scholarly journals The importance of a surface organic layer in simulating permafrost thermal and carbon dynamics

2015 ◽  
Vol 9 (3) ◽  
pp. 3137-3163 ◽  
Author(s):  
E. Jafarov ◽  
K. Schaefer
Keyword(s):  
Soil Carbon ◽  
Layer Thickness ◽  
Active Layer ◽  
Carbon Dynamics ◽  
Frozen Soil ◽  
Organic Layer ◽  
Active Layer Thickness ◽  
Frozen Ground ◽  
Dynamic Surface ◽  
Thermal Dynamics

Abstract. Permafrost-affected soils contain twice as much carbon as currently exists in the atmosphere. Studies show that warming of the perennially frozen ground could initiate significant release of the frozen soil carbon into the atmosphere. To reduce the uncertainty associated with the modeling of the permafrost carbon feedback it is important to start with the observed soil carbon distribution and to better address permafrost thermal and carbon dynamics. We used the recent Northern Circumpolar Soil Carbon Dataset to simulate present soil organic carbon (SOC) distribution in permafrost-affected soils under the steady state climate forcing. We implemented a dynamic surface organic layer with vertical carbon redistribution and dynamic root growth controlled by active layer thickness to improve modeling of the permafrost thermodynamics. Our results indicate that a dynamic surface organic layer improved permafrost thermal dynamics and simulated active layer thickness, allowing better simulation of the observed SOC densities and their spatial distribution.

scholarly journals The importance of a surface organic layer in simulating permafrost thermal and carbon dynamics

2016 ◽  
Vol 10 (1) ◽  
pp. 465-475 ◽  
Author(s):  
Elchin Jafarov ◽  
Kevin Schaefer
Keyword(s):  
Soil Carbon ◽  
Carbon Dynamics ◽  
Frozen Soil ◽  
Organic Layer ◽  
Active Layer Thickness ◽  
Frozen Ground ◽  
Initial Amount ◽  
Dynamic Surface ◽  
Carbon Redistribution ◽  
Significant Release

Abstract. Permafrost-affected soils contain twice as much carbon as currently exists in the atmosphere. Studies show that warming of the perennially frozen ground could initiate significant release of the frozen soil carbon into the atmosphere. Initializing the frozen permafrost carbon with the observed soil carbon distribution from the Northern Circumpolar Soil Carbon Database reduces the uncertainty associated with the modeling of the permafrost carbon feedback. To improve permafrost thermal and carbon dynamics we implemented a dynamic surface organic layer with vertical carbon redistribution, and introduced dynamic root growth controlled by active layer thickness, which improved soil carbon exchange between frozen and thawed pools. These changes increased the initial amount of simulated frozen carbon from 313 to 560 Gt C, consistent with observed frozen carbon stocks, and increased the spatial correlation of the simulated and observed distribution of frozen carbon from 0.12 to 0.63.

Contrasting thermal responses of permafrost to winter warming events under different snow regimes in the subarctic

2021 ◽  
Author(s):  
Didac Pascual Descarrega ◽  
Margareta Johansson
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Snow Depth ◽  
Thermal Response ◽  
Winter Precipitation ◽  
The Arctic ◽  
Active Layer Thickness ◽  
Thermal Dynamics ◽  
Winter Warming

