Presence Of Permafrost Research Articles

Transitional rock glaciers at sea level in northern Norway

Abstract. Rock glaciers are geomorphological expressions of permafrost. Close to sea level in northernmost Norway, in the subarctic Nordkinn peninsula, we have observed several rock glaciers that appear to be active now or were active in the recent past. Active rock glaciers at this elevation have never before been described in Fennoscandia, and they are outside the climatic limits of present-day permafrost according to models. In this study, we have investigated whether or not these rock glaciers are active under the current climate situation. We made detailed geomorphological maps of three rock glacier areas in Nordkinn and investigated the regional ground dynamics using synthetic aperture radar interferometry (InSAR). One of the rock glaciers, namely the Ivarsfjorden rock glacier, was investigated in more detail by combining observations of vertical and horizontal changes from optical images acquired by airborne and terrestrial sensors and terrestrial laser scans (TLSs). The subsurface of the same rock glacier was investigated using a combination of electrical resistivity tomography (ERT) and refraction seismic tomography (RST). We also measured ground surface temperatures between 2016 and 2020, complemented by investigations using an infrared thermal camera, and a multi-decadal climatic analysis. We mapped the rock glaciers in the innermost parts of Store and Lille Skogfjorden as relict, while the more active ones are in the mouths of both fjords, fed by active talus in the upper slopes. Several of the rock glaciers cross over both the Younger Dryas shoreline (25 m a.s.l.) and the Early to Mid-Holocene shoreline at 13 m a.s.l. Both InSAR and optical remote sensing observations reveal low yearly movement rates (centimetres to millimetres per year). The ERT and RST suggest that there is no longer permafrost and ground ice in the rock glacier, while temperature observations on the front slope indicate freezing conditions also in summer. Based on the in situ temperature measurements and the interpolated regional temperature data, we show that the mean annual air temperature (MAAT) of the region has risen by 2 ∘C since the late 19th century to about 1.5 ∘C in the last decade. MAATs below 0 ∘C 100–150 years ago suggest that new rock glacier lobes may have formed at the end of the Little Ice Age (LIA). These combined results indicate that the Nordkinn rock glaciers are transitioning from active to relict stages. The study shows that transitional rock glaciers are still affected by creep, rock falls, snow avalanches, etc., and are not entirely dynamically dead features. Our contrasting results concerning permafrost presence and rock glacier activity show the importance of a multi-methodological approach when investigating slope processes in the edge zones of permafrost influence.

Revised proposed classification for human modified soils in Canada: Anthroposolic order

As the global human population and associated anthropogenic activities rapidly increase, so does the areal extent of disturbed soils. Regulatory frameworks must incorporate reclamation criteria and management options for these disturbed soils, requiring consistent descriptions and interpretations. Many human-altered soils cannot be classified using the current Canadian System of Soil Classification (CSSC), thus an Anthroposolic order is proposed. Anthroposols are soils that are highly modified or constructed by human activity, with one or more natural horizons removed and replaced, added to, or significantly modified. Disturbed horizons are anthropic in origin and contain materials significantly modified physically and/or chemically by human activities. Three great groups are defined by the presence of anthropogenic artefacts and organic carbon content. Eight subgroups are based on the amount of organic material, thickness of horizons, material composition, hydrologic regime, and presence of permafrost. Traditional phases and modifiers are used as in the CSSC. The proposed classification has been revised from the original publication in 2012 after field testing and discussion among soil scientists across Canada. This revised classification is proposed for inclusion in the revised CSSC, to account for the very large and expanding aerial extent of disturbed soils in Canada, and to remain current with other global soil taxonomy systems.

