Soil organic carbon stocks in permafrost-affected soils in West Greenland
Graphical abstract.
Introduction
During the past century, warming of local Arctic climate (> 60°N) was approximately 0.09 K per decade, whereas on the entire northern hemisphere temperatures rose only by 0.06 K per decade (McBean, 2005; Intergovernmental Panel on Climate Change (IPCC), 2001). Soil temperatures at the permafrost table of artic soils already increased by 3 K since the 1980s (Lemke et al., 2007, Vaughan et al., 2013). Different models predict an increase of the global mean surface temperature of up to 4.8 K until 2100 (Intergovernmental Panel on Climate Change (IPCC), 2008). Especially winter air temperatures will be significantly warmer (4–7 K) across the terrestrial Arctic (> 60°N Arctic Climate Impact Assessment, 2004). With rising air temperature, carbon sequestered in permafrost-affected soils is likely to decompose to a larger extend and become a source of atmospheric carbon. Increasing active-layer depth and altered hydrological conditions can lead to intensified mineralization, which is followed by higher carbon turnover rates and CO2 emission from soils (Dutta et al., 2006, Koven et al., 2009, Schuur et al., 2008, Wagner and Liebner, 2009, Zimov, 2006). Permafrost-affected soils cover about 27% of the terrestrial surface above 50°N (Jones et al., 2009). A high amount of soil organic carbon (SOC) is currently frozen and thereby partially excluded from interactions with the atmosphere and biogeochemical cycles (Wagner and Liebner, 2009).
The SOC pool in the first 300 cm of arctic soils includes about 50% of the estimated global terrestrial belowground organic carbon, which makes about 1024 Pg C and up to 496 Pg (1 Pg = 1015 g) within the uppermost one meter (Tarnocai et al., 2009). Compared to the ocean and to the forest carbon pool the carbon pool of permafrost-affected soils is sensitive to warming and changing hydrological circumstances (Gruber et al., 2004, McGuire et al., 2009, Schuur et al., 2009). Especially lowlands in the permafrost zone, which are common in the Arctic and Subarctic, hold large amounts of labile SOC (e.g. approx. 60 kg m− 2 0–100 cm in bogs of the Usa Basin, Siberia, Hugelius and Kuhry, 2009) and are prone to change under climate warming (Christensen, 2004, Khvorostyanov et al., 2008).
SOC stocks in arctic permafrost-affected soils, particularly Cryosols and Histosols, were underestimated for many years (Tarnocai et al., 2009, Burnham and Sletten, 2010) and the knowledge about SOC dynamics in periglacial landscapes is little compared to the assumed dimension of the influence of carbon dynamics on global warming. In addition to the underestimation of SOC stocks in permafrost-affected soils in the Arctic, which is mainly due to a lack of knowledge about specific soil processes, to limited depth consideration, and underestimation of landscape heterogeneity, our knowledge of the spatial distribution of SOC in periglacial landscapes is quite limited (Jobbagy and Jackson, 2000, Ping et al., 2008, Tarnocai et al., 2009). Since soils in general are in the “front line” (Schmidt et al., 2011) of global environmental change it is important to improve global estimations by conducting regional to local research and including i.e. deeper soil layers, and consideration and calculation of uncertainties. Local studies, e.g. from Alaska, Canada or Siberia, give a picture about SOC stock distribution in specific study areas, but this is not sufficient to create a global SOC distribution map. Ping et al. (2008) combined local SOC measurements with the distribution of landscape types and proved that this approach leads to a regional assessment of SOC stocks. To improve knowledge about local SOC distribution further studies are necessary, which also account for small-scale landscape heterogeneity and focus on other regions (cf. Kuhry et al., 2002).
In our study, we investigate the SOC stocks and their spatial and vertical distribution in the low mountain ranges of West Greenland adjacent to the inland ice margin. We chose a formerly glaciated valley southeast of Kangerlussuaq which exhibits the characteristic landscape structure, soils and sediments under periglacial climate conditions. The main objective of our investigation is to quantify the SOC stocks of permafrost-affected soils in relation to characteristic landscape units (valley bottom, crest, north-facing and south-facing slopes).