<p>Winter warming events (WWE) in the Swedish subarctic are abrupt and short-lasting (hours-to-days) events of positive air temperature that occur during wintertime, sometimes accompanied by rainfall (rain on snow; ROS). These events cause changes in snow properties, which affect the below-ground thermal regime that, in turn, controls a suite of ecosystem processes ranging from microbial activity to permafrost and vegetation dynamics. For instance, winter melting can cause ground warming due to the shortening of the snow cover season, or ground cooling as the reduced snow depth and the formation of refrozen layers of high thermal conductivity at the base of the snowpack facilitate the release of soil heat. Apart from these interacting processes, the overall impacts of WWE on ground temperatures may also depend on the timing of the events and the preceding snowpack characteristics. The frequency and intensity of these events in the Arctic, including the Swedish subarctic, has increased remarkably during the recent decades, and is expected to increase even further during the 21st Century. In addition, snow depth (not necessarily snow duration) is projected to increase in many parts of the Arctic, including the Swedish subarctic. In 2005, a manipulation experiment was set up on a lowland permafrost mire in the Swedish subarctic, to simulate projected future increases in winter precipitation. In this study, we analyse this 15-year record of ground temperature, active layer thickness, and meteorological variables, to evaluate the short- (days to weeks) and long-term (up to 1 year) impacts of WWE on the thermal dynamics of lowland permafrost, and provide new insights into the influence of the timing of WWE and the underlying snowpack conditions on the thermal response of permafrost. On the short-term, the thermal responses to WWE are faster and stronger in areas with a shallow snowpack (5-10 cm), although these responses are more persistent in areas with a thicker snowpack (>25 cm), especially after ROS events. On the long term, permafrost in areas with a thicker snowpack exhibit a more durable warming response to WWE that results in thicker active layers at the end of the season. On the contrary, we do not observe a correlation between WWE and end of season active layer thickness in areas with a shallow snowpack. </p>

Climate warming and active layer thaw in the boreal and tundra environments of the Mackenzie Valley

2007 ◽  
Vol 44 (6) ◽  
pp. 733-743 ◽  
Author(s):  
Ming-ko Woo ◽  
Michael Mollinga ◽  
Sharon L Smith
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Climate Warming ◽  
Probability Distributions ◽  
Organic Layer ◽  
Active Layer Thickness ◽  
Near Surface ◽  
Ground Temperatures ◽  
Thaw Depth ◽  
Mineral Soils

The variability of maximum active layer thickness in boreal and tundra environments has important implications for hydrological processes, terrestrial and aquatic ecosystems, and the integrity of northern infrastructure. For most planning and management purposes, the long-term probability distribution of active layer thickness is of primary interest. A robust method is presented to calculate maximum active layer thickness, employing the Stefan equation to compute phase change of moisture in soils and using air temperature as the sole climatic forcing variable. Near-surface ground temperatures (boundary condition for the Stefan equation) were estimated based on empirical relationships established for several sites in the Mackenzie valley. Simulations were performed for typically saturated mineral soils, overlain with varying thickness of peat in boreal and tundra environments. The probability distributions of simulated maximum active layer thickness encompass the range of measured thaw depths provided by field data. The effects of climate warming under A2 and B2 scenarios for 2050 and 2100 were investigated. Under the A2 scenario in 2100, the simulated median thaw depth under a thin organic cover may increase by 0.3 m, to reach 1 m depth for a tundra site and 1.6 m depth for a boreal site. The median thaw depth in 2100 is dampened by about 50% under a 1 m thick organic layer. Without an insulating organic cover, thaw penetration can increase to reach 1.7 m at the tundra site. The simulations provide quantitative support that future thaw penetration in permafrost terrain will deepen differentially depending on location and soil.

scholarly journals Linking tundra vegetation, snow, soil temperature, and permafrost

2020 ◽  
Vol 17 (16) ◽  
pp. 4261-4279
Author(s):  
Inge Grünberg ◽  
Evan J. Wilcox ◽  
Simon Zwieback ◽  
Philip Marsh ◽  
Julia Boike
Keyword(s):  
Soil Temperature ◽  
Snow Cover ◽  
Layer Thickness ◽  
Active Layer ◽  
Vegetation Change ◽  
Vegetation Type ◽  
Spatial Scales ◽  
Active Layer Thickness ◽  
Vegetation Types ◽  
Thermal Dynamics

