.4 1669.7 7 1993.6 1671.4 6 1993.8 1671.1 6 1994.0 1668.8 6 1994.1 1669.2 6 1994.2 1670.1 6 1994.3 1670.4 6 1994.3 1669.3 6 1994.4 1675.5 6 1994.9 1677.7 5 1994.9 1677.2 5 1995.1 1680.4 5 1995.1 1679.7 5 1995.2 1681.9 5 1995.3 1681.2 5 1995.4 1681.2 5 1995.5 1678.6 4 1995.6 1677.6 4 1995.6 1677.9 4 1995.6 1678.8 4 1995.7 1680.5 4 1995.8 1682.8 4 1995.9 1683.6 4 1995.9 1684.0 4 Smoothed line through the ice core data (75 year smoothing spline). From Figure 2. year AD CH4 (ppb) 1010 667.1 990 1015 668.7 985 1020 670.3 980 1025 671.8 975 1030 673.1 970 1035 674.4 965 1040 675.4 960 1045 676.3 955 1050 676.9 950 1055 677.3 945 1060 677.5 940 1065 677.5 935 1070 677.5 930 1075 677.4 925 1080 677.3 920 1085 677.2 915 1090 677.2 910 1095 677.4 905 1100 677.7 900 1105 678.2 895 1110 678.9 890 1115 679.7 885 1120 680.6 880 1125 681.6 875 1130 682.5 870 1135 683.5 865 1140 684.4 860 1145 685.2 855 1150 685.9 850 1155 686.5 845 1160 686.9 840 1165 687.0 835 1170 687.0 830 1175 686.8 825 1180 686.4 820 1185 685.6 815 1190 684.7 810 1195 683.4 805 1200 681.8 800 1205 679.9 795 1210 677.8 790 1215 675.6 785 1220 673.3 780 1225 671.0 775 1230 668.7 770 1235 666.6 765 1240 664.7 760 1245 663.1 755 1250 661.9 750 1255 661.1 745 1260 660.6 740 1265 660.4 735 1270 660.5 730 1275 660.9 725 1280 661.5 720 1285 662.3 715 1290 663.2 710 1295 664.3 705 1300 665.5 700 1305 666.7 695 1310 667.9 690 1315 669.1 685 1320 670.3 680 1325 671.4 675 1330 672.5 670 1335 673.3 665 1340 674.1 660 1345 674.7 655 1350 675.3 650 1355 675.8 645 1360 676.2 640 1365 676.5 635 1370 676.8 630 1375 677.1 625 1380 677.3 620 1385 677.6 615 1390 677.8 610 1395 678.1 605 1400 678.4 600 1405 678.6 595 1410 678.8 590 1415 679.0 585 1420 679.1 580 1425 679.1 575 1430 679.1 570 1435 678.9 565 1440 678.6 560 1445 678.2 555 1450 677.7 550 1455 677.1 545 1460 676.7 540 1465 676.7 535 1470 677.4 530 1475 678.8 525 1480 680.7 520 1485 683.0 515 1490 685.5 510 1495 688.2 505 1500 690.8 500 1505 693.1 495 1510 695.3 490 1515 697.1 485 1520 698.7 480 1525 699.9 475 1530 700.8 470 1535 701.3 465 1540 701.2 460 1545 700.5 455 1550 698.9 450 1555 696.4 445 1560 693.2 440 1565 689.5 435 1570 685.5 430 1575 681.5 425 1580 677.7 420 1585 674.3 415 1590 671.7 410 1595 670.1 405 1600 669.5 400 1605 669.7 395 1610 670.6 390 1615 671.8 385 1620 673.2 380 1625 674.4 375 1630 675.4 370 1635 676.2 365 1640 677.0 360 1645 677.9 355 1650 678.9 350 1655 680.2 345 1660 681.6 340 1665 682.8 335 1670 683.7 330 1675 684.2 325 1680 683.9 320 1685 682.9 315 1690 681.2 310 1695 679.4 305 1700 677.8 300 1705 676.5 295 1710 675.7 290 1715 675.5 285 1720 676.1 280 1725 677.5 275 1730 679.8 270 1735 682.8 265 1740 686.2 260 1745 689.9 255 1750 693.7 250 1755 697.4 245 1760 700.9 240 1765 704.2 235 1770 707.4 230 1775 710.4 225 1780 713.4 220 1785 716.4 215 1790 719.5 210 1795 722.9 205 1800 726.8 200 1805 731.0 195 1810 735.4 190 1815 