Monitoring of Thermokarst Lake Changes and Coastal Dynamics in Permafrost Landscapes of the East Siberian Sea Region Using High Resolution Imagery and DEM Data

The coastal region bordering the East-Siberian Sea is covered by ice-rich Yedoma deposits, which are extremely vulnerable to thaw in the course of climate warming in the high latitudes. Widespread permafrost degradation throughout the Arctic resulted in relief changes on ground-ice-cored Yedoma uplands. In order to track dynamics of these processes in the Kolyma lowland tundra at Cape Maly Chukochy (N 72.08°, E 159.9°), we used a set of very high resolution remote sensing imagery (GeoEye and historical airphotos) which were compared with DEM data (TanDEM-X and derived from WorldView-2). Analysis of meteorological data have put observed changes into the context of warming and wetting trends. Yedoma uplands represent flat bogged areas featuring a high number of thermokarst ponds with an average size of 5-10 in diameter. Our image dataset revealed a doubling in the number and areal coverage of ponds from 1972 to 2009 and a further twofold increase until 2013, while thermokarst lakes that formed within Yedoma deposits increased by 7-10 %, being partially in agreement with studies conducted elsewhere in the Arctic. Coastal erosion rates from 1972 until 2013 were high and 1,5 m per year on average. We used the areal extend of thermokarst mounds (baydzherakhs) on Yedoma slopes as indicator for ground ice melt and our estimates show a baydzherakhs coverage increase of 20 % by 2013. All these changes highlight the activation and acceleration of permafrost degradation on Yedoma uplands in response to increasing air temperatures and precipitation in the East-Siberian Sea coastal region

Innovative methods in the training of veterinarians

The purpose of the study is to analyze the process of integration of the method of case study with the elements of business games in the educational process of an agrarian university. By means of participant and non-participant observation in experimental student groups, the authors prove that the sophisticated innovative case study technology used in the classroom in the form of independent work combined with a business game creates conditions for the development of professional clinical thinking in students, as well as for the improvement of their creative and research abilities. It is found that the development of applied cases for independent work with their further use in business games during practical classes contributes to deeper assimilation of the learning material and provides for the development of both universal and professional competencies

Past and present thermokarst lake dynamics in the Yedoma Ice Complex region of North-Eastern Yakutia

Thermokarst lakes are typical components of the yedoma-alas dominated relief in the coastal lowlands of North- Eastern Yakutia and formed as a result of thawing Late Pleistocene ice-rich Yedoma Ice Complex (IC) deposits. The aim of our study is to estimate thermokarst lake area changes from the early Holocene onwards based on RS data. The decrease of thermokarst lake area from the early Holocene, taking into account total alas depression areas, is as much as 81-83 %. Modern climate warming has led to a general trend of thermokarst lake area decrease. Lake drainage occurs mostly on elevated sites with high Yedoma IC fraction while lake area increase is typical for low-lying areas with a small Yedoma IC fraction. The area increase of thermokarst ponds on flat, boggy yedoma surfaces indicates ice wedge degradation in response to rising summer air temperatures and precipitation

