Abstract
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.
Highlights
Methane (CH4) and nitrous oxide (N2O) are currently the second- and third-most potent well-mixed anthropogenic greenhouse gases after carbon dioxide (CO2) (Myhre et al, 2013)
We present CH4 and N2O composite datasets from the European Project for Ice Coring in Antarctica (EPICA) Dome C (EDC) ice core including 150 new measurements covering the time interval 145– 125 ka, combined with the published data of Loulergue et al Published by Copernicus Publications on behalf of the European Geosciences Union
Our centennial-scale records show the progressions of the overall ∼ 390 and ∼ 60 ppb increase in CH4 and N2O concentration (Fig. 1), respectively, from the end of the Penultimate Glacial Maximum (PGM) to the beginning of the Last Interglacial (LIG)
Summary
Methane (CH4) and nitrous oxide (N2O) are currently the second- and third-most potent well-mixed anthropogenic greenhouse gases after carbon dioxide (CO2) (Myhre et al, 2013). The impact of these trace gases on the Earth’s radiative balance in the future depends on the sensitivity of natural sources to anthropogenic warming. Ice core records of CH4 and N2O concentrations combined with temperature reconstructions revealed the natural variability of these gases and their coupling to climate change during the glacial cycles of the past 800 000 years. Records resolving short-term fluctuations within deglaciations are limited to TI, owing to the availability of multiple high-accumulation ice cores
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