title: Isotopic constraints on marine and terrestrial N2O emissions during the last deglaciation.
abstract: Nitrous oxide (N2O) is an important greenhouse gas and ozone-depleting substance that has anthropogenic as well as natural marine and terrestrial sources. The tropospheric N2O concentrations have varied substantially in the past in concert with changing climate on glacial-interglacial and millennial timescales. It is not well understood, however, how N2O emissions from marine and terrestrial sources change in response to varying environmental conditions. The distinct isotopic compositions of marine and terrestrial N2O sources can help disentangle the relative changes in marine and terrestrial N2O emissions during past climate variations. Here we present N2O concentration and isotopic data for the last deglaciation, from 16,000 to 10,000 years before present, retrieved from air bubbles trapped in polar ice at Taylor Glacier, Antarctica. With the help of our data and a box model of the N2O cycle, we find a 30 per cent increase in total N2O emissions from the late glacial to the interglacial, with terrestrial and marine emissions contributing equally to the overall increase and generally evolving in parallel over the last deglaciation, even though there is no a priori connection between the drivers of the two sources. However, we find that terrestrial emissions dominated on centennial timescales, consistent with a state-of-the-art dynamic global vegetation and land surface process model that suggests that during the last deglaciation emission changes were strongly influenced by temperature and precipitation patterns over land surfaces. The results improve our understanding of the drivers of natural N2O emissions and are consistent with the idea that natural N2O emissions will probably increase in response to anthropogenic warming.
authors.affiliation: 1] College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA [2] Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland.
authors.forename: Adrian
authors.initials: A
authors.lastname: Schilt
authors.affiliation: College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Brook
authors.affiliation: College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Bauska
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, California 92037, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Baggenstos
authors.affiliation: Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland.
authors.forename: Hubertus
authors.initials: H
authors.lastname: Fischer
authors.affiliation: Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland.
authors.forename: Fortunat
authors.initials: F
authors.lastname: Joos
authors.affiliation: Department of Earth and Environmental Sciences, University of Rochester, Rochester, New York 14627, USA.
authors.forename: Vasilii V
authors.initials: VV
authors.lastname: Petrenko
authors.affiliation: National Institute of Water and Atmospheric Research, Wellington 6021, New Zealand.
authors.forename: Hinrich
authors.initials: H
authors.lastname: Schaefer
authors.affiliation: Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland.
authors.forename: Jochen
authors.initials: J
authors.lastname: Schmitt
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, California 92037, USA.
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Severinghaus
authors.affiliation: Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland.
authors.forename: Renato
authors.initials: R
authors.lastname: Spahni
authors.affiliation: Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Stocker
mesh_terms: D000864:Antarctic Regions; D059001:Aquatic Organisms / Q000378:metabolism*; D001272:Atmosphere / Q000737:chemistry*; D057232:Global Warming; D049690:History, Ancient; D046448:Ice Cover; D009587:Nitrogen Isotopes / Q000032:analysis; D009609:Nitrous Oxide / Q000032:analysis / Q000266:history / Q000378:metabolism*; D010103:Oxygen Isotopes / Q000032:analysis; D011891:Rain; D013696:Temperature; D013997:Time Factors
chemical_list: D009587:Nitrogen Isotopes; D010103:Oxygen Isotopes; D009609:Nitrous Oxide