TY - JOUR

T1 - A snapshot of CO2 and CH4 evolution in a thermokarst pond near Igarka, northern Siberia

AU - Blodau, Christian

AU - Rees, Rainer

AU - Flessa, Heiner

AU - Rodionov, Andrej

AU - Guggenberger, Georg

AU - Knorr, Klaus Holger

AU - Shibistova, Olga

AU - Zrazhevskaya, Galina

AU - Mikheeva, Natalia

AU - Kasansky, Oleg A.

PY - 2008/8/19

Y1 - 2008/8/19

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=69549124252&partnerID=8YFLogxK

U2 - 10.1029/2007JG000652

DO - 10.1029/2007JG000652

M3 - Article

AN - SCOPUS:69549124252

VL - 113

JO - Journal of Geophysical Research: Biogeosciences

JF - Journal of Geophysical Research: Biogeosciences

SN - 0148-0227

IS - 3

M1 - G03023

ER -