Abstract. Connections between vegetation and soil thermal dynamics are critical for estimating the vulnerability of permafrost to thaw with continued climate warming and vegetation changes. The interplay of complex biophysical processes results in a highly heterogeneous soil temperature distribution on small spatial scales. Moreover, the link between topsoil temperature and active layer thickness remains poorly constrained. Sixty-eight temperature loggers were installed at 1–3 cm depth to record the distribution of topsoil temperatures at the Trail Valley Creek study site in the northwestern Canadian Arctic. The measurements were distributed across six different vegetation types characteristic for this landscape. Two years of topsoil temperature data were analysed statistically to identify temporal and spatial characteristics and their relationship to vegetation, snow cover, and active layer thickness. The mean annual topsoil temperature varied between −3.7 and 0.1 ∘C within 0.5 km2. The observed variation can, to a large degree, be explained by variation in snow cover. Differences in snow depth are strongly related with vegetation type and show complex associations with late-summer thaw depth. While cold winter soil temperature is associated with deep active layers in the following summer for lichen and dwarf shrub tundra, we observed the opposite beneath tall shrubs and tussocks. In contrast to winter observations, summer topsoil temperature is similar below all vegetation types with an average summer topsoil temperature difference of less than 1 ∘C. Moreover, there is no significant relationship between summer soil temperature or cumulative positive degree days and active layer thickness. Altogether, our results demonstrate the high spatial variability of topsoil temperature and active layer thickness even within specific vegetation types. Given that vegetation type defines the direction of the relationship between topsoil temperature and active layer thickness in winter and summer, estimates of permafrost vulnerability based on remote sensing or model results will need to incorporate complex local feedback mechanisms of vegetation change and permafrost thaw.

scholarly journals Analysis of Permafrost Thermal Dynamics and Response to Climate Change in the CMIP5 Earth System Models

2013 ◽  
Vol 26 (6) ◽  
pp. 1877-1900 ◽  
Author(s):  
Charles D. Koven ◽  
William J. Riley ◽  
Alex Stern
Keyword(s):  
Soil Temperature ◽  
Layer Thickness ◽  
Active Layer ◽  
Air Temperature ◽  
High Latitude ◽  
Cmip5 Models ◽  
Active Layer Thickness ◽  
Thermal Dynamics ◽  
Wide Range ◽  
Soil Temperatures

Abstract The authors analyze global climate model predictions of soil temperature [from the Coupled Model Intercomparison Project phase 5 (CMIP5) database] to assess the models’ representation of current-climate soil thermal dynamics and their predictions of permafrost thaw during the twenty-first century. The authors compare the models’ predictions with observations of active layer thickness, air temperature, and soil temperature and with theoretically expected relationships between active layer thickness and air temperature annual mean- and seasonal-cycle amplitude. Models show a wide range of current permafrost areas, active layer statistics (cumulative distributions, correlations with mean annual air temperature, and amplitude of seasonal air temperature cycle), and ability to accurately model the coupling between soil and air temperatures at high latitudes. Many of the between-model differences can be traced to differences in the coupling between either near-surface air and shallow soil temperatures or shallow and deeper (1 m) soil temperatures, which in turn reflect differences in snow physics and soil hydrology. The models are compared with observational datasets to benchmark several aspects of the permafrost-relevant physics of the models. The CMIP5 models following multiple representative concentration pathways (RCP) show a wide range of predictions for permafrost loss: 2%–66% for RCP2.6, 15%–87% for RCP4.5, and 30%–99% for RCP8.5. Normalizing the amount of permafrost loss by the amount of high-latitude warming in the RCP4.5 scenario, the models predict an absolute loss of 1.6 ± 0.7 million km2 permafrost per 1°C high-latitude warming, or a fractional loss of 6%–29% °C−1.

