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  • 1
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    Retreat of top cliff of Kurungnakh Island, Lena Delta, Siberia, Russia, 2010-2014, with links to shapefiles (2015)
    PANGAEA
    In:  Alfred Wegener Institute - Research Unit Potsdam
    Details
    Publication Date: 2023-01-13
    Description: Thawing-induced cliff top retreat in permafrost landscapes is mainly due to thermo-erosion. Ground-ice-rich permafrost landscapes are specifically vulnerable to thermo-erosion and may show high degradation rates. Within the HGF Alliance Remote Sensing and the FP7 PAGE21 permafrost programs we investigated how SAR and optical remote sensing can contribute to the monitoring of erosion rates of ice-rich cliffs in Arctic Siberia (Lena Delta, Russia). We produced two different vector products: i) Intra-annual cliff top retreat based on TerraSAR-X (TSX) satellite data (2012-2014): High-temporal resolution time series of TSX satellite data allow the inter-annual and intra-annual monitoring of the upper cliff-line retreat also under bad weather conditions and continuous cloud coverage. This published SAR product contains the retreating upper cliff lines of a 1.5 km long part of eroding ice-rich coast of Kurungnakh Island in the central Lena Delta. The upper cliff line was mapped using a thresholding approach for images acquired in the years 2012, 2013 and 2014 for the months June (2013, 2014), July (2013, 2014), August (2012, 2013, 2014) and September (2013, 2014). The cliff top retreat vector product is called 'upper_cliff_TerraSAR-X'. While the 2014 cliff lines show a clear retreat of 2 to 3 m/month, the cliff top lines for 2012 and 2013 are not chronologically ordered. However, lines from the end of the season of a year are always close to the lines from the beginning of the next summer season, indicating low cliff retreat in winter. ii) 4-year cliff top retreat based on optical satellite data (2010-2014): Long-term cliff top retreat could be assessed with two high-spatial resolution optical satellite images (GeoEye-1, 2010-08-05 and Worldview-1, 2014-08-19). The cliff top retreat vector product is called 'upper_cliff_optical'. Results: The long-term cliff top retreat derived from optical satellite data are 35 m cliff retreat within 4 years. The higher-temporal resolution SAR data equivalently show long-term rates of 18 m within 2 years and nearly now degradation activities in winter but maximum erosion rates in summer months.The Intra-seasonal cliff top retreat lines from 2014 show a rate of 2 to 3 m per month.
    Keywords: AWI Arctic Land Expedition; DATE/TIME; Date/time end; File content; Kurungnakh_Island; Lena2013; RU-Land_2013_Lena; SAT; Satellite remote sensing; Uniform resource locator/link to file
    Type: Dataset
    Format: text/tab-separated-values, 6 data points
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    DATA PANGAEA
  • 2
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    Exploring the applicability of high temporal resolution SAR for monitoring permafrost landscapes (2016)
    In:  EPIC3ESA Living Planet Symposium 2016, Prague, 2016-05-09-2016-05-14
    Details
    Publication Date: 2016-07-05
    Description: Permafrost is stated as an essential climate variable by the World Meteorological Organization and is an important physical landscape component of high-latitude environments. The variability of the permafrost ecosystem parameters soil moisture (SM) as well as freeze-thaw (FT) has a strong impact on rapid permafrost degradation, on surface energy and water fluxes as well as on biogeochemical processes. Thus information about the mentioned parameters in high temporal and spatial resolution is important for the understanding of processes in permafrost landscapes. Synthetic aperture radar (SAR) operates independently of cloud coverage and polar night and today’s SAR satellite systems provide imagery with high temporal and spatial resolution. Existing operational satellite SAR data products of SM and FT are available only in coarse-scale resolution. We are investigating high-spatial resolution SAR of TerraSAR-X (TSX), and in future ALOS-2, Sentinel-1, as well as optical very high resolution satellite imagery in combination with in-situ experimental monitoring data to investigate the spatiotemporal variability of permafrost disturbances, SM and FT on the watershed scale. Our study site for rapid permafrost degradation is an actively eroding ice- and organic-rich permafrost riverbank from the so called Ice-Complex within the central Lena Delta, Siberia. Our studies on SM and FT focus on a small scale watershed on Herschel Island along the western Yukon Coast, Canada and can potentially be transferred to the Ice-Complex permafrost landscape