Remote sensing of broad-scale controls on large river anabranching

River patterns reflect complex geomorphological processes and affect ecosystems and human development along floodplains. Physical controls on anabranching development have been studied primarily at local scales on relatively small rivers (i.e., discharge <1000 m3 s−1). However, there has been little systematic quantification of river anabranching (development of stable multiple channels) for large rivers globally. Here, we use remote sensing, cloud computing, and geospatial analysis to explore the importance of water surface slope, floodplain topography, sediment supply, substrate lithology, and permafrost to anabranching throughout 20 of the world's largest river basins. We use Landsat-derived surface water extent to compute an anabranching index (Ai) for ∼1 M km of river reaches, and compare it with global datasets of water surface slope, available floodplain extent, substrate lithology, and permafrost. We find that ∼49 ± 19% of large-river mainstems are anabranching, ranging from at least ∼17% (Mekong) to as much as ∼84% (Ob’). At the basin scale, anabranching channels comprise at least ∼17% (Yenisey) to as much as ∼55% (Kolyma) of all Landsat-observable river reaches, with a mean global value of 35 ± 11%. Anabranching channel patterns are most commonly associated with low water surface slope (normalized slope < 0.2; absolute slope < 0.2 m km−1) accompanying wide floodplains (normalized floodplain width > 0.6; absolute width > 42 km). Cross-sectionally averaged channel width increases in the most intensely anabranching reaches, suggesting net sediment storage due to reduced stream power. Unconsolidated sedimentary substrates promote both the prevalence and intensity of anabranching, whereas the presence of permafrost enhances intensity only. Overall, our results identify pervasive channel anabranching and some important control mechanisms throughout the world's large river basins, with strong implications for satellite-based discharge retrievals. We conclude that global analyses afforded by remote sensing and cloud computing offer additional, complementary approaches to traditional field-based approaches for understanding large river geomorphic processes and channel forms.

What explains the year-to-year variation in growing season timing of boreal black spruce forests?

Amplified climate warming in high latitudes is expected to affect growing season timing of the vast boreal biome. It is unclear whether the presence of permafrost (perennially frozen ground) might have an influence on changes in growing season timing. This study examined how different environmental variables explained, either directly or indirectly, the variation in growing season timing of boreal forest stands with and without permafrost. We expected that environmental variables explaining the variation in growing season timing differed or had different explanatory power depending on permafrost presence or absence. The growing season was delineated from daily gross primary productivity (GPP) time series derived from 40 site-year data of net ecosystem carbon dioxide exchange measured with eddy covariance techniques over five black spruce (Picea mariana [Mill.])-dominated boreal forest stands in North America. In permafrost-free forest stands, a combination of start in canopy ‘green-up’ in spring and the timing of air and soil temperature increasing above freezing explained the start-of-season (SOSGPP). Results from commonality analysis and structural equation modeling suggest that canopy ‘green-up’ and air temperature directly affected SOSGPP in permafrost-free forest stands. In addition, soil temperature acted as mediator for an indirect effect of air temperature on SOSGPP. In contrast, none of the environmental variables, or their combination, explained the variation in SOSGPP in forest stands with permafrost. The explanatory power of environmental variables was more consistent regarding the end-of-season (EOSGPP). In both, forest stands with and without permafrost, EOSGPP was directly explained by mean soil water content in the fall and the first day of continuous snowpack formation. A better understanding how environmental variables control SOSGPP and EOSGPP in forest stands with and without permafrost will help to refine parameterizations of the boreal biome in Earth system models.

Inflow of surface and groundwater to Lake Ladoga based on stable isotope (2H, 18O) composition

