Activation of old carbon by erosion of coastal and subsea permafrost in Arctic Siberia

Abstract

The future trajectory of greenhouse gas concentrations depends on interactions between climate and the biogeosphere. Thawing of Arctic permafrost could release significant amounts of carbon into the atmosphere in this century. Ancient Ice Complex deposits outcropping along the ~7,000-kilometre-long coastline of the East Siberian Arctic Shelf (ESAS), and associated shallow subsea permafrost, are two large pools of permafrost carbon, yet their vulnerabilities towards thawing and decomposition are largely unknown. Recent Arctic warming is stronger than has been predicted by several degrees, and is particularly pronounced over the coastal ESAS region. There is thus a pressing need to improve our understanding of the links between permafrost carbon and climate in this relatively inaccessible region. Here we show that extensive release of carbon from these Ice Complex deposits dominates (57 ± 2 per cent) the sedimentary carbon budget of the ESAS, the world’s largest continental shelf, overwhelming the marine and topsoil terrestrial components. Inverse modelling of the dual-carbon isotope composition of organic carbon accumulating in ESAS surface sediments, using Monte Carlo simulations to account for uncertainties, suggests that 44 ± 10 teragrams of old carbon is activated annually from Ice Complex permafrost, an order of magnitude more than has been suggested by previous studies. We estimate that about two-thirds (66 ± 16 per cent) of this old carbon escapes to the atmosphere as carbon dioxide, with the remainder being re-buried in shelf sediments. Thermal collapse and erosion of these carbon-rich Pleistocene coastline and seafloor deposits may accelerate with Arctic amplification of climate warming.

Marine CDOM accumulation during a coastal Arctic mesocosm experiment: No response to elevated pCO2 levels

“…There has been a dramatic decrease in the extent, thickness, and volume of Arctic sea ice [Stroeve et al, 2012;Laxon et al, 2013], warming of the Atlantic Water inflow to the Arctic Ocean [Polyakov et al, 2005[Polyakov et al, , 2011Walczowski and Piechura, 2007], increasing freshwater discharge [Peterson et al, 2002] which in turn can increase the supply of terrigenous organic material [Stedmon et al, 2011], as will increased rates of coastal permafrost erosion and thawing [Arctic Climate Impact Assessment, 2005;Vonk et al, 2012]. Additionally, changes in biogeochemical element cycling including rapid increase in Arctic Ocean acidity [AMAP, 2013], occurrence of stratospheric ozone depletions over the Arctic [Manney et al, 2011], and other ongoing changes may have far reaching consequences for the fragile Arctic marine ecosystem [Post et al, 2013].…”

Collapsing Arctic coastlines

“…Coastal erosion rates as high as 25 m yr -1 (refs 2,3) together with the large amount of organic matter frozen in permafrost 4,5 are resulting in an annual release of 14.0 Tg (10 12 grams) of particulate organic carbon into the nearshore zone 6,7 . This carbon flux is in the same order of magnitude as the yearly contribution from all Arctic rivers, or the vertical net methane (CH 4 ) emissions from terrestrial permafrost 8 .…”

Robust, spatially scanning, open-path TDLAS hygrometer using retro-reflective foils for fast tomographic 2-D water vapor concentration field measurements

“…A highly topical example comes from environmental science: as the permafrost in arctic regions is gradually thawing, gases that affect the climate effect, such as methane, carbon dioxide or water vapor, are emitted from the soil (Anisimov and Nelson, 1997;Nakano et al, 2000;O'Connor et al, 2010;Schuur, 2009;Vonk et al, 2012;Zimov et al, 2006). This process is suspected to lead to a positive feedback on the greenhouse effect, which would increase the soil emissions even further (Field et al, 2007;Heimann and Reichstein, 2008;Luke and Cox, 2011;Olefeldt et al, 2013;Schuur, 2009).…”

“…This process is suspected to lead to a positive feedback on the greenhouse effect, which would increase the soil emissions even further (Field et al, 2007;Heimann and Reichstein, 2008;Luke and Cox, 2011;Olefeldt et al, 2013;Schuur, 2009). Although it is already known that such gases are released, there is, as of yet, little information on their absolute concentrations (O'Connor et al, 2010;Schuur, 2009;Schuur and Abbott, 2011;Vonk et al, 2012).…”