Organic carbon and total nitrogen stocks in soils of the Lena River Delta

Abstract. The Lena River Delta, which is the largest delta in the Arctic, extends over an area of 32 000 km2 and likely holds more than half of the entire soil organic carbon mass stored in the seven major deltas in the northern permafrost regions. The geomorphic units of the Lena River Delta which were formed by true deltaic sedimentation processes are a Holocene river terrace and the active floodplains. Their mean soil organic carbon stocks for the upper 1 m of soils were estimated at 29 kg m−2 ± 10 kg m−2 and at 14 kg m−2 ± 7 kg m−2, respectively. For the depth of 1 m, the total soil organic carbon pool of the Holocene river terrace was estimated at 121 Tg ± 43 Tg, and the soil organic carbon pool of the active floodplains was estimated at 120 Tg ± 66 Tg. The mass of soil organic carbon stored within the observed seasonally thawed active layer was estimated at about 127 Tg assuming an average maximum active layer depth of 50 cm. The soil organic carbon mass which is stored in the perennially frozen ground below 50 cm soil depth, which is excluded from intense biogeochemical exchange with the atmosphere, was estimated at 113 Tg. The mean nitrogen (N) stocks for the upper 1 m of soils were estimated at 1.2 kg m−2 ± 0.4 kg m−2 for the Holocene river terrace and at 0.9 kg m−2 ± 0.4 kg m−2 for the active floodplain levels, respectively. For the depth of 1 m, the total N pool of the river terrace was estimated at 4.8 Tg ± 1.5 Tg, and the total N pool of the floodplains was estimated at 7.7 Tg ± 3.6 Tg. Considering the projections for deepening of the seasonally thawed active layer up to 120 cm in the Lena River Delta region within the 21st century, these large carbon and nitrogen stocks could become increasingly available for decomposition and mineralization processes.

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Organic carbon and total nitrogen stocks in soils of the Lena River Delta

Biogeosciences ◽

10.5194/bg-10-3507-2013 ◽

2013 ◽

Vol 10 (6) ◽

pp. 3507-3524 ◽

Cited By ~ 50

Author(s):

S. Zubrzycki ◽

L. Kutzbach ◽

G. Grosse ◽

A. Desyatkin ◽

E.-M. Pfeiffer

Keyword(s):

Organic Carbon ◽

Active Layer ◽

River Delta ◽

The Arctic ◽

River Terrace ◽

Total N ◽

Lena River ◽

The Holocene ◽

Lena River Delta ◽

N Pool

Abstract. The Lena River Delta, which is the largest delta in the Arctic, extends over an area of 32 000 km2 and likely holds more than half of the entire soil organic carbon (SOC) mass stored in the seven major deltas in the northern permafrost regions. The geomorphic units of the Lena River Delta which were formed by true deltaic sedimentation processes are a Holocene river terrace and the active floodplains. Their mean SOC stocks for the upper 1 m of soils were estimated at 29 kg m−2 &pm; 10 kg m−2 and at 14 kg m−2 ± 7 kg m−2, respectively. For the depth of 1 m, the total SOC pool of the Holocene river terrace was estimated at 121 Tg ± 43 Tg, and the SOC pool of the active floodplains was estimated at 120 Tg ± 66 Tg. The mass of SOC stored within the observed seasonally thawed active layer was estimated at about 127 Tg assuming an average maximum active layer depth of 50 cm. The SOC mass which is stored in the perennially frozen ground at the increment 50–100 cm soil depth, which is currently excluded from intense biogeochemical exchange with the atmosphere, was estimated at 113 Tg. The mean nitrogen (N) stocks for the upper 1 m of soils were estimated at 1.2 kg m−2 ± 0.4 kg m−2 for the Holocene river terrace and at 0.9 kg m−2 ± 0.4 kg m−2 for the active floodplain levels, respectively. For the depth of 1 m, the total N pool of the river terrace was estimated at 4.8 Tg ± 1.5 Tg, and the total N pool of the floodplains was estimated at 7.7 Tg ± 3.6 Tg. Considering the projections for deepening of the seasonally thawed active layer up to 120 cm in the Lena River Delta region within the 21st century, these large carbon and nitrogen stocks could become increasingly available for decomposition and mineralization processes.