Landsat-Based Trend Analysis of Lake Dynamics across Northern Permafrost Regions

Lakes are a ubiquitous landscape feature in northern permafrost regions. They have a strong impact on carbon, energy and water fluxes and can be quite responsive to climate change. The monitoring of lake change in northern high latitudes, at a sufficiently accurate spatial and temporal resolution, is crucial for understanding the underlying processes driving lake change. To date, lake change studies in permafrost regions were based on a variety of different sources, image acquisition periods and single snapshots, and localized analysis, which hinders the comparison of different regions. Here, we present a methodology based on machine-learning based classification of robust trends of multi-spectral indices of Landsat data (TM, ETM+, OLI) and object-based lake detection, to analyze and compare the individual, local and regional lake dynamics of four different study sites (Alaska North Slope, Western Alaska, Central Yakutia, Kolyma Lowland) in the northern permafrost zone from 1999 to 2014. Regional patterns of lake area change on the Alaska North Slope (−0.69%), Western Alaska (−2.82%), and Kolyma Lowland (−0.51%) largely include increases due to thermokarst lake expansion, but more dominant lake area losses due to catastrophic lake drainage events. In contrast, Central Yakutia showed a remarkable increase in lake area of 48.48%, likely resulting from warmer and wetter climate conditions over the latter half of the study period. Within all study regions, variability in lake dynamics was associated with differences in permafrost characteristics, landscape position (i.e., upland vs. lowland), and surface geology. With the global availability of Landsat data and a consistent methodology for processing the input data derived from robust trends of multi-spectral indices, we demonstrate a transferability, scalability and consistency of lake change analysis within the northern permafrost region

Elevation Change Detection for Quantification of Extensive Permafrost Thaw Subsidence in East Siberian Coastal Lowlands

Permanently frozen ground in the Arctic is being destabilized by continuing permafrost degradation, an indicator of climate change in the northern high latitudes. Accelerated coastal erosion due to sea ice reduction and an increased intensity of ground settlement through ground ice melt caused by rising summer air temperatures result in widespread geomorphological activity. The objective of our study is to analyze time series of repeat terrestrial laser scanning (rLiDAR) for quantification of extensive land surface lowering through thaw subsidence, which is the main unknown in terms of recent landscape development in the vast but neglected coastal lowlands of the East Siberian Arctic. These in-situ data provide the basis for calibration and validation of large scale surface change assessments using very high resolution space-borne elevation data with high precision. Complementing our surveys, we conducted botanical mapping. This allows us to relate elevation differences to specific surface conditions and enhances our capabilities to extrapolate our local observations to larger areas through land-cover classifications of multispectral remote sensing data such as Sentinel-2. Additionally, highly detailed digital elevation models (DEMs) with sub-metre accuracy have been photogrammetrically derived from satellite stereo data. These DEMs contain valuable terrain height information for 3D change detection, in case of DEMs representing the state of a study area at different points in time. The results show that elevation differences are almost always negative. When calculated as rates over time, land surface lowering in the ground-ice-rich Siberian coastal lowlands permafrost amounts to 3-10 cm per year

Ponding vs. baydzherakh formation on Yedoma uplands: Implications for modern thermokarst development and thaw subsidence in North Yakutia

