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Soil Organic Carbon Pools in the Northern Circumpolar Permafrost Region


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1] The Northern Circumpolar Soil Carbon Database was developed in order to determine carbon pools in soils of the northern circumpolar permafrost region. The area of all soils in the northern permafrost region is approximately 18,782 Â 10 3 km 2 , or approximately 16% of the global soil area. In the northern permafrost region, organic soils (peatlands) and cryoturbated permafrost-affected mineral soils have the highest mean soil organic carbon contents (32.2–69.6 kg m À2). Here we report a new estimate of the carbon pools in soils of the northern permafrost region, including deeper layers and pools not accounted for in previous analyses. Carbon pools were estimated to be 191.29 Pg for the 0–30 cm depth, 495.80 Pg for the 0–100 cm depth, and 1024.00 Pg for the 0–300 cm depth. Our estimate for the first meter of soil alone is about double that reported for this region in previous analyses. Carbon pools in layers deeper than 300 cm were estimated to be 407 Pg in yedoma deposits and 241 Pg in deltaic deposits. In total, the northern permafrost region contains approximately 1672 Pg of organic carbon, of which approximately 1466 Pg, or 88%, occurs in perennially frozen soils and deposits. This 1672 Pg of organic carbon would account for approximately 50% of the estimated global belowground organic carbon pool.
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Soil organic carbon pools in the northern circumpolar permafrost
C. Tarnocai,
J. G. Canadell,
E. A. G. Schuur,
P. Kuhry,
G. Mazhitova,
and S. Zimov
Received 13 August 2008; revised 1 April 2009; accepted 3 April 2009; published 27 June 2009.
[1]The Northern Circumpolar Soil Carbon Database was developed in order to
determine carbon pools in soils of the northern circumpolar permafrost region. The area
of all soils in the northern permafrost region is approximately 18,782 10
approximately 16% of the global soil area. In the northern permafrost region, organic
soils (peatlands) and cryoturbated permafrost-affected mineral soils have the highest
mean soil organic carbon contents (32.269.6 kg m
). Here we report a new estimate of
the carbon pools in soils of the northern permafrost region, including deeper layers
and pools not accounted for in previous analyses. Carbon pools were estimated to be
191.29 Pg for the 030 cm depth, 495.80 Pg for the 0 100 cm depth, and 1024.00 Pg for
the 0300 cm depth. Our estimate for the first meter of soil alone is about double
that reported for this region in previous analyses. Carbon pools in layers deeper than
300 cm were estimated to be 407 Pg in yedoma deposits and 241 Pg in deltaic deposits. In
total, the northern permafrost region contains approximately 1672 Pg of organic
carbon, of which approximately 1466 Pg, or 88%, occurs in perennially frozen soils and
deposits. This 1672 Pg of organic carbon would account for approximately 50% of the
estimated global belowground organic carbon pool.
Citation: Tarnocai, C., J. G. Canadell, E. A. G. Schuur, P. Kuhry, G. Mazhitova, and S. Zimov (2009), Soil organic carbon pools in
the northern circumpolar permafrost region, Global Biogeochem. Cycles,23, GB2023, doi:10.1029/2008GB003327.
1. Introduction
[2] The biosphere holds large carbon pools which, if
destabilized through changes in climate and land use, can
lead to accelerated emissions of greenhouse gases to the
atmosphere [Gruber et al., 2004]. Global climate-carbon
models that account for only a few of these large pools
show that carbon-climate feedbacks can lead to an average
of 50 to 100 ppm additional CO
in the atmosphere by the
end of this century [Friedlingstein et al., 2006]. Therefore,
it is important that future climate models include all major
carbon pools and the processes that control their long-term
carbon balance [Canadell et al., 2007].
[3] Carbon stored in permafrost regions is one of the least
understood and potentially most significant carbon-climate
feedbacks because of the size of the carbon pools and the
intensity of climate forcing at high latitudes [Schuur et al.,
2008]. The areal extent of permafrost soils and the carbon
pools they contain have been underestimated since, in the
past, the specific soil processes that lead to long-term
carbon sequestration were not taken into account [Post et
al., 1982; Jobba´gy and Jackson, 2000].
[4] There are a number of estimates of global soil organic
carbon pools. Estimates for the 0 100 cm depth include
1220 Pg [Sombroek et al., 1993], 1395 Pg [Post et al.,
1982], 1462 to 1548 Pg [Batjes, 1996], 1502 Pg [Jobba´gy
and Jackson, 2000], and 1576 Pg [Eswaran et al., 1993].
Batjes [1996] also reports global organic carbon pools for
the 0200 cm depth (2376 2456 Pg) and Jobba´gy and
Jackson [2000] report global organic carbon pools for both
the 100 200 cm (491 Pg) and 200 300 cm (351 Pg)
[5] Few estimates exist of the size and spatial distribution
of carbon pools in permafrost regions. Post et al. [1982]
estimate that soils in the tundra zone contain, globally,
approximately 191.8 Pg of organic carbon. This estimate,
however, is based on only 30 samples to a depth of 100 cm.
Tarnocai et al. [2003], using the Northern and Mid
Latitudes Soil Database (NMLSD), estimated that the
organic carbon pool in the 0100 cm depth of Cryosols
(permafrost-affected soils) in the northern circumpolar
GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 23, GB2023, doi:10.1029/2008GB003327, 2009
Research Branch, Agriculture and Agri-Food Canada, Ottawa, Ontario,
Global Carbon Project, Marine and Atmospheric Research, CSIRO,
Canberra, ACT, Australia.
Department of Botany, University of Florida, Gainesville, Florida,
Department of Physical Geography and Quaternary Geology,
Stockholm University, Stockholm, Sweden.
Komi Science Center, Russian Academy of Sciences, Syktyvkar,
Deceased 22 February 2009.
Northeast Science Station, Russian Academy of Sciences, Cherskii,
Copyright 2009 by the American Geophysical Union.
GB2023 1of11
region was approximately 268 Pg. Since then, however, the
availability of new data sets in the Northern Circumpolar
Soil Carbon Database (NCSCD) has shown that the
NMLSD greatly underestimated the area of permafrost-
affected soils in Eurasia.
[6] This paper reports new estimates of the organic
carbon pools in both permafrost-affected and nonpermafrost
soils in the northern circumpolar permafrost region. The
new estimates, unlike those from previous analyses, include
deeper layers, down to 300 cm, and additional carbon pools
to depths greater than 300 cm for deltaic and yedoma
2. Materials and Methods
2.1. Northern Circumpolar Permafrost Region
[7] The study area encompasses the northern circumpolar
permafrost region. This region is divided into four zones on
the basis of the percentage of the land area underlain by
permafrost (Figure 1): the Continuous Permafrost Zone
(90 to 100%), the Discontinuous Permafrost Zone
(50 to <90%), the Sporadic Permafrost Zone (10 to
<50%), and the Isolated Patches Permafrost Zone (0 to
<10%) [Brown et al., 1997].