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Landscape controls and vertical variability of soil organic carbon storage in permafrost-affected soils of the Lena River Delta

CATENA ◽

10.1016/j.catena.2016.07.048 ◽

2016 ◽

Vol 147 ◽

pp. 725-741 ◽

Cited By ~ 28

Author(s):

Matthias Benjamin Siewert ◽

Gustaf Hugelius ◽

Birgit Heim ◽

Samuel Faucherre

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Carbon Storage ◽

River Delta ◽

Lena River ◽

Soil Organic Carbon Storage ◽

Organic Carbon Storage ◽

Lena River Delta ◽

Vertical Variability

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Origin and Pathways of Dissolved Organic Carbon in a Small Catchment in the Lena River Delta

Frontiers in Earth Science ◽

10.3389/feart.2021.759085 ◽

2022 ◽

Vol 9 ◽

Author(s):

Lydia Stolpmann ◽

Gesine Mollenhauer ◽

Anne Morgenstern ◽

Jens S. Hammes ◽

Julia Boike ◽

...

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

River Delta ◽

Aquatic Systems ◽

The Arctic ◽

Small Catchment ◽

Lena River ◽

Thermokarst Lake ◽

Doc Concentration ◽

Lena River Delta

The Arctic is rich in aquatic systems and experiences rapid warming due to climate change. The accelerated warming causes permafrost thaw and the mobilization of organic carbon. When dissolved organic carbon is mobilized, this DOC can be transported to aquatic systems and degraded in the water bodies and further downstream. Here, we analyze the influence of different landscape components on DOC concentrations and export in a small (6.45 km2) stream catchment in the Lena River Delta. The catchment includes lakes and ponds, with the flow path from Pleistocene yedoma deposits across Holocene non-yedoma deposits to the river outlet. In addition to DOC concentrations, we use radiocarbon dating of DOC as well as stable oxygen and hydrogen isotopes (δ18O and δD) to assess the origin of DOC. We find significantly higher DOC concentrations in the Pleistocene yedoma area of the catchment compared to the Holocene non-yedoma area with medians of 5 and 4.5 mg L−1 (p < 0.05), respectively. When yedoma thaw streams with high DOC concentration reach a large yedoma thermokarst lake, we observe an abrupt decrease in DOC concentration, which we attribute to dilution and lake processes such as mineralization. The DOC ages in the large thermokarst lake (between 3,428 and 3,637 14C y BP) can be attributed to a mixing of mobilized old yedoma and Holocene carbon. Further downstream after the large thermokarst lake, we find progressively younger DOC ages in the stream water to its mouth, paired with decreasing DOC concentrations. This process could result from dilution with leaching water from Holocene deposits and/or emission of ancient yedoma carbon to the atmosphere. Our study shows that thermokarst lakes and ponds may act as DOC filters, predominantly by diluting incoming waters of higher DOC concentrations or by re-mineralizing DOC to CO2 and CH4. Nevertheless, our results also confirm that the small catchment still contributes DOC on the order of 1.2 kg km−2 per day from a permafrost landscape with ice-rich yedoma deposits to the Lena River.

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Transient modeling of the ground thermal conditions using satellite data in the Lena River Delta, Siberia

10.5194/tc-2016-130 ◽

2016 ◽

Cited By ~ 1

Author(s):

Sebastian Westermann ◽

Maria Peter ◽

Moritz Langer ◽

Georg Schwamborn ◽

Lutz Schirrmeister ◽

...

Keyword(s):

Surface Temperature ◽

Layer Thickness ◽

Active Layer ◽

Thermal Conditions ◽

River Delta ◽

Active Layer Thickness ◽

Lena River ◽

Ground Temperatures ◽

Lena River Delta

Abstract. Permafrost is a sensitive element of the cryosphere, but operational monitoring of the ground thermal conditions on large spatial scales is still lacking. Here, we demonstrate a remote-sensing based scheme that is capable of estimating the transient evolution of ground temperatures and active layer thickness by means of the ground thermal model CryoGrid 2. The scheme is applied to an area of approx. 16 000 km2 in the Lena River Delta in NE Siberia for a period of 14 years. The forcing data sets at 1 km spatial and weekly temporal resolution are synthesized from satellite products (MODIS Land Surface Temperature, MODIS Snow Extent, GlobSnow Snow Water Equivalent) and fields of meteorological variables from the ERA-interim reanalysis. To assign spatially distributed ground thermal properties, a stratigraphic classification based on geomorphological observations and mapping is constructed which accounts for the large-scale patterns of sediment types, ground ice and surface properties in the Lena River Delta. A comparison of the model forcing to in-situ measurements on Samoylov Island in the southern part of the study area yields a satisfactory agreement both for surface temperature, snow depth and timing of the onset and termination of the winter snow cover. The model results are compared to observations of ground temperatures and thaw depths at nine sites in in the Lena River Delta which suggests that thaw depths are in most cases reproduced to within 0.1 m or less and multi-year averages of ground temperatures within 1 to 1.5 °C. The warmest ground temperatures are calculated for grid cells close to the main river channels in the south, as well as areas with sandy sediments and low organic and ice contents in the central delta, where also the largest thaw depths occur. On the other hand, the coldest temperatures are modeled for the eastern part, an area with low surface temperatures and snow depths. The lowest thaw depths are modeled for Yedoma permafrost featuring very high ground ice and soil organic contents in the southern parts of the delta. The comparison to in-situ observations indicates that the satellite-based model scheme is generally capable of estimating the thermal state of permafrost and its time evolution in the Lena River Delta. The approach could hence be a first step towards remote detection of ground thermal conditions and active layer thickness in permafrost areas.