Stable isotope (deuterium – 2H and oxygen-18 – 18O) surveys of water in Lake Ladoga and several rivers and small lakes within its watershed were conducted during 2012–2018. Over these 6 years, specific spatial and time differences in water isotope composition of Ladoga and small water bodies and streams were found. These differences depended firstly, on wetland type and the lakes distribution on the watershed and secondly, on groundwater discharge and type of lithological substrate (geological sediments or crystalline rocks). Besides landscape, climate (air temperature, precipitation, evapotranspiration) is a main physical factor which controls all scales of the stable isotope variations. In modern times, the sub-latitudinal gradient of climate but also presence of permafrost in the past effects the stable isotope variation. The isotopic composition divides the tributaries of Ladoga into three groups with a wide range of δ18O seasonal variations, and a significant atmospheric component. The isotopic composition of Ladoga water is generally stable ranging from δ18O = −11.7 to −9.5‰ (average δ18O = −10.6‰), δ2H = −84 to −74‰ (average δ2H = −78‰). The effect of evaporation is clearly seen due to accumulation of deuterium and oxygen-18 and a shift to the right from the Local Meteoric Water Line of δ2Hversusδ18O diagram. In Lake Ladoga there is a local deviation of δ18O which can be explained by subaqueous discharge of groundwater from Riphean sediments.

Study of Condensate Absorption Capacity in Exposed Soil when Water Recedes at the Bottom of Hoh Xil Lake, Qinghai

In order to investigate the characteristics of the condensate absorption capacity in an exposed sandy bottom when water recedes, the characteristics of condensate variation, condensate formation time, condensate volume, and its absorption capacity were investigated in July 2021, using a micro-osmometer. The research area was the artificial water-retention layer and bare ground of the exposed sandy bottom, formed under the influence of the warming-wetting trend that occurs when water recedes in the salt-lake area of the Qinghai-Tibet Plateau, as well as two conditions: underpass and under sealed. According to the results, the time of condensation generation during the observation period in the salt-lake area of Hoh Xil begins at about 0:00 and ends at about 10:00 The artificial water-retention layer had little influence on the condensation generation time, and the trend of the condensation rate is the same. The unidirectional condensation of water in near-surface air is significantly better under artificial water-retention layer conditions than under bare ground conditions, with condensation occurring three times more frequently than under bare ground conditions. The amount of water condensation in the lower part of the soil under artificial aquifer conditions is 2.588 times greater than that in the near-ground air, while the amount of water condensation in the lower part of the soil under bare ground conditions is 1.783 times greater than that in the near-ground air. The total amount of bi-directional condensation under artificial water-retention layer conditions is slightly less than that in bare ground conditions, while the total amount of unidirectional condensation under artificial water-retention layer conditions is significantly higher, indicating that the artificial water-retention layer contributes to the absorption of water from near-surface air. Due to the presence of permafrost in the Qinghai-Tibet Plateau region, the zero-flux surface transport of evanescent heat in the salt-lake area of Hoh Xil lies approximately within 30 cm from the surface to the ground. The analogous humidity coefficient characterizes the condensate absorption capacity coefficient as the storage capacity of condensate in the surface layer of the soil in a certain area, providing strong evidence that the condensate absorption capacity is higher under the artificial water-retention layer conditions than in bare ground, regardless of whether the condensation is bi-directional or unidirectional. The results of this study can provide a theoretical basis for condensate absorption capacity and vegetation restoration in the bare ecologically degraded areas of the lake bottom.

Study of the Cryosphere of the Zeravshan and Hissar Ranges (Tien Shan)

The paper presents brief results of studying the cryosphere of the Zeravshan and Hissar ranges. At the same time, the rate of change in the area of glaciers over the past almost a hundred years and the presence and degradation of permafrost during this time were considered. The actual description of the numerical method for estimating the depth of soil freezing based on data on the thickness of the snow cover and air temperature was also given. An example of the use of this numerical method for estimating the depth of soil freezing on slopes was given in order to map the cryolithozone of the Zeravshan and Hissar ranges. According to the calculations, the ground under the snow cover remains frozen on the Anzob pass from December to April. The power of the accumulated snow cover can reach one and a half meters or more. At the same time, the soil under the snow-covered surface freezes according to calculations by an average of 1.5 m. Thus, the proposed method for calculating the dynamics of the depth of soil freezing based on data on air temperature and the thickness of snow cover made it possible to assess the freezing of soil as a factor of soil stability during the construction of village and avalanche protection structures. Thus, the Anzob pass belongs to the area of seasonal freezing of rocks, taking into account the gradient of the average annual temperature of rocks, we can conclude that the appearance of permafrost rocks on the Hissar ridge can be expected at altitudes of more than 4,000 meters.