in the Lena Delta. Automated micro-stations with near to surface soil moisture and temperature sensors were installed in the Lena Delta (since 2013) and on Herschel Island (since 2015). Field work on Herschel Island and the Lena Delta included handheld soil moisture measurements as well as extensive soil sampling. In spring 2015 we conducted a GPS survey in the Lena Delta along the test site and installed a time-lapse camera as well as wooden poles with 50cm distance perpendicular to a rapidly eroding cliff top sequence. Time-lapse images were acquired from late June to late August. We used TSX backscatter time-series from the years 2012, 2013, 2014 and 2015 to analyze rapidly eroding cliff tops along the riverbank within the central Lena Delta. Pre-processing was performed using the Next ESA SAR toolbox (NEST) and included radiometric calibration and conversion to backscatter coefficient sigma nought, multilooking and an ellipsoid corrected geocoding. We then used a threshold approach to visualize the transition line between undisturbed tundra surface and actively eroding cliff prior to mapping. Very high resolution orthorectified optical satellite images acquired in August 2010 and August 2014 were used as validation datasets for the TSX-derived results. The TSX extracted annual retreat rates are in the same range as the ones from the optical reference dataset. The intra-annual TSX-derived cliff top retreat lines from 2014 at the test site showed rates of 2 to 3 m per month. The time-lapse field data at the same place showed similar results in summer 2015. The TSX backscatter time-series show a high potential for the monitoring of rapid permafrost degradation with high spatial and temporal resolution. The results are valuable for the understanding of intra-seasonal permafrost degradation dynamics. Future work on Herschel Island and the Lena Delta will focus on soil moisture and freeze/thaw dynamics on the watershed scale. ALOS-2, Sentinel-1 and TSX datasets are planned to be used and cross-validated with the field datasets. The presented project is embedded in the German Helmholtz Alliance Earth System Dynamics (EDA) network and builds on existing datasets from the FP7 within the PAGE21 project. TSX-datasets were kindly provided by the Department Land Surface from the German Aerospace Agency (DLR).
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 3
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    Intra-annual dynamics of ice-rich riverbank erosion in the central Lena Delta (2016)
    In:  EPIC3XI. International Conference on Permafrost, Potsdam, Germany, 2016-06-20-2016-06-24
    Details
    Publication Date: 2016-07-05
    Description: Arctic warming accelerates the rapid degradation of ice- and organic-rich permafrost landscapes through thermokarst and thermal-erosion. These processes lead to the retreat of ice-rich coasts, riverbanks, lake shorelines, to surface subsidence and gullying. The subsequent reactivation of ancient carbon previously stored in the eroded ice- and organic-rich sediments could have tremendous impact on the carbon cycle from regional to global scale. Yet, information at high temporal and spatial resolution is often lacking to describe the rates and the timing of permafrost degradation. Synthetic aperture radar (SAR), which operates independently of atmospheric distortions, is particularly valuable to alleviate these issues because of its potential for high temporal resolution monitoring in a region where cloud cover often limits the use of optical satellite imagery. In this study, we used SAR data to investigate the spatiotemporal dynamic of a rapidly degrading ice- and organic-rich up to 50-m-high and 2000-m long riverbank in the central Lena Delta. Our main objectives were to 1) assess the applicability of synthetic aperture radar (SAR) satellite data for high-temporal resolution monitoring of rapidly eroding riverbanks and 2) to identify the seasonal timing of ice-rich permafrost riverbank erosion. We analyzed a unique time-series of high-spatial and temporal SAR images from the German TerraSAR-X (TSX) satellite, operating in X-band wavelength, as well as very high resolution optical satellite imagery and in-situ time-lapse data. We processed 77 HH- polarized SAR backscatter images with acquisition dates between August 2012 and October 2015. The imagery was first pre-processed using the Sentinel-1 toolbox from the European Space Agency. We then applied a thresholding to better identify the transition line from undisturbed tundra surface to the actively eroding cliff we refer to as cliff top line. We then calculated cliff top retreat rates and finally compared these with environmental baseline data to identify the main driving factors of riverbank retreat. Visual interpretation of