Background
The authors write that "temperatures at northern high latitudes have risen more quickly than the global average, increasing the potential of permafrost thaw and release of stored organic carbon (C)," citing Schuur et al. (2009), Tarnocai et al. (2009) and Grosse et al. (2011)." However, they also note that "an understudied and important component of the permafrost organic C pool is the accumulation of peat in drained thermokarst lake basins" - which consist of irregular surfaces of marshy hollows and small hummocks - as has been noted to occur by Nowacki et al. (2002) and Grosse et al. (2013). And the question thus arises: Which phenomenon prevails over the other?

What was done
In broaching this question, Klein et al. say they "analyzed a permafrost sediment core from a thermokarst basin on the Yukon-Kuskokwim Delta in southwestern Alaska to estimate: 1) when a thermokarst lake drained and a peatland initiated; 2) changes in lake and peatland CAR [carbon accumulation rate]; and 3) peatland water-table depth variability."

What was learned
The three U.S. researchers report that "the average apparent CAR increased tenfold following lake drainage, from ~12 to 120 gC/m²/year after peatland establishment," and that "after transition to a Sphagnum-dominated peatland ~1700, CAR reduced gradually before more than doubling from the mid-1970s to the early 1980s, potentially in response to a 1977 Pacific Decadal Oscillation shift that saw average annual temperatures increase nearly 1.5°C."

What it means
Klein et al. conclude the report of their work by stating that the results they obtained "suggest that drainage of thermokarst lakes in northern regions could produce basins that accumulate organic-rich peat," noting that "these vegetated basins might be a persistent C sink that increases with warming," to the extent that "the C accumulated in these vegetated drained basins under current warming might help offset some of the C released from thawing permafrost and thermokarst features in northern regions."

References
Grosse, G., Harden, J., Turetsky, M., McGuire, A.D., Camill, P., Tarnocai, C., Frolking, S., Schuur, E.A.D., Jorgenson, T., Marchenko, S., Romanovsky, V., Wickland, K.P., French, N., Waldrop, M., Bourgeau-Chavez, L. and Striegl, R.G. 2011. Vulnerability of high latitude soil carbon in North America to disturbance. Journal of Geophysical Research 116: 1-23.

Grosse, G., Jones, B. and Arp, C. 2013. Thermokarst lakes, drainage, and drained basins. In: Shroder, J.F., Giardino, R. and Harbor, J. (Eds.), Treatise on Geomorphology. Glacial and Periglacial Geomorphology 8: 325-353.

Nowacki, G.J., Spencer, P., Fleming, M. and Jorgenson, T. 2002. Unified Ecoregions of Alaska. U.S. Geological Survey Open File Report 02-297.

Schuur, E.A.G., Vogel, J.G., Crummer, K.G., Lee, H., Sickman, J.O and Osterkamp, T.E. 2009. The effect of permafrost thaw on old carbon release and net carbon exchange from tundra. Nature 459: 556-559.

Tamocai, C., Canadell, J.G., Schuur, E.A.G., Kuhry, P., Mazhitova, G. and Zimov, S. 2009. Soil organic carbon pools in the northern circumpolar permafrost region. Global Biogeochemical Cycles 23: 1-11.