Preprints
https://doi.org/10.5194/bg-2021-109
https://doi.org/10.5194/bg-2021-109

  06 May 2021

06 May 2021

Review status: this preprint is currently under review for the journal BG.

Fluvial carbon dioxide emission from the Lena River basin during spring flood

Sergey N. Vorobyev1, Jan Karlsson2, Yuri Y. Kolesnichenko1, Mikhail Koretz3, and Oleg S. Pokrovsky4,5 Sergey N. Vorobyev et al.
  • 1BIO-GEO-CLIM Laboratory, Tomsk State University, Tomsk, Russia
  • 2Climate Impacts Research Centre (CIRC), Department of Ecology and Environmental Science, Umeå University, Linnaeus väg 6, 901 87 Umeå, Sweden
  • 3V.N. Sukachev Institute of Forest of the Siberian Branch of Russian Academy of Sciences, Krasnoyarsk, Russia
  • 4Geosciences and Environment Toulouse, UMR 5563 CNRS, 14 Avenue Edouard Belin 31400 Toulouse, France
  • 5N. Laverov Federal Center for Integrated Arctic Research, Russian Academy of Sciences, Arkhangelsk, Russia

Abstract. Greenhouse gas (GHG) emissions from inland waters of permafrost-affected regions is one of the key factor of circumpolar aquatic ecosystem response to climate warming and permafrost thaw. Riverine systems of central and eastern Siberia contribute a significant part of the water and carbon (C) export to the Arctic Ocean, yet their C exchange with the atmosphere remain poorly known due to lack of in-situ GHG concentration and emission estimates. Here we present the results of continuous in-situ pCO2 measurements over a 2600-km transect of the Lena River main stem and lower reaches of 20 major tributaries (together representing watershed area of 1,661,000 km2, 66 % of the Lena’s basin), conducted at the peak of the spring flood. The pCO2 in Lena (range 400–1400 µatm) and tributaries (range 400–1600 µatm) was oversaturated and remained generally stable (within ca. 20 %) over the night/day period and across the river channels. The pCO2 in tributaries increased northward with mean annual temperature decrease and permafrost increase; this change was positively correlated with C stock in soil and the proportion of deciduous needle-leaf forest and riparian vegetation. Based on gas transfer coefficients obtained from rivers of the Siberian permafrost zone, we calculated CO2 emission for the main stem and tributaries. Typical fluxes ranged from 1 to 2 g C m−2 d−1 (> 99 % CO2, < 1 % CH4) which is comparable with CO2 emission measured in Kolyma, Yukon and Mackenzie and permafrost-affected rivers in western Siberia. The areal C emissions from lotic waters of the Lena watershed were quantified via taking into account the total area of permanent and seasonal water of the Lena basin (28,000 km2). Assuming 6 months of the year of open water period and no emission under ice, the annual C emissions from the whole Lena basin range from 5 to 10 Tg C yr−1, which is comparable to the DOC and DIC lateral export to the Arctic Ocean.

Sergey N. Vorobyev et al.

Status: open (until 07 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-109', Anonymous Referee #1, 08 Jun 2021 reply
    • AC1: 'Reply on RC1', O.S. Pokrovsky, 11 Jun 2021 reply
  • RC2: 'Comment on bg-2021-109', Anonymous Referee #2, 16 Jun 2021 reply

Sergey N. Vorobyev et al.

Sergey N. Vorobyev et al.

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Short summary
In order to quantify riverine carbon (C) exchange with the atmosphere in permafrost regions, we report a first assessment of CO2 and CH4 concentration and fluxes of the largest permafrost-affected river, the Lena River, during the peak of spring flow. The results allowed identifying environmental factors controlling GHG concentrations and emission in the Lena River watershed; this new knowledge can be used for foreseeing future changes in C balance in permafrost-affected Arctic rivers.
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