EPICA Dronning Maud Land CO2 Data for the Last Millennium ----------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program ----------------------------------------------------------------------- NOTE: PLEASE CITE CONTRIBUTORS WHEN USING THIS DATA!!!!! NAME OF DATA SET: EPICA Dronning Maud Land CO2 Data for the Last Millennium LAST UPDATE: 12/2005 (Original receipt by WDC Paleo) CONTRIBUTORS: Urs Siegenthaler, Eric Monnin, Kenji Kawamura, Renato Spahni, Jakob Schwander, Bernhard Stauffer, Thomas F. Stocker Climate and Environmental Physics, Physics Institute, University of Bern, Switzerland Jean-Marc Barnola Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE, CNRS-UJF), Grenoble, France Hubertus Fischer Alfred-Wegener-Institute for Polar and Marine Research (AWI), Bremerhaven, Germany. IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2005-081 SUGGESTED DATA CITATION: Siegenthaler, U., et al. 2005. EPICA Dronning Maud Land CO2 Data for the Last Millennium. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2005-081. NOAA/NCDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Siegenthaler, U., E. Monnin, K. Kawamura, R. Spahni, J. Schwander, B. Stauffer, T.F. Stocker, J.-M. Barnola and H. Fischer. 2005. Supporting evidence from the EPICA Dronning Maud Land ice core for atmospheric CO2 changes during the past millennium. Tellus 57B, 51-57(7), doi: 10.1111/j.1600-0889.2005.00131.x. ABSTRACT: The most direct method of investigating past variations of the atmospheric CO2 concentration before 1958, when continuous direct atmospheric CO2 measurements started, is the analysis of air extracted from suitable ice cores. Here we present a new detailed CO2 record from the Dronning Maud Land (DML) ice core, drilled in the framework of the European Project for Ice Coring in Antarctica (EPICA) and some new measurements on a previously drilled ice core from the South Pole. The DML CO2 record shows an increase from about 278 to 282 parts per million by volume (ppmv) between AD 1000 and AD 1200 and a fairly continuous decrease to a mean value of about 277 ppmv around AD 1700. While the new South Pole measurements agree well with DML at the minimum at AD 1700 they are on average about 2 ppmv lower during the period AD 1000-1500. Published measurements from the coastal high-accumulation site Law Dome are considered as very reliable because of the reproducibility of the measurements, high temporal resolution and an accurate time scale. Other Antarctic ice cores could not, or only partly, reproduce the pre-industrial measurements from Law Dome. A comparison of the trends of DML and Law Dome shows a general agreement. However we should be able to rule out co-variations caused by the same artefact. Two possible effects are discussed, first production of CO2 by chemical reactions and second diffusion of dissolved air through the ice matrix into the bubbles. While the first effect cannot be totally excluded, comparison of the Law Dome and DML record shows that dissolved air diffusing to bubbles cannot be responsible for the pre-industrial variation. Therefore, the new record is not a proof of the Law Dome results but the first very strong support from an ice core of the Antarctic plateau. GEOGRAPHIC REGION: Antarctica PERIOD OF RECORD: 950 - 1890 AD FUNDING SOURCES: This work is a contribution to the "European Project for Ice Coring in Antarctica" (EPICA), a joint ESF (European Science Foundation)/EC scientific programme, funded by the European Commission and by national contributions from Belgium, Denmark, France, Germany, Italy, the Netherlands, Norway, Sweden, Switzerland and the United Kingdom. The measurements were supported by the Swiss NSF, University of Bern and the "Bundesamt für Energie". DESCRIPTION: We measured samples covering the time period from 950 to 1900 yr A.D. on 71 and 14 depth intervals of the DML and the South Pole ice core, respectively. At each depth interval of 60-100 mm, six samples were measured. The DML and South Pole data are corrected for gravitational separation of gases in the firn column based on the barometric formula to get closer to the true atmospheric value. For DML, a tentative timescale was used by adjusting the DML timescale to Dome C by comparing the records of electrical conductivity of both cores. The difference of gas age/ice age (D age) was assumed as 825 yrs. For the South Pole record, a new timescale was calculated, because an event recorded with the electrical conductivity method (ECM) attributed to a volcanic eruption in 1259 yr A.D. [Langway et al., 1988] indicates that the timescale used in Siegenthaler et