the TSX time-series showed that the cliff of the riverbank is only visible in the months June to October. Annual erosion rates were in the same range when comparing the optical reference with the SAR datasets. The in-situ time-lapse data for the summer of 2015 showed similar results for the intra-annual erosion compared to the SAR derived results. Based on the SAR dataset we detected mostly constant erosion rates at our test site throughout the thawing period for the years 2013, 2014 and 2015. Our results show that the cliff-top at the test site retreats constantly over the thawing season rather than event driven (i.e. through the spring peak discharge only). The studied cliff top is protected from spring flood events by sandbanks in front of the riverbank. However, runoff caused by permafrost thaw, precipitation and flooding will degrade the protecting sand banks and consequently will lead to a reconnection of the cliff system to the Lena River System, even when water level is lower towards the end of the thawing season. We conclude that x-band backscatter time-series are valuable for monitoring rapid permafrost degradation with high spatial and temporal resolution. Our results indicate that cliff top erosion of ice-rich riverbanks takes place constantly over the thawing period and is not event driven.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 4
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    Analyzing intra-seasonal dynamics of ice-rich permafrost degradation in the Lena Delta using TerraSAR-X backscatter time-series (2015)
    In:  EPIC3ArcticNet Annual Scientific Meeting 2015, Vancouver, Canada, 2015-12-07-2015-12-11
    Details
    Publication Date: 2016-07-08
    Description: Arctic warming is leading to substantial changes of Arctic environments, such as the rapid degradation of ice- and organic-rich permafrost coasts and riverbanks. Reactivation of these ancient carbon pools and the release of carbon to the atmosphere could further accelerate climate warming. Short and long term annual retreat rates of permafrost coasts and riverbanks are mostly based on optical aerial and satellite imagery. However, in the Arctic cloud coverage often limits the use of optical remote sensing. Synthetic aperture radar (SAR) systems operate unaffected by atmospheric distortions. SAR data with high temporal resolution imagery can be used to detect seasonal variations of coastal retreat. The TerraSAR-X (TSX) satellite of the German Space Agency (DLR) is a X-band active microwave system that provides high-spatial (2 m ground resolution) and temporal resolution (11 day repeat period). We used a TSX backscatter time-series from the years 2012, 2013, 2014 and 2015 to analyze rapidly eroding cliff tops along an ice- and organic-rich permafrost riverbank within the central Lena Delta. The images were analyzed using a threshold approach. The clearly visible transition line between undisturbed tundra surface and actively eroding cliff was subsequently mapped for every image. Very high resolution optical satellite images acquired in August 2010 and August 2014 were used to validate the TSX results. In spring 2015 we conducted a GPS survey and installed a time-lapse camera as well as wooden poles with 50cm distance perpendicular to a rapidly eroding cliff top sequence. Time-lapse images were acquired from late June to late August. The TSX extracted annual retreat rates are in the same range as the ones from the optical reference dataset. The intra-seasonal cliff top retreat lines from 2014 showed equal rates of 2 to 3 m per month. The time-lapse field data at the same place showed similar rates in summer 2015. TSX backscatter time-series show a high potential for monitoring rapid permafrost degradation with high spatial and temporal resolution. The results are valuable for the understanding of degradation process dynamics within a summer season. In the second part of the project we will focus on near to surface soil moisture and freeze and thaw dynamics on the watershed scale on Herschel Island, Yukon territory. In summer 2015 we installed four automated stations that measure near to surface soil moisture and temperature within a watershed on Herschel Island.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 5
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    TerraSAR-X Time Series Fill a Gap in Spaceborne Snowmelt Monitoring of Small Arctic Catchments—A Case Study on Qikiqtaruk(Herschel Island), Canada (2018)
    MDPI
    In:  EPIC3Remote Sensing, MDPI, 10(1155)
    Details
    Publication Date: 2019-08-23
