Letter | Published:

Extensive loss of past permafrost carbon but a net accumulation into present-day soils

Naturevolume 560pages219222 (2018) | Download Citation

Abstract

Atmospheric concentrations of carbon dioxide increased between the Last Glacial Maximum (LGM, around 21,000 years ago) and the preindustrial era1. It is thought that the evolution of this atmospheric carbon dioxide (and that of atmospheric methane) during the glacial-to-interglacial transition was influenced by organic carbon that was stored in permafrost during the LGM and then underwent decomposition and release following thaw2,3. It has also been suggested that the rather erratic atmospheric δ13C and ∆14C signals seen during deglaciation1,4 could partly be explained by the presence of a large terrestrial inert LGM carbon stock, despite the biosphere being less productive (and therefore storing less carbon)5,6. Here we present an empirically derived estimate of the carbon stored in permafrost during the LGM by reconstructing the extent and carbon content of LGM biomes, peatland regions and deep sedimentary deposits. We find that the total estimated soil carbon stock for the LGM northern permafrost region is smaller than the estimated present-day storage (in both permafrost and non-permafrost soils) for the same region. A substantial decrease in the permafrost area from the LGM to the present day has been accompanied by a roughly 400-petagram increase in the total soil carbon stock. This increase in soil carbon suggests that permafrost carbon has made no net contribution to the atmospheric carbon pool since the LGM. However, our results also indicate potential postglacial reductions in the portion of the carbon stock that is trapped in permafrost, of around 1,000 petagrams, supporting earlier studies7. We further find that carbon has shifted from being primarily stored in permafrost mineral soils and loess deposits during the LGM, to being roughly equally divided between peatlands, mineral soils and permafrost loess deposits today.

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References

  1. 1.

    Schmitt, J. et al. Carbon isotope constraints on the deglacial CO2 rise from ice cores. Science 336, 711–714 (2012).

  2. 2.

    Crichton, K. A., Bouttes, N., Roche, D. M., Chappellaz, J. & Krinner, G. Permafrost carbon as a missing link to explain CO2 changes during the last deglaciation. Nat. Geosci. 9, 683–686 (2016); corrigendum 9, 795 (2016).

  3. 3.

    Walter, K. M., Edwards, M. E., Grosse, G., Zimov, S. A. & Chapin, F. S. III. Thermokarst lakes as a source of atmospheric CH4 during the last deglaciation. Science 318, 633–636 (2007).

  4. 4.

    Broecker, W. & Barker, S. A. 190‰ drop in atmosphere’s ∆14C during the ‘Mystery Interval’ (17.5 to 14.5 kyr). Earth Planet. Sci. Lett. 256, 90–99 (2007).

  5. 5.

    Ciais, P. et al. Large inert carbon pool in the terrestrial biosphere during the Last Glacial Maximum. Nat. Geosci. 5, 74–79 (2011).

  6. 6.

    Zimov, N. S. et al. Carbon storage in permafrost and soils of the mammoth tundra-steppe biome: role in the global carbon budget. Geophys. Res. Lett. 36, L02502 (2009).

  7. 7.

    Anthony, K. M. W. et al. A shift of thermokarst lakes from carbon sources to sinks during the Holocene epoch. Nature 511, 452–456 (2014).

  8. 8.

    Adams, J. M., Faure, H., Faure-Denard, L., McGlade, J. M. & Woodward, F. I. Increases in terrestrial carbon storage from the Last Glacial Maximum to the present. Nature 348, 711–714 (1990).

  9. 9.

    Prentice, I. C., Harrison, S. P. & Bartlein, P. J. Global vegetation and terrestrial carbon cycle changes after the last ice age. New Phytol. 189, 988–998 (2011).

  10. 10.

    Hugelius, G. et al. Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps. Biogeosciences 11, 6573–6593 (2014).

  11. 11.

    Lindgren, A., Hugelius, G., Kuhry, P., Christensen, T. R. & Vandenberghe, J. GIS-based maps and area estimates of Northern Hemisphere permafrost extent during the Last Glacial Maximum. Permafr. Periglac. Process. 27, 6–16 (2016).

