On carbon transport and fate in the East Siberian Arctic land–shelf–atmosphere system

Abstract

This review paper summarizes current understanding of the transport of organic carbon to, and the fate of organic carbon within, the East Siberian Arctic Shelf (ESAS), and of processes determining carbon dioxide (CO 2 ) and methane (CH 4 ) fluxes from the ESAS to the atmosphere achieved from analyzing the data sets obtained on 20 expeditions performed from 1999 to 2011. This study of the ESAS was aimed at investigating how redistribution of old carbon from degrading terrestrial and sub-sea permafrost and from coastal erosion contributes to the carbon pool of the ESAS, how changes in the hydrological cycle of the surrounding land and alteration of terrestrial carbon cycles affect the hydrological and biogeochemical parameters of shelf water masses, and which factors control CH 4 and CO 2 emissions from the ESAS. This report describes selected results achieved by a developing international scientific partnership that has been crucial at every stage of the study and will be even more important in the future.

Space–time dynamics of carbon and environmental parameters related to carbon dioxide emissions in the Buor-Khaya Bay and adjacent part of the Laptev Sea

“…Under the Type 2 sedimentation conditions, the highest POC levels were measured in an eastward direction, reflecting river plume propagation from the delta channels to the BKB interior . The δ 13 C of sea water POC in 2005 ranged from −26.4 to −28.5 ‰, typical values for both river-borne and coastal erosion-borne POC (Semiletov, 1999a,b;Kodina et al, 2001Kodina et al, , 2002Semiletov et al, 2012;Sánchez-Garcia et al, 2011;Vonk et al, 2010Vonk et al, , 2012, while in 2008, δ 13 C of POC varied from −24.3 ‰ to −32.2 ‰ (Fig. 7); this depletion reflects the strong terrestrial influence of the river plume extending eastward from the Lena Delta.…”

“…The ESAS makes up a significant fraction (∼ 25 %) of the shelf and holds > 80 % of the Arctic shelf sub-sea permafrost and permafrost-related unique Arctic shelf hydrates (Soloviev, 1987;ACIA, 2004;Shakhova et al, 2010a). It accepts about 30 % of Arctic river discharge, and is surrounded by a coastline that exhibits the highest rates of coastal erosion in the world (Rachold et al, 2004;Grigoriev et al, 2006;Semiletov et al, 2011Semiletov et al, , 2012Vonk et al, 2012). The ESAS not only responds to the ongoing Arctic warming, but also accommodates the signal of the terrestrial ecosystems' response which is delivered to the ESAS by Arctic rivers (Guo et al, 2004;Porcelli et al, 2009;Gustafsson et al, 2011;Proshutinsky et al, 2012;Feng et al, 2013).…”

“…The coastal zone of the ESAS plays the most important role in this response, because incoming river-borne signals and in situ marine signals first interact in this zone. Processes that develop here include carbon transport, accumulation, and transformation, and seaward export of particulate and dissolved materials to offshore shelf/slope regions (Dudarev et al, 2003(Dudarev et al, , 2006van Dongen et al, 2008;Cooke et al, 2009;Alling et al, 2010;Pipko et al, 2011b;Sánchez-Garcia et al, 2011;Semiletov et al, 2012;Vetrov et al, 2008;Vonk et al, 2012;Feng et al, 2013). In addition, the warming effect of river runoff on the underlying sub-sea permafrost also begins in the coastal zone (Shakhova et al, 2009a, b;Semiletov et al, 2011;Nicolsky and Shakhova, 2010;Nicolsky et al, 2012).…”

“…Its transformation in shelf water sooner rather than later results in the high partial pressure of CO 2 (pCO 2 ) observed in the water (Semiletov, 1999a,b;Semiletov et al, , 2011Semiletov et al, , 2012Pipko et al, 2005Pipko et al, , 2008Pipko et al, , 2011aAnderson et al, 2009Anderson et al, , 2011. Dissolved OC (DOC) is believed to be brought mainly by rivers and to be a relatively inert carbon stock in the near-shore zone, because its pool turnover time is significantly greater than the shelf water residence time (Dittmar and Kattner, 2003;Alling et al, 2010).…”

Shifted energy fluxes, increased Bowen ratios, and reduced thaw depths linked with drainage-induced changes in permafrost ecosystem structure

“…Interactions between permafrost, climate, hydrology, and ecology have the potential to cause dramatic changes (e.g., McGuire et al, 2002;Hinzman et al, 2005) via mechanisms that are currently poorly monitored and therefore highly unpredictable (Heimann and Reichstein, 2008;van Huissteden and Dolman, 2012;Rawlins et al, 2015). The associated changes in the energy transfer between surface and atmosphere Langer et al, 2011a, b) and the emission patterns of greenhouse gases (Koven et al, 2011) raise the need for experimental studies in this region that address the key uncertainties linked to the functioning of the Arctic in the Earth's climate system (Semiletov et al, 2012).…”