2.2. Northern Circumpolar Soil Carbon Database
[8] The new estimates of organic carbon pools in soils of
the permafrost region were calculated using the NCSCD
(C. Tarnocai et al., 2007, Research Branch, Agriculture
and Agri-Food Canada, Ottawa; available at http://
zip, hereinafter referred to as Tarnocai et al., unpublished
data, 2007). This database contains over ten thousand
polygons, with each polygon (mapping unit) containing
one or more named soils or soil taxa that form the basis
for determining the carbon pools. Data for North America
and Europe are available in digital form in local soil data-
bases that have been compiled from existing soil survey
maps (Table 1). For remote areas in North America, where
detailed soil maps are unavailable, pedon, climate, and
vegetation data, together with high-quality LANDSAT
imagery, were used to delineate polygons. For Russia,
Greenland, Iceland, Kazakhstan, Mongolia, and Svalbard
spatial soil information was digitized as it was only
available as hard copy maps (Table 1).
[9] Data used to calculate carbon content (kg m
) were
derived from multiple pedon databases (the pedon, or soil
profile, is the basic soil unit used for describing, sampling,
and classifying soils). The North American portion of the
NCSCD was built up using 1038 pedons from northern
Canada and 131 pedons from Alaska. The Eurasian portion
of the NCSCD includes a newly assembled database
containing soil organic carbon content data for 253 Russian
pedons. Two existing databases also were used to obtain
Russian data, the West Siberian Lowland Peatland GIS Data
Collection, containing data for 90 peat cores [Sheng et al.,
2004; Smith et al., 2000, 2004], and the Usa Basin database,
containing information for 266 mineral and organic soils
[Kuhry et al., 2002; Mazhitova et al., 2003]. Information
from Batjes [1996] was also used for Eurasian soils
(including Russia), especially for those soils where no
pedon information was available.
2.2.1. Computation of Soil Carbon Content
[10] Representative pedons for each soil taxon (Eurasia)
or named soil (North America) were selected. Data for
the various layers that compose each named soil (North
America) and each soil taxon (Eurasia) were entered into the
database and were used to calculate the carbon content of
each named soil in the polygon.
[11] The Soil Organic Carbon Content (SOCC, kg m
was calculated for each named soil (North America) and for
the representative pedons for each soil taxon (Eurasia) using
the formula
where Cis the organic carbon (% weight), BD is the bulk
density (g cm
), Tis the soil layer thickness, and CF is the
coarse fragments and/or ice content (% weight). Using this
information, the SOCC was then calculated for the 0 30,
0100, 100 200 and 200 300 cm depths, or layers, for all
pedons and these data were stored in the database. The
percentages of the SOCC occurring in the 0 100, 100 200
and 200300 cm depths of each major soil were then
calculated on the basis of a total soil depth of 0 300 cm.
2.2.2. Computation of Soil Carbon Mass
[12] The Soil Organic Carbon Mass (SOCM, Pg) was then
determined by multiplying the SOCC of the specific soil
by the area of each such soil component in the polygon.
When summed, these data provide information on the
SOCM of each soil in each permafrost zone in the northern
circumpolar region.
[13] For the North American portion of the study area, the
SOCM for Histels and Histosols (peatlands) was calculated
for the 0100 cm depth and for the total depth of the peat
deposit since this depth was included in the database. Since
not all peat deposits in the Eurasian portion extend to
300 cm, the depth data obtained from the Usa and West
Siberian databases [Kuhry et al., 2002; Sheng et al., 2004]
were used to determine the percent distribution of peat in
three depth categories, 0100 cm (100%), 0 200 cm
(50%), and 0300 cm (10%). These percentages were then
used to adjust the SOCM calculated for the various depths
of the Eurasian peat soils (Histels and Histosols).
[14] Inceptisols were the only unfrozen mineral soils for
which deep carbon data were available. The SOCM for
these soils was calculated on the basis of data indicating that
the 100200 cm layer of the Inceptisols contained approx-
imately 80% of the SOCC contained in the 0 100 cm layer
and that the 200300 cm layer contained no organic carbon.
It was assumed that, like the Inceptisols, the other unfrozen
mineral soils would also contain no soil organic carbon in
the 200300 cm layer.
2.3. Additional Deep Carbon Pools
[15] In addition to the soil carbon in the 0 300 cm depth,
we are also reporting the two deep carbon pools (greater
than 300 cm) described below.
[16] Yedoma deposits. These perennially frozen, loess-
like (wind-blown) deposits, which have an average depth of
approximately 25 m, contain large amounts of organic
carbon and ice, mainly in the form of ice wedges [Zimov et
al., 2006b]. Using SOCC data from the NCSCD, we
calculated the SOCM for the 0 300 cm layer of these
deposits. This value was then deducted from the value
obtained for the 025 m depth in order to avoid double
counting the 0300 cm layer.
[17] River deltas. Information on the thickness of these
alluvial deposits and the concentration of organic carbon in
them is very scarce, except for the delta sediments of the
Mackenzie River in the Northwest Territories of Canada.
Thus, this delta was used in this assessment as a model to
estimate the carbon mass contained in the major northern
[18] The Mackenzie delta covers approximately
13,500 km
, half of which is covered by shallow lakes
and river channels. On the basis of five Mackenzie delta soil
profiles [Tarnocai et al., 1993; C. Tarnocai and H. Veldhuis,
unpublished data, 1980, 1984], this delta has an SOCC of
Figure 1. Northern circumpolar permafrost map (derived from information by Brown et al. [1997]).
Table 1. Data Sources for the NCSCD
Country or Region Scale Type of Data Source
USA 1:250,000 Digital Soil Survey Staff [1999]
Canada 1:1,000,000 Digital C. Tarnocai and B. Lacelle (1996)
Russia 1:2,500,000 Soil map Fridland [1988] and Naumov [1993]
Kazakhstan 1:2,500,000 Soil map Uspanov [1976]
Mongolia 1:3,000,000 Soil map Dorzhgotov and Nogina [1990]
Greenland 1:7,500,000 Soil map Jakobsen and Eiby [1997]
Scandinavia 1:1,000,000 Digital European Soil Bureau [1999]
Iceland 1:1,500,000 Soil map Arnalds and Gretarsson [2001]
The Soil Organic Carbon Digital Database of Canada, Research Branch, Agriculture and Agri-Food Canada, Ottawa, 1996;
available at
65 kg m
. The average thickness of delta deposits was
calculated to be 50 m (on the basis of drill core data). In
order to avoid double counting the upper 0 300 cm of the
terrestrial portion of the delta, calculation of the SOCC was
based on the 3 50 m depth. For deposits under water
bodies, which are assumed to have an average depth of
5 m, the SOCC was calculated for a thickness of 45 m. It
was also assumed that the rate of organic matter accumu-
lation in recent decades was similar to that occurring in the
past. In addition, it should be pointed out that the SOCC
included only the carbon in the fine organic matter
(<2 mm); coarse organic matter (logs, driftwood, etc.) was
not included in these calculations.
2.4. Analytical Methods
[19] The carbon concentration (C%) was determined by
using either the Walkley-Black method or the LECO CHN
analyzer (after treating the samples with HCl to remove
inorganic carbon) [Sheldrick, 1984]. Bulk density (BD) was
determined by using core or clod samples, and coarse
fragments (>2 mm size) were either estimated or a sieve
method was used. It should be pointed out, however, that
the methods used to obtain the analytical data were not
always clearly identified in the original sources, a common
problem in global studies of soil carbon pools.