    Description: The timing of snowmelt is an important turning point in the seasonal cycle of small Arctic catchments. The TerraSAR-X (TSX) satellite mission is a synthetic aperture radar system (SAR) with high potential to measure the high spatiotemporal variability of snow cover extent (SCE) and fractional snow cover (FSC) on the small catchment scale. We investigate the performance of multi-polarized and multi-pass TSX X-Band SAR data in monitoring SCE and FSC in small Arctic tundra catchments of Qikiqtaruk (Herschel Island) off the Yukon Coast in the Western Canadian Arctic. We applied a threshold based segmentation on ratio images between TSX images with wet snow and a dry snow reference, and tested the performance of two different thresholds. We quantitatively compared TSX- and Landsat 8-derived SCE maps using confusion matrices and analyzed the spatiotemporal dynamics of snowmelt from 2015 to 2017 using TSX, Landsat 8 and in situ time lapse data. Our data showed that the quality of SCE maps from TSX X-Band data is strongly influenced by polarization and to a lesser degree by incidence angle. VH polarized TSX data performed best in deriving SCE when compared to Landsat 8. TSX derived SCE maps from VH polarization detected late lying snow patches that were not detected by Landsat 8. Results of a local assessment of TSX FSC against the in situ data showed that TSX FSC accurately captured the temporal dynamics of different snow melt regimes that were related to topographic characteristics of the studied catchments. Both in situ and TSX FSC showed a longer snowmelt period in a catchment with higher contributions of steep valleys and a shorter snowmelt period in a catchment with higher contributions of upland terrain. Landsat 8 had fundamental data gaps during the snowmelt period in all 3 years due to cloud cover. The results also revealed that by choosing a positive threshold of 1 dB, detection of ice layers due to diurnal temperature variations resulted in a more accurate estimation of snow cover than a negative threshold that detects wet snow alone. We find that TSX X-Band data in VH polarization performs at a comparable quality to Landsat 8 in deriving SCE maps when a positive threshold is used. We conclude that TSX data polarization can be used to accurately monitor snowmelt events at high temporal and spatial resolution, overcoming limitations of Landsat 8, which due to cloud related data gaps generally only indicated the onset and end of snowmelt.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    New results of the very high-resolution UAV surveys of the Yukon coast: Border to King Point (2018)
    In:  EPIC3Arctic Net, Ottawa, 2018-12-10-2018-12-14
    Details
    Publication Date: 2020-11-23
    Description: Climate models indicate the highest warming rates for the high latitudes, especially for the Arctic. Recent estimates indicate that the release of previously frozen organic carbon and its transformation into greenhouse gases may push global climate warming above the 1.5 °C targeted in the COP21 Paris Agreement (Schuur et al., 2015). Despite efforts to include carbon fluxes from permafrost degradation in climate models, the lateral fluxes of organic matter from land to sea are still not accounted for (Vonk and Gustafsson, 2013). Arctic permafrost coasts are major carbon (Schuur et al., 2015) and mercury pools (Schuster et al 2018) and represent about 34% of Earth’s coastline, with large sectors affected by significant erosion rates (Fritz et al, 2017). Year-round reduction in Arctic sea ice is forecasted and by the end of the 21st century, models indicate a decrease in sea ice area ranging from 43 to 94% in September and from 8 to 34% in February (IPCC, 2014). An increase of the sea-ice free season duration will expose coasts to wave action, extending the erosion into the shoulder seasons. Changing climate will also modify the contribution of terrestrial erosion, e.g. thermokarst, gully erosion and retrogressive thaw slumps (Fritz et al., 2015, Ramage et al 2017, 2018, Irrgang et al 2018). Understanding the current processes and both inter- and intra-annual dynamics of coastal erosion in the Arctic is essential to better predict future coastal erosion rates and hence to improve carbon and contaminant flux estimates. Following previous research by the Geological Research of Canada and the Alfred Wegener Institute, in July-August 2018, we resurveyed several long-term monitoring sites from the Canada-US border to King Point: Border, Clarence, Nunaluk, Herschel’s slumps A, B, C, D and Tina’s, Stokes West, Kay Point and King Point. Traditionally the repeat surveys were conducted using a DGPS survey along fixed transects that cross-cutted each site. In 2018, we have partially repeated the DGPS surveying and surveyed all sites with a SenseFly RTK ebee UAV with a S.O.D.A. camera and a Trimble R4 base station, allowing for preliminary model accuracies of ci. 10 cm. The poster shows the results of the 2018 surveys and first comparisons with data from previous seasons, including a discussion of the main results and methodological adjustments that may be needed for the 2019 surveys. This research is integrated in the H2020 European Union project Nunataryuk - Permafrost thaw and the changing Arctic coast, science for socioeconomic adaptation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev , info:eu-repo/semantics/conferenceObject
