GISP2 Ice Core Dansgaard-Oeschger Event 21 Methane and d15N Data ----------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program ----------------------------------------------------------------------- NOTE: PLEASE CITE CONTRIBUTORS WHEN USING THIS DATA!!!!! NAME OF DATA SET: GISP2 Ice Core Dansgaard-Oeschger Event 21 Methane and d15N Data LAST UPDATE: 11/2007 (Original receipt by WDC Paleo) CONTRIBUTOR: Alexi M. Grachev, Oregon State University IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2007-103 SUGGESTED DATA CITATION: Grachev, A.M., et al. 2007. GISP2 Ice Core Dansgaard-Oeschger Event 21 Methane and d15N Data. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2007-103. NOAA/NCDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Grachev, A.M., E. J. Brook, and J. P. Severinghaus. 2007. Abrupt changes in atmospheric methane at the MIS 5b–5a transition. Geophys. Res. Lett., 34, L20703, doi:10.1029/2007GL029799. ABSTRACT: New ice core analyses show that the prominent rise in atmospheric methane concentration at Dansgaard-Oeschger event 21 was interrupted by a century-long 20% decline, which was previously unrecognized. The reversal was found in a new ~100-year resolution study of methane in the GISP2 ice core, encompassing the beginning of D-O event 21, which also corresponds to the transition from MIS 5b to 5a. Although a corresponding reversal (within age uncertainty) is observed in climate proxies measured in GISP2 ice, including d18Oice, electrical conductivity, light scattering, and several ions, this feature has not been discussed previously. Abrupt changes in methane are paralleled by changes in d15N of trapped air, a quantity that reflects local temperature change at Greenland summit. The reversal described here supports the hypothesis that climate can be unstable during major transitions, as was previously described for the last deglaciation. ADDITIONAL REFERENCES: Brook E.J., T. Sowers, and J. Orchardo. 1996. Rapid variations in atmospheric methane concentration during the past 110,000 years. Science, 273, 1087-1091. Dlugokencky et al. 2005. Conversion of NOAA atmospheric dry air CH4 mole fractions to a gravimetrically prepared standard scale. Journal of Geophysical Research, 110 (D18): Art. No. D18306. GEOGRAPHIC REGION: Greenland PERIOD OF RECORD: 86 - 82 KYrBP FUNDING SOURCES: Gary Comer Science and Education Foundation, National Science Foundation (USA) grants OPP 0126057 and ATM 0602395 to EJB and ANT05-38657 to JPS. DESCRIPTION: High-resolution (~100-year) methane and d15N2 of trapped gas from the Greenland Ice Sheet 2 (GISP2) ice core in the interval near Dansgaard- Oeschger Event 21, approximately 85 KYrBP. DATA: 1. Methane Methane concentrations from GISP2, 2668 -2690 meters. All starting ice blocks were ~10 cm long initially and trimmed off by ~0.5 cm at both ends during duplicate sample preparation. Methane concentrations are reported on the NOAA04 gravimetric scale [Dlugokencky et al. 2005] Column 1: Top depth in meters (GISP2) Column 1: Bottom depth in meters (GISP2) Column 1: Average depth in meters (GISP2) Column 4: Age of gas (years) after Brook et al. 1996 Column 5: Methane concentration value (ppb) for ice sample from a given depth, average of 4 measurements Column 6: Standard error (s.d./sqrt(2)) Column 7: Methane concentration value (ppb) for a second ice sample from same depth, average of 4 measurements Column 8: Standard error (s.d./sqrt(2)) DepthTop DepthBot. DepthAvg. GasAge Methane Error Methane Error 2668.43 2668.53 2668.48 82195 660 2 661 2 2669.23 2669.34 2669.29 82352 679 3 672 4 2670.17 2670.27 2670.22 82534 639 4 639 3 2671.18 2671.28 2671.23 82733 679 2 672 3 2671.50 2671.60 2671.55 82797 674 2 683 4 2672.17 2672.27 2672.22 82934 693 1 701 2 2672.50 2672.60 2672.55 83002 674 4 682 3 2673.17 2673.27 2673.22 83143 660 3 667 2 2673.50 2673.60 2673.55 83213 650 2 652 3 2674.28 2674.38 2674.33 83359 686 1 683 3 2674.60 2674.70 2674.65 83413 675 3 672 1 2675.17 2675.27 2675.22 83510 661 3 663 3 2675.60 2675.70 2675.65 83582 705 2 706 5 2676.17 2676.27 2676.22 83678 700 1 694 2 2676.60 2676.70 2676.65 83749 700 1 704 2 2677.17 2677.27 2677.22 83842 717 2 716 1 2677.60 2677.70 2677.65 83913 718 2 716 3 2678.17 2678.27 2678.22 84016 720 3 722 5 2678.60 2678.70 2678.65 84101 712 2 715 2 2679.20 2679.30 2679.25 84221 551 1 555 4 2679.60 2679.70 2679.65 84300 497 2 497 3 2680.25 2680.35 2680.30 84420 516 0 520 1 2680.50 2680.60 2680.55 84465 527 1 528 1 2680.80 2680.90 2680.85 84518 561 2 565 2 2681.25 2681.35 2681.30 84598 643 2 641 2 2681.35 2681.45 2681.40 84616 593 1 589 1 2681.50 2681.60 2681.55 84643 511 1 510 3 2682.10 2682.20 2682.15 84753 481 1 481 2 2682.50 2682.60 2682.55 84830 483 1 479 2 2683.00 2683.10 2683.05 84929 483 2 485 1 2683.50 2683.60 2683.55 85029 484 1 489 2 2684.16 2684.26 2684.21 85162 484 2 481 2 2684.50 2684.60 2684.55 85231 474 3 476 2 2685.00 2685.10 2685.05 85330 474 2 477 3 2685.50 2685.60 2685.55 85428 456 2 453 1 2686.00 2686.10 2686.05 85524 464 2 465 3 2686.50 2686.60 2686.55 85618 461 4 463 2 2687.00 2687.10 2687.05 85711 464 1 460 1 2687.50 2687.60 2687.55 85803 470 1 467 3 2688.00 2688.10 2688.05 85899 459 0 456 1 2688.50 2688.60 2688.55 86000 463 1 465 4 2689.10 2689.20 2689.15 86125 454 1 454 1 2689.50 2689.60 2689.55 86212 459 1 457 2 2690.02 2690.12 2690.07 86334 458 1 481 2 2. N-15 of N2 d15N of trapped air from GISP2, 2667 -2684 meters. All starting ice blocks were ~10 cm long initially (starting blocks different than for methane analyses). Column 1: Average depth in meters (GISP2) Column 2: Age of gas (years) after Brook et al. 1996 Column 3: d15N value (per mil) for ice sample from a given depth, replicate 1 Column 4: d15N value (per mil) for ice sample, replicate 2 Column 5: d15N value (per mil) for ice sample, replicate 3 Depth GasAge d15N d15N d15N 2677.32 83858 0.429 0.437 0.436 2677.75 83930 0.459 0.459 2678.32 84036 0.516 0.519 0.518 2678.65 84101 0.533 0.533 2679.25 84221 0.464 0.466 2679.65 84300 0.405 0.407 2680.20 84402 0.395 0.393 2680.45 84447 0.396 0.396 2680.75 84500 0.407 0.406 2681.30 84598 0.503 0.501 2681.40 84616 0.490 0.490 0.486 2681.65 84661 0.437 0.435 2682.25 84772 0.422 0.419 2682.65 84850 0.414 0.416 2683.15 84949 0.422 0.421 2683.65 85049 0.419 0.422