# Bipolar Holocene Composite Ice Core CH4, d13C, and dD Data #----------------------------------------------------------------------- # World Data Service for Paleoclimatology, Boulder # and # NOAA Paleoclimatology Program # National Centers for Environmental Information (NCEI) #----------------------------------------------------------------------- # Template Version 3.0 # Encoding: UTF-8 # NOTE: Please cite Publication, and Online_Resource and date accessed when using these data. # If there is no publication information, please cite Investigators, Title, and Online_Resource and date accessed. # # Online_Resource: https://www.ncdc.noaa.gov/paleo/study/25350 # Description: NOAA Landing Page # Online_Resource: https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-dd.txt # Description: NOAA location of the template # # Original_Source_URL: # Description: # # Description/Documentation lines begin with # # Data lines have no # # # Archive: Ice Core # # Dataset DOI: # # Parameter_Keywords: atmospheric gas, carbon isotopes, hydrogen isotopes #-------------------- # Contribution_Date # Date: 2018-12-07 #-------------------- # File_Last_Modified_Date # Date: 2018-12-07 #-------------------- # Title # Study_Name: Bipolar Holocene Composite Ice Core CH4, d13C, and dD Data #-------------------- # Investigators # Investigators: Beck, J.; Bock, M.; Schmitt, J.; Seth, B.; Blunier, T.; Fischer, H. #-------------------- # Description_Notes_and_Keywords # Description: Ice core Holocene composite Northern (GISP2, GRIP, NGRIP) and Southern (EDC, EDML, TALDICE, WAIS) Hemisphere methane (CH4), # carbon isotope (d13C), and hydrogen isotope (dD) data. Stable hydrogen isotopes of methane (dD-CH4) data measured on the EDML ice core; # EDML age scale according to synchronised CH4 data; dD-CH4 data are free of krypton interference during the mass spectrometric analysis # and corrected for gravitational enrichment (see Beck et al., 2018) # Provided Keywords: Holocene, methane, hydroge istotpes, dD, dD-CH4, dD(CH4), ice core, EDML, Antarctica #-------------------- # Publication # Authors: Jonas Beck, Michael Bock, Jochen Schmitt, Barbara Seth, Thomas Blunier, and Hubertus Fischer # Published_Date_or_Year: 2018-11-30 # Published_Title: Bipolar carbon and hydrogen isotope constraints on the Holocene methane budget # Journal_Name: Biogeosciences # Volume: 15 # Edition: # Issue: # Pages: 7155-7175 # Report_Number: # DOI: 10.5194/bg-15-7155-2018 # Online_Resource: https://www.biogeosciences.net/15/7155/2018/ # Full_Citation: # Abstract: Atmospheric methane concentration shows a well-known decrease over the first half of the Holocene following the Northern Hemisphere summer insolation before it started to increase again to preindustrial values. There is a debate about what caused this change in the methane concentration evolution, in particular, whether an early anthropogenic influence or natural emissions led to the reversal of the atmospheric CH4 concentration evolution. Here, we present new methane concentration and stable hydrogen and carbon isotope data measured on ice core samples from both Greenland and Antarctica over the Holocene. With the help of a two-box model and the full suite of CH4 parameters, the new data allow us to quantify the total methane emissions in the Northern Hemisphere and Southern Hemisphere separately as well as their stable isotopic signatures, while interpretation of isotopic records of only one hemisphere may lead to erroneous conclusions. For the first half of the Holocene our results indicate an asynchronous decrease in Northern Hemisphere and Southern Hemisphere CH4 emissions by more than 30 Tg CH4 yr-1 in total, accompanied by a drop in the northern carbon isotopic source signature of about -3 per mil. This cannot be explained by a change in the source mix alone but requires shifts in the isotopic signature of the sources themselves caused by changes in the precursor material for the methane production. In the second half of the Holocene, global CH4 emissions increased by about 30 Tg CH4 yr-1, while preindustrial isotopic emission signatures remained more or less constant. However, our results show that this early increase in methane emissions took place in the Southern Hemisphere, while Northern Hemisphere emissions started to increase only about 2000 years ago. Accordingly, natural emissions in the southern tropics appear to be the main cause of the CH4 increase starting 5000 years before present, not supporting an early anthropogenic influence on the global methane budget by East Asian land use changes. #------------------ # Publication # Authors: Michael Bock, Jochen Schmitt, Jonas Beck, Barbara Seth, Jérôme Chappellaz, and Hubertus Fischer # Published_Date_or_Year: 2017-07-18 # Published_Title: Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4 ice core records # Journal_Name: Proceedings of the National Academy of Sciences of the United States of America # Volume: 114 # Edition: # Issue: 29 # Pages: E5778-E5786 # Report_Number: # DOI: 10.1073/pnas.1613883114 # Online_Resource: http://www.pnas.org/content/114/29/E5778 # Full_Citation: # Abstract: Atmospheric methane (CH4) records reconstructed from polar ice cores represent an integrated view on processes predominantly taking place in the terrestrial biogeosphere. Here, we present dual stable isotopic methane records [d13CH4 and dD(CH4)] from four Antarctic ice cores, which provide improved constraints on past changes in natural methane sources. Our isotope data show that tropical wetlands and seasonally inundated floodplains are most likely the