3. Results
3.1. Permafrost-Affected and Nonpermafrost Soils
3.1.1. Soil Area
[20] The total area of soils in the northern circumpolar
permafrost region is 18,782 10
, with approximately
65% of the area occurring in Eurasia and 35% in North
America and Greenland. The largest portion of this soil area
(54%) lies within the Continuous Permafrost Zone, with the
remaining 46% being split approximately equally between
the Discontinuous, Sporadic, and Isolated Patches perma-
frost zones (Table 2). The distribution of the various soil
orders that occur in this region is shown in Figure 2.
[21] Peatlands, which are a common feature of all perma-
frost zones, cover about 3556 10
, or approximately
19% of the soil area of the northern circumpolar permafrost
region (Table 3). The area of peatlands in the permafrost
region of North America is 1048 10
and in Eurasia,
2508 10
3.1.2. Carbon Content Carbon Content at 0 100 cm
[22] The mean SOCC values calculated for the 0100 cm
depth in soils of the northern permafrost region are given in
Table 4 and their distribution is shown in Figure 3. Histels
(perennially frozen peatland soils, Gelisols) and Histosols
(unfrozen peatland soils) have the highest SOCC values,
with mean values of 66.6 kg m
(maximum 133 kg m
for Histels and 69.6 kg m
(maximum 130 kg m
Histosols. The mean SOCC values for mineral Gelisols are
22.6 kg m
(Orthels) and 32.2 kg m
(Turbels), with
Turbels having the highest mean and maximum (126 kg m
SOCC values for mineral soils. In some cases these mean
and maximum values for Turbels are as much as three times
those for unfrozen mineral soils (Table 4).
[23] The standard deviation (SD) was greatest for Histels
(53.3) and Histosols (56.9) (Table 4), probably because of
the variable depth of peat deposits, the different types of
peat materials, the degree of decomposition, and the mineral
(ash) content. Turbels (27.4), Orthels (21.4), and Spodosols
(20.2) had the second greatest standard deviations. Their
relatively large values are probably due to the various
thicknesses of surface organic material associated with them
and, for Turbels, also to variability in the amounts of
cryoturbated organic materials they contain. Carbon Content at 0 300 cm
[24] There are a number of processes that cause carbon to
be incorporated into the deeper layers of soils: cryoturbation
for Turbels, repeated deposition of organic-rich material for
Orthels (alluvium), and long-term deposition of organic
materials for Histels and Histosols [Bockheim, 2007;
Tarnocai and Stolbovoy, 2006].
[25] SOCC values for those soils with deeper layers
(below 100 cm) were calculated on the basis of a limited
number of available pedons (Table 5). The lowest SOCC
values occur in Orthels (without alluvium), a noncryoturbated,
permafrost-affected soil, and in Inceptisols, a nonpermafrost
soil. Neither of these soils has carbon occurring at depths
below 200 cm because they have no mechanisms other than
deep roots, leaching, or burial to move carbon into the deeper
soil layers. In addition, since the vegetation on these soils is
generally shallow rooted, it contributes very little or no carbon
to the deeper soil layers.
[26] Turbels contain approximately 38% of their carbon in
the upper 100 cm, 33% at 100200 cm, and 28% at 200
300 cm, representing a 5% decrease in carbon content per
100 cm. Orthels (alluvium) have about 80% of their carbon
distributed equally between the upper two layers (0
200 cm), with approximately 20% in the third layer
(200300 cm). These levels of carbon probably also occur
at depths greater than 300 cm in some of these deposits.
[27] For Histosols the SOCC is approximately evenly
distributed in the three layers. The slight variation is
probably due to the origin of the peat material and amount
of mineral content. The distribution of carbon in Histels is
similar to that in Histosols, but the carbon content drops
somewhat in the third layer, probably because of the
increased ice content in this layer. The levels of carbon in
the 200300 cm depth of these soils indicate that similar
carbon levels probably also occur at greater depths, depend-
ing on the total depth of the peat deposit.
3.1.3. Carbon Mass Carbon Mass at 0 100 cm
[28] The total soil organic carbon mass (SOCM) in the 0
100 cm depth is 495.80 Pg (Table 6) with peat deposits
containing approximately 150.46 Pg, or 30% of this mass
Table 2. Areas of All Soils in the Permafrost Zones
Permafrost Zones
Area (10
North America
Eurasia Total
Continuous 2,868 7,255 10,123
Discontinuous 1,443 1,649 3,092
Sporadic 1,149 1,444 2,593
Isolated patches 1,186 1,788 2,974
Total 6,646 12,136 18,782
Includes Greenland.
Figure 2. Distribution of soils in the northern circumpolar permafrost region based on the NCSCD
(Tarnocai et al., unpublished data, 2007). Note that the legend entries followed by asterisks refer to
another U.S. taxonomic level.
(Table 7). Approximately two thirds (67%) of the total soil
organic carbon mass is in the Eurasian portion of the
northern circumpolar permafrost region with the remainder
(33%) in the North American portion. The Continuous
Permafrost Zone contains 60% of the SOCM and the other
three zones together contain 40%. Carbon Mass at 100 300 cm
[29] The total soil organic carbon mass (SOCM) in the
100300 cm depth is 528.2 Pg (Table 8). For Turbels,
approximately 36% of the SOCM occurs in the first 100 cm
and 64% occurs in the 100300 cm layers. Thus, two thirds
of the SOCM is missed if only the 0100 cm layer is
sampled. This explains, to some extent, the smaller
estimates in previous analyses. For Orthels, all of the
SOCM occurs in the 0 200 cm layers with approximately
97% in the first 100 cm and 3% in the 100200 cm layer
(Table 8).
[30] For unfrozen mineral soils, deep soil data is available
only for the Inceptisols. For these soils, the first 100 cm
contains approximately 68% of the SOCM and the 100
200 cm layer contains approximately 32% (Table 8), with
no organic carbon occurring deeper than 200 cm. The
carbon in these soils originated dominantly from roots
and, to a lesser extent, from dissolved illuviated organic
matter. Since these soils are associated with shallow-rooted
vegetation, most of the organic carbon occurs in the upper
layer of the soil.
3.2. Additional Carbon Pools
[31] The organic carbon pools in all soils in the northern
permafrost region were determined uniformly to a depth of
300 cm. The deltaic, or alluvial, deposits and yedoma
deposits, however, cover vast areas and contain large
amounts of organic carbon below the 300 cm depth. While
the future fate of these deep carbon pools is beyond the
scope of this paper, mechanisms currently exist that can
Table 3. Areas of Peatlands in the Permafrost Zones
Permafrost Zones
Peatland Area (10
North America
Eurasia Total
Continuous 228 1895 2123
Discontinuous 272 159 431
Sporadic 321 240 561
Isolated patches 227 214 441
Total 1048 2508 3556
Includes Greenland.
Figure 3. Distribution of soil organic carbon contents in the northern circumpolar permafrost region
based on the NCSCD (Tarnocai et al., unpublished data, 2007).
rapidly expose deep permafrost carbon to thaw [Schuur et
al., 2008]. Thus, the first step is to quantify the size of these
deep permafrost carbon pools.