  12. 12.

    Zhu, D. et al. Simulating soil organic carbon in yedoma deposits during the Last Glacial Maximum in a land surface model. Geophys. Res. Lett. 43, 5133–5142 (2016).

  13. 13.

    Brovkin, V. et al. Comparative carbon cycle dynamics of the present and last interglacial. Quat. Sci. Rev. 137, 15–32 (2016).

  14. 14.

    Kleinen, T., Brovkin, V. & Munhoven, G. Modelled interglacial carbon cycle dynamics during the Holocene, the Eemian and Marine Isotope Stage (MIS) 11. Clim. Past 12, 2145–2160 (2016).

  15. 15.

    Grichuk, V. P. in Late Quaternary Environments of the Soviet Union (ed. Velichko, A. A.) 155–178 (Longman, London, 1984).

  16. 16.

    Dyke, A. S. Late Quaternary vegetation history of northern North America based on pollen, macrofossil, and faunal remains. Geogr. Phys. Quat. 59, 211–262 (2005).

  17. 17.

    Baryshnikov, G. A. & Markova, A. K. in Paleoclimates and Paleoenvironments of Extra-tropical Regions of the Northern Hemisphere. Late Pleistocene–Holocene. Atlas-monograph (ed. Velichko, A. A.) 79–87 (GEOS, Moscow, 2009).

  18. 18.

    Gruber, S. Derivation and analysis of a high-resolution estimate of global permafrost zonation. Cryosphere 6, 221–233 (2012).

  19. 19.

    Olson, D. M. et al. Terrestrial ecoregions of the world: a new map of life on Earth. Bioscience 51, 933–938 (2001).

  20. 20.

    Hugelius, G. et al. The northern circumpolar soil carbon database: spatially distributed datasets of soil coverage and soil carbon storage in the northern permafrost regions. Earth Syst. Sci. Data 5, 3–13 (2013).

  21. 21.

    Ding, J. et al. The permafrost carbon inventory on the Tibetan Plateau: a new evaluation using deep sediment cores. Glob. Change Biol. 22, 2688–2701 (2016).

  22. 22.

    Macdonald, G. M. et al. Rapid early development of circumarctic peatlands and atmospheric CH4 and CO2 variations. Science 314, 285–288 (2006).

  23. 23.

    Schuur, E. A. G. et al. Climate change and the permafrost carbon feedback. Nature 520, 171–179 (2015).

  24. 24.

    Kleman, J. & Hattestrand, C. Frozen-bed Fennoscandian and Laurentide ice sheets during the Last Glacial Maximum. Nature 402, 63–66 (1999).

  25. 25.

    Harden, J. W., Sundquist, E. T., Stallard, R. F. & Mark, R. K. Dynamics of soil carbon during deglaciation of the Laurentide Ice Sheet. Science 258, 1921–1924 (1992).

  26. 26.

    Loisel, J. et al. Insights and issues with estimating northern peatland carbon stocks and fluxes since the Last Glacial Maximum. Earth Sci. Rev. 165, 59–80 (2017).

  27. 27.

    Yu, Z. C. Northern peatland carbon stocks and dynamics: a review. Biogeosciences 9, 4071–4085 (2012).

  28. 28.

    Willerslev, E. et al. Fifty thousand years of Arctic vegetation and megafaunal diet. Nature 506, 47–51 (2014).

  29. 29.

    Norby, R. J. & Zak, D. R. Ecological lessons from free-air CO2 enrichment (FACE) experiments. Annu. Rev. Ecol. Evol. Syst. 42, 181–203 (2011).

  30. 30.

    Yurtsev, B. A. The Pleistocene ‘tundra-steppe’ and the productivity paradox: the landscape approach. Quat. Sci. Rev. 20, 165–174 (2001).

  31. 31.

    Lorenzen, E. D. et al. Species-specific responses of Late Quaternary megafauna to climate and humans. Nature 479, 359–364 (2011).

  32. 32.

    Nogués-Bravo, D., Rodríguez, J., Hortal, J., Batra, P. & Araújo, M. B. Climate change, humans, and the extinction of the woolly mammoth. PLoS Biol. 6, e79 (2008).

