CH4 and N2O fluctuations during the penultimate deglaciation

Loïc Schmidely , Christoph Nehrbass-Ahles (1) , Jochen Schmitt , Juhyeong Han , Lucas Silva , Jinwha Shin , Fortunat Joos (1) , Jérôme Chappellaz (2) , Hubertus Fischer (1) , Thomas Stocker (3)

1 CEP - Climate and Environmental Physics [Bern]
2 UGA - Université Grenoble Alpes
3 NCCR PlanetS - National Centre of Competence in Research PlanetS

Abstract. Deglaciations are characterized by the largest natural changes in methane (CH4) and nitrous oxide (N2O) concentrations of the past 800 000 years. Reconstructions of millennial- to centennial-scale variability within these periods are mostly restricted to the last deglaciation. In this study, we present composite records of CH4 and N2O concentrations from the EPICA Dome C ice core covering the penultimate deglaciation at temporal resolutions of ∼100 years. Our data permit the identification of centennial-scale fluctuations during the transition from glacial to interglacial levels. At ∼134 000 and ∼129 000 years before present (hereafter ka), both CH4 and N2O increased on centennial timescales. These abrupt rises are similar to the fluctuations associated with the Dansgaard–Oeschger events identified in the last glacial period. In addition, gradually rising N2O levels at ∼130 ka resemble a pattern of increasing N2O concentrations on millennial timescales characterizing the later part of Heinrich stadials. Overall, the events in CH4 and N2O during the penultimate deglaciation exhibit modes of variability that are also found during the last deglaciation and glacial cycle, suggesting that the processes leading to changes in emission during the transitions were similar but their timing differed.

Domaines: Sciences de l'environnement; Planète et Univers [physics]

Loïc Schmidely, Christoph Nehrbass-Ahles, Jochen Schmitt, Juhyeong Han, Lucas Silva, et al.. CH4 and N2O fluctuations during the penultimate deglaciation. Climate of the Past, 2021, 17 (4), pp.1627-1643. ⟨10.5194/cp-17-1627-2021⟩. ⟨hal-03418313⟩