3.2.1. Yedoma Deposits
[32] These deposits, which were formed by the deposition
of sediments in unglaciated areas during glacial periods,
occur in areas that, at that time, were covered by a
mammoth steppe-tundra ecosystem. According to Zimov
et al. [2006b], these perennially frozen yedoma sediments
cover more than 1 million km
, have an average depth of
approximately 25 m, and contain 2 5% organic carbon. In
continental areas, the yedoma sediments contain 1 5%
organic carbon by dry mass (maximum 30%) [Zimov et
al., 2006a; Dutta et al., 2006] and in wetter areas they
contain 230% organic carbon [Schirrmeister et al., 2002].
Using an average carbon concentration of 2.6%, Zimov et
al. [2006b] estimated that that these sediments contain
approximately 500 Pg of carbon, subsequently revised to
450 Pg [Zimov et al., 2006a]. On the basis of this revised
estimate, yedoma sediments were found to contain 407 Pg
of organic carbon in the 325 m depth.
3.2.2. Deltaic Deposits
[33] The major river deltas included are those of the
Yukon and Colville rivers in Alaska, USA, the Mackenzie
River in the Northwest Territories of Canada, and the Lena,
Pechora, Ob, and Kolyma rivers in northern Russia. Sedi-
ments deposited by rivers contain organic matter. Since the
deposition is recurring, these freshly deposited materials are
buried by the new deposits and, in most cases, become
perennially frozen. This deposition is especially active on
the river deltas, where the deposited sediments can reach
several tens of meters in thickness. Although little informa-
tion, other than the area they cover, is available for the
major deltas of the circumpolar permafrost region, informa-
tion on the thickness of the deposits and the concentration
of organic carbon in them is available for the Mackenzie
River delta. Therefore, this delta was used as a model to
estimate the carbon mass in the major northern deltas. On
the basis of this model, we estimated that the seven major
river deltas contain a total of 241 Pg of SOCM in layers
deeper than 300 cm (Table 9).
4. Discussion
[34] Our estimates indicate that the northern circumpolar
permafrost region contains 1024.00 Pg of soil organic
carbon in the surface 0300 cm depth, with an additional
648 Pg of carbon locked in deep layers of yedoma (407 Pg)
and deltaic (241 Pg) deposits. In total, the northern circum-
polar permafrost region contains 1672 Pg of organic carbon,
of which 1466 Pg (88%) occurs in perennially frozen soils
and deposits. This 1672 Pg of organic carbon is a signifi-
cantly larger pool than previous estimates have given. Thus,
the northern circumpolar permafrost region contains
approximately 50% of the reported global belowground
organic carbon pool.
[35] Previous northern latitude nonpeatland soil carbon
pools were estimated to be in the range of 150 191 Pg
carbon for boreal forest [Apps et al., 1993; Jobba´gy and
Jackson, 2000], and 60144 Pg carbon for tundra [Apps et
al., 1993; Gilmanov and Oechel, 1995; Jobba´gy and
Jackson, 2000; Oechel et al., 1993]. Some widely cited
estimates quantify the soil carbon pool in northern peatlands
as 419455 Pg [Gorham, 1991; Apps et al., 1993]. The
difference, in large part, between our new estimate and
previous estimates is the recognition and quantification of
significant carbon below 100 cm outside of peatlands,
although direct comparisons need to be made with caution
because of differences among studies.
[36] Estimates of global soil organic carbon pools for the
0100 cm depth range between 1220 and 1576 Pg
[Eswaran et al., 1993; Sombroek et al., 1993; Batjes,
1996]. Batjes [1996] reported that soil organic carbon pools
for the 0200 cm depth were 2376 2456 Pg while Jobba´gy
Table 4. Mean Soil Organic Carbon Contents for the Upper 0
100 cm in Soils
SOCC (kg m
SD Number of PedonsMean Range
Histels 66.6 21 – 133 53.3 87
Turbels 32.2 1 – 126 27.4 256
Orthels 22.6 0.1 – 65 21.4 131
Histosols 69.6 6 – 130 56.9 417
Andisols 25.4
unknown 8.3 unknown
Spodosols 24.7 2– 110 20.2 6
Aquic suborders 20.1 1 – 94 9.7 531
Inceptisols 15.3 0.5 – 93 9.4 871
Vertisols 13.5 6– 27 7.3 11
Entisols 9.9 6 – 75 15.8 198
Mollisols 9.6 1 – 42 8.3 422
Natric suborders 9.1 6 – 40 7.6 67
Alfisols 8.9
unknown 6.9 533
Aridisols 3.0
unknown 6.6 unknown
U.S. taxonomy [Soil Survey Staff, 1999].
SOCC data are from Batjes [1996].
Table 5. Mean Soil Organic Carbon Contents and Ranges for the Various Soil Layers to a Depth of 300 cm
(kg m
Number of Pedons0 – 100 cm 100 – 200 cm 200 – 300 cm Total (0 – 300 cm)
Turbels 61.0 (28 – 89) 53.1 (22 – 106) 45.1 (30 – 60) 159.2 8
Orthels (without alluvium) 4.5 (0.5 – 9) 1.6 (0.1 – 3) 0 6.1 4
Orthels (alluvium) 142.6 (142 – 143) 142.5 (142 – 143) 67.0 (66 – 68) 352.1 2
Histels 67.2 (31 – 171) 62.0 (22 – 128) 41.5 (20 – 94) 170.7 13
Histosols 64.7 (61 – 67) 62.6 (16 – 88) 67.5 (16 – 92) 194.8 15
Inceptisols 12.6 (7 – 22) 10.3 (1 – 23) 0 22.9 3
Calculated using only the deep pedons, so values do not match those in Table 4 for the 0– 100 cm depth of the same soils. Ranges are given in
and Jackson [2000] indicated that the pools for this depth
were 1993 Pg and for the 0300 cm depth were 2344 Pg.
These global estimates indicate that soils in the northern
circumpolar permafrost region contain approximately 33%
of the global organic carbon in the 0100 cm depth and
44% of that in the 0300 cm depth.
4.1. Carbon Pools and Data Uncertainty
[37] The spatial and soil data used in this paper were
derived from a number of sources that had different rates of
accuracy and uncertainty. Therefore, assigning a single
confidence value to the new carbon estimate for the entire
northern circumpolar region would not be realistic. Instead,
we have divided this area into two subregions and have
assigned the confidence levels used in the IPCC Fourth
Assessment. As a result, we have medium to high confi-
dence (6680%) in the North American data (for the 0
100 cm depth) since the carbon database, the largest data
set, was tested by the methods indicated below and low to
medium confidence (33 66%) in the equivalent Eurasian
data, a smaller data set (section 2.2). We have very low to
low confidence (<33%) in the soil carbon estimates for the
deeper soil layers and for the other deposits since they are
based on an even smaller data set (Table 5).
[38] Data available for estimating carbon pools are limited
and are associated with numerous gaps and uncertainties.
SOCM data generated for the 0 100 cm depth in soils is
based on the largest pedon data set, especially for the North
American portion of the permafrost area. However, SOCM
data generated for greater depths are based on smaller data
sets and will require future improvements.