On the Spin‐Up Strategy for Spatial Modeling of Permafrost Dynamics: A Case Study on the Qinghai‐Tibet Plateau

AbstractSpin‐up is essential to provide initial conditions for land surface models (LSM) when they cannot be given reliably as in the application to regional permafrost change studies. In this study, the impacts of spin‐up strategy including total spin‐up length and cycling scheme on modeling of permafrost dynamics on the Qinghai‐Tibet Plateau (QTP) were evaluated through two groups of experiments using a modified Noah LSM. The first group aims to test different total spin‐up lengths and the second group for different cycling schemes. The results show that the presence of permafrost prolongs the convergence of the model. Vertically, the slowest convergence is observed at the permafrost table. The insufficiency of total spin‐up length is prone to underestimate permafrost area and overestimate the degradation rate. Different cycling schemes considerably affect the resulting initial thermal fields and result in degradation rates with a difference of 3.37 × 103 km2/a on the QTP, which exceeds the difference (2.92 × 103 km2/a) in the degradation rates reported in existing studies. The multi‐year cycling scheme is generally preferred, but overlong cycle length should be avoided to prevent the introduction of climate change trends in the spin‐up period. We recommend a spin‐up strategy of a 500‐year cycling with the first 5‐ to 10‐year of forcing for modeling permafrost on the QTP with the Noah LSM. Our findings highlight the importance of the spin‐up strategy, which is usually neglected in present LSM‐based permafrost modeling studies.

Role of rock glaciers and other high-altitude depositional units in the hydrology of the mountain watersheds of the Northern Patagonian Andes

Mountain depositional landforms are important units for freshwater supply in regions with water deficits and significant droughts during the summer season. In the Northern Patagonian Andes, the cold climatic events during the Pleistocene period left a large number of glacial and periglacial depositional landforms, among which a glacial cirque called La Hoya stands out. An analysis of geomorphological landforms, climatic data, soil temperature, flows in springs and streams, electrical conductivity measurements, and stable isotope determination of water, were made to study the hydrological role of these depositional mountain landforms. In this region, precipitations are concentrate during the winter season when an important snow cover accumulates and persists until spring. During winter and spring seasons, part of the snowmelt infiltrates, being kept in solid states inside the depositional landforms, and part of it contributes to the runoff between winter and summer. At the ends of spring and early summer, the snowmelt is the main water contribution to the La Hoya watershed. During late summer and autumn, the most important water contribution is from groundwater discharge. Where glacial ice is absent and the presence of permafrost is limited or non-existent, morphosedimentary units are important landforms for water storage and streams sustenance. This is the case of the city of Esquel, which depends exclusively on the “Los Bandidos” stream for water supply, which is sustained throughout the year by these landforms. The increase in temperature and the decrease in precipitation in this region highlights the importance of the high-altitude depositional landforms for the capture, storage, and distribution of water resources in the Northern Patagonian Andes.

Influence of Tanks Design Features on Earthquake Resistance in Permafrost Areas

Tanks for the storage of oil and gas play a special role in the oil and gas industry. During the construction and design of such structures in difficult geological conditions, increased attention is paid to their safe operation. The combined manifestation of seismic impacts and the presence of permafrost can pose an increased danger. The article presents an analysis of the various components of an oil and gas storage system. A comparative analysis of the seismic resistance of storage tanks was carried out, taking into account the presence of a thawed permafrost base in the base. It is shown that during thawing, the permafrost base can greatly affect the seismic resistance of the structure.