  33. 33.

    Tarasov, P. E. et al. Last glacial maximum biomes reconstructed from pollen and plant macrofossil data from northern Eurasia. J. Biogeogr. 27, 609–620 (2000).

  34. 34.

    Andreev, A. A. et al. Paleoenvironmental changes in Northeastern Siberia during the Late Quaternary—evidence from pollen records of the Bykovsky Peninsula. Polarforschung 70, 13–25 (2000).

  35. 35.

    Andreev, A. A. et al. Vegetation and climate history in the Laptev Sea region (Arctic Siberia) during Late Quaternary inferred from pollen records. Quat. Sci. Rev. 30, 2182–2199 (2011).

  36. 36.

    Ni, J., Cao, X., Jeltsch, F. & Herzschuh, U. Biome distribution over the last 22,000yr in China. Palaeogeogr. Palaeoclimatol. Palaeoecol. 409, 33–47 (2014).

  37. 37.

    Fuchs, M., Kuhry, P. & Hugelius, G. Low below-ground organic carbon storage in a subarctic Alpine permafrost environment. Cryosphere 9, 427–438 (2015).

  38. 38.

    GMTED2010. The Global Multi-resolution Terrain Elevation Data 2010. US Geological Survey (USGS) Earth Resources Observation & Science (EROS) Center https://topotools.cr.usgs.gov (2011).

  39. 39.

    Dalrymple, J. B., Blong, R. J. & Conacher, A. J. A hypothetical nine unit landsurface model. Z. Geomorphol. 12, 60–76 (1968).

  40. 40.

    Halsey, L. A., Vitt, D. H. & Gignac, L. D. Sphagnum-dominated peatlands in North America since the Last Glacial Maximum: their occurrence and extent. Bryologist 103, 334–352 (2000).

  41. 41.

    Gajewski, K., Viau, A., Sawada, M., Atkinson, D. & Wilson, S. Sphagnum peatland distribution in North America and Eurasia during the past 21,000 years. Glob. Biogeochem. Cycles 15, 297–310 (2001).

  42. 42.

    Baker, R. G., Sullivan, A. E., Hallber, G. R. & Horton, D. G. Vegetational changes in Western Illinois during the onset of Late Wisconsinan glaciation. Ecology 70, 1363–1376 (1989).

  43. 43.

    Magyari, E., Jakab, G., Rudner, E. & Sümegi, P. Palynological and plant macrofossil data on Late Pleistocene short-term climatic oscillations in North-Eastern Hungary. Acta Palaeobot. 2 (Suppl.), 491–502 (1999).

  44. 44.

    Heusser, C. J. Palynology and phytogeographical significance of a late-Pleistocene refugium near Kalaloch, Washington. Quat. Res. 2, 189–201 (1972).

  45. 45.

    Baker, R. G. et al. A full-glacial biota from southeastern Iowa, USA. J. Quat. Sci. 1, 91–107 (1986).

  46. 46.

    Baker, R. G., Bettis, E. A. I. & Horton, D. G. Late Wisconsinan-early Holocene riparian paleoenvironment in southeastern Iowa. Geol. Soc. Am. Bull. 105, 206–212 (1993).

  47. 47.

    Elias, S. A., Short, S. K., Nelson, C. H. & Birks, H. H. Life and times of the Bering land bridge. Nature 382, 60–63 (1996).

  48. 48.

    Lowery, D., Wah, J. & Rick, T. Post-Last Glacial Maximum dune sequence for the ‘Parsonburg’ Formation at Elliot’s Island, Maryland. Curr. Res. Pleistocene 28, 103–104 (2011).

  49. 49.

    Zhao, Y. et al. Peatland initiation and carbon accumulation in China over the last 50,000 years. Earth Sci. Rev. 128, 139–146 (2014).

  50. 50.

    Andreev, A. A. et al. Late Pleistocene and Holocene vegetation and climate on the Taymyr Lowland, northern Siberia. Quat. Res. 57, 138–150 (2002).

