CH₄ and N₂O fluctuations during the penultimate deglaciation

• Main Authors: L. Schmidely, C. Nehrbass-Ahles, J. Schmitt, J. Han, L. Silva, J. Shin, F. Joos, J. Chappellaz, H. Fischer, T. F. Stocker
• Format: Article
• Language: English
• Published: Copernicus Publications 2021-08-01
• Series: Climate of the Past
• Online Access: https://cp.copernicus.org/articles/17/1627/2021/cp-17-1627-2021.pdf

<p>Deglaciations are characterized by the largest natural changes in methane (CH<span class="inline-formula">₄</span>) and nitrous oxide (N<span class="inline-formula">₂</span>O) 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 CH<span class="inline-formula">₄</span> and N<span class="inline-formula">₂</span>O concentrations from the EPICA Dome C ice core covering the penultimate deglaciation at temporal resolutions of <span class="inline-formula">∼100</span> years. Our data permit the identification of centennial-scale fluctuations during the transition from glacial to interglacial levels. At <span class="inline-formula">∼134 000</span> and <span class="inline-formula">∼129 000</span> years before present (hereafter ka), both CH<span class="inline-formula">₄</span> and N<span class="inline-formula">₂</span>O 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 N<span class="inline-formula">₂</span>O levels at <span class="inline-formula">∼130</span> ka resemble a pattern of increasing N<span class="inline-formula">₂</span>O concentrations on millennial timescales characterizing the later part of Heinrich stadials. Overall, the events in CH<span class="inline-formula">₄</span> and N<span class="inline-formula">₂</span>O 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.</p>