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High-resolution interpolar difference of atmospheric methane around the Last Glacial Maximum
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2012 (English)In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 9Article in journal (Refereed) Published
Abstract [en]

Reconstructions of past atmospheric methane concentrations are available from ice cores from both Greenland and Antarctica. The difference observed between the two polar methane concentration levels represents a valuable constraint on the geographical location of the methane sources. Here we present new high-resolution methane records from the North Greenland Ice Core Project (NGRIP) and the European Project for Ice Coring in Antarctica (EPICA) Dronning Maud Land (EDML) ice cores covering Termination 1, the Last Glacial Maximum, and parts of the last glacial back to 32 000 years before present. Due to the high resolution of the records, the synchronisation between the ice cores from NGRIP and EDML is considerably improved, and the interpolar concentration difference of methane is determined with unprecedented precision and temporal resolution. Relative to the mean methane concentration, we find a rather stable positive relative interpolar difference throughout the record with its minimum value of 3.7+/-0.7% between 21 900-21 200 years before present, which is higher than previously estimated in this interval close to the Last Glacial Maximum. This implies that Northern Hemisphere boreal wetland sources were never completely shut off during the peak glacial, as suggested from previous bipolar methane concentration records. Starting at 21 000 years before present, i.e. several millennia prior to the transition into the Holocene, the relative interpolar difference becomes even more positive and stays at a fairly stable level of 6.5+/-0.8% during Termination 1. We thus find that the boreal and tropical methane sources increased by approximately the same factor during Termination 1. We hypothesise that latitudinal shifts in the Intertropical Convergence Zone (ITCZ) and the monsoon system contribute, either by dislocation of the methane source regions or, in case of the ITCZ, also by changing the relative atmospheric volumes of the Northern and Southern Hemispheres, to the subtle variations in the relative interpolar concentration difference on glacial/interglacial as well as on millennial time scales.

Place, publisher, year, edition, pages
2012. Vol. 9
Keyword [en]
deep ice core late pleistocene nitrous-oxide ch4 gradient greenland antarctica holocene records period emissions Environmental Sciences & Ecology Geology
Research subject
SWEDARCTIC 1997, NordGRIP 1997; SWEDARCTIC 1998, NordGRIP 1998; SWEDARCTIC 1999, NordGRIP 1999; SWEDARCTIC 2000, NordGRIP 2000; SWEDARCTIC 2001, NordGRIP 2001; SWEDARCTIC 2002, NordGRIP 2002; SWEDARCTIC 2003, NordGRIP 2003; SWEDARCTIC 2004, NordGRIP 2004; SWEDARP 1997/98, EPICA 1997/98; SWEDARP 2001/02, EPICA 2001/02; SWEDARP 2002/03, EPICA 2002/03; SWEDARP 2003/04, EPICA 2003/04; SWEDARP 2004/05, EPICA 2004/05; SWEDARP 2005/06, EPICA 2005/06
Identifiers
URN: urn:nbn:se:polar:diva-1885DOI: 10.5194/bg-9-3961-2012OAI: oai:DiVA.org:polar-1885DiVA: diva2:810843
Note

ISI Document Delivery No.: 029CG Times Cited: 15 Cited Reference Count: 54 Baumgartner, M. Schilt, A. Eicher, O. Schmitt, J. Schwander, J. Spahni, R. Fischer, H. Stocker, T. F. Schmitt, Jochen/B-7893-2009; Fischer, Hubertus/A-1211-2014; Stocker, Thomas/B-1273-2013 Schmitt, Jochen/0000-0003-4695-3029; Fischer, Hubertus/0000-0002-2787-4221; University of Bern; Swiss National Science Foundation; Monaco Foundation; Denmark (SHF); Belgium (FNRS-CFB); France (IPEV); France (INSU/CNRS); Germany (AWI); Iceland (RannIs); Japan (MEXT); Sweden (SPRS); Switzerland (SNF); United States of America (NSF); United States of America (Office of Polar Programs); EU We thank Jerome Chappellaz for helpful comments. The very detailed and constructive review comments by J. G. Levine and L. Mitchell have improved the presentation of the material. This work, which is a contribution to the North Greenland Ice Core Project (NGRIP) and the European Project for Ice Coring in Antarctica (EPICA), was supported by the University of Bern, the Swiss National Science Foundation, and the Prince Albert II of Monaco Foundation.NGRIP is coordinated by the Department of Geophysics at the Niels Bohr Institute for Astronomy, Physics and Geophysics, University of Copenhagen. It is supported by Funding Agencies in Denmark (SHF), Belgium (FNRS-CFB), France (IPEV and INSU/CNRS), Germany (AWI), Iceland (RannIs), Japan (MEXT), Sweden (SPRS), Switzerland (SNF) and the United States of America (NSF, Office of Polar Programs). EPICA is a joint European Science Foundation/European Commission scientific program, funded by the EU and by national contributions from Belgium, Denmark, France, Germany, Italy, the Netherlands, Norway, Sweden, Switzerland and the UK. The main logistic support was provided by IPEV and PNRA (at Dome C) and AWI (at Dronning Maud Land). This is EPICA publication no. 290. 15 Copernicus gesellschaft mbh Gottingen Ecology; Geosciences, Multidisciplinary

Available from: 2015-05-08 Created: 2015-05-06 Last updated: 2015-06-12

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Citation style
  • apa
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