@phdthesis{Ramage2018, author = {Ramage, Justine Lucille}, title = {Impact of Hillslope Thermokarst on the Nearshore Carbon Budget Along the Yukon Coast, Canada}, doi = {10.25932/publishup-42186}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-421867}, school = {Universit{\"a}t Potsdam}, pages = {xvii, 103}, year = {2018}, abstract = {In ice-rich permafrost regions, changes in the permafrost thermal regime cause surface disturbances. These changes are amplified by the increase in air temperatures recorded in the Arctic in the past decades. Thermokarst is a process that leads to surface subsidence and formation of characteristic landforms following thawing of ice-rich permafrost or melting of massive ice. Thermokarst is widespread on hillslopes and the number of associated landforms is increasing in the Arctic. Through this process large amounts of material are eroded and transported to the sea or accumulate along hillslopes. While hillslope thermokarst modifies terrestrial and aquatic ecosystems, there is limited understanding of its environmental impact at a regional scale. In this thesis we quantify the environmental impacts of hillslope thermokarst on the valley and nearshore ecosystems along the Yukon Coast, Canada. Using supervised machine learning, we identified geomorphic factors that favour the development of coastal retrogressive thaw slump (RTS), one of the most dynamic hillslope thermokarst landform. Coastal geomorphology and ground ice type and content play a major role in RTS occurrence. Using aerial photographs and satellite imagery, we traced the evolution of RTSs between 1952 and 2011. During this time, the number and areal coverage of RTSs increased by 73\%. RTSs eroded and partly released to the nearshore zone organic carbon contained in millions of cubic meters of material. Our results show that 56\% of the RTSs identified along the coast in 2011 have eroded 16.6 × 10^6 m3 of material; a large part (45\%) was transported alongshore due to coastal processes. Moreover, we show that RTSs are a major contributor to the carbon budget in the nearshore ecosystem: 17\% of the coastal RTSs identified in 2011 contributed annually up to 0.6\% of the organic carbon released by coastal retreat along the Yukon Coast. To assess the impact of hillslope thermokarst on the terrestrial ecosystem, we measured the spatial distribution of soil organic carbon (SOC) and total nitrogen (TN) along hillslopes in three Arctic valleys. We highlight the high spatial variability in the distribution of SOC and TN in the valleys. This distribution is caused by complex soil processes occurring along the hillslopes. Hillslope thermokarst impacts the degradation of organic matter and affects the storage of SOC and TN.}, language = {de} } @article{RamageFortierHugeliusetal.2019, author = {Ramage, Justine Lucille and Fortier, Daniel and Hugelius, Gustaf and Lantuit, Hugues and Morgenstern, Anne}, title = {Distribution of carbon and nitrogen along hillslopes in three valleys on Herschel Island, Yukon Territory, Canada}, series = {Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution}, volume = {178}, journal = {Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0341-8162}, doi = {10.1016/j.catena.2019.02.029}, pages = {132 -- 140}, year = {2019}, abstract = {Thermokarst results from the thawing of ice-rich permafrost and alters the biogeochemical cycling in the Arctic by reworking soil material and redistributing soil organic carbon (SOC) and total nitrogen (TN) along uplands, hillslopes, and lowlands. Understanding the impact of this redistribution is key to better estimating the storage of SOC in permafrost terrains. However, there are insufficient studies quantifying long-term impacts of thaw processes on the distribution of SOC and TN along hillslopes. We address this issue by providing estimates of SOC and TN stocks along the hillslopes of three valleys located on Herschel Island (Yukon, Canada), and by discussing the impact of hillslope thermokarst on the variability of SOC and TN stocks. We found that the average SOC and TN 0-100 cm stocks in the valleys were 26.4 +/- 8.9 kg C m(-2) and 2.1 +/- 0.6 kg N m(-2). We highlight the strong variability in the soils physical and geochemical properties within hillslope positions. High SOC stocks were found at the summits, essentially due to burial of organic matter by cryoturbation, and at the toeslopes due to impeded drainage which favored peat formation and SOC accumulation. The average carbon-to-nitrogen ratio in the valleys was 12.9, ranging from 9.7 to 18.9, and was significantly higher at the summits compared to the backslopes and footslopes (p < 0.05), suggesting a degradation of SOC downhill. Carbon and nitrogen contents and stocks were significantly lower on 16\% of the sites that were previously affected by hillslope thermokarst (p < 0.05). Our results showed that lateral redistribution of SOC and TN due to hillslope thermokarst has a strong impact on the SOC storage in ice-rich permafrost terrains.