Vostok, Antarctica Ice Core 4G-2 61-58KYr Methane and d15N Data Fourteau, K.; Faïn, X.; Martinerie, P.; Landais, A.; Ekaykin, A.A.; Lipenkov, V.; Chappellaz, J.A. Fourteau, K. Faïn, X. Martinerie, P. Landais, A. Ekaykin, A.A. Lipenkov, V. Chappellaz, J.A. earth science/paleoclimate/ice cores (depth,null,null,meter,null,ice cores,null,null,N,null) earth science/paleoclimate/ice cores (methane,bulk atmosphere,null,parts per billion,null,ice cores,corrected,continuous flow analysis|optical feedback cavity enhanced absorption spectroscopy,N,corrected for contamination and calibrated) earth science/paleoclimate/ice cores (methane,bulk atmosphere,null,parts per billion,null,ice cores,corrected,continuous flow analysis|optical feedback cavity enhanced absorption spectroscopy,N,values corresponding to layering artifacts removed) earth science/paleoclimate/ice cores (delta 15N,bulk atmosphere,null,per mil AIR,null,ice cores,null,null,N,values measured by mass spectrometry in extracted air after water and CO2 trap and corrected for O2/N2 chemical slope) earth science/paleoclimate/ice cores (gas age,null,null,calendar year before present,null,ice cores,null,null,N,null) earth science/paleoclimate/ice core earth science/paleoclimate/ice core earth science/paleoclimate/ice core (Vostok>LATITUDE -78.47>LONGITUDE 106.8) We investigate for the first time the loss and alteration of past atmospheric information from air trapping mechanisms under low-accumulation conditions through continuous CH4 (and CO) measurements. Methane concentration changes were measured over the Dansgaard-Oeschger event 17 (DO-17, - 60 000 yr BP) in the Antarctic Vostok 4G-2 ice core. Measurements were performed using continuous-flow analysis combined with laser spectroscopy. The results highlight many anomalous layers at the centimeter scale that are unevenly distributed along the ice core. The anomalous methane mixing ratios differ from those in the immediate surrounding layers by up to 50 ppbv. This phenomenon can be theoretically reproduced by a simple layered trapping model, creating very localized gas age scale inversions. We propose a method for cleaning the record of anomalous values that aims at minimizing the bias in the overall signal. Once the layered-trapping-induced anomalies are removed from the record, DO-17 appears to be smoother than its equivalent record from the high-accumulation WAIS Divide ice core. This is expected due to the slower sinking and densification speeds of firn layers at lower accumulation. However, the degree of smoothing appears surprisingly similar between modern and DO-17 conditions at Vostok. This suggests that glacial records of trace gases from low-accumulation sites in the East Antarctic plateau can provide a better time resolution of past atmospheric composition changes than previously expected. We also developed a numerical method to extract the gas age distributions in ice layers after the removal of the anomalous layers based on comparison with a weakly smoothed record. It is particularly adapted for the conditions of the East Antarctic plateau, as it helps to characterize smoothing for a large range of very low-temperature and low-accumulation conditions. STUDY NOTES: Vostok, Antarctica 61-58 kY 4G-2 ice core methane mixing ratio. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Fourteau, K. Investigator : Faïn, X. Investigator : Martinerie, P. Investigator : Landais, A. Investigator : Ekaykin, A.A. Investigator : Lipenkov, V. Investigator : Chappellaz, J.A. 2017-12-07 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/23210 https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/vostok2017ch4.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/vostok2017d15n.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/vostok2017age.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/vostok2017ch4.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/vostok2017d15n.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/vostok2017age.txt English https://www.ncdc.noaa.gov/paleo/study/23210 https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/vostok2017ch4.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/vostok2017d15n.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/vostok2017age.txt Kévin Fourteau, Xavier Faïn, Patricia Martinerie, Amaëlle Landais, Alexey A. Ekaykin, Vladimir Ya. Lipenkov, and Jérôme Chappellaz2017Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditionsClimate of the Past13121815-183010.5194/cp-13-1815-2017https://www.clim-past.net/13/1815/2017/ START YEAR: 60829 cal yr BP * END YEAR: 57907 cal yr BP 106.8 -78.47 106.8 -78.47