controlling sources of atmospheric methane variations for the current and two older interglacials and their preceding glacial maxima. The changes in these sources are steered by variations in temperature, precipitation, and the water table as modulated by insolation, (local) sea level, and monsoon intensity. Based on our dD(CH4) constraint, it seems that geologic emissions of methane may play a steady but only minor role in atmospheric CH4 changes and that the glacial budget is not dominated by these sources. Superimposed on the glacial/interglacial variations is a marked difference in both isotope records, with systematically higher values during the last 25,000 y compared with older time periods. This shift cannot be explained by climatic changes. Rather, our isotopic methane budget points to a marked increase in fire activity, possibly caused by biome changes and accumulation of fuel related to the late Pleistocene megafauna extinction, which took place in the course of the last glacial. #------------------ # Publication # Authors: M. Bock, J. Schmitt, J. Beck, R. Schneider, and H. Fischer # Published_Date_or_Year: 2014-07-04 # Published_Title: Improving accuracy and precision of ice core dD(CH4) analyses using methane pre-pyrolysis and hydrogen post-pyrolysis trapping and subsequent chromatographic separation # Journal_Name: Atmospheric Measurement Techniques # Volume: 7 # Edition: # Issue: 7 # Pages: 1999-2012 # Report_Number: # DOI: 10.5194/amt-7-1999-2014 # Online_Resource: https://www.atmos-meas-tech.net/7/1999/2014/ # Full_Citation: # Abstract: Firn and polar ice cores offer the only direct palaeoatmospheric archive. Analyses of past greenhouse gas concentrations and their isotopic compositions in air bubbles in the ice can help to constrain changes in global biogeochemical cycles in the past. For the analysis of the hydrogen isotopic composition of methane (dD(CH4) or d2H(CH4)) 0.5 to 1.5 kg of ice was hitherto used. Here we present a method to improve precision and reduce the sample amount for dD(CH4) measurements in (ice core) air. Pre-concentrated methane is focused in front of a high temperature oven (pre-pyrolysis trapping), and molecular hydrogen formed by pyrolysis is trapped afterwards (post-pyrolysis trapping), both on a carbon-PLOT capillary at -196C. Argon, oxygen, nitrogen, carbon monoxide, unpyrolysed methane and krypton are trapped together with H2 and must be separated using a second short, cooled chromatographic column to ensure accurate results. Pre- and post-pyrolysis trapping largely removes the isotopic fractionation induced during chromatographic separation and results in a narrow peak in the mass spectrometer. Air standards can be measured with a precision better than 1 permil. For polar ice samples from glacial periods, we estimate a precision of 2.3 permil for 350 g of ice (or roughly 30 mL - at standard temperature and pressure (STP) - of air) with 350 ppb of methane. This corresponds to recent tropospheric air samples (about 1900 ppb CH4) of about 6 mL (STP) or about 500 pmol of pure CH4. #------------------ # Funding_Agency # Funding_Agency_Name: European Research Council # Grant: 226172 #------------------ # Funding_Agency # Funding_Agency_Name: Swiss National Science Foundation # Grant: #------------------ # Site_Information # Site_Name: EDML # Location: Antarctica # Country: # Northernmost_Latitude: -79.0 # Southernmost_Latitude: -79.0 # Easternmost_Longitude: -0.07 # Westernmost_Longitude: -0.07 # Elevation: 2774 m #------------------ # Data_Collection # Collection_Name: Beck2018SouthdD # Earliest_Year: 11489 # Most_Recent_Year: 604 # Time_Unit: Cal. Year BP # Core_Length: # Notes: #------------------ # Chronology_Information # Chronology: # #---------------- # Variables # # Data variables follow are preceded by "##" in columns one and two. # Data line variables format: one per line, shortname-tab-variable components (what, material, error, units, seasonality, data type,detail, method, C or N for Character or Numeric data, free text) # ## depth_m depth, , , m, , , , ,N, ## gas_age_calBP age, gas, , calendar years before present, , , , ,N, synchronised age scales (see Beck et al. 2018 section 2.3.1) present defined as 1950 CE ## dD_raw delta 2H, methane, , per mil VSMOW, ,ice core,raw,isotope ratio mass spectrometry,N, ## dD_corr delta 2H, methane, , per mil VSMOW, ,ice core,corrected,isotope ratio mass spectrometry,N,corrected for gravitational settling ## dD_err delta 2H, methane, one standard error, per mil VSMOW, ,ice core,,,N, ## data_origin data origin,,,,,,,,C,reference to orginal publication # #---------------- # Data: # Data lines follow (have no #) # Data line format - tab-delimited text, variable short name as header # Missing Values: # depth_m gas_age_calBP dD_raw dD_corr dD_err data_origin 127.58 604.2 -71.2 -71.7 2.3 EDML_Bock2017 182.41 1414.9 -70.9 -71.3 2.3 EDML_Bock2017 195.50 1605.0 -67.5 -68.0 2.3 EDML_Bock2017 230.38 2066.1 -70.2 -70.6 2.3 EDML_Bock2017 268.45 2653.3 -71.6 -72.0 2.3 EDML_Bock2017 303.48 3212.9 -67.6 -68.1 2.3 EDML_Bock2017 352.44 4059.8 -72.8 -73.3 2.3 EDML_Bock2017 375.19 4470.5 -74.8 -75.3 2.3 EDML_Bock2017 424.44 5401.9 -73.3 -73.7 2.3 EDML_Bock2017 471.50 6340.2 -73.6 -74.0 2.3 EDML_Bock2017 484.18 6510.2 -76.7 -77.1 2.3 EDML_Bock2017 518.19 7152.7 -74.1 -74.6 2.3 EDML_Bock2017 567.33 8191.1 -69.9 -70.3 2.3 EDML_Bock2017 615.15 9266.9 -71.5 -71.9 2.3 EDML_Bock2017 639.48 9862.7 -72.9 -73.3 2.3 EDML_Bock2017 663.51 10396.7 -71.3 -71.8 2.3 EDML_Bock2017 686.43 10925.0 -63.6 -64.0 2.3 EDML_Bock2017 711.54 11489.1 -61.8 -62.2 2.3 EDML_Bock2017