Short time changes of permafrost degradation triggered by anthropogenic impact and climatic events in Yamal Peninsula, Western Siberia 2010 – 2013/2015

The Arctic is affected by rapid climate change, which has substantial impact on permafrost regions and the world as a whole (Raynolds et al., 2014). In the last 30 years Arctic temperatures have risen 0.6 °C per decade, twice as fast as the global average (AMAP, 2011, Schuur et al., 2015). This in turn leads to the degradation of ice-rich permafrost (Grosse et al., 2011) and modifies drainage, increases mass movements and alters landscapes (Nelson et al., 2001; Anisimov et al., 2007, Romanovsky et al., 2010b). Although permafrost regions are not densely populated, their economic importance has increased substantially in recent decades. This is related to the abundance of natural resources in the polar region and improved methods of hydrocarbon extraction, transportation networks to population centers and engineering maintenance systems (Nelson et al., 2002; Mazhitova et al., 2004, AMAP, 2011). The Yamal Peninsula in North West Siberia is experiencing some of the most rapid land cover and land use changes in the Arctic due to a combination of climate change and gas development in one of the most extensive industrial complexes (Kumpula et al., 2006; Walker et al., 2011; Leibman et al., 2015). Specific geological conditions with nutrient-poor sands, massive tabular ground ice and extensive landslides intensify these impacts (Walker et al., 2011). The combination of high natural erosion potential and anthropogenic influence cause extremely intensive rates of erosion (Gubarkov et al., 2014). A considerable amount of recent work has focused on the effects of industrial development to ecological and social implications (Forbes, 1999; Kumpula et al., 2010; Walker et al., 2011). This study aims at exemplarily investigating a region that has been affected by natural and anthropogenic large-scale disturbances within a very short period. The construction of the world’s northernmost railway for the Bovanenkvo Gas Field was finished in 2010. In addition the region experienced an extremly warm and wet summer in 2012. The objectives of this study are • to map surface disturbances of central Yamal between 2010 and 2013/2015 based on highresolution satellite imagery and on the most recent SPOT5-TAKE-5 imagery in 2015, • to quantify natural and anthropogenic impacts in terms of permafrost degradation, • to use meteorological data from the nearest climate station (Marre Sale, Yamal) and from reanalyses climate data on air temperature and precipitation

Spatial patterns of arctic tundra vegetation properties on different soils along the Eurasia Arctic Transect, and insights for a changing Arctic

Vegetation properties of arctic tundra vary dramatically across its full latitudinal extent, yet few studies have quantified tundra ecosystem properties across latitudinal gradients with field-based observations that can be related to remotely sensed proxies. Here we present data from field sampling of six locations along the Eurasia Arctic Transect in northwestern Siberia. We collected data on the aboveground vegetation biomass, the normalized difference vegetation index (NDVI), and the leaf area index (LAI) for both sandy and loamy soil types, and analyzed their spatial patterns. Aboveground biomass, NDVI, and LAI all increased with increasing summer warmth index (SWI—sum of monthly mean temperatures > 0 °C), although functions differed, as did sandy vs. loamy sites. Shrub biomass increased non-linearly with SWI, although shrub type biomass diverged with soil texture in the southernmost locations, with greater evergreen shrub biomass on sandy sites, and greater deciduous shrub biomass on loamy sites. Moss biomass peaked in the center of the gradient, whereas lichen biomass generally increased with SWI. Total aboveground biomass varied by two orders of magnitude, and shrubs increased from 0 g m−2 at the northernmost sites to >500 g m−2 at the forest-tundra ecotone. Current observations and estimates of increases in total aboveground and shrub biomass with climate warming in the Arctic fall short of what would represent a 'subzonal shift' based on our spatial data. Non-vascular (moss and lichen) biomass is a dominant component (>90% of the photosynthetic biomass) of the vegetation across the full extent of arctic tundra, and should continue to be recognized as crucial for Earth system modeling. This study is one of only a few that present data on tundra vegetation across the temperature extent of the biome, providing (a) key links to satellite-based vegetation indices, (b) baseline field-data for ecosystem change studies, and (c) context for the ongoing changes in arctic tundra vegetation.Non peer reviewe

Northern Hemisphere permafrost map based on TTOP modelling for 2000-2016 at 1 km²scale