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Assessments of Organic Carbon Stabilization Using the Spectroscopic Characteristics of Humic Acids Separated from Soils of the Lena River Delta

Separations ◽

10.3390/separations8060087 ◽

2021 ◽

Vol 8 (6) ◽

pp. 87

Author(s):

Vyacheslav Polyakov ◽

Evgeny Abakumov

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Organic Carbon ◽

Humic Acids ◽

Terrestrial Ecosystems ◽

River Delta ◽

The Arctic ◽

Lena River ◽

Organic Matter Stabilization ◽

Lena River Delta

In the Arctic zone, where up to 1024 × 1013 kg of organic matter is stored in permafrost-affected soils, soil organic matter consists of about 50% humic substances. Based on the analysis of the molecular composition of humic acids, we assessed the processes of accumulation of the key structural fragments, their transformations and the stabilization rates of carbon pools in soils in general. The landscape of the Lena River delta is the largest storage of stabilized organic matter in the Arctic. There is active accumulation and deposition of a significant amount of soil organic carbon from terrestrial ecosystems in a permafrost state. Under ongoing climate change, carbon emission fluxes into the atmosphere are estimated to be higher than the sequestration and storing of carbon compounds. Thus, investigation of soil organic matter stabilization mechanisms and rates is quite an urgent topic regarding polar soils. For study of molecular elemental composition, humic acids were separated from the soils of the Lena River delta. Key structural fragments of humic matter were identified and quantified by CP/MAS 13C NMR spectroscopy: carboxyl (–COOR); carbonyl (–C=O); CH3–; CH2–; CH-aliphatic; –C-OR alcohols, esters and carbohydrates; and the phenolic (Ar-OH), quinone (Ar = O) and aromatic (Ar–) groups as benchmark Cryosols of the Lena delta river terrestrial ecosystem. Under the conditions of thermodynamic evolutionary selection, during the change between the dry and wet seasons, up to 41% of aromatic and carboxyl fragments accumulated in humic acids. Data obtained showed that three main groups of carbon played the most important role in soil organic matter stabilization, namely C, H-alkyls ((CH2)n/CH/C and CH3), aromatic compounds (C-C/C-H, C-O) and an OCH group (OCH/OCq). The variations of these carbon species’ content in separated humics, with special reference to soil–permafrost organic profiles’ recalcitrance in the current environment, is discussed.

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Transient modeling of the ground thermal conditions using satellite data in the Lena River delta, Siberia

The Cryosphere ◽

10.5194/tc-11-1441-2017 ◽

2017 ◽

Vol 11 (3) ◽

pp. 1441-1463 ◽

Cited By ~ 19

Author(s):

Sebastian Westermann ◽

Maria Peter ◽

Moritz Langer ◽

Georg Schwamborn ◽

Lutz Schirrmeister ◽

...

Keyword(s):