  51. 51.

    Paus, A., Svendsen, J. I. & Matiouchkov, A. Late Weichselian (Valdaian) and Holocene vegetation and environmental history of the northern Timan Ridge, European Arctic Russia. Quat. Sci. Rev. 22, 2285–2302 (2003).

  52. 52.

    de Beaulieu, J.-L. & Reille, M. A long Upper Pleistocene pollen record from Les Echets, near Lyon, France. Boreas 13, 111–132 (1984).

  53. 53.

    Magyari, E. K. et al. Vegetation and environmental responses to climate forcing during the Last Glacial Maximum and deglaciation in the East Carpathians: attenuated response to maximum cooling and increased biomass burning. Quat. Sci. Rev. 106, 278–298 (2014).

  54. 54.

    Bos, J. A. A., Bohncke, S. J. P., Kasse, C. & Vandenberghe, J. Vegetation and climate during the Weichselian early glacial and pleniglacial in the Niederlausitz, eastern Germany—macrofossil and pollen evidence. J. Quat. Sci. 16, 269–289 (2001).

  55. 55.

    Müller, S. et al. Late Quaternary vegetation and environments in the Verkhoyansk Mountains region (NE Asia) reconstructed from a 50-kyr fossil pollen record from Lake Billyakh. Quat. Sci. Rev. 29, 2071–2086 (2010).

  56. 56.

    Demske, D. et al. Late glacial and Holocene vegetation and regional climate variability evidenced in high-resolution pollen records from Lake Baikal. Global Planet. Change 46, 255–279 (2005).

  57. 57.

    Igarashi, Y. & Zharov, A. E. Climate and vegetation change during the late Pleistocene and early Holocene in Sakhalin and Hokkaido, northeast Asia. Quat. Int. 237, 24–31 (2011).

  58. 58.

    Svendsen, J. I. et al. Glacial and vegetation history of the Polar Ural Mountains in northern Russia during the Last Ice Age, Marine Isotope Stages 5-2. Quat. Sci. Rev. 92, 409–428 (2014).

  59. 59.

    Zech, M. et al. Quaternary vegetation changes derived from a loess-like permafrost palaeosol sequence in northeast Siberia using alkane biomarker and pollen analyses. Boreas 39, 540–550 (2010).

  60. 60.

    Wetterich, S. et al. Last Glacial Maximum records in permafrost of the East Siberian Arctic. Quat. Sci. Rev. 30, 3139–3151 (2011).

  61. 61.

    Wetterich, S. et al. Palaeoenvironmental dynamics inferred from late Quaternary permafrost deposits on Kurungnakh Island, Lena Delta, Northeast Siberia, Russia. Quat. Sci. Rev. 27, 1523–1540 (2008).

  62. 62.

    Shichi, K. et al. Vegetation response in the southern Lake Baikal region to abrupt climate events over the past 33 cal kyr. Palaeogeogr. Palaeoclimatol. Palaeoecol. 375, 70–82 (2013).

  63. 63.

    Bolikhovskaya, N. S. & Shunkov, M. V. Pleistocene environments of Northwestern Altai: vegetation and climate. Archaeol. Ethnol. Anthropol. Eurasia 42, 2–17 (2014).

  64. 64.

    Neotoma Paleoecology Database. Neotoma, https://www.neotomadb.org/ (2016).

  65. 65.

    Grieser, J., Gommes, R., Cofield, S. & Barandi, M. Data sources for FAO worldmaps of Koeppen climatologies and climatic net primary production. Food and Agriculture Organization of the United Nations http://www.fao.org/nr/climpag/globgrids/KC_commondata_en.asp (2006).

  66. 66.

    Gorczynski, W. Sur le calcul du degré de continentalisme et son application dans la climatologie. Geogr. Ann. 2, 324–331 (1920).

  67. 67.

    Scheff, J., Seager, R., Liu, H. & Coats, S. Are glacials dry? Consequences for paleoclimatology and for greenhouse warming. J. Clim. 30, 6593–6609 (2017).

  68. 68.

