CH4 and N2O fluctuations during the penultimate deglaciation

• Main Authors: Schmidely, Loïc, Nehrbass-Ahles, Christoph, Schmitt, Jochen, Han, Juhyeong, Silva, Lucas, Shin, Jinwha, Joos, Fortunat, Chappellaz, Jérôme, Fischer, Hubertus, Stocker, Thomas F.
• Format: Text
• Language: English
• Published: 2020
• Subjects: Dansgaard-Oeschger events; EPICA; ice core
• Online Access: https://doi.org/10.5194/cp-2020-131; https://cp.copernicus.org/preprints/cp-2020-131/

Deglaciations are characterized by the largest natural changes in methane (CH 4 ) and nitrous oxide (N 2 O) concentrations of the past 800 thousand 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 CH 4 and N 2 O concentrations from the EPICA Dome C ice core covering the penultimate deglaciation at temporal resolutions of about ~ 100 years. Our data permit the identification of centennial-scale fluctuations standing out of the overall transition to interglacial levels. These features occurred in concert with reinvigorations of the Atlantic Meridional Overturning Circulation (AMOC) and northward shifts of the Intertropical Convergence Zone. The abrupt CH 4 and N 2 O rises at about ~ 134 and ~ 128 thousand of years before present (hereafter ka BP) are assimilated to the fluctuations accompanying the Dansgaard–Oeschger events of the last glacial period, while rising N 2 O levels at ~ 130.5 ka BP are assimilated to a pattern of increasing N 2 O concentrations that characterized the end of Heinrich stadials. We suggest the 130.5-ka event to be driven by a partial reinvigoration of the AMOC. Overall, the CH 4 and N 2 O fluctuations during the penultimate deglaciation exhibit modes of variability that are also found during the last deglaciation. However, trace gas responses may differ for similar type of climatic events, as exemplified by the reduced amplitude and duration of the 134-ka event compared to the fluctuations of the Bølling–Allerød during the last deglaciation.