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  • 7
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    Monitoring Inter- and Intra-Seasonal Dynamics of Rapidly Degrading Ice-Rich Permafrost Riverbanks in the Lena Delta with TerraSAR-X Time Series (2017)
    Multidisciplinary Digital Publishing Institute
    In:  EPIC3Remote Sensing, Multidisciplinary Digital Publishing Institute, 10(1), ISSN: 2072-4292
    Details
    Publication Date: 2020-06-14
    Description: Arctic warming is leading to substantial changes to permafrost including rapid degradation of ice and ice-rich coasts and riverbanks. In this study, we present and evaluate a high spatiotemporal resolution three-year time series of X-Band microwave satellite data from the TerraSAR-X (TSX) satellite to quantify cliff-top erosion (CTE) of an ice-rich permafrost riverbank in the central Lena Delta. We apply a threshold on TSX backscatter images and automatically extract cliff-top lines to derive intra- and inter-annual CTE. In order to examine the drivers of erosion we statistically compare CTE with climatic baseline data using linear mixed models and analysis of variance (ANOVA). Our evaluation of TSX-derived CTE against annual optical-derived CTE and seasonal in situ measurements showed good agreement between all three datasets. We observed continuous erosion from June to September in 2014 and 2015 with no significant seasonality across the thawing season. We found the highest net annual cliff-top erosion of 6.9 m in 2014, in accordance with above-average mean temperatures and thawing degree days as well as low precipitation. We found high net annual erosion and erosion variability in 2015 associated with moderate mean temperatures but above average precipitation. According to linear mixed models, climate parameters alone could not explain intra-seasonal erosional patterns and additional factors such as ground ice content likely drive the observed erosion. Finally, mean backscatter intensity on the cliff surface decreased from −5.29 to −6.69 dB from 2013 to 2015, respectively, likely resulting from changes in surface geometry and properties that could be connected to partial slope stabilization. Overall, we conclude that X-Band backscatter time series can successfully be used to complement optical remote sensing and in situ monitoring of rapid tundra permafrost erosion at riverbanks and coasts by reliably providing information about intra-seasonal dynamics.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
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    Thermo‐erosional valleys in Siberian ice‐rich permafrost (2021)
    Details
    Publication Date: 2021-07-04
    Description: Thermal erosion is a major mechanism of permafrost degradation, resulting in characteristic landforms. We inventory thermo‐erosional valleys in ice‐rich coastal lowlands adjacent to the Siberian Laptev Sea based on remote sensing, Geographic Information System (GIS), and field investigations for a first regional assessment of their spatial distribution and characteristics. Three study areas with similar geological (Yedoma Ice Complex) but diverse geomorphological conditions vary in valley areal extent, incision depth, and branching geometry. The most extensive valley networks are incised deeply (up to 35 m) into the broad inclined lowland around Mamontov Klyk. The flat, low‐lying plain forming the Buor Khaya Peninsula is more degraded by thermokarst and characterized by long valleys of lower depth with short tributaries. Small, isolated Yedoma Ice Complex remnants in the Lena River Delta predominantly exhibit shorter but deep valleys. Based on these hydrographical network and topography assessments, we discuss geomorphological and hydrological connections to erosion processes. Relative catchment size along with regional slope interact with other Holocene relief‐forming processes such as thermokarst and neotectonics. Our findings suggest that thermo‐erosional valleys are prominent, hitherto overlooked permafrost degradation landforms that add to impacts on biogeochemical cycling, sediment transport, and hydrology in the degrading Siberian Yedoma Ice Complex.
    Description: Christiane Nüsslein‐Volhard Foundation
    Description: European Research Council http://dx.doi.org/10.13039/501100000781
    Description: German Academic Exchange Service DAAD P.R.I.M.E.
