noaa-icecore-25350 Bipolar Holocene Composite Ice Core CH4, d13C, and dD Data Beck, J.; Bock, M.; Schmitt, J.; Seth, B.; Blunier, T.; Fischer, H. Bipolar Holocene Composite Ice Core CH4, d13C, and dD Data 2018-12-07 NCDC-Paleoclimatology ONLINE Files Pending https://www.ncdc.noaa.gov/paleo/study/25350 Investigator J. Beck Investigator M. Bock Investigator J. Schmitt Investigator B. Seth Investigator T. Blunier Investigator H. Fischer earth science paleoclimate ice core carbon isotopes earth science paleoclimate ice core hydrogen isotopes earth science paleoclimate ice core atmospheric gas geoscientificInformation 11978 cal yr BP 38 cal yr BP Complete -90 90 -180 180 2315 2917 Geographic Region Global Global>LATITUDE >LONGITUDE Continent Antarctica Talos Dome TALDICE>LATITUDE -72.8166>LONGITUDE 159.1833 Continent Antarctica EPICA Dronning Maud Land>LATITUDE -75>LONGITUDE .07 Continent North America Greenland Greenland Ice Core Composite>LATITUDE >LONGITUDE Continent Antarctica Antarctic Ice Core Composite>LATITUDE >LONGITUDE Continent North America Greenland NGRIP>LATITUDE 75.1>LONGITUDE -42.33 None Please cite original publication, online resource, dataset and publication DOIs (where available), and date accessed when using downloaded data. If there is no publication information, please cite investigator, title, online resource, and date accessed. The appearance of external links associated with a dataset does not constitute endorsement by the Department of Commerce/National Oceanic and Atmospheric Administration of external Web sites or the information, products or services contained therein. For other than authorized activities, the Department of Commerce/NOAA does not exercise any editorial control over the information you may find at these locations. These links are provided consistent with the stated purpose of this Department of Commerce/NOAA Web site. English DOC/NOAA/NESDIS/NCEI National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce https://www.ncdc.noaa.gov/data-access/paleoclimatology-data DATA Center Contact Bruce Bauer bruce.a.bauer@noaa.gov paleo@noaa.gov 303-497-6280 303-497-6513

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Boulder CO 80305-3328 USA online ASCII Jonas Beck, Michael Bock, Jochen Schmitt, Barbara Seth, Thomas Blunier, and Hubertus Fischer 2018 Biogeosciences 15 7155-7175 10.5194/bg-15-7155-2018 https://www.biogeosciences.net/15/7155/2018/

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. STUDY NOTES: Ice core Holocene composite Northern (GISP2, GRIP, and NGRIP) and Southern (WAIS, TALDICE, EDC) Hemisphere methane (CH4), carbon isotope (d13C), and hydrogen isotope (dD) data

GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-ch4.txt NOAA Template File; Greenland Ice Core Composite Methane Data GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-d13c.txt NOAA Template File; TALDICE Methane Carbon Isotope Data GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-d13c.txt NOAA Template File; NGRIP Methane Carbon Isotope Data GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-dd.txt NOAA Template File; EDML Methane Hydrogen Isotope Data GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018splines-inversions.txt NOAA Template File; Splines and Inversions GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-ch4.txt NOAA Template File; Antarctic Ice Core Composite Methane Data GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-dd.txt NOAA Template File; NGRIP Methane Hydrogen Isotope Data USA/NOAA DIF Version 9.8.4 2018-12-11 2018-12-11