Permafrost is a key element of the cryosphere and an essential climate variable in the Global Climate Observing System. There is no remote-sensing method available to reliably monitor the permafrost thermal state. To estimate permafrost distribution at a hemispheric scale, we employ an equilibrium state model for the temperature at the top of the permafrost (TTOP model) for the 2000–2016 period, driven by remotely-sensed land surface temperatures, down-scaled ERA-Interim climate reanalysis data, tundra wetness classes and landcover map from the ESA Landcover Climate Change Initiative (CCI) project. Subgrid variability of ground temperatures due to snow and landcover variability is represented in the model using subpixel statistics. The results are validated against borehole measurements and reviewed regionally. The accuracy of the modelled mean annual ground temperature (MAGT) at the top of the permafrost is ±2 °C when compared to permafrost borehole data. The modelled permafrost area (MAGT 0) is around 21 × 106 km2 (22% of exposed land area), which is approximately 2 × 106 km2 less than estimated previously. Detailed comparisons at a regional scale show that the model performs well in sparsely vegetated tundra regions and mountains, but is less accurate in densely vegetated boreal spruce and larch forests

Northern Hemisphere permafrost map based on TTOP modelling for 2000–2016 at 1 km2 scale

Permafrost is a key element of the cryosphere and an essential climate variable in the Global Climate Observing System. There is no remote-sensing method available to reliably monitor the permafrost thermal state. To estimate permafrost distribution at a hemispheric scale, we employ an equilibrium state model for the temperature at the top of the permafrost (TTOP model) for the 2000–2016 period, driven by remotely- sensed land surface temperatures, down-scaled ERA-Interim climate reanalysis data, tundra wetness classes and landcover map from the ESA Landcover Climate Change Initiative (CCI) project. Subgrid variability of ground temperatures due to snow and landcover variability is represented in the model using subpixel statistics. The results are validated against borehole measurements and reviewed regionally. The accuracy of the modelled mean annual ground temperature (MAGT) at the top of the permafrost is ±2 °C when compared to permafrost borehole data. The modelled permafrost area (MAGT 0) is around 21 × 106 km2 (22% of exposed land area), which is approximately 2 × 106 km2 less than estimated previously. Detailed comparisons at a regional scale show that the model performs well in sparsely vegetated tundra regions and mountains, but is less accurate in densely vegetated boreal spruce and larch forests

The impact of permafrost thaw and climatic fluctuations on the geochemistry of thermokarst lakes of Yamal peninsula

Climate warming in the Arctic might lead to increase of organic matter inflow to lakes by accelerating permafrost thaw and vegetation dynamics. Colored fraction of dissolved organic matter (CDOM) is a significant component of the aquatic ecosystems including thermokarst lakes in the high Arctic. The work presents results of study of CDOM in thermokarst lakes of Yamal peninsula (Western Siberia, Russia). CDOM absorption and spectral slope(S) values, suspended matter concentrations (SPM) in several thermokarst lakes were obtained during 2011 – 2015 field campaigns. Lake characteristics were compared with different catchment properties (cryogenic processes, geomorphology, productivity of vegetation, snow accumulation), hydrology (drainage regimes, seasonal water level changes, volume of lake water) as well as with climatic controls (air temperature, atmospheric precipitation). The climatic fluctuations and thermal denudation in the shore line seem to be responsible for the additional portion of terrestrial organic input into the thermokarst lakes. Measured CDOM concentration is at least twice higher in lakes affected by thermal denudation (and accompanied by declined S values) than in not affected lakes. The increase of CDOM concentration in 2012 compared to that in 2011 is probably due to higher summer air temperature and higher amount of atmospheric precipitation. Decrease of S values explains the increase of mobilized organic matter recently stored in permafrost in past years. Generally, variation of CDOM in studied lakes is very high due to different conditions in which the lakes are located. The catchment properties (especially vegetation) may explain the differences in CDOM concentrations between Yamal lakes. The presence of high productive shrubs and sedges in this particular area makes the CDOM concentration parameter comparable with more southern regions like taiga within the tree line

Yamal lakes (Siberia): properties derived from optical and SAR remote sensing

In this study a number of approaches was used to understand the process of organic transport to the lakes in several key sites of Russian Arctic. Among these approaches were i) direct field observations of “lake – catchment” systems, water sampling (2011-2014), geodetic (2011, 2014) and bathymetric (2012,2014), and snow (2013) measurements; ii) very high spatial resolution (GeoEye, QuickBird) optical remote sensing data application in lake water state investigations as well as the analysis of vegetation properties of catchments; iii) radar remote sensing (TerraSAR-X) data application to assess lake extent form year to year as well as to detect seasonal surface movements. It was established, that geochemical properties of thermokarst lakes could vary a lot in the different key sites depending on the geographic position and geomorphology. Climatic fluctuations led to various cryogenic activations (cryogenic landslides, thermocirques) and as a consequence, these activations resulted in a strong impact on redistribution of substances and changes in biochemical composition of the water bodies