Natural gas content of the “Five-meter” coal seam of the Neryungrinskoye field

The article examines, analyzes and consolidates the results of research (direct and indirect research methods) of the gas content of the “Five-meter” seam of the Neryungrinsky coal deposit, which is slated for underground mining. The article also presents the criteria that determine the representativeness of the tested samples by the direct method, which allow the introduction of indirect methods for studying the gas content of the “Pyatimetrovy” formation of the Neryungri field without losing the reliability of the results. As a result of the analysis of the factual material and the geological situation at the field, as well as taking into account the data on the current state of open pit mining at the field, the following were identified: the main factors influencing the degree and nature of the gas content of the Pyatimetrovy layer of the Neryungrinskoye field; composition of gases, the inflow of which is expected to enter the mine atmosphere during mining operations to extract coal from the “Five-meter” seam by the underground method. The main results of the research presented in the article are: the identification of two main gas zones of the “Five-meter” formation with the construction of a gas zoning diagram along the depth of the formation; determination of the presence of gas traps at the field with low production rate of free gas, which are determined by the presence of permafrost in the field; establishing the influence of open pit mining at the deposit on the activation of the natural degassing process of the coal seam and its host rocks at the present stage. The quantitative indicators of the methane content of the coal seam in the field have been established, it has been noted that natural gases in the host rocks are identical to those in the reservoir.

Integrated environmental records in Late Pleistocene Poland: The paleofluvial regime and paleoclimate inferred from Krosinko site

Multiproxy analyses performed at the Krosinko site in the Warsaw–Berlin ice marginal valley have provided data that characterize the depositional conditions, the paleofluvial regime, and the paleoclimate and help reconstruct the paleo-environment at a time of significant sediment (alluvium) accumulation (starting in central Poland ca. 45 ka BP). The sedimentological study, including sand-grain morphology and micromorphology analyses, reveals the presence at Krosinko of a meandering river and of a braided river during the Eemian (MIS 5e) and Upper Pleniweichselian (MIS 2), respectively. The fluvial regime changed over time, from low-energy, through high-energy, to low-energy, as documented by the differently formed sedimentary units A–D (vertical sedimentary succession from base to top: sandy silt, sand, gravelly sand, and sand). Sedimentary unit A and the lower part of unit B were accumulated in the Eemian interglacial (MIS 5e) by the low-energy meandering river. The high-energy fluvial environment during the Weichselian is associated with long, intense sediment transport, organic remains, and flints, as confirmed by taphonomic studies on conifer cones (Picea cf. abies) and wood remains (Juniperus). The river operated under distinct environmental conditions. First, during the accumulation of the upper part of unit B and unit C, there was a strong influence of freezing and aeolian weathering, which weakened significantly over time (unit D). This in turn indicates a change in climate from periglacial (upper part of unit B and unit C), when we also document the presence of permafrost in the subsurface or relatively deep seasonal frost, to temperate (unit D). With warming in the Holocene (MIS 1), an oxbow lake developed in Krosinko, the presence of which is recorded by peat.

In-situ temperatures and thermal properties of the East Siberian Arctic shelf sediments: Key input for understanding the dynamics of subsea permafrost