740.0 185 1820 744.7 180 1825 749.4 175 1830 753.9 170 1835 758.5 165 1840 763.2 160 1845 768.4 155 1850 774.1 150 1855 780.3 145 1860 787.2 140 1865 794.6 135 1870 802.4 130 1875 810.5 125 1880 818.9 120 1885 827.9 115 1890 838.3 110 1895 850.6 105 1900 865.4 100 1905 882.8 95 1910 903.1 90 1915 925.7 85 1920 950.2 80 1925 975.6 75 1930 1001.0 70 1935 1026.4 65 1940 1052.6 60 1945 1081.3 55 1950 1115.7 50 1955 1158.7 45 1960 1211.1 40 1965 1272.1 35 1970 1339.8 30 1975 1410.7 25 1980 1482.2 20 Global mixing ratios calculated over the last 1000 years from Antarctic and Greenland measurements. Smoothing spline fit with 75 year cut off (Table 2 part 1 Etheridge et al., 1998) Also appear in IPCC WGI TAR Chapter 4 Figure 1 and Summary for Policymakers Figures 2 and 11 air age CH4 (ppb) 1010 676.0 990 1020 679.2 980 1030 682.0 970 1040 684.3 960 1050 685.8 950 1060 686.4 940 1070 686.4 930 1080 687.0 920 1090 688.5 910 1100 690.4 900 1110 692.7 890 1120 695.3 880 1130 698.4 870 1140 701.5 860 1150 704.3 850 1160 706.8 840 1170 707.4 830 1180 706.3 820 1190 704.5 810 1200 701.9 800 1210 698.6 790 1220 694.3 780 1230 690.0 770 1240 686.0 760 1250 682.8 750 1260 680.6 740 1270 679.1 730 1280 678.3 720 1290 679.3 710 1300 680.9 700 1310 682.6 690 1320 684.2 680 1330 685.8 670 1340 686.9 660 1350 687.8 650 1360 688.5 640 1370 689.0 630 1380 689.4 620 1390 689.5 610 1400 689.7 600 1410 689.8 590 1420 689.9 580 1430 689.7 570 1440 689.2 560 1450 688.5 550 1460 687.7 540 1470 689.3 530 1480 693.4 520 1490 698.4 510 1500 703.8 500 1510 708.6 490 1520 712.3 480 1530 715.1 470 1540 716.9 460 1550 716.9 450 1560 713.7 440 1570 707.4 430 1580 700.9 420 1590 695.6 410 1600 692.7 400 1610 691.9 390 1620 692.0 380 1630 691.8 370 1640 691.3 360 1650 691.5 350 1660 693.7 340 1670 695.5 330 1680 696.1 320 1690 694.9 310 1700 693.3 300 1710 692.5 290 1720 693.2 280 1730 696.1 270 1740 702.3 260 1750 710.2 250 1760 717.8 240 1770 725.0 230 1780 730.7 220 1790 734.9 210 1800 741.6 200 1810 750.8 190 1820 760.3 180 1830 769.8 170 1840 779.4 160 1850 791.6 150 1860 805.6 140 1870 821.0 130 1880 837.1 120 1890 856.6 110 Smoothing from here down has 12.5 year cut-off (Table 2 part 2 Etheridge et al., 1998) 1900 879.4 100 1902 887.9 98 1904 896.5 96 1906 905.3 94 1908 914.4 92 1910 924.0 90 1912 933.9 88 1914 944.3 86 1916 955.1 84 1918 966.4 82 1920 978.1 80 1922 989.9 78 1924 1001.8 76 1926 1013.6 74 1928 1025.0 72 1930 1036.2 70 1932 1047.2 68 1934 1058.0 66 1936 1068.7 64 1938 1078.9 62 1940 1088.9 60 1942 1099.0 58 1944 1109.4 56 1946 1120.6 54 1948 1133.2 52 1950 1147.5 50 1952 1163.8 48 1954 1182.1 46 1956 1202.4 44 1958 1224.2 42 1960 1247.5 40 1962 1272.2 38 1964 1298.4 36 1966 1326.0 34 1968 1355.3 32 1970 1386.0 30 1972 1417.5 28 1974 1449.3 26 1976 1481.5 24 1978 1514.0 22 1980 1547.1 20 1982 1580.9 18 1984 1614.2 16 1986 1644.9 14 1988 1671.6 12 1990 1694.3 10 1992 1714.0 8