Deglacial mobilization of pre-aged terrestrial carbon from degrading permafrost

Abstract

The mobilization of glacial permafrost carbon during the last glacial–interglacial transition has been suggested by indirect evidence to be an additional and significant source of greenhouse gases to the atmosphere, especially at times of rapid sea-level rise. Here we present the first direct evidence for the release of ancient carbon from degrading permafrost in East Asia during the last 17 kyrs, using biomarkers and radiocarbon dating of terrigenous material found in two sediment cores from the Okhotsk Sea. Upscaling our results to the whole Arctic shelf area, we show by carbon cycle simulations that deglacial permafrost-carbon release through sea-level rise likely contributed significantly to the changes in atmospheric CO2 around 14.6 and 11.5 kyrs BP.

Radiocarbon Evidence for the Contribution of the Southern Indian Ocean to the Evolution of Atmospheric CO2 Over the Last 32,000 Years

“…The covariation of atmospheric CO 2 and Δ 14 C implies a process acting upon both patterns. As this 190‰ decrease cannot be explained by the atmospheric formation of 14 C (Broecker, 2009;Broecker & Barker, 2007;Butzin et al, 2012;Laj et al, 2002;Reimer et al, 2013), the release of old, and therefore 14 C-depleted CO 2 from a large carbon reservoir such as permafrost soils (Köhler et al, 2014;Winterfeld et al, 2018) and/or the deep ocean (Burke and Robinson, 2012;Ronge et al, 2016;Skinner et al, 2010;Skinner et al, 2015) is considered the most likely driver. The sequestration of carbon (CO 2 ) within the deeper ocean would require a major climate-response of polar upwelling regions and thus significant changes in global deep water circulation (Sigman et al, 2010).…”

Permafrost-carbon mobilization in Beringia caused by deglacial meltwater runoff, sea-level rise and warming

“…Most studies investigating the contributions of terrestrial carbon to the atmospheric changes are indirect, as they rely on interpreting atmospheric records with carbon-cycle models (Köhler et al 2014, Bauska et al 2016, Crichton et al 2016. However, the assumed timing of carbon release from degrading permafrost is very poorly constrained by proxy data as deglacial records of carbon mobilization are very sparse , Winterfeld et al 2018, Martens et al 2019.…”

The Late Mesozoic‐Cenozoic Arctic Ocean Climate and Sea Ice History: A Challenge for Past and Future Scientific Ocean Drilling

“…Huge amounts of soil organic carbon are currently stored frozen in permafrost soils (e.g., Tarnocai et al, 2009;Zimov et al, 2009), and vast amounts of methane, in a solid form as gas hydrates, are trapped in permafrost and at shallow depths in cold ocean sediments (e.g., Romanovskii et al, 2005). With increasing temperature of the permafrost (Romanovsky et al, 2010) and the water at the seafloor, as a result of increased surface warming in Arctic regions (Stocker et al, 2013), a widespread increase in the thickness of the thawed layer and the decomposition of hydrates could lead to the release of large quantities of CH 4 (and CO 2 ) to the atmosphere (ACIA, 2004(ACIA, , 2005Anisimov et al, 1997;Goulden et al, 1998;Michaelson et al, 1996) as well as an enhanced mobilization and export of old, previously frozen soil-derived organic carbon (e.g., Bröder et al, 2018;Bröder et al, 2019;Schuur et al, 2008;Tesi et al, 2016;Vonk et al, 2012;Winterfeld et al, 2015Winterfeld et al, , 2018. The release of these greenhouse gases in turn would create a positive feedback mechanism that can amplify regional and global warming.…”