Significant reserves of methane (CH4) are held in the Arctic shelf, but the release of CH4 to the overlying ocean and, subsequently, to the atmosphere has been believed to be restricted by impermeable subsea permafrost, which has sealed the upper sediment layers for thousands of years. Our studies demonstrate progressive degradation of subsea permafrost which controls the scales of CH4 release from the sediment into the water-atmospheric system. Thus, new knowledge about the thermal state of subsea permafrost is crucial for better understanding of the permafrost -hydrate system and associated CH4 release from the East Siberian Arctic Shelf (ESAS) – the broadest and shallowest shelf in the World Ocean, which contains about 80% of subsea permafrost and giant pools of hydrates. Meanwhile, the ESAS, still presents large knowledge gaps in many aspects, especially with respect to subsea permafrost distribution and physical properties of bottom sediments. New field data show that the ESAS has an unfrozen (ice-free) upper sediment layer, which in-situ temperature is −1.0 to −1.8 °C and 0.6оС above the freezing point. On one hand, these cold temperature patterns may be related to the presence of subsea permafrost, which currently primarily occurs in the part of the ESAS that is shallower than 100 m, while ice-bearing sediments may also exist locally under deeper water in the Laptev Sea. On the other hand, the negative bottom sediment temperatures of −1.8 °C measured on the Laptev Sea continental slope sediments underlying water columns as deep as down to 330 m may result from dissociation of gas hydrates or possibly from dense water cascading down from the shelf. In contrast, data collected on recent expeditions in the northern Laptev shelf, zones of warmer bottom temperatures are coinciding with methane seeps, likely induced by seismic and tectonic activity in the area. These warm temperatures are not seen in the East Siberian Sea area, not even in areas of methane seeps, yet with little seismic activity.The thermal conductivity and heat capacity of bottom sediments recorded in the database of thermal parameters for the ESAS areas mainly depend on their lithification degree (density or porosity), moisture content, and particle size distribution. The thermal conductivity and heat capacity average about 1.0 W/(m·K) and 2900 kJ/(m3·K), with ±20% and ±10% variance, respectively, in all sampled Arctic sediments to a sub-bottom interval of 0–0.5 m.

Modern Environmental-Economic Situation and Public Health in the Arctic Zone of the Republic of Sakha (Yakutia)

The article is devoted to the consideration of the main parameters of environmental pollution in the Arctic zone of the Republic of Sakha (Yakutia), AZRS, as well as to the analysis of their impact on the health status of the popula- tion of this region. The collected data indicate that the main source of pollutants in this case is the mining industry, additional sources are the energy sector, transport and reindeer husbandry. Their negative impact is enhanced by such natural features of the regional natural environment as the slow decomposition of pollutants due to the annual predominance of low temperatures and, due to the presence of permafrost, their concentration in the upper soil layers. As a result of the study of the state of health of the population of the AZRS, the main composition of regional pathologies was determined, and a territorial picture of the incidence of the population of the region was compiled. An assessment of the state of regional health care is given and some proposals are formulated to improve the ef- ficiency of its work.

Ostatni epizod vistuliańskiego chłodu: cechy diagnostyczne w obszarach ekstraglacjalnych

The general trend of paleogeographic events is dependent on global climate changes. In the analysis of short geological periods, a large role should be assigned to local conditions, understood both in the regional sense and, above all, at the microscale, i.e. the specificity of sites with different morphological location and lithological properties of the substratum, generating a strictly local course of morphogenetic processes reflected in geological records. In this context, a large role should be assigned to the smallest marks of disturbances. Interpretation difficulties that researchers of the Younger Dryas often encounter result from the small thickness of the sub-surface sediment and its weathering changes. The article shows how a detailed analysis of data from the abiotic sphere can be used to reconstruct the conditions prevailing in short geological periods. The area of study is situated in central Poland in an extraglacial zone of the last Quaternary ice sheet that during the Vistulian remained under periglacial conditions (Fig. 1). Among the diagnostic properties are: sedimentological palaeohydrological marks, traces of permafrost re-aggradation, oversnow deposits, aeolian specificity and random events. Changes in the hydrological regimes in rivers are reflected in changes in the sedimentary record showing effective floods (Fig. 2) and together with raising of groundwater table registered in biogenic baśni point two distinct phases of humidity. Traces of permafrost re-aggradation are scarce and found only in particular localities (e.g., under peatlands), but the environmental context of involutions reported from study sites allow us to conclude a return of frozen substratum (Figs 2, 4). The smallscale fissure and fault network in the deposits of the youngest unit of dry periglacial valleys dated to the Younger Dryas were linked to deposition on patches of frozen snow that lasted for several summers and, afterwards, a collapse of he deposit due to melting (Fig. 5). This process did not require the presence of permafrost. In the aeolian environment, the cool conditions of the Younger Dryas resulted locally in the deposition of thin sand covers (Figs 6, 8), which, in favourable topographic conditions, could even form initial dune ramparts (Fig. 7). In the Younger Dryas environment, morphogenetic processes may have been activated by a random event not necessarily associated with global climatic change. One potential example is traces of wildfires registered in a depositional sequence of the Żabieniec site.