[39] The North American soil organic carbon estimates
presented in this paper were generated using data from the
NCSCD, which is an updated version of the Canadian Soil
Organic Carbon Database (CSOCD). Bhatti et al. [2002]
compared carbon estimates generated by the CSOCD with
carbon values generated by both the Carbon Budget Model
of the Canadian Forest Sector (CBM-CFS2) and the Boreal
Forest Transect Case Study (BFTCS). They found that the
CSOCD generated slightly lower carbon values than the
CBM-CFS2 carbon model, but that there was good agree-
ment between CSOCD- and BFTCS-generated values.
[40] Although SOCM data are available for the perma-
frost region in Eurasia, Stolbovoi [2000] provides only
estimates of 297 Pg for the 0 100 cm depth and 373 Pg
for the 0200 cm depth for the SOCM of all soils in Russia.
In order to shed some light on the reliability of the Eurasian
soil organic carbon data, organic soils (Histels and unfrozen
Table 6. Organic Carbon Mass at Depths of 0 30 cm and 0
100 cm in All Soils
North America
Eurasia Total
0 – 30 cm 0 – 100 cm 0 – 30 cm 0 – 100 cm 0 –100 cm
Continuous 31.2 78.3 79.2 220.2 298.5
Discontinuous 12.2 29.6 13.3 37.7 67.3
Sporadic 10.9 26.2 15.5 36.7 62.9
Isolated patches 12.6 30.6 16.4 36.5 67.1
Total 66.9 164.7 124.4 331.1 495.8
Including Greenland.
Table 7. Soil Organic Carbon Mass for the Total Depth of the Peat
Deposits in North America and Eurasia
North America Eurasia Total
Continuous 21.8 1.5 23.3 120.9 144.2
Discontinuous 26.6 0.8 27.4 10.7 38.1
Sporadic 30.6 0.3 30.9 16.1 47.0
Isolated patches 32.9 0 32.9 15.1 48.0
Total 111.9 2.6 114.5 162.8 277.3
Calculated for the total depth of the peat deposit.
Calculated using the Peatlands of Canada database (C. Tarnocai et al.,
2005, Research Branch, Agriculture and Agri-Food Canada, Ottawa;
available at
Calculated using the Northern and Mid-Latitude Soil Database
[Cryosol Working Group, 2004].
Table 8. Soil Organic Carbon Mass Values to a Depth of 300 cm
for Major Soil Groups
0 – 100 cm 100– 200 cm 200 – 300 cm 0– 300 cm
Gelisols 351.5 – – 818.0
Turbels 211.9 207.2 162.2 581.3
Orthels 51.3 1.7 0 53.0
Histels 88.3 – 183.7
Alfisols 4.6 1.4 0 6.0
Inceptisols 23.2 10.8 0 34.0
Spodosols 28.4 9.4 0 37.8
Aquic suborders 4.2 2.8 0 7.0
Mollisols 10.7 2.1 0 12.8
Entisols 6.6 2.1 0 8.7
Histosols 62.2 – 94.3
Aridisols 1.3 0.3 0 1.6
Vertisols 0
Andisols 2.9 0.7 0 3.6
Natric suborders 0.2 0 0 0.2
Total 495.8 – 1024.0
U.S. taxonomy [Soil Survey Staff, 1999].
Calculated for the total depths of the various peat deposits but not
separated into layers for depths >100 cm.
SOCM <0.0001 Pg.
Table 9. Areas and Total Organic Carbon Mass Below 300 cm for
Major Deltas in the Northern Permafrost Region
River Delta Area (km
) Total Carbon Mass
Yukon 5,280
Colville 1,687
Mackenzie 13,500
Lena 43,563
Pechora 8,737
Ob 4,000
Kolyma 3,000
Total 79,767 241
Carbon masses for all deltas were determined using the carbon content
calculated for the Mackenzie River Delta.
Information on major world deltas is available from J. M. Coleman and
O. K. Huh (unpublished data, 2004, available at
Mackenzie Delta information is available from Mackenzie River Basin
Board [2004].
Ob River data are available from The Unabridged Hutchinson
Encyclopedia, available at
Pavlov et al. [1994].
organic soils) were used as a test since this data is available
for Russian peatlands, which account for most of the peat-
lands in Eurasia. In Russia, organic soils and peatlands, by
definition, contain 30 cm or more of organic material (in
North America organic soils and peatlands contain 40 cm or
more of organic material). Various estimates of the areas
and SOCM of Russian peatlands are 1162 10
94 Pg [Stolbovoi, 2000], 1650 10
and 215 Pg
[Botch et al., 1995], and 2730 10
and 118 Pg
[Efremov et al., 1998]. For comparison, our paper gives an
estimated area of 2508 10
(Table 3) and an SOCM
of 162.80 Pg (Table 7) for the total depth of the peat deposit
in the permafrost zones of Eurasia. It is evident that the
areas and carbon masses in published estimates vary widely
(1162– 2730 10
and 94 215 Pg). These large
variations occur because of the poor inventory and limited
amount of reliable pedon data available for these soils. This
supports the levels of accuracy for estimates of peat carbon
established by Efremov et al. [1998] of ±1015 percent for
the European part of Russia and ±2030 percent for the
Asian part of the country.
[41] The SOCC values of unfrozen and noncryoturbated
frozen mineral soils in the permafrost region are similar to
those of soils in the temperate region. In these soils, the
organic matter that is deposited on the soil surface is not
affected by cryoturbation. Some soluble organic matter may
move downward, but there is no mechanism for moving
organic matter from the surface into the deeper soil layers
and preserving it from decomposition and wildfires. Since
most of the belowground carbon in these soils originates
from roots, its residence time is thus relatively short.
4.2. Vulnerability of Carbon in Permafrost
[42] Permafrost degradation resulting from warmer tem-
peratures at high latitudes and changes in precipitation (e.g.,
increased snowfall leads to increased degradation) is
now widely reported [Payette et al., 2004; Camill, 2005;
Jorgenson et al., 2006]. Projections show that almost all
near-surface permafrost will disappear by the end of this
century [Lawrence et al., 2008] with the active layer
deepening at a decreasing rate as we move northward.
[43] Both depth and spatial distribution of permafrost
degradation will result in different degrees of vulnerability
of the various carbon pools as reported by Schuur et al.
[2008]. Carbon in near-surface permafrost is, and will be,
the most vulnerable pool during this century given the
retreat of permafrost to deeper layers. However, as perma-
frost thaws, the newly formed thermokarst lakes act as
conduits of both surface heat to deeper layers and deep
methane to the surface [Zimov et al., 2006a].
[44] Modeling work also suggests that global warming
could trigger an irreversible process of thawing as self-
sustaining heat generated by microbial activity leads to deep
soil respiration in a multicentury timeframe. This process,
which could continue even after warming has stabilized or
stopped, would result in long-term sustained chronic emis-
sions of CO
and CH
[Khvorostyanov et al., 2008]. Since
the yedoma deposits reported in this study occur in cold
permafrost, they are unlikely to show self-sustaining heat
generation although they can still be significant carbon
sources of 0.2 Pg C a
(or 1 Pg C a
of CO
-eq) into
the next century [Khvorostyanov et al., 2008].