    Bartlein, P. J. et al. Pollen-based continental climate reconstructions at 6 and 21 ka: a global synthesis. Clim. Dyn. 37, 775–802 (2011).

  69. 69.

    Brown, J., Ferrains, O., Heginbottom, J. & Melnikov, E. Circum-Arctic map of permafrost and ground-ice conditions, version 2. National Snow and Ice Data Center https://nsidc.org/data/ggd318 (2002).

  70. 70.

    Hugelius, G. et al. A new data set for estimating organic carbon storage to 3 m depth in soils of the northern circumpolar permafrost region. Earth Syst. Sci. Data 5, 393–402 (2013).

  71. 71.

    Batjes, N. H. Harmonized soil property values for broad-scale modelling (WISE30sec) with estimates of global soil carbon stocks. Geoderma 269, 61–68 (2016).

  72. 72.

    Jobbágy, E. G. & Jackson, R. B. The vertical distribution of soil organic carbon and its relation to climate and vegetation. Ecol. Appl. 10, 423–436 (2000).

  73. 73.

    Gorham, E. Northern peatlands: role in the carbon cycle and probable responses to climatic warming. Ecol. Appl. 1, 182–195 (1991).

  74. 74.

    Lehner, B. & Döll, P. Development and validation of a global database of lakes, reservoirs and wetlands. J. Hydrol. 296, 1–22 (2004).

  75. 75.

    Amosov, M. Lake-levels, vegetation and climate in Central Asia during the Last Glacial Maximum. Russ. Geogr. Soc. Her. (in Russian) 910–911, 1–14 (2014).

  76. 76.

    Ebel, T., Melles, M. & Niessen, F. in Land-Ocean Systems in the Siberian Arctic: Dynamics and History (eds Kassens, H. et al.) 425–435 (Springer, Berlin, 1999).

  77. 77.

    Colman, S. M., Carter, S. J., Hatton, J. & Haskell, B. J. Cores collected in Lake Baikal, Siberia, by the U.S. Geological Survey, 1990 to 1992: Visual Descriptions, Photographs, X-radiographs, Bulk-Density Measurements, and Grain-Size Analyses (US Dept Interior Geol. Surv. Open-File Report 94-445, 1992).

  78. 78.

    Orem, W. H., Colman, S. M. & Lerch, H. E. Lignin phenols in sediments of Lake Baikal, Siberia: application to paleoenvironmental studies. Org. Geochem. 27, 153–172 (1997).

  79. 79.

    Teller, J. T. & Last, W. M. Late Quaternary History of Lake Manitoba, Canada. Quat. Int. 16, 97–116 (1981).

  80. 80.

    Lim, J., Woodward, J., Tulaczyk, S., Christoffersen, P. & Cummings, S. P. Analysis of the microbial community and geochemistry of a sediment core from Great Slave Lake, Canada. Antonie van Leeuwenhoek 99, 423–430 (2011).

  81. 81.

    Ruesch, A. & Gibbs, H. K. New IPCC Tier-1 Global Biomass Carbon Map for the Year 2000. Carbon Dioxide Information Analysis Center http://cdiac.ess-dive.lbl.gov (2008).

  82. 82.

    Ehlers, J., Gibbard, P. & Hughes, P. Quaternary Glaciations—Extent and Chronology: A Closer Look (Elsevier, London, 2011).

  83. 83.

    Clark, P. U. et al. The Last Glacial Maximum. Science 325, 710–714 (2009).

  84. 84.

    Amante, C. & Eakins, B. W. ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis (NOAA Technical Memorandum NESDIS-NGDC-24, Boulder, Colorado, 2009).

  85. 85.

    Siewert, M. B., Hugelius, G., Heim, B. & Faucherre, S. Landscape controls and vertical variability of soil organic carbon storage in permafrost-affected soils of the Lena River Delta. Catena 147, 725–741 (2016).

  86. 86.

    Lewis, G., Fosberg, M., McDole, R. & Chugg, J. Distribution and some properties of loess in south-central and south-eastern Idaho. Soil Sci. Soc. Am. Proc. 39, 1165–1168 (1975).

  87. 87.