The study area is located in the Umimmalissuaq valley in West Greenland near Kangerlussuaq, where the ice sheet forms flat outlet glaciers onto a low mountain range. The distance from ice sheet to the coast is about 150 km. Kangerlussuaq area is dominated by an E–W and ENE–WSW oriented valley system, which leads the melt water to the sea. The Umimmalissuaq valley, about 30 km SE of Kangerlussuaq, stretches from the ice cap to the west for approximately five kilometers. The study area in the Umimmalissuaq valley expands from the terminal/lateral moraine of the Ørkendalen glacier (66°56′50″ N, 49°58′53″ W) to a melt water lake in the west (66°56′14″ N, 56°06′12″ W). In the north and south, it is bordered by mountain ranges with topographic differences of about 100 m and in the south partly by the lake Umimmalissuup Tasinngua (Fig. 1; names taken from Scholz and Grottenthaler, 1988; suppl. Mat. Soil_pits_JHenkner_2016_Geoderma.kmz).
The Kangerlussuaq Airport weather station shows an arctic continental climate with an annual mean air temperature of − 5.7 °C and 149 mm annual mean precipitation (1976–1999 (Cappelen et al., 2001, Carstensen and Jørgensen, 2009)). Summer day temperatures are about 15 °C (June–August), highest precipitation occurs in August (33 mm). In summer, there are about 150 snow-free and 80 consecutive frost-free days (Bullard, 2011). The study area itself is likely to be slightly colder but sunnier, drier and with higher wind speed compared to Kangerlussuaq (situated around 35 km west of the ice margin), because of its location adjacent to the ice margin. The bimodal wind regime is dominated by katabatic winds from the ice sheet, channeling in the valley especially in winter, and westerly winds generated by Atlantic storms, which are less frequent and less strong (Dijkmans and Törnqvist, 1991). Recent climate data for the period 1979–2008 (Boas and Wang, 2011) already show warming and higher precipitation (mean annual air temperature − 4.8 °C, mean annual precipitation 257 mm) with a particular increase of winter temperature and summer precipitation.
The bedrock in the Umimmalissuaq valley is mainly Precambrian gneiss, extensively covered by glacial, glaciofluvial or aeolian material (Scholz and Grottenthaler, 1988, Henriksen, 2008, Ozols and Broll, 2003). Non-calcareous aeolian sand and silt forms the uppermost parent material of soils, underlying glacial material contains larger rocks. Soils are mostly dry, water saturated conditions were measured on the north-facing slope only a few days in summer (Hanebeck, 2012). Although mapped as continuous permafrost regime (Maurer, 2007), the soils in the Umimmalissuaq valley show characteristics of a discontinuous permafrost regime depending on topography. Permafrost is present within about 1 m from the soil surface on north-facing slopes. The active layer depth varies throughout the valley and could not be assessed in the valley bottom or south-facing slopes.
The study area of Umimmalissuaq valley is located within the moraines of the Umîvît/Keglen (according to Ten Brink, 1975) dated to around 7300 cal b2k (UtC-1987, UtC-1990, after Van Tatenhove et al., 1996). Small moraines stretch across the valley from the north to the south, a larger one, reaching up to 20 m above the valley bottom, stretches northeast to southwest and west (Fig. 1). Accordingly, deglaciation in this area began about 7300 years ago, which gives a maximum age for the beginning of the accumulation of SOC. The SOC stocks from 0 to 30 cm depth in crest positions/south facing slopes accumulated within around 2000 years (AMS14C dates of bulk SOM from profile C39 in 36–40 cm depth: 19 cal BCE to 233 cal CE (Erl-16,616) and in 49–53 cm depth 7–244 cal CE). This reflects a slow accumulation and decomposition rate of organic matter (cf. Wagner et al., 2009).
Deflation forms and sediment accumulation occur due to active aeolian sediment transport seaward along the valley (Müller et al., 2016). Further geomorphologic features are ice-wedge polygons at north-facing slopes and ice-wedge pseudomorphs and earth hummocks at the valley bottom (Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5). Vegetation is mainly controlled by microtopography, depth to bedrock or permafrost, and the strong continental climate, especially wind speed and direction (Ozols and Broll, 2003).
