Articles | Volume 15, issue 3
Biogeosciences, 15, 953–971, 2018
Biogeosciences, 15, 953–971, 2018

Research article 16 Feb 2018

Research article | 16 Feb 2018

Carbon and nitrogen pools in thermokarst-affected permafrost landscapes in Arctic Siberia

Matthias Fuchs1,2, Guido Grosse1,2, Jens Strauss1, Frank Günther1, Mikhail Grigoriev3, Georgy M. Maximov3, and Gustaf Hugelius4 Matthias Fuchs et al.
  • 1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Department of Periglacial Research, 14473 Potsdam, Germany
  • 2University of Potsdam, Institute of Earth and Environmental Science, 14467 Potsdam, Germany
  • 3Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Science, 677010 Yakutsk, Russia
  • 4Department of Physical Geography, Stockholm University, 106 91 Stockholm, Sweden

Abstract. Ice-rich yedoma-dominated landscapes store considerable amounts of organic carbon (C) and nitrogen (N) and are vulnerable to degradation under climate warming. We investigate the C and N pools in two thermokarst-affected yedoma landscapes – on Sobo-Sise Island and on Bykovsky Peninsula in the north of eastern Siberia. Soil cores up to 3 m depth were collected along geomorphic gradients and analysed for organic C and N contents. A high vertical sampling density in the profiles allowed the calculation of C and N stocks for short soil column intervals and enhanced understanding of within-core parameter variability. Profile-level C and N stocks were scaled to the landscape level based on landform classifications from 5 m resolution, multispectral RapidEye satellite imagery. Mean landscape C and N storage in the first metre of soil for Sobo-Sise Island is estimated to be 20.2 kg C m−2 and 1.8 kg N m−2 and for Bykovsky Peninsula 25.9 kg C m−2 and 2.2 kg N m−2. Radiocarbon dating demonstrates the Holocene age of thermokarst basin deposits but also suggests the presence of thick Holocene-age cover layers which can reach up to 2 m on top of intact yedoma landforms. Reconstructed sedimentation rates of 0.10–0.57 mm yr−1 suggest sustained mineral soil accumulation across all investigated landforms. Both yedoma and thermokarst landforms are characterized by limited accumulation of organic soil layers (peat).

We further estimate that an active layer deepening of about 100 cm will increase organic C availability in a seasonally thawed state in the two study areas by  ∼  5.8 Tg (13.2 kg C m−2). Our study demonstrates the importance of increasing the number of C and N storage inventories in ice-rich yedoma and thermokarst environments in order to account for high variability of permafrost and thermokarst environments in pan-permafrost soil C and N pool estimates.

Short summary
Our paper investigates soil organic carbon and nitrogen in permafrost soils on Sobo-Sise Island and Bykovsky Peninsula in the north of eastern Siberia. We collected and analysed permafrost soil cores and upscaled carbon and nitrogen stocks to landscape level. We found large amounts of carbon and nitrogen stored in these frozen soils, reconstructed sedimentation rates and estimated the potential increase in organic carbon availability if permafrost continues to thaw and active layer deepens.
Final-revised paper