Preprints
https://doi.org/10.5194/tc-2022-36
https://doi.org/10.5194/tc-2022-36
 
21 Feb 2022
21 Feb 2022
Status: a revised version of this preprint is currently under review for the journal TC.

Accelerated Mobilization of Organic Carbon from Retrogressive Thaw Slumps on the Northern Taymyr Peninsula

Philipp Bernhard1, Simon Zwieback2, and Irena Hajnsek1,3 Philipp Bernhard et al.
  • 1Institute of Environmental Engineering, ETH Zurich, 8093 Zurich, Switzerland ETH Zürich
  • 2Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775 USA
  • 3Microwaves and Radar Institute, German Aerospace Center (DLR) e.V., 82234 Wessling, Germany

Abstract. With climate change, Arctic hillslopes above ice-rich permafrost are vulnerable to enhanced mass wasting and organic carbon mobilization. In this study we use TanDEM-X-derived digital elevation models to document an approximately 43-fold increase in thaw slumping and concomitant 28-fold increase in carbon mobilization on the Taymyr Peninsula from 2010 to 2021. The available observations allowed us to compare two time-periods, from 2010/11 to 2016/17 and from 2017/18 to 2020/21, and contrast Retrogressive Thaw Slump (RTS) activity between these periods. We find that all quantities describing RTS activity increased in the observed period. The total volumetric change per year increased from about 0.17 · 106 m3 yr−1 to 7.4 · 106 m3 yr−1, a 43-fold increase. The observed surge in RTS activity is mainly driven by the initiation of new RTS, indicated by the 17-fold increase in active RTS numbers from 82 to 1404 and the relative low average volumetric change rate per RTS increase of 2.3. In annual Sentinel-2 imagery, the number of detected RTSs in a subregion increased 10-fold in 2020. This coincides with a severe heatwave that occurred in northern Siberia in 2020. The area-to-volume scaling of the RTSs varied only slightly over time, despite the 2020 heatwave, indicating a robustness of the relationship to such an event. To estimate the slump-mobilized organic carbon, we intersected the elevation changes with a soil organic carbon (SOC) map, with contrasting assumptions about the deep carbon pool and massive ice content. We estimated that the SOC mobilization rate increase 28-fold. The normalization of the SOC mobilization rate to our study region yields values of 11 gC yr−1 m−2 with a confidence interval of 5 to 38 gC yr−1 m−2. Comparison to an independent estimate of the Net Ecosystem Exchange of 4.1 ± 13.0 gC yr−1 m−2 illustrates the importance of RTS activity to the carbon cycle. These results underscore that mass wasting is an important but commonly neglected component of the Arctic carbon cycle, and particularly sensitive to extreme events.

Philipp Bernhard et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2022-36', Justine Ramage, 28 Mar 2022
    • AC1: 'Reply on RC1', Philipp Bernhard, 11 May 2022
  • RC2: 'Comment on tc-2022-36', Nina Nesterova, 06 Apr 2022
    • AC2: 'Reply on RC2', Philipp Bernhard, 11 May 2022

Philipp Bernhard et al.

Data sets

Dataset for "Accelerated Mobilization of Organic Carbon from Retrogressive Thaw Slumps on the Northern Taymyr Peninsula" Philipp Bernhard https://doi.org/10.3929/ethz-b-000529493

Philipp Bernhard et al.

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Short summary
With climate change, Arctic hillslopes above ice-rich permafrost are vulnerable to enhanced carbon mobilization. In this work elevation change estimates generated from satellite observations reveal a substantial acceleration of carbon mobilization on the Taymyr Peninsula in Siberia between 2010 to 2021. The strong increase occurred in 2020 which coincides with a severe Siberian heatwave and highlights that carbon mobilization can responded sharply and non-linearly to increasing temperatures.