Section snippets
Methods
Field work was done in summer 2009 and 2011. All in all 39 soil profiles were described according to WRB 2006 (FAO, 2006, IUSS Working Group WRB, 2015) and the German classification system (Ad-hoc Arbeitsgruppe Boden, 2005) and sampled. A categorical assessment of current soil moisture was done (FAO, 2006). The soil profiles are located along four catenas reaching from the top of a north-facing hill through the valley to the opposing south-facing hill (Fig. 1).
Bulk soil samples were taken
Field soil inventory
This study showed that the most common reference soil group (IUSS Working Group WRB, 2015) in the Umimmalissuaq valley is the Haplic Regosol occurring on ridges, slopes, and at the valley bottom (25 soil profiles, Table 1). The suffix qualifiers Humic, Siltic, Eutric, and Turbic were used in this order of frequency. Prefix qualifiers of the 13 Cryosols range from the obvious Turbic and Glacic to Mollic, Histic and Folic indicating cryoturbation, low temperature, and high SOC content. Cryosols
SOC stocks in the Umimmalissuaq valley
Many studies dealing with SOC stocks of arctic permafrost (-affected) soils cover a global to regional scale giving a general picture usually of the first 100 cm (Table 6). Local arctic studies focusing on one area often show a more heterogeneous picture arriving at higher SOC stocks and lead to an improved general record about the amount and spatial distribution of SOC stored in arctic permafrost (-affected) soils than estimations using global data sets (Kuhry et al., 2002). SOC stocks of the
Conclusions
This study presents landscape units as a reliable option to serve as proxies for SOC stocks. The landscape units represent the controlling environmental factors on a small-scale and might be easily identified with remote sensing for larger areas. Our field data proves the importance of small-scale studies considering SOC stocks and landscape heterogeneity. The analysis of the SOC stocks in the Umimmalissuaq valley in West Greenland leads to the following findings and conclusions:
- -
The spatial
Acknowledgements
Many thanks go to the field colleagues Michael Müller, Jürgen Förth, and Christian Wolf and to Richard Szydlak for drawing Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5. PK is greatly indebted to Herbert Scholz (München), who firstly introduced him to the grand landscape of Greenland. We appreciated also the most valuable comments and specific remarks by two unknown reviewers.
The field work was funded by: The Association for Geography and Ethnology Stuttgart (GEV, //www.lindenmuseum.de/en/support/aid-association-gev/
References (85)
- et al.
The effects of slope orientation on plant growth, developmental instability and susceptibility to herbivores
J. Arid Environ.
(2003) - et al.
Pedogenesis, permafrost, substrate and topography: plot and landscape scale interrelations of weathering processes on the central-eastern Tibetan Plateau
Geoderma
(2014) - et al.
Recognition of cryoturbation for classifying permafrost-affected soils
Geoderma
(1998) Dust generation on a proglacial floodplain, West Greenland
Aeolian Res.
(2011)- et al.
Spatial and vertical variation of soil carbon at two grassland sites — implications for measuring soil carbon stocks
Geoderma
(2007) - et al.
High-arctic soil CO2 and CH4 production controlled by temperature, water, freezing and snow
- et al.
Soil and plant community-characteristics and dynamics at Zackenberg
- et al.
The Greenland ice sheet during the past 658,300,000 years: a review
- et al.
Soil carbon distribution in Alaska in relation to soil-forming factors
Geoderma
(2011) - et al.
Quality and potential biodegradability of soil organic matter preserved in permafrost of Siberian tussock tundra
Soil Biol. Biochem.
(2007)
Implications for deglaciation chronology from new AMS age determinations in central West Greenland
Quat. Res.
A continuous record of Holocene eolian activity in West Greenland
Quat. Res.
Effect of permafrost on the formation of soil organic carbon pools and their physical–chemical properties in the eastern Swiss Alps
Catena
Bodenkundliche kartieranleitung
Impacts of a Warming Arctic
Pedogenesis, permafrost, and soil moisture as controlling factors for soil nitrogen and carbon contents across the Tibetan Plateau
Glob. Chang. Biol.