Permafrost landscapes of Northern Yakutia recently experienced a widespread warming of mean annual air temperatures and mean positive daily air temperatures during the arctic summer (Federov et al, 2014). Especially in the tundra zone this has led to increased active layer thickness (ALT) and suggests that thermokarst processes reactivate or intensify. However, particularly in the light of the enormous area underlain by ice and carbon-rich permafrost, still only few observations of permafrost-thaw related landscape dynamics exist. Permafrost degradation has consequences for local hydrology, ecosystems, biogeochemical cycling, and sometimes communities. For example in East Siberia, widespread and irreversible thaw subsidence of up to 11 cm per year has been detected on the arctic island Muostakh (Günther et al., 2015), where coastal erosion at average rates of 1.8 m/yr has not only reduced the island’s area by 25% over more than 60 years, but also provides a constant renewal of the erosional base. In this case, favorable drainage conditions provide the prerequisite for active layer thickness deepening during warm summers, when ground ice stability thresholds are exceeded and ground ice thaw and subsequent terrain lowering take place. Our combined approach of ground-based ALT measurements and remote sensing-derived observations of elevation change revealed an inverse connection of shallow seasonal thaw and strong long-term subsidence, which is related to the minimum depth where permafrost thaw encounters pure ground ice bodies. In this study, we focus not only on monitoring thermokarst and subsidence, but also aim to find commonalities and differences of change or no change on yedoma uplands, slopes, and thaw depressions on the landscape scale using multi-temporal digital elevation models (DEMs) from historical aerial photographies, modern satellite stereo imagery, and on-site repeat laser scanning campaigns. In this context, a best practice strategy for remote sensing data fusion combining 2D and 3D information from very high resolution imagery (GeoEye, WorldView, Kompsat, Alos Prism), complemented by local field measurements (meterology, ground temperature, geodetic surveys) on the Bykovsky Peninsula and Sobo-Sise in the Lena Delta, has been developed. In order to capture a large variety of sites across the Yedoma region, additional sites at Cape Mamontov Klyk in the Anabar-Olenyok Lowland, Bolshoy Lyakhovsky on the New Siberian Islands, and Cape Maliy Chukochiy in the Kolyma Lowland with less or no topographical ground control, were considered from the perspective of larger areal coverage. Our high spatial resolution monitoring for the last decades and in comparison for the last years, shows that the current relief development in ice-rich permafrost enhances not only drainage of thermokarst lakes, but also drainage of the entire terrain, which leads to the formation of thermokarst mounds (baydzherakhs) on slopes of yedoma uplands. In contrast, simultaneous ponding on poorly drained massive Yedoma blocks in immediate proximity, suggests thermokarst development. However, formation of new thermokarst lakes on yedoma uplands is limited by topographical and stratigraphical constraints (Morgenstern et al., 2011). Geomorphological mapping of Yedoma and Alas surfaces, baydzherakh fields and areas of newly formed ponds allows to differentiate and link observed topographical changes to specific processes of either thermokarst or denudation. First results show that widespread modern baydzherakh formation is indicative for large-scale permafrost thaw subsidence on yedoma uplands. References: Morgenstern, A., Grosse, G., Günther, F., Fedorova, I. & L. Schirrmeister [2011]: Spatial analyses of thermokarst lakes and basins in Yedoma landscapes of the Lena Delta, The Cryosphere, 5, 849-867, doi:10.5194/tc-5-849-2011. Günther, F., Overduin, P.P., Yakshina, I.A., Opel, T., Baranskaya, A.V. & M.N. Grigoriev [2015]: Observing Muostakh disappear: permafrost thaw subsidence and erosion of a ground-ice-rich island in response to arctic summer warming and sea ice reduction, The Cryosphere, 9, 151-178, doi:10.5194/tc-9-151-2015

Landscapes and thermokarst lake area changes in Yedoma regions under modern climate conditions, Kolyma lowland tundra