    Description: Helmholtz‐Gemeinschaft http://dx.doi.org/10.13039/501100001656
    Description: Polar Geospatial Center, NSF‐OPP awards
    Description: RapidEye Science Archive (RESA)
    Description: Russian Foundation for Basic Research http://dx.doi.org/10.13039/501100002261
    Description: Studienstiftung des Deutschen Volkes http://dx.doi.org/10.13039/501100004350
    Description: Universität Potsdam http://dx.doi.org/10.13039/501100004238
    Description: BMBF KoPf
    Keywords: 551.3 ; geomorphology ; periglacial landscapes ; permafrost degradation ; thermal erosion ; valley distribution ; Yedoma Ice Complex
    Type: article
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  • 9
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    Degradation of Ice Complex deposits in the Laptev Sea region - Geomorphological investigations combining remote sensing, GIS, and field data (2015)
    V.B. Sochava Institute of Geography SB RAS Publishers
    In:  EPIC3IX All-Russian Conference on Quaternary Research, Irkutsk, Russia, 2015-09-15-2015-09-20Irkutsk, Russia, V.B. Sochava Institute of Geography SB RAS Publishers
    Details
    Publication Date: 2015-12-09
    Description: Возросший научный интерес к деградации ледового комплекса в последнее время вызван актуальностью вопросов климатических изменений. Высокая уязвимость многолетнемерзлых отложений ледового комплекса связана с высоким содержанием в нем льда и лабильных органических веществ, что при потеплении климата, может привести к высвобождению парниковых газов в атмосферу. Термокарст и термоэрозия – два основных типа деградации многолетнемерзлых пород арктических равнин, и в частности регионов распространения ледового комплекса. Эти процессы и формирующиеся в результате формы рельефа способствуют высвобождению органических веществ в атмосферу и в гидросферу, а также могут оказать существенное влияние на водные и энергетические балансы подверженных их влиянию ландшафтов. В то время как термокарстовые процессы широко изучены, процессы термоэрозии исследованы недостаточно, несмотря на то, что соответствующие им формы рельефа, такие как термоэрозионные овраги, долины и долинные сети, широко распространены в регионе ледового комплекса. Нами было исследовано 1) воздействие термоэрозионных процессов на трансформацию рельефа в регионе моря Лаптевых с начала голоцена и 2) интенсивность современных термоэрозионных процессов и развитие форм рельефа в дельте р. Лены. Исследование и описание термоэрозионных форм рельефа на региональном уровне с использованием ГИС-анализа данных дистанционного зондирования, цифровых моделей рельефа и полевых исследований показали, что в Голоцене в некоторых частях дельты термоэрозия оказывала сильное влияние на деградацию ледового комплекса и гораздо более значительное, чем термокарст. Значительные различия в морфологии и пространственном распределении водотоков и термоэрозионных оврагов наблюдались между различными районами ледового комплекса, что связано с разницей размеров исследуемых районов, их рельефом и преобладающими криолитологическими свойствами, а также со степенью предыдущей деградации ледового комплекса термокарстом. Сравнение спутниковых снимков, полученных в период с 1964 по 2011 год показывает увеличение длины термоэрозионных водотоков и долин в пределах ледового комплекса дельты р. Лены на 1,6 %. При этом интенсивность современных термоэрозионных процессов сильно отличается в различных частях дельты, а также в течение различных промежутков времени.
    Repository Name: EPIC Alfred Wegener Institut
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  • 10
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    Characterizing thermo-erosional landforms in Siberian ice-rich permafrost. Morphometric investigations in the Lena Delta using high-resolution satellite imagery and digital elevation models (2015)
    In:  EPIC378 p.
    Details
    Publication Date: 2015-03-12
    Description: Rapid warming of the Arctic promotes widespread degradation of permafrost and affects the stability of arctic ecosystems. Thermokarst and thermal erosion are two major processes of permafrost degradation. The spatial extent of thermo-erosional processes and related landforms (e.g. gullies and valleys) and their impact on the widespread degradation of permafrost remains not well quantified. Addressing this research gap, this study is using a combination of field data, high-resolution satellite data and photogrammetically derived digital elevation models (DEMs) to conduct a detailed inventory and spatial analysis of thermo-erosional landforms in order to understand their dynamics as well as their relevance for permafrost degradation. The study area in the central Lena Delta is mainly composed of ice- and organic-rich and syngenetically frozen deposits of Late Pleistocene age called Ice Complex. Besides polygonal tundra, thermokarst lakes, wide thermokarst depressions and undisturbed Ice Complex surfaces the study area features a broad variety of thermo-erosional valleys. During an expedition in summer 2013 RTK GPS measurements of 11 ground control points and 28 transversal and 4 longitudinal profiles were conducted in three key sites. Geometric data fusion of GeoEye-1, RapidEye and ALOS PRISM datasets was performed and several high-resolution DEMs were generated. The DEMs were evaluated for absolute height and slope against the field dataset and the thermo-erosional stream network was mapped and morphometric analysis of the identified features was performed. The highest DEM accuracy was achieved when using a combination of six stereopairs from the years 2006 and 2009. The DEM derived transversal and longitudinal profiles reflect the actual shape and morphometry of the valleys. The identified stream network shows levels of high organization within thermokarst depressions and is poorly developed on the Ice Complex surface. The stream orientation tends to follow the height gradient of the study area towards north¬west, while streams outside of thermokarst depression show two main directions that could reflect the polygonal network in the ground. Accompanying permafrost warming thermokarst and thermo-erosional activity will further promote permafrost degradation. In this context thermo-erosional stream networks will expand within the Ice Complex and act as a major agent for the transport of remobilized fossil organic carbon to the Laptev Sea system.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Thesis , notRev
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