Modelling Permafrost Distribution in Western Himalaya Using Remote Sensing and Field Observations

The presence and extent of permafrost in the Himalaya, which is a vital component of the cryosphere, remains severely under-researched with its future climatic-driven trajectory only partly understood and the future consequences on high-altitude ecosystem tentatively sketched out. Previous studies and available permafrost maps for the Himalaya relied primarily upon the modelled meteorological inputs to further model the likelihood of permafrost. Here, as a maiden attempt, we have quantified the distribution of permafrost at 30 m grid-resolution in the Western Himalaya using observations from multisource satellite datasets for estimating input parameters, namely temperature, potential incoming solar radiation (PISR), slope, aspect and land use, and cover. The results have been compared to previous studies and have been validated through field investigations and geomorphological proxies associated with permafrost presence. A large part of the study area is barren land (~69%) due to its extremely resistive climate condition with ~62% of the total area having a mean annual air temperature of (MAAT) &lt;1 °C. There is a high inter-annual variability indicated by varying standard deviation (1–3 °C) associated with MAAT with low standard deviation in southern part of the study area indicating low variations in areas with high temperatures and vice-versa. The majority of the study area is northerly (~36%) and southerly (~38%) oriented, receiving PISR between 1 and 2.5 MW/m2. The analysis of permafrost distribution using biennial mean air temperature (BMAT) for 2002-04 to 2018-20 suggests that the ~25% of the total study area has continuous permafrost, ~35% has discontinuous permafrost, ~1.5% has sporadic permafrost, and ~39% has no permafrost presence. The temporal analysis of permafrost distribution indicates a significant decrease in the permafrost cover in general and discontinuous permafrost in particular, from 2002-04 to 2018-20, with a loss of around 3% for the total area (~8340.48 km2). The present study will serve as an analogue for future permafrost studies to help understand the permafrost dynamics associated with the effects of the recent abrupt rise in temperature and change in precipitation pattern in the region.

Diagnosis of Atmospheric Drivers of High-Latitude Evapotranspiration Using Structural Equation Modeling

Evapotranspiration (ET) is a relevant component of the surface moisture budget and is associated with different drivers. The interrelated drivers cause variations at daily to interannual timescales. This study uses structural equation modeling to diagnose the drivers over an ensemble of 45 high-latitude sites, each of which provides at least several years of in situ measurements, including latent heat fluxes derived from eddy covariance flux towers. The sites are grouped by vegetation type (tundra, forest) and the presence or absence of permafrost to determine how the relative importance of different drivers depends on land surface characteristics. Factor analysis is used to quantify the common variance among the variables, while a path analysis procedure is used to assess the independent contributions of different variables. The variability of ET at forest sites generally shows a stronger dependence on relative humidity, while ET at tundra sites is more temperature-limited than moisture-limited. The path analysis shows that ET has a stronger direct correlation with solar radiation than with any other measured variable. Wind speed has the largest independent contribution to ET variability. The independent contribution of solar radiation is smaller because solar radiation also affects ET through various other drivers. The independent contribution of wind speed is especially apparent at forest wetland sites. For both tundra and forest vegetation, temperature loads higher on the first factor when permafrost is present, implying that ET will become less sensitive to temperature as permafrost thaws.