[45] Global warming, thermokarst formation, and fire
frequency will push the net carbon balance and full radiative
forcing of permafrost degradation in directions often deter-
mined by regional conditions. This heterogeneity of the
regional net carbon balance is well illustrated by the
decrease in the net ecosystem productivity (NEP) in warm
and dry/wet regions in Alaska over the past two decades,
while NEP increased in the colder and wetter regions
[Thompson et al., 2006]. Fire will trigger additional ther-
mokarst collapse, accelerating permafrost degradation and
subsequent peat formation [Myers-Smith et al., 2008]. Not
taking into account these complex interactions, Zhuang et
al. [2006] estimated net emissions from thawing permafrost
in the northern high latitudes at 7 17 Pg in 100 years, while
Davidson and Janssens [2006] report a potential carbon loss
of 100 Pg C over the same timeframe.
[46] The significance of having more accurate informa-
tion about the distribution of carbon in permafrost and the
size of the overall pool is well illustrated by the following
example. Gruber et al. [2004] estimated that as much as
100 Pg of carbon could be released from thawing perma-
frost over this century, a 25% loss from the 400 Pg carbon
pool on which they based their calculations. Extrapolating
their analyses using our new carbon pool estimate would
yield a potential carbon loss four times greater. This alone
would account for the entire upper range of the multiple
carbon-climate feedbacks currently estimated by climate
models [Friedlingstein et al., 2006]. Even taking into
account the possibility that this is an extreme case and that
there will be other mechanisms which might remove carbon
from the atmosphere (e.g., enhanced plant uptake and
northward forest migration), the potential for significant
feedbacks from permafrost carbon could be realized with
only a small fraction of the total pool being thawed and
released to the atmosphere. More recently, Raupach and
Canadell [2008], using a simple carbon-climate model and
a smaller frozen carbon pool (1000 Pg), showed that, if 10%
of the permafrost were to thaw, the feedback from CO
emissions could result in an additional 0.7°C and a CO
increment of 80 ppm by the end of this century. Landscape
and small-scale processes, which control the thawing of
permafrost and the subsequent decomposition of organic
matter, are the key processes that limit our ability to
constrain the future net carbon balance of permafrost
5. Conclusions
[47] The data presented in this paper indicate the large
amount of organic carbon stored in soils of the northern
circumpolar permafrost region. These new estimates will
help to provide a more reliable prediction for the effect of
global change and human activities on this carbon.
[48] 1. Northern circumpolar soils are estimated to cover
approximately 18,782 10
and contain about 191 Pg
of organic carbon in the 030 cm depth, 496 Pg of organic
carbon in the 0100 cm depth, and 1024 Pg of organic
carbon in the 0300 cm depth. Our estimate for the first
meter of soil alone is approximately double that reported in
previous analyses.
[49] 2. We also estimated the organic carbon pools in less
known and studied frozen deposits. These are the deltaic
deposits and the Siberian yedoma sediments, which contain
approximately 648 Pg of organic carbon at depths greater
than 300 cm. The 0 300 cm carbon pool estimates for these
deposits are included in the estimates given in point 1.
[50] 3. In the northern circumpolar permafrost region all
carbon pools combined contain approximately 1672 Pg of
organic carbon, which is approximately 50% of the global
belowground organic carbon and almost an order of
magnitude higher than that used in many global biogeo-
chemical and climate modeling studies (200 300 Pg C
from the FAO soil database).
[51] 4. Our confidence in the North American soil carbon
estimates for the 0 100 cm depth is medium to high (66
80%) while our confidence in the equivalent Eurasian
portion is low to medium (33 66%) since the estimates
are based on a smaller data set. Our confidence in carbon
estimates for the deeper soils layers and for the other
deposits is the lowest (<33%) since they are based on even
smaller data sets.
[52] 5. The data reported in this study show that the
amount of carbon stored in northern circumpolar soils
and, thus, the potential for carbon-climate feedbacks from
this region, where the greatest global warming is predicted
to occur, has been hugely underestimated. This study more
than doubles the size of the carbon pools in the northern
circumpolar region, the area that can ultimately be exposed
to new environmental conditions more amenable to decom-
position of organic matter and, therefore, to its associated
release of carbon dioxide or methane.
[53]Acknowledgments. This paper is a contribution to the activity
Vulnerabilities of the Carbon Cycle under the umbrella of the Global
Carbon Project of the Earth System Science Partnership. Funding for a
workshop series was provided by (1) the National Center for Ecological
Analysis and Synthesis, a center funded by NSF grant DEB-00-72909, the
University of California at Santa Barbara, and the State of California, and
(2) UNESCO through a grant to the Global Carbon Project (on behalf of
IGBP and WCRP). This paper is also a contribution to the activities of the
International Polar Year and the International Permafrost Association (IPA).
We thank Jerry Brown (past president of IPA) for his continuous support
and encouragement during the preparation of this paper and Chris Field for
his leadership in the NCEAS group. We would also like to thank Vladimir
Stolbovoi, Sergey Goryachkin, and Chien-Lu Ping for providing some of
the Russian and North American pedon data. Special thanks are also due to
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Box 18, 678830 Cherskii, Russia. (
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... Since this trend is expected to continue in the future, Northern Hemisphere permafrost ecosystems are at exceptional risk of degradation. The Arctic permafrost region stores about 50 % of the belowground organic carbon stocks on Earth (Hugelius et al., 2014), with an estimated pool of organic C of between 1307 and 1672 Gt (Hugelius et al., 2014;Tarnocai et al., 2009). Based on several independent approaches, it is estimated that 130 to 160 Gt C could be released by 2100 under a high warming scenario (i.e., Representative Concentration Pathway scenario 8.5; Schuur et al., material would constitute a substantial positive feedback with ongoing warming trends. ...
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Large-herbivore grazing has been shown to substantially alter tundra soil and vegetation properties as well as carbon fluxes, yet observational evidence to quantify the impact of herbivore introduction into Arctic permafrost ecosystems remains sparse. In this study we investigated growing-season CO2 and CH4 fluxes with flux chambers on a former wet tussock tundra inside Pleistocene Park, a landscape experiment in northeast Siberia with a 22-year history of grazing. Reference data for an undisturbed system were collected on a nearby ungrazed tussock tundra. Linked to a reduction in soil moisture, topsoil temperatures at the grazed site reacted 1 order of magnitude faster to changes in air temperatures compared to the ungrazed site and were significantly higher, and the difference strongly decreased with depth. Overall, both GPP (gross primary productivity, i.e., CO2 uptake by photosynthesis) and Reco (ecosystem respiration, i.e., CO2 release from the ecosystem) were significantly higher at the grazed site with notable variations across plots at each site. The increases in CO2 component fluxes largely compensated for each other, leaving NEE (net ecosystem exchange) similar across grazed and ungrazed sites for the observation period. Soil moisture and CH4 fluxes at the grazed site decreased over the observation period, while in contrast the constantly waterlogged soils at the ungrazed site kept CH4 fluxes at significantly higher levels. Our results indicate that grazing of large herbivores may promote topsoil warming and drying, in this way effectively accelerating CO2 turnover while decreasing methane emissions in the summer months of peak ecosystem activity. Since we lack quantitative information on the pre-treatment status of the grazed ecosystem, however, these findings need to be considered qualitative trends for the peak growing season, and absolute differences between treatments are subject to elevated uncertainty. Moreover, our experiment did not include autumn and winter fluxes, and thus no inferences can be made for the annual NEE and CH4 budgets in tundra ecosystems.