    Romanovsky, N. N. Fundamentals of Cryogenics of Lithosphere (Moscow Univ. Press, Moscow, 1993).

  88. 88.

    Busacca, A. & McDonald, E. Regional sedimentation of late Quaternary loess on the Columbia Plateau: sediment source areas and loess distribution patterns, regional geology of Washington State. Washingt. Div. Geol. Earth Resour. Bull. 80, 181–190 (1994).

  89. 89.

    Bettis, E. A., Muhs, D. R., Roberts, H. M. & Wintle, A. G. Last Glacial loess in the conterminous USA. Quat. Sci. Rev. 22, 1907–1946 (2003).

  90. 90.

    Haase, D. et al. Loess in Europe-its spatial distribution based on a European Loess Map, scale 1:2,500,000. Quat. Sci. Rev. 26, 1301–1312 (2007).

  91. 91.

    Muhs, D. R. The geologic records of dust in the quaternary. Aeolian Res. 9, 3–48 (2013).

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Acknowledgements

This study was funded by a French–Swedish cooperation grant from the Swedish Research Council (349-2012-6293), and by the European Union (EU) Joint Programming Initiative (JPI) Climate Constraining Uncertainties in the Permafrost–Climate Feedback (COUP) consortium. G.H. acknowledges a Marie Curie Skłodowska and Swedish Research Council International Career Grant (INCA; no. 330-2014-6417). We also acknowledge J.-O. Persson at the Department of Mathematics, Stockholm University, who assisted with statistical consulting, and the Bolin Centre for Climate Research for hosting the data.

Reviewer information

Nature thanks V. Brovkin, N. Pastick and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author information

Affiliations

  1. Department of Physical Geography, Stockholm University, Stockholm, Sweden

    • Amelie Lindgren
    • , Gustaf Hugelius
    •  & Peter Kuhry
  2. Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden

    • Amelie Lindgren
    • , Gustaf Hugelius
    •  & Peter Kuhry

Authors

  1. Search for Amelie Lindgren in:

  2. Search for Gustaf Hugelius in:

  3. Search for Peter Kuhry in:

Contributions

A.L. was responsible for data collection, digitization of data, and analysis of data from past environments, excluding deep loess deposits. P.K. was responsible for the review and analysis of deep loess deposits. G.H. was responsible for estimates of modern carbon pools. All authors contributed substantially to formulating the research idea, interpreting the results and writing the paper.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Amelie Lindgren.

Extended data figures and tables

  1. Extended Data Fig. 1 LGM peat region.

    The reconstructed peat region is based on already-reconstructed areas40,41, Sphagnum spore evidence, and the occurrence of peat42,43 or peaty layers44,45,46,47,48,49. The colouring and size of these points show the percentage of the total pollen sum that was spores (not algae) and our interpretation of the reliability of the dating. Indicative ages are better constrained than speculative ages (see Supplementary Information). Evidence of dated peat or peaty deposits is shown in dark brown. Data for ice sheets and glaciers are modified from ref. 82, and the permafrost region11 is included for reference.

  2. Extended Data Fig. 2 Loess and Yedoma deposits during the LGM.

    The deposits were compiled from several data sources86,87,88,89,90,91, and separated into sections (shown with Roman numerals) as described in Methods and Supplementary Information. The loess extent outside of the LGM continuous permafrost region is included for reference89. A tentative area of Yedoma extent on the shelf is also included. We assume that this area had the same degree of dissection as the Yedoma on land (see Supplementary Information). Data for ice sheets and glaciers are modified from ref. 82, and the permafrost region11 is included for reference. PF, permafrost.

  3. Extended Data Fig. 3 LGM mega biomes and LGM mammal assemblages.

    Assemblages of mammoths, horses, bison, reindeer, wholly rhinoceroses and muskoxen17,31,32 dated to between 18 kyr bp and 26 kyr bp indicate an environment that was productive enough to support megafauna (see Supplementary Information). Note that none of the data points within the Fennoscandian Ice Sheet are younger than 19 kyr bp. Data for ice sheets and glaciers are modified from ref. 82.

