A snapshot of CO₂ and CH₄ evolution in a thermokarst pond near Igarka, northern Siberia

authored by

Christian Blodau, Rainer Rees, Heiner Flessa, Andrej Rodionov, Georg Guggenberger, Klaus Holger Knorr, Olga Shibistova, Galina Zrazhevskaya, Natalia Mikheeva, Oleg A. Kasansky

Abstract

Thermokarst wetlands and ponds in the subarctic, which are located in land surface depressions resulting from permafrost melt, are strong sources of CH₄, but little is known about respiration processes supporting these emissions. We determined CH₄ fluxes and concentration profiles of dissolved gases and anions and some δ¹³C ratios of CO ₂ and CH₄ in a thermokarst pond and adjacent smaller thermokarst depressions in the forest tundra near Igarka, northern Siberia in August 2006. Methane was emitted at 110-170 mg m^-2 d^-1 and produced mostly by CO₂ reduction, which also provided high Gibbs free energies on the order of 50-70 KJ mol^-1 H₂ due to high H₂concentrations. The diffusive flux calculated from CH ₄ gradients in the floating mat contributed <2% to emissions. CH₄ was apparently not oxidized deeper than 20 cm into the floating mat and the water body below. Anaerobic respiration required to reproduce nonsteady state CO₂ concentration maxima in the floating mat above the water body was 30-80 nmol cm^-3 d^-1 or 250 mg m ^-2 d^-1 and thus on a similar order of magnitude as CH ₄ fluxes. The results suggest that floating mat-covered thermokarst ponds located in northern Siberian bogs effectively convert recently fixed carbon into CH₄ and thus allow for emissions independently from the finite, bog-derived carbon source. The relative contribution of recently fixed and old bog-derived carbon to C fluxes requires further investigation, however.

External Organisation(s)

University of Bayreuth
University of Göttingen
Russian Academy of Sciences (RAS)
Martin Luther University Halle-Wittenberg

Type

Article

Journal

Journal of Geophysical Research: Biogeosciences

Volume

113

ISSN

0148-0227

Publication date

19.08.2008

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Geophysics, Forestry, Oceanography, Aquatic Science, Ecology, Water Science and Technology, Soil Science, Geochemistry and Petrology, Earth-Surface Processes, Atmospheric Science, Earth and Planetary Sciences (miscellaneous), Space and Planetary Science, Palaeontology

Sustainable Development Goals

SDG 15 - Life on Land

Electronic version(s)

https://doi.org/10.1029/2007JG000652 (Access: Closed)