}, language = {en} } @article{RamageIrrgangHerzschuhetal.2017, author = {Ramage, Justine Lucille and Irrgang, Anna Maria and Herzschuh, Ulrike and Morgenstern, Anne and Couture, Nicole and Lantuit, Hugues}, title = {Terrain controls on the occurrence of coastal retrogressive thaw slumps along the Yukon Coast, Canada}, series = {Journal of geophysical research : Earth surface}, volume = {122}, journal = {Journal of geophysical research : Earth surface}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9003}, doi = {10.1002/2017JF004231}, pages = {1619 -- 1634}, year = {2017}, abstract = {Retrogressive thaw slumps (RTSs) are among the most active landforms in the Arctic; their number has increased significantly over the past decades. While processes initiating discrete RTSs are well identified, the major terrain controls on the development of coastal RTSs at a regional scale are not yet defined. Our research reveals the main geomorphic factors that determine the development of RTSs along a 238km segment of the Yukon Coast, Canada. We (1) show the current extent of RTSs, (2) ascertain the factors controlling their activity and initiation, and (3) explain the spatial differences in the density and areal coverage of RTSs. We mapped and classified 287 RTSs using high-resolution satellite images acquired in 2011. We highlighted the main terrain controls over their development using univariate regression trees model. Coastal geomorphology influenced both the activity and initiation of RTSs: active RTSs and RTSs initiated after 1972 occurred primarily on terrains with slope angles greater than 3.9 degrees and 5.9 degrees, respectively. The density and areal coverage of RTSs were constrained by the volume and thickness of massive ice bodies. Differences in rates of coastal change along the coast did not affect the model. We infer that rates of coastal change averaged over a 39year period are unable to reflect the complex relationship between RTSs and coastline dynamics. We emphasize the need for large-scale studies of RTSs to evaluate their impact on the ecosystem and to measure their contribution to the global carbon budget. Plain Language Summary Retrogressive thaw slumps, henceforth slumps are a type of landslides that occur when permafrost thaws. Slumps are active landforms: they develop quickly and extend over several hectares. Satellite imagery allows to map such slumps over large areas. Our research shows where slumps develop along a 238 km segment of the Yukon Coast in Canada and explains which environments are most suitable for slump occurrence. We found that active and newly developed slumps were triggered where coastal slopes were greater than 3.9 degrees and 5.9 degrees, respectively. We explain that coastal erosion influences the development of slumps by modifying coastal slopes. We found that the highest density of slumps as well as the largest slumps occurred on terrains with high amounts of ice bodies in the ground. This study provides tools to better identify areas in the Arctic that are prone to slump development.}, language = {en} } @article{RamageIrrgangMorgensternetal.2018, author = {Ramage, Justine Lucille and Irrgang, Anna Maria and Morgenstern, Anne and Lantuit, Hugues}, title = {Increasing coastal slump activity impacts the release of sediment and organic carbon into the Arctic Ocean}, series = {Biogeosciences}, volume = {15}, journal = {Biogeosciences}, number = {5}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1726-4170}, doi = {10.5194/bg-15-1483-2018}, pages = {1483 -- 1495}, year = {2018}, abstract = {Retrogressive thaw slumps (RTSs) are among the most active thermokarst landforms in the Arctic and deliver a large amount of material to the Arctic Ocean. However, their contribution to the organic carbon (OC) budget is unknown. We provide the first estimate of the contribution of RTSs to the nearshore OC budget of the Yukon Coast, Canada, and describe the evolution of coastal RTSs between 1952 and 2011 in this area. We (1) describe the evolution of RTSs between 1952 and 2011; (2) calculate the volume of eroded material and stocks of OC mobilized through slumping, including soil organic carbon (SOC) and dissolved organic carbon (DOC); and (3) estimate the OC fluxes mobilized through slumping between 1972 and 2011. We identified RTSs using high- resolution satellite imagery from 2011 and geocoded aerial photographs from 1952 and 1972. To estimate the volume of eroded material, we applied spline interpolation on an airborne lidar dataset acquired in July 2013. We inferred the stocks of mobilized SOC and DOC from existing related literature. Our results show a 73\% increase in the number of RTSs and 14\% areal expansion between 1952 and 2011. In the study area, RTSs displaced at least 16.6 x 10(6) m(3) of material, 53\% of which was ice, and mobilized 145.9 x 10(6) kg of OC. Between 1972 and 2011, 49 RTSs displaced 8.6 x 10(3) m(3) yr(-1) of material, adding 0.6\% to the OC flux released by coastal retreat along the Yukon Coast. Our results show that the contribution of RTSs to the nearshore OC budget is non-negligible and should be included when estimating the quantity of OC released from the Arctic coast to the ocean.