Bipolar Holocene Composite Ice Core CH4, d13C, and dD Data Beck, J.; Bock, M.; Schmitt, J.; Seth, B.; Blunier, T.; Fischer, H. Beck, J. Bock, M. Schmitt, J. Seth, B. Blunier, T. Fischer, H. earth science/paleoclimate/ice core earth science/paleoclimate/ice core earth science/paleoclimate/ice core (Global>LATITUDE >LONGITUDE ) (Talos Dome TALDICE>LATITUDE -72.8166>LONGITUDE 159.1833) (EPICA Dronning Maud Land>LATITUDE -75>LONGITUDE .07) (Greenland Ice Core Composite>LATITUDE >LONGITUDE ) (Antarctic Ice Core Composite>LATITUDE >LONGITUDE ) (NGRIP>LATITUDE 75.1>LONGITUDE -42.33) 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 NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Beck, J. Investigator : Bock, M. Investigator : Schmitt, J. Investigator : Seth, B. Investigator : Blunier, T. Investigator : Fischer, H. 2018-12-07 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/25350 https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-ch4.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-d13c.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-d13c.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-dd.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018splines-inversions.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-ch4.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-dd.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-ch4.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-d13c.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-d13c.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-dd.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018splines-inversions.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-ch4.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-dd.txt English https://www.ncdc.noaa.gov/paleo/study/25350 https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-ch4.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-d13c.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-d13c.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-dd.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018splines-inversions.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/beck2018south-ch4.txt https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/beck2018north-dd.txt Jonas Beck, Michael Bock, Jochen Schmitt, Barbara Seth, Thomas Blunier, and Hubertus Fischer2018Bipolar carbon and hydrogen isotope constraints on the Holocene methane budgetBiogeosciences157155-717510.5194/bg-15-7155-2018https://www.biogeosciences.net/15/7155/2018/ START YEAR: 11978 cal yr BP * END YEAR: 38 cal yr BP -180 -90 180 90