al. [1988] is too young at this depth. This results in a lower average accumulation rate of 76.2 kg m-2yr-1 compared to the previously used value of 84 kg m-2yr-1. On average, the South Pole scale was about 200 yrs too young over the last millennium. Core locations: DML: 75°00'S, 00°04'E, 2892 m above sea level South Pole: 90°S DATA: 1. DML measurements: Column 1: DML depth (m) Column 2: DML gasage (years before AD 1950) Column 3: DML gasage (yr AD) Column 4: CO2 concentration (parts per million by volume) is a mean value of 6 neighboring samples Column 5: Same as column 4 but corrected for gravitational separation of gases in the firn column Column 6: sigma mean (parts per million by volume) is one sigma of the mean value depth Gasage Gasage CO2 mean CO2 Corr. sigma mean (m) (yrBP1950) (yrAD) (ppmv) (ppmv) (ppmv) 160.66 991.7 958.3 279.19 277.30 0.76 157.95 952.6 997.4 281.05 279.15 1.12 157.66 948.3 1001.7 279.57 277.68 1.25 157.06 939.7 1010.3 280.26 278.36 1.00 155.95 923.7 1026.3 278.11 276.23 0.81 155.15 912.1 1037.9 279.08 277.19 0.71 154.96 909.4 1040.6 282.60 280.69 1.05 154.06 896.4 1053.6 282.02 280.12 1.11 151.95 866.1 1083.9 281.91 280.00 0.63 151.16 854.6 1095.4 282.82 280.91 0.84 150.86 850.4 1099.6 283.01 281.09 1.47 150.06 838.9 1111.1 284.50 282.58 0.49 148.96 823.1 1126.9 283.55 281.64 1.22 148.06 810.2 1139.8 284.11 282.19 0.42 145.95 779.9 1170.1 282.62 280.71 0.36 145.65 775.6 1174.4 282.08 280.17 1.51 145.06 767.2 1182.8 283.83 281.91 0.80 144.96 765.7 1184.3 285.83 283.90 1.19 144.06 752.9 1197.1 283.49 281.58 0.99 141.95 722.8 1227.2 284.71 282.78 0.66 141.04 709.8 1240.2 283.40 281.48 0.92 140.95 708.5 1241.5 284.63 282.71 0.62 140.06 695.8 1254.2 283.75 281.83 1.40 137.95 665.8 1284.2 282.15 280.25 1.00 137.06 653.1 1296.9 282.51 280.60 0.68 136.95 651.6 1298.4 284.42 282.50 1.67 136.06 638.9 1311.1 281.63 279.72 1.02 134.95 623.2 1326.8 282.94 281.03 0.81 134.06 610.5 1339.5 284.98 283.05 0.87 133.95 609.0 1341.0 282.19 280.29 1.13 133.04 596.2 1353.8 283.60 281.68 1.00 130.95 566.6 1383.4 282.16 280.25 0.78 130.06 554.1 1395.9 282.75 280.83 0.39 127.95 524.4 1425.6 281.52 279.61 0.41 127.26 514.7 1435.3 280.83 278.93 0.40 127.04 511.6 1438.4 285.82 283.88 0.82 126.95 510.3 1439.7 282.53 280.62 0.77 126.06 497.9 1452.1 281.99 280.09 0.63 124.95 482.3 1467.7 280.94 279.04 0.49 124.07 470.0 1480.0 280.21 278.31 0.80 122.93 454.0 1496.0 283.06 281.14 1.86 122.06 441.9 1508.1 282.76 280.85 1.47 120.95 426.4 1523.6 280.54 278.64 1.15 120.06 414.1 1535.9 283.56 281.64 1.02 119.96 412.6 1537.4 283.40 281.49 0.95 119.06 400.1 1549.9 281.11 279.21 0.63 116.95 371.0 1579.0 283.18 281.27 1.05 116.66 366.9 1583.1 280.52 278.62 0.44 116.06 358.7 1591.3 280.84 278.94 0.41 114.95 343.4 1606.6 280.22 278.32 1.07 114.15 332.4 1617.6 279.61 277.72 0.70 112.95 315.8 1634.2 281.95 280.04 0.90 111.96 302.3 1647.7 280.59 278.69 1.22 110.96 288.6 1661.4 279.57 277.68 1.08 109.96 274.9 1675.1 278.23 276.35 0.52 108.96 261.3 1688.7 280.47 278.58 1.68 107.96 247.7 1702.3 278.18 276.30 1.33 106.96 234.2 1715.8 280.49 278.59 2.45 105.96 220.7 1729.3 281.08 279.18 1.65 104.96 207.2 1742.8 280.53 278.63 1.08 103.96 193.8 1756.2 276.88 275.01 1.06 102.94 180.1 1769.9 279.60 277.71 1.44 102.06 168.4 1781.6 284.56 282.63 2.62 100.96 153.6 1796.4 280.28 278.38 0.91 99.96 140.4 1809.6 281.62 279.72 1.04 98.96 127.1 1822.9 283.30 281.38 1.33 97.96 113.9 1836.1 283.13 281.22 0.46 96.96 100.7 1849.3 287.80 285.85 1.94 95.96 87.7 1862.3 288.40 286.45 1.88 94.96 74.6 1875.4 290.39 288.42 1.04 93.96 61.5 1888.5 290.63 288.66 1.42 2. South Pole measurements: Column 1: South Pole depth (m) Column 2: South Pole gasage (years before AD 1950) Column 3: South Pole gasage (yr AD) Column 4: CO2 concentration (parts per million by volume) is a mean value of 6 neighboring samples Column 5: Same as column 4 but corrected for gravitational separation of gases in the firn column Column 6: sigma mean (parts per million by volume) is one sigma of the mean value depth Gasage Gasage CO2 mean CO2 Corr. sigma mean (m) (yrBP1950) YearAD (ppmv) (ppmv) (ppmv) 192.40 993.3 956.7 278.98 276.43 0.77 173.46 751.1 1198.9 281.51 278.94 0.56 171.42 725.3 1224.7 281.63 279.06 0.56 164.33 635.8 1314.2 281.26 278.69 0.82 161.09 595.1 1354.9 281.86 279.29 1.79 159.90 580.2 1369.8 283.30 280.71 0.90 153.92 505.5 1444.5 281.00 278.43 0.92 153.64 502.0 1448.0 280.66 278.09 0.90 143.70 379.3 1570.7 280.50 277.94 0.43 143.26 374.0 1576.0 280.18 277.62 0.35 138.72 318.6 1631.4 280.08 277.52 1.20 132.72 246.1 1703.9 278.55 276.01 1.32 132.06 238.2 1711.8 278.63 276.09 1.09 129.95 212.9 1737.1 279.95 277.39 0.77