Recent landscape changes in the Yedoma region are particularly pronounced in varying thermokarst lake areas reflecting the reaction of the land surface on modern climate changes. However, although thermokarst lake change detection is essential for the quantification of water body expansion and drainage within a region, remote sensing-derived surface reflection trends additionally provide valuable information about the general landscape development. The aim of this research is to reveal the regularities of landscape and thermokarst lakes area changes in the Kolyma lowland tundra in comparison with meteorological data and geological and geomorphological features. The Kolyma lowland tundra occupies about 44500 km2 and is located in Northeast Yakutia within the continuous permafrost zone. Mapping of Quaternary deposits using Landsat images shows that Yedoma (Last Pleistocene remnants formed by ice-rich silty to sandy syngenetic deposits with large polygonal ice wedges) occupies only 16 % of the entire region, while the largest part of it is occupied by alas complex (72 %), formed as a result of Yedoma thaw during the Holocene (Veremeeva and Glushkova, 2016). For the analysis of the landscape and thermokarst lakes area changes of the last 15 years, the entire available Landsat archive from 1999 until 2015 was used for time-series analysis. For this purpose around 800 scenes were processed with an automated workflow, undergoing several necessary processing steps, such as masking, data distribution and calculation of multi-spectral indices. Multi-spectral indices (Landsat Tasseled Cap, NDVI, NDWI, NDMI) were calculated for each unobstructed (cloud-, shadow- and snow-free) observation within the summer months (June to September) between 1999 and 2015. A robust linear trend analysis has been applied to each pixel for the spatial representation of changes of different land surface properties over the observation period. This map shows the magnitude and direction of changes for each multi-spectral index, which are used as proxies for different land-surface properties. For single locations, the entire time-series can be further analyzed in more detail. For the period from 1999 till 2005 air temperatures and precipitation have been analysed for several weather stations that existed in the region. The Landsat time series analysis for the last 15 years shows that the northern part of the region became wetter over the last 5 – 6 years. The alases are particularly affected by the wetting trend. The analysis of the meteo-data shows a trend of increasing air temperature and especially precipitation during the summer from 2010. The wetness increase, particularly on the coastal zone, is supported by the fact that air temperature trends are the largest at near-coastal meteorological stations. This increase of air temperatures and precipitation is likely connected to the reduced sea ice cover (Bekryaev et al., 2010). The strongest wetness increase were observed in the most northern part of the region within a 50 km wide zone along the East-Siberian sea shore between lowest stream of the Alazeya and Galgavaam rivers. This region is characterised by average terrain heights about 10-20 m, the yedoma and thermokarst lakes area here is about 10-20 %. There are less increase of wetness in the southern and eastern part of the coastal zone between Galgavaam and Bolshaya Chukochya rivers which is characterized by average heights of 0-10 m. The lakes area here is about 40 % and yedoma covers less then 10 % of the territory. Thus the strongest wetness trend for the northern coastal zone can be explained by the high degree of yedoma preservation and its thawing due to the coastal location and higher impact of the increasing temperatures and precipitation. For the recent past from 1999 to 2015, thermokarst lake changes were analysed visually based on the time series trend. For most thermokarst lakes of the Kolyma lowland tundra lake area was increasing from 1999 till 2015, however the trend is not significant. Some of the lakes partially or completely drained. Thermokarst lakes area coverage was quantified based on seven Landsat 8 images for the time period 2013 – 2014. In order to ensure consistency regarding surface moisture, only images acquired from August till September have been used. Atmospheric correction of each image was done for radiometric normalization across the dataset. An increase in ground resolution of the 30m multi-spectral data was achieved through resolution merge with the panchromatic channel to 15m pixel size. Subsequent mosaicking, classification and raster to vector conversion was done for the entire Kolyma lowland tundra. Thermokarst lakes cover about 12.9 % of the Kolyma lowland tundra. For the key investigation area located in the southern tundra around Lake Bolshoy Oler, which covers an area of 2800 km2 , a comparison with lakes mapped in CORONA images from July 21, 1965 and lakes mapped in the 2014 Landsat mosaic was carried for analysis of changes over time during a period of up to 50 years. The overall thermokarst lake area for this region in 1965 and 2014 was 590 and 549 km2 respectively. This corresponds to a limnicity decrease of 1.5 % within the study site from 21.1 to 19.6 %. About one third of this lake area decrease is due to partial drainage of big lakes with the area in 1965 and 2014 of 141.8 and 96.3 km2, respectively. Analysis of the summer air temperature and precipitation trends from the 1965 till 2015 also shown the trend of their increasing. Therefore, despite the fact that many persistent thermokarst lakes in the Kolyma lowland tundra are increasing in area, modern climate conditions generally seem to favor further relief drainage development. Consequently, thermokarst lake drainage outpaces thermokarst lake growth. This heterogeneous pattern suggests that permafrost degradation and aggradation in the region proceed simultaneously close together. Acknowledgements: This study was supported by the Russian foundation for basic research grant 14-05-31368 and by the ERC grant 338335. References: Bekryaev R.V., Polyakov I.V., Alexeev V.A. 2010. Role of polar amplification in temperature variations and modern Arctic warming. J. Clim. 23(14): 3888– 906. Veremeeva A.A., Gklushkova N.V. 2016. Relief formation in the regions of the Ice Complex deposit occurrence: remote sensing and GIS-studies, tundra zone of Kolyma lowland, Northeast Siberia. Earth’s Cryosphere, vol. XX, 1, pp.15-25