Contrasted effects of climate change on low-altitude relict Pinus uncinata stands in the Northern French Alps

This paper reports on climate-induced growth changes in relict, low-altitude mountain pines (Pinus uncinata Mill. ex. Mirb.) from two refugia with cold microclimates located in the Northern French Alps. The P. uncinata stands analyzed grow at the lower bound of their ecological limit and are thus thought to be sensitive indicators of ongoing climate change. Using dendroecological approaches, we compare tree-ring growth at two closely spaced low-altitude stands in the Chartreuse massif (French Alps): La Plagne and Cirque de Bresson. La Plagne is a N-NW-exposed, ventilated slope with cold air circulating in the scree during summer, and the presence of sporadic permafrost as well as ground overcooling, whereas Cirque de Bresson is located on a small, S-exposed fan with sporadic avalanche activity. At both sites, growth responses of P. uncinata to changes in twentieth and twenty-first centuries temperature and precipitation conditions were investigated by means of moving correlation analyses. At Cirque de Bresson, a significant and rapid decline in tree-ring widths has been observed since the early 1990s. We attribute this decline to (i) increasing air temperatures at the beginning of the growing season (May–June) as well as to (ii) a decrease in soil water potential. At La Plagne, we do not detect any significant trend between the higher summer temperatures and tree growth, presumably as a result of the circulation of cold air in the scree slope, which is thought to maintain fresh and humid soil conditions and therefore favor tree growth. These forest stands provide prime examples on how dendroecology can contribute to the study of the dynamics and local variability of tree growth and climate change in relict forest populations with high ecological and conservation values.

Similarities and distinctions in the genesis of salt-affected soils in different regions of the south of Eastern Siberia

Soil salinization is determined by a set of factors, which can be subdivided into sources and mechanisms. The south of Eastern Siberia is characterized by the mountainous topography with numerous intermontane depressions, a large number of tectonic faults and springs. Hydromorphic surface-saline soils of sulfate and chloride-sulfate chemistry predominate. In Tuva, the share of chloride salinity increases, which is associated with the presence of salt rocks, and the percentage of soda-saline soils decreases sharply. In Buryatia, the percentage of soda salinity is higher than in other regions. In Khakasia, despite the gypsum deposits, the percentage of soda-saline soils is also significant, which is related to irrigation practices. Sharper differences are observed in individual basins of the regions, the salinity of which is determined by the presence of salinization sources in the given area, as well as by the mechanisms and conditions of soil salinization. For example, the presence of permafrost prevents the leaching of chlorides from the profile leading to the development of chloride salinization, or an increase in the alkalinity associated with the magnesium bicarbonate in slightly arid intermontane depressions of Buryatia and high–mountain depressions of Tuva.

First evidence of rock wall permafrost in the Pyrenees (Vignemale peak, 3,298 m a.s.l., 42°46′16″N/0°08′33″W)

AbstractPermafrost is a relevant component of the Pyrenean high mountains, triggering a wide range of geomorphological cryogenic processes. Although in the past decades there has been an increase in frozen ground studies in the Pyrenees, there are no specific studies about rock wall permafrost, its presence, distribution, thermal regime, or historical evolution. This work combines measured rock surface temperatures (RSTs, from August 2013 to April 2016) along an elevation profile (four sites) on the north facing the rock wall of the Vignemale peak (3,298 m a.s.l., 42°46′16″N/0°08′33″W) and temperature modeling (CryoGRID2) to determine the presence of permafrost and to analyze its evolution since the mid‐20th century. Simulations are run with various RST forcings and bedrock properties to account for forcing data uncertainty and varying degrees of rock fracturing. Results reveal that warm permafrost may have existed down to 2,600 m a.s.l. until the early 1980s and that warm permafrost is currently found at ~2,800 m a.s.l. and up to 3,000 m a.s.l. Cold (&lt;−2°C) permafrost may exist above 3,100–3,200 m a.s.l. Systematic investigations on rock wall permafrost must be conducted to refine those results in the Pyrenees. The elevation shift in warm permafrost suggests an imminent disappearance of permafrost in the Vignemale peak.