Interannual variability of air-sea CO<sub>2</sub> fluxes and carbonate system parameters in the East Siberian Sea

Abstract

Over the past couple of decades it has become apparent that air-land-sea interactions in the Arctic have a substantial impact on the composition of the overlying atmosphere (ACIA, 2004). The Arctic Ocean is small (only ~4% of the total World Ocean), but it is surrounded by offshore and onshore permafrost which thaws at increasing rates under warming conditions releasing carbon dioxide (CO₂) into the water and atmosphere. This work summarizes data collected from three expeditions in the coastal-shelf zone of the East Siberian Sea (ESS) in September 2003, 2004 and late August–September 2008. It is proposed that the western part of the ESS represents a river- and coastal erosion-dominated ocean margin that is a source for atmospheric CO₂. It receives substantial river discharge that also adds organic matter, both dissolved and particulate. This in combination with significant input of organic matter from coastal erosion makes this region being of dominantly heterotrophic character. The eastern part of the ESS is a Pacific water-dominated autotrophic area. It's a high-productive zone, which acts as a sink for atmospheric CO₂. The year to year dynamics of partial pressure of CO₂ in the surface water as well as the sea-air flux of CO₂ varied substantially. In some years the ESS shelf can be mainly heterotrophic and serve as strong source of CO₂ (year 2004). Another year significant part of the ESS, where gross primary production exceeds community respiration, acts as a sink for the atmospheric CO₂ and the net CO₂ flux into the atmosphere is weak (year 2008). High variability of carbon system parameters observed in the ESS shelf is determined by many factors such as riverine runoff, advection of waters from adjacent seas, coastal erosion, primary production/respiration etc. The dynamics of the CO₂ sea-air exchange is determined by ocean processes but also by atmospheric circulation which hence has a significant impact on the CO₂ sea-air exchange. In this contribution the sea-air CO₂ fluxes were evaluated in the ESS based on measured carbonate system (CS) parameters data and annual sea-to-air CO₂ fluxes were estimated. It was shown that the total ESS shelf is a net source of CO₂ for the atmosphere at a range from 0.5×10¹² to 3.3×10¹² g C

The spatial and interannual dynamics of the surface water carbonate system and air–sea CO<sub>2</sub> fluxes in the outer shelf and slope of the Eurasian Arctic Ocean

“…Supersaturation was observed not only in the shallow shelf sea, as previously described in literature (Anderson et al, 2009(Anderson et al, , 2011Pipko et al, 2005Pipko et al, , 2011bSemiletov et al, 2007Semiletov et al, , 2012, but also in the adjacent deepwater area. The likely causes of the detected pCO 2 distribution are the anomalous dynamics of atmospheric processes, in particular the deep low-pressure area over land and highpressure area over the ocean, as well as the sharp reduction in sea-ice coverage.…”

“…For riverine A T , the average value of 840 µmol kg −1 was applied, which is typical of the largest Siberian rivers (the Ob, Yenisei, and Lena rivers) during the warm season ; up to 90 % of the total river discharge enters the Arctic seas during this season (Dittmar and Kattner, 2003). The sea-ice values of salinity and A T are taken from Fransson et al (2009); the Atlantic-derived water values of salinity and A T are taken from Pipko et al (2011b).…”

“…Studies of the Barents Sea carbonate system (Årthun et al, 2012;Lauvset et al, 2013;Pipko et al, 2011b;Yakushev and Sørensen, 2013) as well as the ESAS waters (Anderson et al, 2009(Anderson et al, , 2011Pipko et al, 2011aPipko et al, , 2015Pipko et al, , 2016Semiletov et al, 2012Semiletov et al, , 2013Semiletov et al, , 2016 have been performed during the last decade. The Kara Sea remains less studied in the context of carbonate system dynamics and the main research was accomplished in the shallow part of this sea (Makkaveev et al, 2010(Makkaveev et al, , 2015.…”

East Siberian Sea, an Arctic region of very high biogeochemical activity

“…10). For the latter the largest gradients is found in the frontal zone between the low saline and lowtransparent heterotrophic local shelf waters and the high productive and high-transparent Pacific-derived autotrophic waters (Pipko et al, 2005(Pipko et al, , 2011Semiletov et al, 2005Semiletov et al, , 2007. The dissolved CH 4 concentration is mostly related to the location of seabed CH 4 sources inside the fault zones and through taliks (Nikolsky and Shakhova, 2010;Shakhova et al, 2010a, b).…”

Carbon mineralization in Laptev and East Siberian sea shelf and slope sediment

“…Nevertheless, these data indicate that the contribution of the benthic DIC flux to the total CO 2 production in the outer East Siberian Sea and Laptev Sea is small. This conclusion, however, does not necessarily extend to the inner parts of the Laptev Sea and the western parts of the East Siberian Sea, where CO 2 supersaturation has been reported by Pipko et al (2011). Anderson et al (2009) estimated a DIC excess of 10 Tg C by evaluating data from the Laptev and East Siberian seas collected in the summer of 2008 and suggested that this excess was caused mainly by terrestrial organic matter decomposition.…”