Lehrbuch der Bodenkunde: Scheffer/Schachtschabel
Weather and climate data from Greenland 1958–2010: observation data with description
Spatial distribution of soil organic carbon in northwest Greenland and underestimates of high Arctic carbon stores
Glob. Biogeochem. Cycles
The observed climate of Greenland, 1958–99 - with climatological standard normals, 1961–90
Weather and climate data from Greenland 1958–2008: dataset available for research and educational purposes. Descriptions and documentation of observations of temperature, precipitation, wind, could cover, air pressure, humidity and depth of snow
Thawing sub-arctic permafrost: effects on vegetation and methane emissions
Geophys. Res. Lett.
Modern periglacial Eolian deposits and landforms in the Sondre Stromfjord Area, West Greenland and their palaeoenvironmental implications
Soil organic carbon pools and stocks in permafrost-affected soils on the Tibetan Plateau
PLoS One
Vertical distribution of soil organic carbon density in relation to land use/cover, altitude and slope aspect in the eastern Himalayas
Land
Potential carbon release from permafrost soils of northeastern Siberia
Glob. Chang. Biol.
Influence of vegetation, temperature, and water content on soil carbon distribution and mineralization in four high Arctic soils
Arct. Antarct. Alp. Res.
Land-atmosphere energy exchange in Arctic tundra and boreal forest: available data and feedbacks to climate
Glob. Chang. Biol.
Guidelines for Soil Description, Rome
Typische Vegetationsgesellschaften und Oberirdische Vertikalstruktur Von Zwergsträuchern in Abhängigkeit Von Abiotischen Umweltfaktoren in West–Grönland
Soil organic carbon storage in mountain grasslands of the Pyrenees: effects of climate and topography
Biogeochemistry
Magnitude and sources of uncertainties in soil organic carbon (SOC) stock assessments at various scales
Eur. J. Soil Sci.
The vulnerability of the carbon cycle in the 21
Carbon in tundra soils in the Lake Labaz region of arctic Siberia
Eur. J. Soil Sci.
Monitoring (2009–2011) Von Bodentemperatur und Bodenfeuchte in Der Auftauzone Westgrönlands: Auswertung Von Messreihen Unterschiedlicher Tiefenstufen Sowie Deren Vergleich Mit Klimadaten Der Station Kangerlussuaq
Geological History of Greenland: Four billion Years of Earth Evolution
Controls over carbon storage and turnover in high-latitude soils
Glob. Chang. Biol.
Community assembly along proglacial chronosequences in the high Arctic: vegetation and soil development in north-west Svalbard
J. Ecol.
A new dataset for estimating organic carbon storage to 3 m depth in soils of the northern circumpolar permafrost region
Earth Syst. Sci. Data
Landscape partitioning and environmental gradient analyses of soil organic carbon in a permafrost environment
Glob. Biogeochem. Cycles
Soil organic carbon pools in a periglacial landscape: a case study from the Central Canadian Arctic
Permafr. Periglac. Process.
Climate Change 2001: Synthesis Report. A Contribution of Working Groups I, II, and III to the Third Assessment Report of the Intergovernmental Panel on Climate Change
Cited by (18)
Terrestrial ecosystems of West Greenland
2020, Encyclopedia of the World's BiomesA carbon mass-balance budget for a periglacial catchment in West Greenland – Linking the terrestrial and aquatic systems
2020, Science of the Total EnvironmentCitation Excerpt :This discrepancy might have several causes. First, Anderson et al. (2009) based their calculations for the terrestrial system on a carbon pool of 6.7 kg C m−2 (Jensen et al., 2006), which is about one third of the average SOC pool down to 100 cm for the TBL catchment and much lower than SOC pools reported from other places in Greenland (Elberling et al., 2004; Palmtag et al., 2015; Henkner et al., 2016). Second, even though the carbon accumulation rates in the sediments of TBL are in the lower range of those reported in Anderson et al. (2009), their total lake sediment carbon pools are much higher (42 kg C m−2) than what we find in TBL.
Driving Factors That Reduce Soil Carbon, Sugar, and Microbial Biomass in Degraded Alpine Grasslands
2019, Rangeland Ecology and ManagementIce wedge polygon stability on steep slopes in West Greenland related to temperature and moisture dynamics of the active layer
2023, Permafrost and Periglacial ProcessesMicrobial iron cycling during palsa hillslope collapse promotes greenhouse gas emissions before complete permafrost thaw
2022, Communications Earth and Environment