Vertical electric resistivity sounding of natural and anthropogenically affected cryosols of Fildes Peninsula, Western Antarctica

2017 ◽  
Vol 7 (2) ◽  
pp. 109-122 ◽  
Author(s):  
Evgeny Abakumov
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Soil Layer ◽  
Soil Surface ◽  
Electric Resistivity ◽  
Natural Soil ◽  
Organic Layer ◽  
Active Layer Thickness ◽  
Permafrost Degradation ◽  
Fildes Peninsula

Natural and anthropogenically-affected Cryosols of the Fildes Peninsula (King George Island, NWAntarcticPeninsula) from the surroundings of Russian polar station Bellingshausen were investigated by vertical electric sounding. The aim of the study was to asses the thawing depth and active layer thickness. Natural Turbic Croysols showed lesser thickness of active layer than the soils of former reclaimed wastes disposals. Average thickness of the active layer was 0.3-0.4 m in natural soil and 1.3-1.4 m in anthropogenically-affected ones. This was affected by the change in the temperature regime of soils, and related to the destruction of upper organic layer and mechanical disturbance of the active soil layer on the waste polygons. Itwasshown,thattheuseof vertical electric soundingmethodologyinthesoilsurveysisusefulfor the identificationofthe permafrostdepthwithoutdiggingofsoilpit.Thismethodallowstheidentificationofsoilheterogeneity, because the electric resistivity (ER) values are strongly affected by soil properties. ER also intensively changes on the border of differentgeochemicalregimes,i.e.ontheborderoftheactivelayerandthepermafrost. The lowest ER values were found for the upper organic horizons, the highest for permafrost table. Technogenic Superficial Formations exhibit lower resistivity values than natural soils. Therefore, disposition of WP and disturbance of the soil surface, results in permafrost degradation and an increase in the active layer thickness. 

scholarly journals Frozen ground and snow cover monitoring in Livingston and Deception islands, Antarctica: preliminary results of the 2015-2019 PERMASNOW project

2020 ◽  
Vol 46 (1) ◽  
pp. 187-222
Author(s):  
M.A. De Pablo ◽  
J.J. Jiménez ◽  
M. Ramos ◽  
M. Prieto ◽  
A. Molina ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Snow Cover ◽  
Layer Thickness ◽  
Active Layer ◽  
Remote Sensing Data ◽  
Active Layer Thickness ◽  
Frozen Ground ◽  
Snow Layer ◽  
Sensing Data ◽  
Monitoring Stations

Since 2006, our research team has been establishing in the islands of Livingston and Deception, (South Shetland archipelago, Antarctica) several monitoring stations of the active layer thickness within the international network Circumpolar Active Layer Monitoring (CALM), and the ground thermal regime for the Ground Terrestrial Network-Permafrost (GTN-P). Both networks were developed within the International Permafrost Association (IPA). In the GTN-P stations, in addition to the temperature of the air, soil, and terrain at different depths, the snow thickness is also monitored by snow poles. Since 2006, a delay in the disappearance of the snow layer has been observed, which could explain the variations we observed in the active layer thickness and permafrost temperatures. Therefore, in late 2015 our research group started the PERMASNOW project (2015-2019) to pay attention to the effect of snow cover on ground thermal This project had two different ways to study the snow cover. On the first hand, in early 2017 we deployed new instrumentation, including new time lapse cameras, snow poles with high number of sensors and a complete and complex set of instruments and sensors to configure a snow pack analyzer station providing 32 environmental and snow parameters. We used the data acquired along 2017 and 2018 years with the new instruments, together with the available from all our already existing sensors, to study in detail the snow cover. On the other hand, remote sensing data were used to try to map the snow cover, not only at our monitoring stations but the entire islands in order to map and study the snow cover distribution, as well as to start the way for future permafrost mapping in the entire islands. MODIS-derived surface temperatures and albedo products were used to detect the snow cover and to test the surface temperature. Since cloud presence limited the acquisition of valid observations of MODIS sensor, we also analyzed Terrasar X data to overcome this limitation. Remote sensing data validation required the acquirement of in situ ground-true data, consisting on data from our permanent instruments, as well as ad hoc measurements in the field (snow cover mapping, snow pits, albedo characterization, etc.). Although the project is finished, the data analysis is still ongoing. We present here the different research tasks we are developing as well as the most important results we already obtained about the snow cover. These results confirm how the snow cover duration has been changing in the last years, affecting the ground thermal behavior.

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