Remote Sensing ◽

Layer Thickness ◽

Active Layer ◽

Thermal Conditions ◽

River Delta ◽

Active Layer Thickness ◽

Lena River ◽

Ground Temperatures ◽

Lena River Delta

Abstract. Permafrost is a sensitive element of the cryosphere, but operational monitoring of the ground thermal conditions on large spatial scales is still lacking. Here, we demonstrate a remote-sensing-based scheme that is capable of estimating the transient evolution of ground temperatures and active layer thickness by means of the ground thermal model CryoGrid 2. The scheme is applied to an area of approximately 16 000 km2 in the Lena River delta (LRD) in NE Siberia for a period of 14 years. The forcing data sets at 1 km spatial and weekly temporal resolution are synthesized from satellite products and fields of meteorological variables from the ERA-Interim reanalysis. To assign spatially distributed ground thermal properties, a stratigraphic classification based on geomorphological observations and mapping is constructed, which accounts for the large-scale patterns of sediment types, ground ice and surface properties in the Lena River delta. A comparison of the model forcing to in situ measurements on Samoylov Island in the southern part of the study area yields an acceptable agreement for the purpose of ground thermal modeling, for surface temperature, snow depth, and timing of the onset and termination of the winter snow cover. The model results are compared to observations of ground temperatures and thaw depths at nine sites in the Lena River delta, suggesting that thaw depths are in most cases reproduced to within 0.1 m or less and multi-year averages of ground temperatures within 1–2 °C. Comparison of monthly average temperatures at depths of 2–3 m in five boreholes yielded an RMSE of 1.1 °C and a bias of −0.9 °C for the model results. The highest ground temperatures are calculated for grid cells close to the main river channels in the south as well as areas with sandy sediments and low organic and ice contents in the central delta, where also the largest thaw depths occur. On the other hand, the lowest temperatures are modeled for the eastern part, which is an area with low surface temperatures and snow depths. The lowest thaw depths are modeled for Yedoma permafrost featuring very high ground ice and soil organic contents in the southern parts of the delta. The comparison to in situ observations indicates that transient ground temperature modeling forced by remote-sensing data is generally capable of estimating the thermal state of permafrost (TSP) and its time evolution in the Lena River delta. The approach could hence be a first step towards remote detection of ground thermal conditions and active layer thickness in permafrost areas.

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Spatiotemporal variability of methane emissions of tundra landscapes in the Lena River Delta, Siberia

10.5194/egusphere-egu2020-17937 ◽

2020 ◽

Author(s):

Lars Kutzbach ◽

Norman Rößger ◽

Tim Eckhardt ◽

Christian Knoblauch ◽

Torsten Sachs ◽

...

Keyword(s):

Spatial Variability ◽

Growing Season ◽

Landscape Scale ◽

River Delta ◽

The Other ◽

Permafrost Degradation ◽

River Terrace ◽

Lena River ◽

River Terraces ◽

Lena River Delta

Increased methane (CH4) release from a warming Arctic is expected to be a major feedback on the global climate. However, due to the complex effects of climate change on arctic geoecosystems, projections of future CH4 emissions are highly uncertain. CH4 emissions from complex tundra landscapes will be controlled not only by direct climatic effects on production, oxidation and transport of CH4 but, importantly, also by geomorphology and hydrology changes caused by gradual or abrupt permafrost degradation. Therefore, improving our understanding of both the temporal dynamics and the spatial heterogeneity of CH4 fluxes on multiple scales is still necessary.Here, we present pedon- and landscape-scale CH4 flux measurements at two widespread tundra landscapes (active floodplains and late-holocene river terraces) of the Lena River Delta in the Siberian Arctic (72.4&#176; N, 126.5&#176; E). The dominating scales of spatial variability of soil, vegetation and CH4 fluxes differ between the two landscapes of different geological development stage. The active floodplains are characterized by sandy beaches and ridges, and backswamp depressions, forming a mesorelief with height differences of several meters on horizontal scales of 10-1000 m. On the other hand, the river terraces are characterized by the formation of ice-wedge polygons, which lead to a regular microrelief with height differences of several decimeters on horizontal scales of 1 to 10 meters. CH4 fluxes were investigated on the landscape scale with the eddy covariance method (15 campaigns during 2002-2018 at the river terrace, 2 campaigns 2014-2015 at the floodplain) and on the pedon scale with chamber methods (campaigns at different sites in 2002, 2006, 2013, 2014, 2015).Average growing season (June-September) CH4 flux for the floodplain was 166 &#177; 4 mmol m-2 (n=2) and for the river terrace 100 &#177; 25 mmol m-2 (n=15). There was pronounced spatial variability of CH4 fluxes within both tundra landscapes types. On the river terrace, growing season CH4 flux was only 20-40 mmol m-2 at elevated polygon rims and polygon high centers, respectively, and up to 300 mmol m-2 at polygon low centers. On the floodplain, CH4 flux was as low as 5 mmol m-2 at sandy ridges and above 400 mmol m-2 in backswamp depressions. Mean growing season CH4 fluxes at the river terrace were positively linearly correlated (r2 = 0.9, n=15) to growing-degree-days (base temperature of 5 &#176;C). Our findings suggest that a warmer climate stimulates the production of CH4, which is directly reflected in increased CH4 emissions. On the other hand, warming effects on CH4 oxidation appear limited because transport processes that bypass the soil oxidation zone, i.e. plant-mediated transport and ebullition, dominate CH4 emission from wet tundra landscapes. However, since CH4 emissions strongly vary with (micro-)topographical situation within tundra landscapes, the changes of geomorphology and hydrology due to permafrost degradation will probably be the dominating driver of future CH4 emissions from arctic tundra landscapes.

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