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Rapid Sediment Re-Deposition May Limit

Carbon Release during Catastrophic

Thermokarst Lake Drainage

Brian S. Burnham*, School of Geosciences, University of Aberdeen, Aberdeen, AB24 3UE, UK; Peter P. Flaig, Bureau of Economic
Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712, USA; Brice R. Rea, Matteo Spagnolo,
School of Geosciences, University of Aberdeen, Aberdeen, AB24 3UE, UK; Michael H. Young, Bureau of Economic Geology, Jackson
School of Geosciences, The University of Texas at Austin, Austin, Texas 78712, USA

A CARBON SOURCE A complex relationship of interlinked carbon store because the liberated SOC is
Arctic soil organic carbon (SOC), the processes (e.g., climate, precipitation, ero- vulnerable to degradation and GHG release
largest terrestrial organic carbon reservoir sion) drives permafrost degradation and (Vonk and Gustafsson, 2013), resulting in
(Tarnocai et al., 2009; Schuur et al., 2015), differential land subsidence that generates a net flux (positive) to the atmospheric
is typically locked up in permafrost thermokarst lakes (van Huissteden et al., carbon pool.
(Tarnocai et al., 2009; Olefeldt et al., 2016; 2011) (Fig. 1), which expand slowly through Catastrophic drainage events may increase
Turetsky et al., 2020), but is under threat. heat conduction, enhancing permafrost in frequency (Jones et al., 2020), but the fate
The mean annual air temperature in the thaw and mass wasting at lake margins. of released carbon is poorly constrained. A
Arctic is rising twice as fast as the global Thermokarst lake expansion is projected to first-order approximation of carbon released
average (Schuur et al., 2015). Permafrost continue under future climate warming by erosion during catastrophic thermokarst
will further degrade, exposing significant (Smith et al., 2005; Walter, et al., 2006; van lake drainage events suggests that a signifi-
quantities of SOC to decomposition and Huissteden et al., 2011). Thermokarst lakes cant volume of the eroded material, and
respiration, releasing greenhouse gases may also drain catastrophically (Mackay, potentially SOC, is rapidly re-deposited
(GHG), like CO and CH , into the atmo- 1988), creating thermo-erosion gullies (hours to days) (Jones and Arp, 2015) in
4
2
sphere (Walter et al., 2006; Mackelprang et (Figs. 1B and 1C) that result in substantial proximal downstream deltas/subaerial fans
al., 2011; Cory et al., 2014; Turetsky et al., (discharge rates up to 25 m s ; Jones and (Fig. 1B), limiting the net carbon release.
3 –1
2020), driving a feedback loop of increasing Arp, 2015) sediment and SOC erosion from Data on SOC volumes partitioned into par-
air temperatures and degrading permafrost lake margins and along drainage channels. ticulate organic carbon (POC) available for
(Schuur et al., 2015). This is assumed to decrease the permafrost re-deposition, or dissolved organic carbon

A -164.76 C Before drainage D T1
AK N Narrow
drainage L1 f
500 km N channel L1 sediments L2 sediments
B Filled lake Lacustrine w d 1 L2 f
Before drainage (L1) f delta absent Permafrost 1 not to scale
T1 A A’
A Catastrophic drainage
Increasing Mid-drainage
C channel
A’ Drained lake (L1 ) d width & depth Sediment + SOC remobilization
Lacustrine Delta/fan formation
66.45 delta forming SOC burial
Filled lake (L2 ) f T2
Maximum After drainage T3 SOC
channel
width & depth L1 d
d 2 L2 f
Lacustrine
delta formed w 2
After drainage 300 m 150 m T3 A Drainage channel (connected to L1) A’
Figure 1. Catastrophic lake drainage and lacustrine delta formation. (A) Approximate location of the five thermokarst lakes analyzed herein. (B) Planet
CubeSat imagery of two thermokarst lakes (Lake ID 99492) showing images before (L1 ) and after (L1 ) drainage, where lake L1 rapidly drained into lake L2
f
d
(L2 ). (C) Satellite imagery showing L1 drainage through a preexisting channel (T1: 27 Sept. 2017) that evolved into a thermo-erosion gulley (T2: 7 June 2018).
f
This event eroded, transported, and deposited large volumes of sediment and remobilized soil organic carbon (SOC) into the delta in L2 (T3: 11 July 2020).
(D) Schematic model of L1 drainage, creation of a thermo-erosion gulley, and deposition of a delta in L2. AK—Alaska.
GSA Today, v. 32, https://doi.org/10.1130/GSATG529GW.1. CC-BY-NC.
*Email: brian.burnham@abdn.ac.uk

60 GSA TODAY | May 2022