... Pendugaan cadangan karbon biomasa N. biserrata dan A. intrusa ini sangat rendah apabila dibandingkan dengan pendugaan cadangan karbon biomasa pelepah kelapa sawit, M. malabatricum dan Cycas sp di perkebunan kelapa sawit rakyat Nanggroe Aceh Darussalam (lahan gambut) sebesar 9.4-12.2 t ha-1 tahun-1 (Maswar, 2009;Lasco, 2002), dan cadangan karbon biomasa di hutan tropis Asia yang berkisar antara 40-250 t ha-1 (Tarnocai et al., 2009). ...
Perkebunan kelapa sawit umumnya memiliki tanaman pengganggu yang disebut gulma, dua jenis yang paling umum adalah Nephrolepis biserrata dan Asystasia intrusa. Gulma ini berpotensi untuk dijadikan tanaman penutup tanah di lahan kelapa sawit karena dinilai memiliki efek yang menguntungkan terutama dalam hal kontribusi bahan organik dalam bentuk cadangan karbon tanah. Tujuan dari penelitian ini adalah untuk menganalisis potensi sumbangan karbon tanah Nephrolepis biserrata dan Asytasia intrusa sebagai tanaman penutup tanah di perkebunan kelapa sawit. Penelitian dilakukan dengan rancangan petak terbagi, yaitu pada petak utama digunakan umur tanaman kelapa sawit, sedangkan anak petak berupa pemeliharaan Nephrolepis biserrata dan Asystasia intrusa, masing-masing perlakuan diulang sebanyak 3 kali. Parameter yang diamati adalah berat kering, kecepatan dekomposisi dan potensi cadangan karbon. Hasil penelitian menunjukkan Nephrolepis biserrata menghasilkan biomassa seberat 21,2 - 27,1 ton/ha, lama proses dekomposisi (30-60 hari), karbon dari tanaman (0,9 ton C/ha/tahun) dan stok karbon tanah (14,7-15,7 ton/ha/tahun). Sedangkan Asystasia intrusa menghasilkan biomassa seberat 17,6 - 17,9 ton/ha, lama proses dekomposisi (30-60 hari), karbon dari tanaman (0,9 ton C/ha/tahun) dan stok karbon tanah 13,2-13,9 ton/ha/tahun.
... The melting of ice and snow at high latitudes will cause more radiation to be absorbed by the darker ground and ocean, and models estimate this ice-albedo feedback could contribute an additional 2-4 K of warming in the Arctic by the end of the century in a high-emissions scenario (Cai et al., 2021;Pithan & Mauritsen, 2014). Permafrostperennially frozen soil at high latitudes-contains an estimated 1,300 Pg (Hugelius et al., 2014) to 1,600 Pg (Tarnocai et al., 2009) of carbon, with approximately 500 Pg of this reservoir contained in the topmost meter of soil (1 Pg = 1 Gt = 10 15 g). Globally, permafrost temperatures have increased by an average of 0.29°C over the last two decades (Biskaborn et al., 2019), and as permafrost thaws under strong warming scenarios, an estimated 5%-15% or more of the carbon contained in the permafrost zone may decompose and be released into the atmosphere as CO 2 or CH 4 (Plaza et al., 2019;Schuur et al., 2015). ...
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Stratospheric aerosol injection (SAI) has been shown in climate models to reduce some impacts of global warming in the Arctic, including the loss of sea ice, permafrost thaw, and reduction of Greenland Ice Sheet (GrIS) mass; SAI at high latitudes could preferentially target these impacts. In this study, we use the Community Earth System Model to simulate two Arctic‐focused SAI strategies, which inject at 60°N latitude each spring with injection rates adjusted to either maintain September Arctic sea ice at 2030 levels (“Arctic Low”) or restore it to 2010 levels (“Arctic High”). Both simulations maintain or restore September sea ice to within 10% of their respective targets, reduce permafrost thaw, and increase GrIS surface mass balance by reducing runoff. Arctic High reduces these impacts more effectively than a globally focused SAI strategy that injects similar quantities of SO2 at lower latitudes. However, Arctic‐focused SAI is not merely a “reset button” for the Arctic climate, but brings about a novel climate state, including changes to the seasonal cycles of Northern Hemisphere temperature and sea ice and less high‐latitude carbon uptake relative to SSP2‐4.5. Additionally, while Arctic‐focused SAI produces the most cooling near the pole, its effects are not confined to the Arctic, including detectable cooling throughout most of the northern hemisphere for both simulations, increased mid‐latitude sulfur deposition, and a southward shift of the location of the Intertropical Convergence Zone. For these reasons, it would be incorrect to consider Arctic‐focused SAI as “local” geoengineering, even when compared to a globally focused strategy.
The article summarized the results of long-term observations (20142018) of soil emissions and net CO2 fluxes (20172018) in natural and anthropogenically modified (AI) ecosystems of Arctic tundra on the territory of the archipelago of Svalbard (Barentsburg, 7804N, 1413E). Anthropogenic controls associated with local land use, during the period of their active impact may redouble the emissions of carbon dioxide from soil (0.111 0.021 0.064 0.011 gС m2h1). During the same period, the net C-balance at the sites with active land use is estimated as a source to the atmosphere. Self-recovering after human influence plots (II) demonstrate intermediate values of soil emissions of СО2 between unaffected tundra (I) and plots with active land use (III). With that they demonstrate the greatest net C-sink within the observed range of Photosynthetically Active Radiation as compared to (I) and (III). At the height of the vegetation period unaffected tundra ecosystems demonstrate a neutral net C-balance. The greatest contribution to soil emissions variance make spatial controls (they explain 5666% of variance), whereas temporal factors are responsible for 3.85.5% only. Amongst spatial controls, the thickness of organogenic layer makes the greatest contribution. Inter-annual fluctuations of key factors, among which the most important are the soil moisture and temperature of the upper soil layer, both affect AI and natural ecosystems hence the spatial differences between them remain constant from year to year. According to preliminary estimates, unlike the carbon dioxide, the contribution of methane and nitrous oxide net fluxes in local ecosystems is insignificant and does not depend on human land use.
