Multimolecular tracers of terrestrial carbon transfer across the pan‐Arctic: ¹⁴C characteristics of sedimentary carbon components and their environmental controls

Abstract

Distinguishing the sources, ages, and fate of various terrestrial organic carbon (OC) pools mobilized from heterogeneous Arctic landscapes is key to assessing climatic impacts on the fluvial release of carbon from permafrost. Through molecular 14 C measurements, including novel analyses of suberin-and/or cutin-derived diacids (DAs) and hydroxy fatty acids (FAs), we compared the radiocarbon characteristics of a comprehensive suite of terrestrial markers (including plant wax lipids, cutin, suberin, lignin, and hydroxy phenols) in the sedimentary particles from nine major arctic and subarctic rivers in order to establish a benchmark assessment of the mobilization patterns of terrestrial OC pools across the pan-Arctic. Terrestrial lipids, including suberin-derived longer-chain DAs (C 24,26,28 ), plant wax FAs (C 24,26,28 ), and n-alkanes (C 27,29,31 ), incorporated significant inputs of aged carbon, presumably from deeper soil horizons. Mobilization and translocation of these "old" terrestrial carbon components was dependent on nonlinear processes associated with permafrost distributions. By contrast, shorter-chain (C 16,18 ) DAs and lignin phenols (as well as hydroxy phenols in rivers outside eastern Eurasian Arctic) were much more enriched in 14 C, suggesting incorporation of relatively young carbon supplied by runoff processes from recent vegetation debris and surface layers. Furthermore, the radiocarbon content of terrestrial markers is heavily influenced by specific OC sources and degradation status. Overall, multitracer molecular 14 C analysis sheds new light on the mobilization of terrestrial OC from arctic watersheds. Our findings of distinct ages for various terrestrial carbon components may aid in elucidating fate of different terrestrial OC pools in the face of increasing arctic permafrost thaw.

Permafrost Organic Carbon Mobilization From the Watershed to the Colville River Delta: Evidence From 14C Ramped Pyrolysis and Lignin Biomarkers

“…Our study builds on this previous work using a more comprehensive suite samples from soils, river, and deltaic sediments, collected from the Colville River basin, to more fully investigate the fate and transport of thawing permafrost-derived POC from the upper watershed, to river channels, and eventually the delta. This work constrains permafrost inputs to inner coastal regions (Feng et al, 2015(Feng et al, , 2013Gustafsson et al, 2011;Tesi et al, 2014), as well as deeper waters in the Arctic Ocean (Bröder et al, 2016;Tesi et al, 2016) and adds to our understanding of permafrost carbon cycling and transport along the aquatic continuum in the Arctic.…”

Carbon geochemistry of plankton-dominated samples in the Laptev and East Siberian shelves: contrasts in suspended particle composition

“…Considering the potential allochthonous contribution, we addressed to what extent terrestrial organic material affects the POM (> 10 µm) fraction by quantifying the concentration of lignin phenols and C16-18 hydroxy fatty acids (cutin-derived products). These biomarkers are exclusively formed by terrestrial vegetation and, thus, serve as tracers of land-derived material in the marine environment (Amon et al, 2012;Bröder et al, 2016b;Feng et al, 2015). Upon CuO alkaline oxidation the POM (> 10 µm) samples yielded only traces of lignin phenols while the cutin-derived products were not detected (Fig.…”

The fate of terrigenous dissolved organic carbon on the Eurasian shelves and export to the North Atlantic

“…The Ob, Yenisey, and Lena alone supply $65% of total discharge, $75% of riverine DOC, and $90% of total lignin [Gordeev and Kravchishina, 2009;Amon et al, 2012;Holmes et al, 2012;Mann et al, 2016]. Additional input of tDOC can result from erosion of organic-rich coastal sediments, which are an important source of sediments in the Arctic Seas, especially in the Laptev Sea [Rachold et al, 2004;Feng et al, 2015]. Coastal erosion releases <1 Tg yr 21 of tDOC for the entire Arctic Ocean indicating river discharge is the dominant source of tDOC [Stein and MacDonald, 2004].…”