Newall Glacier and Dome C Ice Core in situ 14C Data --------------------------------------------------------------------- NOAA Paleoclimatology Program and World Data Center for Paleoclimatology, Boulder --------------------------------------------------------------------- NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!! NAME OF DATA SET: Newall Glacier and Dome C Ice Core in situ 14C Data LAST UPDATE: 9/2003 (Original Receipt by WDC Paleo) CONTRIBUTOR: D. Lal, Scripps Institution of Oceanography IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2003-065 SUGGESTED DATA CITATION: Jull, A.J.T., et al., 2003, Newall Glacier and Dome C Ice Core in situ 14C Data, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2003-065. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Jull, A.J.T., D. Lal, D.J. Donahue, P. Mayewski, C. Lorius, D. Raynaud and J.R. Petit, 1994, Measurements of cosmic-ray-produced 14C in firn and ice from antarctica, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 92, Issues 1-4, 3 June 1994, Pages 326-330. doi:10.1016/0168-583X(94)96028-3 ABSTRACT: We have studied the levels of 14C in firn and ice from two regions accumulating ice in Antarctica, Dome C, and Newall Glacier. The observed concentrations indicate variable amounts of in-situ 14C from cosmic-ray spallation of oxygen. 14C appears to be produced as both CO and CO2 in variable amounts, but our results suggest rapid conversion of 14CO to 14CO2. Much of the in-situ 14C is retained which results in a significant modification of the 14C/12C in ice derived from trapping of air at and below the firn-ice transition zone. This means that direct dating of accumulating ice cannot be used without correction for the in-situ 14C. In Newall ice, we see some evidence for an enhancement in in-situ 14C at or near the time of the Maunder Minimum. Results for Dome C firn and ice indicate higher levels of in-situ 14C in older ice. This is due either to a reduced accumulation rate in the past, or possible variations in cosmogenic 14C production. The levels of in-situ 14C in firn and ice, and its impact on 14C dates on trapped CO2 in ice are discussed. GEOGRAPHIC REGION: Antarctica PERIOD OF RECORD: ~18-4 KYrBP (Dome C), ~0-2 KYrBP (Newall) DESCRIPTION: In situ 14C data from the Newall Glacier and Dome C Ice Cores. DATA: Tables 1-3 from Jull et al. 1994. Space-delimited ASCII text - best viewed with fixed width font such as courier. Table 1. Expected content of in-situ and trapped 14C in recent ice samples* Station Altitude Precip 14C production rate Expected in-situ 14C R** Km. cm/yr @surface atoms/g/yr atom/g Newall Glacier 1.75 7.5*** 85 3300 3.7 Dome C 3.24 3.7 160 9900 8.1 Vostok 3.5 2.24 255 20000 21.0 GISP II 3.1 23.0 200 1460 1.7 Dye 3 2.48 50.0 135 458 12.0 * Based on estimated in-situ 14C production rates from Lal et al. 1987, and expected in-situ 14C concentrations for 100% retention from Lal and Jull 1990. ** The parameter R designates the ratio of 14C arising from in-situ production versus 14C from trapped air CO2, using the equation of Lal and Jull 1990. *** Precipitation rate for the last 2000 years. (Mayewski et al. 1995) Table 2. 14C results on Newall Glacier ice samples Sample Depth Weight Air Carriers(cm3) Fm** Fm** 14C 14C 14C Trapped 14C R*** m. Kg. cm3 CO CO2 CO CO2 CO CO2 Tot. est. atom/g atom/g atom/g Firn: NG1 5-6 3.91 19 1.149 1.409 0.1516±0.0022 0.0433±0.0015 1240±50 262±70 1500±75 41 35.6 NG-3 7-8 4.2 52 0.722 0.907 0.0106±0.0012 0.1234±0.0023 266±50 3167±75 3433 105 45.3 NG-3-2 7-8 - - 0.708 0.890 0.0647±0.0019 0.4212±0.0066 59±50 1375±50 1424 - - NG-3-3 7-8 - - 0.692 0.867 0.0283±0.0015 0.2563±0.0025 - - - - - NG-4 8-9 3.58 83 1.127 1.24 0.0103 0.631 93 6296 6389 195 31.8 NG-4-2 8-9 - 38 0.998 1.25 0.0057 - 46 - 92 90 - NG-16 15-16 4.25 69 0.922 0.223* 0.0248±0.0013 4.5685±0.0267 155 6893 7048 134 51.6 NG-16-2 15-16 - - 0.826 0.081* 0.0211±0.0013 nm - nm - - - Ice: NG-61 60-61 3.67 258 1.025 1.13 0.0146±0.0012 0.3006±0.0029 117 2666 2783 423 8.1 NG-61-2 60-61 - - 1.192 1.31 0.0131±0.0014 0.0907±0.0035 123 933 1056 - - Identical sample depths for second and third extractions * No carrier CO2 added ** Fm= fraction of modern (1950 AD) carbon. *** R=ratio of measured in-situ 14C to estimated trapped 14C nm = not measured Table 3. 14C results on Dome C ice samples Sample Depth Weight Air Carriers(cm3) Fm** Fm** 14C 14C 14C Trapped 14C R*** m. Kg. cm3 CO CO2 CO CO2 CO CO2 Tot. est. atom/g atom/g atom/g Ice: DC-195 194.1-194.7 3.71 306 0.875 1.057 0.0710±0.0066 0.483±0.011 485±45 3965±90 4450±100 309 11.3 DC-195-2 194.1-194.7 - 59 0.854 1.036 - - 0±45 75±50 75±65 60 - DC-305 304-305 outer 1.55 166 0.838 1.023 0.0995±0.0031 0.2251±0.0040 1475±50 4130±50 5605 277 19.2 DC-554 554-555 outer 1.85 225 0.767 0.964 0.0387±0.0016 0.3235±0.0055 387±50 4706±50 5093 136 36.4 DC-554 554-555 inner 2.20 322 0.753 0.947 0.0335±0.0016 0.3448±0.0055 255±50 4126±50 4381 163 21.7 DC-554-2 554-555 inner - 82 0.740 0.927 0.0114±0.0013 0.0304±0.0013 35±50 219±50 254 41 - DC-555 555-556 2.75 148 1.393 0.0803 0.0275±0.0014 2.17 457±50 2056±50 2513 67 36.5 Identical sample depths for second and third extractions * No carrier CO2 added ** Fm= fraction of modern (1950 AD) carbon. *** R=ratio of measured in-situ 14C to estimated trapped 14C nm = not measured