Isotopic composition of oxygen (δ18О) and hydrogen (δD) of ice-wedge ice in central Yamal Peninsula

A new data on the isotope composition of oxygen (δ18О) and hydrogen (δD) of the ice-wedge ice in central Yamal Peninsula near Bovanenkovo gas field are presented. In the summer of 2019, ice wedges in the thermal circus of the third sea terrace was studied. On the terrace surface a polygon size of about 10-20 m is widespread. The ice wedge № 1 had a width in the upper part of 1.5, the apparent depth in exposure was 2.3 m. The ice wedge № 2 was stretched perpendicular to of the ice wedge № 1 and had a width of about 60 cm. A fragment of ice wedge № 3 in longitudinal section was opened 20 m from the ice wedges. Age of ice is established by AMS dating to be 13.6 cal. BP. The isotopic signature of ice (average δ18О and δD values were -24.8 and -187.6 ‰ respectively), corresponds to ice-wedges of the Yamal Peninsula formed during the MIS-2 isotope stage (end of Late Pleistocene). The oxygen isotope composition of ice indicates temperatures of the cold period of wedges formation around -22.8 ÷ -26.8 ⁰С (on average 7 ⁰С colder than modern), and January temperatures from -34.2 ÷ -40.2 ⁰С (on average 10 ⁰С colder than modern). For some ice samples, high values of deuterium excess were noted (from 12 to 17 ‰), which is unusual for this type of ice

Floristic complexes on landslides of different age in Central Yamal, West Siberian Low Arctic, Russia

Accurate ground-based datasets are important for correct interpretation of remote sensing data. West-Siberian Arctic has been exposed to rapid land-cover and land-use changes during the last 50 years. Cryogenic  landslides  are important disturbing agents in the region, especially in the central part of the Yamal Peninsula. Different succession stages in the recovery of cryogenic landslides are described at the example of 4 model ones formed respectively in 1989, in the middle of 1970s, in late 1950s or early 1960s and an ancient landslide back scarp dated with radiocarbon method as ca 1000 year old. Botanical survey was performed in 1991 and repeated in 2012, phytosociological study on the same landslides and their surroundings was performed in 1997–2002. Correlation between different syntaxa, age and morphological element of landslide is shown. Both projective cover and species composition change gradually on young and old landslides, though vegetation on the ancient ones did not change during the last 20 years. Pioneer communities on Yamal landslides are dominated by grasses (Deschampsia borealis, Puccinellia sibirica, Calamagrostis holmii, Poa alpigena ssp. colpodea, Dupontia fisheri ).  Proportion of various species differs both between years and different sections of the shear surface. Сarex glareosa indicating saline deposits was recorded on landslides of all stages. Mosses play important role in the recovery and formation of organic horizon on the young landslides. Geochemical properties of the groundwater were analyzed and correlation of different communities with different levels of mineralization of groundwater is shown. Vegetation allows estimate the age of younger landslides and indicates the sites of possible ancient detachment

Mean TerraSAR-X backscatter and in-situ measurements of near surface soil moisture and temperature including vegetation survey in August 2015 on central Yamal (Vaskiny Dachi CALM site)

The active layer above the permafrost, which seasonally thaws during summer, is an important parameter for monitoring the state of permafrost. Its thickness is typically measured locally, but a range of methods which utilize information from satellite data exist. Mostly, the normalized difference vegetation index (NDVI) obtained from optical satellite data is used as a proxy. The applicability has been demonstrated mostly for shallow depths of active-layer thickness (ALT) below approximately 70 cm. Some permafrost areas including central Yamal are, however, characterized by larger ALT. Surface properties including vegetation structure are also represented by microwave backscatter intensity. So far, the potential of such data for estimating ALT has not been explored. We therefore investigated the relationship between ALT and X-band synthetic aperture radar (SAR) backscatter of TerraSAR-X (averages for 10 × 10 m window) in order to examine the possibility of delineating ALT with continuous and larger spatial coverage in this area and compare it to the already-established method of using NDVI from Landsat (30 m). Our results show that the mutual dependency of ALT and TerraSAR-X backscatter on land cover types suggests a connection of both parameters. A range of 5 dB can be observed for an ALT range of 100 cm (40-140 cm), and an R² of 0.66 has been determined over the calibration sites. An increase of ALT with increasing backscatter can be determined. The root mean square error (RMSE) over a comparably heterogeneous validation site with maximum ALT of > 150 cm is 20 cm. Deviations are larger for measurement locations with mixed vegetation types (especially partial coverage by cryptogam crust) with respect to the spatial resolution of the satellite data