TY  - JOUR
A1  - Knoblauch, Christian
A1  - Beer, Christian
A1  - Liebner, Susanne
A1  - Grigoriev, Mikhail N.
A1  - Pfeiffer, Eva-Maria
T1  - Methane production as key to the greenhouse gas budget of thawing permafrost
JF  - Nature climate change
N2  - Permafrost thaw liberates frozen organic carbon, which is decomposed into carbon dioxide (CO2) and methane (CH4). The release of these greenhouse gases (GHGs) forms a positive feedback to atmospheric CO2 and CH4 concentrations and accelerates climate change(1,2). Current studies report a minor importance of CH4 production in water-saturated (anoxic) permafrost soils(3-6) and a stronger permafrost carbon-climate feedback from drained (oxic) soils(1,7). Here we show through seven-year laboratory incubations that equal amounts of CO2 and CH4 are formed in thawing permafrost under anoxic conditions after stable CH4-producing microbial communities have established. Less permafrost carbon was mineralized under anoxic conditions but more CO2-carbon equivalents (CO2Ce) were formed than under oxic conditions when the higher global warming potential (GWP) of CH4 is taken into account(8). A model of organic carbon decomposition, calibrated with the observed decomposition data, predicts a higher loss of permafrost carbon under oxic conditions (113 +/- 58 g CO2-C kgC(-1) (kgC, kilograms of carbon)) by 2100, but a twice as high production of CO2-Ce (241 +/- 138 g CO2-Ce kgC(-1)) under anoxic conditions. These findings challenge the view of a stronger permafrost carbon-climate feedback from drained soils1,7 and emphasize the importance of CH4 production in thawing permafrost on climate-relevant timescales.
Y1  - 2018
U6  - https://doi.org/10.1038/s41558-018-0095-z
SN  - 1758-678X
SN  - 1758-6798
VL  - 8
IS  - 4
SP  - 309
EP  - 312
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Radosavljevic, Boris
A1  - Lantuit, Hugues
A1  - Knoblauch, Christian
A1  - Couture, Nicole
A1  - Herzschuh, Ulrike
A1  - Fritz, Michael
T1  - Arctic nearshore sediment dynamics - an example from Herschel Island - Qikiqtaruk, Canada
JF  - Journal of marine science and engineering
N2  - Increasing arctic coastal erosion rates imply a greater release of sediments and organic matter into the coastal zone. With 213 sediment samples taken around Herschel Island-Qikiqtaruk, Canadian Beaufort Sea, we aimed to gain new insights on sediment dynamics and geochemical properties of a shallow arctic nearshore zone. Spatial characteristics of nearshore sediment texture (moderately to poorly sorted silt) are dictated by hydrodynamic processes, but ice-related processes also play a role. We determined organic matter (OM) distribution and inferred the origin and quality of organic carbon by C/N ratios and stable carbon isotopes delta C-13. The carbon content was higher offshore and in sheltered areas (mean: 1.0 wt.%., S.D.: 0.9) and the C/N ratios also showed a similar spatial pattern (mean: 11.1, S.D.: 3.1), while the delta C-13 (mean: -26.4 parts per thousand VPDB, S.D.: 0.4) distribution was more complex. We compared the geochemical parameters of our study with terrestrial and marine samples from other studies using a bootstrap approach. Sediments of the current study contained 6.5 times and 1.8 times less total organic carbon than undisturbed and disturbed terrestrial sediments, respectively. Therefore, degradation of OM and separation of carbon pools take place on land and continue in the nearshore zone, where OM is leached, mineralized, or transported beyond the study area.
KW  - permafrost
KW  - Arctic Ocean
KW  - stable carbon isotopes
KW  - nitrogen
KW  - sediment
KW  - chemistry
KW  - sediment dynamics
KW  - Beaufort Sea
KW  - grain size
Y1  - 2022
U6  - https://doi.org/10.3390/jmse10111589
SN  - 2077-1312
VL  - 10
IS  - 11
PB  - MDPI
CY  - Basel
ER  -