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The carbon cycle component of the newly developed Earth System Model of intermediate complexity CLIMBER-X is presented. The model represents the cycling of carbon through atmosphere, vegetation, soils, seawater and marine sediments. Exchanges of carbon with geological reservoirs occur through sediment burial, rock weathering and volcanic degassing. The state-of-the-art HAMOCC6 model is employed to simulate ocean biogeochemistry and marine sediments processes. The land model PALADYN simulates the processes related to vegetation and soil carbon dynamics, including permafrost and peatlands. The dust cycle in the model allows for an interactive determination of the input of the micro-nutrient iron into the ocean. A rock weathering scheme is implemented into the model, with the weathering rate depending on lithology, runoff and soil temperature. CLIMBER-X includes a simple representation of the methane cycle, with explicitly modelled natural emissions from land and the assumption of a constant residence time of CH4 in the atmosphere. Carbon isotopes 13C and 14C are tracked through all model compartments and provide a useful diagnostic for model-data comparison. A comprehensive evaluation of the model performance for present–day and the historical period shows that CLIMBER-X is capable of realistically reproducing the historical evolution of atmospheric CO2 and CH4, but also the spatial distribution of carbon on land and the 3D structure of biogeochemical ocean tracers. The analysis of model performance is complemented by an assessment of carbon cycle feedbacks and model sensitivities compared to state-of-the-art CMIP6 models. Enabling interactive carbon cycle in CLIMBER-X results in a relatively minor slow-down of model computational performance by ~20 %, compared to a throughput of ~10,000 simulation years per day on a single node with 16 CPUs on a high performance computer in a climate–only model setup. CLIMBER-X is therefore well suited to investigate the feedbacks between climate and the carbon cycle on temporal scales ranging from decades to >100,000 years.
Mineral protection can slow the effect of warming on the mineralization of organic carbon (OC) in permafrost wetlands, which has an important impact on the dynamics of soil OC. However, the response mechanisms of wetland mineral soil to warming in permafrost areas are unclear. In this study, the soil of the southern edge of the Eurasian permafrost area was selected, and bulk and heavy fraction (HF) soil was subjected to indoor warming incubation experiments using physical fractionation. The results showed that the HF accounted for 51.25 % of the total OC mineralization in the bulk soil, and the δ13C value of the CO2 that was emitted in the HF soil was higher than that of the bulk soil. This indicates the potential availability of mineral soil and that the mineralized OC in the HF was the more stable component. Additionally, the mineralization of the mineral subsoil after warming by 10 °C was only about half of the increase in the organic topsoil, and the temperature sensitivity was significantly negatively correlated with the Fe/Al oxides to OC ratio. The results indicate that under conditions of permafrost degradation, the physical protection of mineral soil at high latitudes is essential for the stability of OC, which may slow the trend of permafrost wetlands becoming carbon sources.
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The northern-high-latitude permafrost contains almost twice the carbon content of the atmosphere, and it is widely considered to be a non-linear and tipping element in the earth's climate system under global warming. Solar geoengineering is a means of mitigating temperature rise and reduces some of the associated climate impacts by increasing the planetary albedo; the permafrost thaw is expected to be moderated under slower temperature rise. We analyze the permafrost response as simulated by five fully coupled earth system models (ESMs) and one offline land surface model under four future scenarios; two solar geoengineering scenarios (G6solar and G6sulfur) based on the high-emission scenario (ssp585) restore the global temperature from the ssp585 levels to the moderate-mitigation scenario (ssp245) levels via solar dimming and stratospheric aerosol injection. G6solar and G6sulfur can slow the northern-high-latitude permafrost degradation but cannot restore the permafrost states from ssp585 to those under ssp245. G6solar and G6sulfur tend to produce a deeper active layer than ssp245 and expose more thawed soil organic carbon (SOC) due to robust residual high-latitude warming, especially over northern Eurasia. G6solar and G6sulfur preserve more SOC of 4.6 ± 4.6 and 3.4 ± 4.8 Pg C (coupled ESM simulations) or 16.4 ± 4.7 and 12.3 ± 7.9 Pg C (offline land surface model simulations), respectively, than ssp585 in the northern near-surface permafrost region. The turnover times of SOC decline slower under G6solar and G6sulfur than ssp585 but faster than ssp245. The permafrost carbon–climate feedback is expected to be weaker under solar geoengineering.
To determine the influence of fire and thermokarst in a boreal landscape, we investigated ~600 years of vegetation succession from peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate that succession proceeded from a terrestrial forest to a sedge-dominated wetland over 100 years ago and to a Sphagnum-dominated bog in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing season temperature record from Fairbanks. The concurrent wetland succession and reduced growth of black spruce trees indicates a non-linear ecosystem-level response to a change in regional climate. In 2001, fire was observed coincident with permafrost collapse and resulted in lateral expansion of the bog. These observations and the peat profile suggest that future warming and/or increased fire disturbance could promote permafrost degradation and bog expansion, and increase carbon storage in the collapse; however, the development of drought conditions could reduce the success of black spruce and Sphagnum, decreasing long-term ecosystem carbon storage in the adjacent landscape.
This study provides estimates of average soil organic carbon content for the Usa Basin in Northeast European Russia, using two independent databases and two separate upscaling tools. The results are very similar despite differences in sample size and spatial resolution. Based on the merged databases and landcover upscaling, the average carbon content in the Usa Basin is 10,7 Kg Cm-2 for the upper 30 cm soil layer, 25,5 Kg C m-2 for a reference 1 m soil depth and 31,2 Kg C m-2 for total soil. The 'peatland' cover classes, with an average 76.3 Kg C m-2 and 30% surface coverage, account for 73% of total organic carbon storage in the Usa Basin. Upland forest and tundra classes have similar average total carbon contents-on the order of 11,2-11,4 Kg C m-2. Detailed regional and national assessments of northern terrestrial carbon pools, upscaled using landcover or soil classification schemes like the one presented here for the Usa Basin, arrive at much higher average total soil carbon estimates than generally cited in the literature from global data sets for tundra and taiga life zones or biomes.
A computer-based soil map for the Usa River (the largest tributary of the Pechora River) basin has been compiled on a scale of 1 : 1 M with the use of the soil classification suggested in the World Reference Base for Soil Resources (1998). Original soil maps used in this work are based on the Russian soil classification. The two classifications have been correlated using a database containing morphological descriptions and analytical data on 403 reference soil profiles. A part of this database (data on 197 soil pits) has been used to assess the reserves of organic carbon in different soils and within the entire basin. Spatial gradients in the distribution of soil carbon reserves within the Usa basin have been analyzed using GIS technologies.
A set of records of North American tundra ecosystems was obtained from the Global Arctic/Alpine Climate/Soil/Plant Productivity Data Base, which contains phytomass, productivity, climatic and soil characteristics for nearly 50 tundra-type ecosystems studied during the past 30 yr in Alaska and N Canada. This information was used to interpolate the necessary data for all the tundra cells (1 × 1 degree) of the simple GIS, based on the Global Vegetation Map and the FAO/UNESCO Soil Map of the World. By integrating the corresponding maps of phytomass and productivity the quantitative estimates of the reserves and productivity fluxes of organic matter in tundra ecosystems of North America and Greenland (4.12 × 106 km2 total area) were obtained: 2.26 Gt above-ground phytomass, 4.99 Gt total phytomass, 91.3 Gt soil organic matter of the active layer; 0.56 Gt/yr above-ground net primary production; 0.98 Gt/yr total net primary production. A phenomenological model relating net primary production of tundra ecosystems to climatic, soil and vegetation factors, was applied to the GIS layers of mean annual temperature, soil organic matter content, and above-ground phytomass density to produce a map of modelled net primary production estimates for North American tundra ecosystems. Taking into account geographical changes in the landscape composition (proportions of the zonal, meadow, mire and aquatic ecosystem types) results in totals of 0.58 Gt/yr for above-ground and 1.16 Gt/yr for total net primary production of tundra ecosystems of North America and Greenland. -from Authors