  4. Extended Data Fig. 4 The LGM mega biomes, and point data from pollen and macrofossil findings.

    The map shows the major biomes within the LGM permafrost region, constructed from three separate empirical maps15,16,17, as well as our additional separation of alpine environments and steep areas18. Biomized pollen data and macrofossil findings9,33,34,35,36 were compared with the reconstruction to assess its accuracy (see Supplementary Information). Data for ice sheets and glaciers are modified from ref. 82.

  5. Extended Data Fig. 5 Regression between continentality and organic soil coverage.

    The organic soil (peat) coverage was calculated from data within the NCSCDv2 database for flat terrain only (see Supplementary Information). The data were aggregated into classes of continentality, determined from the map65 of the Gorczynski continentality index66 (see Methods). The trend indicates that peat coverage in flat terrain is lower in regions with high continentality (R2 = 0.4) than in regions of low continentality.

  6. Extended Data Fig. 6 A schematic presentation of data handling for soil of depth 0–1 m.

    To estimate LGM soil carbon, we used databases to calculate carbon-transfer functions for different biomes. The colouring describes the continuous and discontinuous sections that were separated before applying the biomes as a second filter. Modern-day biomes were overlain with modern-day carbon stocks in permafrost terrain, providing biome-specific information that was translated into transfer functions (see Methods).

  7. Extended Data Fig. 7 Warm-based and cold-based sections of ice sheets and glaciers24,69, both on land and on shelves.

    Cold-based areas are assumed to retain the carbon storage formed before the glaciation. Warm-based ice sheets and glaciers, on the other hand, are erosive, and we assume no preserved carbon storage. Data for ice sheets and glaciers are modified from ref. 82, and the permafrost region11 is included for reference.

  8. Extended Data Table 1 Biome categories included under each ‘mega’ biome for lowland and alpine areas
  9. Extended Data Table 2 Areas, carbon-transfer functions and carbon stocks (in Pg C) at the LGM
  10. Extended Data Table 3 Estimates of areas and carbon stocks (in Pg C) beneath ice sheets and glaciers

Supplementary information

  1. Supplementary Information

    This file contains further description of methods and discussions to clarify our results and includes a full text of our review of deep deposits. It also includes Supplementary Tables 1 and 2. Supplementary Table 1 shows the confusion matrix for the biome reconstruction with ground truth. This table complements the kappa index of accuracy between reconstructed biomes (polygons) and independent point data of biomized pollen counts [9, 33–36]. The point data (103 points) were harmonized into the three mega biomes following the same priority scheme of forest (–steppe) > tundra (–steppe) > steppe (–desert). Supplementary Table 2 shows the sectors, number of sites and publications used for the loess reconstruction. This table describes which publications have been used in the analysis of loess and Yedoma areas. It also specifies how many of the publications from each sector include information such as depth of the deposit, dry bulk density (DBD) and per cent organic carbon (%OC). The deposit depth interval is split up between a younger and older period.

  2. Supplementary Table 3

    This file contains Supplementary Table 3, which shows the area and geochemical properties of loess and Yedoma. Total area and geochemical properties by sector of the 71–19-kyr C stock in current Yedoma deposits, total area and inferred C stocks by sector for other 71–19-kyr loess deposits within the LGM continuous permafrost zone, and currently remaining C stocks in these deposits (following thaw). The area and depth by sector of other 71–19-kyr loess deposits in the LGM discontinuous permafrost zone are given for reference.

  3. Supplementary Table 4

    This file contains Supplementary Table 4, which shows a detailed overview of soil carbon stocks for the LGM and present. Soil C stocks are partitioned into detailed categories, described in column A. For each category, we report area, carbon stock, errors (see Methods for detailed description of different error calculations), and the size of the inert C stock and its errors. An additional sensitivity analysis of the inert C stock is given beneath the main part of the table. This is based on varying the assumptions of permafrost coverage within the discontinuous zone (10% to 90%), and the depth of the active layer (100 cm instead of 30 cm). These errors are included in the overall errors given for the LGM inert C storage. All errors given in row 39 are calculated as the sum of squared errors by column.

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