}, language = {en} } @article{TanskiBergstedtBevingtonetal.2019, author = {Tanski, George and Bergstedt, Helena and Bevington, Alexandre and Bonnaventure, Philip and Bouchard, Frederic and Coch, Caroline and Dumais, Simon and Evgrafova, Alevtina and Frauenfeld, Oliver W. and Frederick, Jennifer and Fritz, Michael and Frolov, Denis and Harder, Silvie and Hartmeyer, Ingo and Heslop, Joanne and Hoegstroem, Elin and Johansson, Margareta and Kraev, Gleb and Kuznetsova, Elena and Lenz, Josefine and Lupachev, Alexey and Magnin, Florence and Martens, Jannik and Maslakov, Alexey and Morgenstern, Anne and Nieuwendam, Alexandre and Oliva, Marc and Radosavljevi, Boris and Ramage, Justine Lucille and Schneider, Andrea and Stanilovskaya, Julia and Strauss, Jens and Trochim, Erin and Vecellio, Daniel J. and Weber, Samuel and Lantuit, Hugues}, title = {The Permafrost Young Researchers Network (PYRN) is getting older}, series = {Polar record}, volume = {55}, journal = {Polar record}, number = {4}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {0032-2474}, doi = {10.1017/S0032247418000645}, pages = {216 -- 219}, year = {2019}, abstract = {A lasting legacy of the International Polar Year (IPY) 2007-2008 was the promotion of the Permafrost Young Researchers Network (PYRN), initially an IPY outreach and education activity by the International Permafrost Association (IPA). With the momentum of IPY, PYRN developed into a thriving network that still connects young permafrost scientists, engineers, and researchers from other disciplines. This research note summarises (1) PYRN's development since 2005 and the IPY's role, (2) the first 2015 PYRN census and survey results, and (3) PYRN's future plans to improve international and interdisciplinary exchange between young researchers. The review concludes that PYRN is an established network within the polar research community that has continually developed since 2005. PYRN's successful activities were largely fostered by IPY. With >200 of the 1200 registered members active and engaged, PYRN is capitalising on the availability of social media tools and rising to meet environmental challenges while maintaining its role as a successful network honouring the legacy of IPY.}, language = {en} } @article{TanskiLantuitRuttoretal.2017, author = {Tanski, George and Lantuit, Hugues and Ruttor, Saskia and Knoblauch, Christian and Radosavljevic, Boris and Strauß, Jens and Wolter, Juliane and Irrgang, Anna Maria and Ramage, Justine Lucille and Fritz, Michael}, title = {Transformation of terrestrial organic matter along thermokarst-affected permafrost coasts in the Arctic}, series = {The science of the total environment : an international journal for scientific research into the environment and its relationship with man}, volume = {581}, journal = {The science of the total environment : an international journal for scientific research into the environment and its relationship with man}, publisher = {Elsevier Science}, address = {Amsterdam}, issn = {0048-9697}, doi = {10.1016/j.scitotenv.2016.12.152}, pages = {434 -- 447}, year = {2017}, abstract = {The changing climate in the Arctic has a profound impact on permafrost coasts, which are subject to intensified thermokarst formation and erosion. Consequently, terrestrial organic matter (OM) is mobilized and transported into the nearshore zone. Yet, little is known about the fate of mobilized OM before and after entering the ocean. In this study we investigated a retrogressive thaw slump (RTS) on Qikiqtaruk - Herschel Island (Yukon coast, Canada). The RTS was classified into an undisturbed, a disturbed (thermokarst-affected) and a nearshore zone and sampled systematically along transects. Samples were analyzed for total and dissolved organic carbon and nitrogen (TOC, DOC, TN, DN), stable carbon isotopes (delta C-13-TOC, delta C-13-DOC), and dissolved inorganic nitrogen (DIN), which were compared between the zones. C/N-ratios, delta C-13 signatures, and ammonium (NH4-N) concentrations were used as indicators for OM degradation along with biomarkers (n-alkanes, n-fatty adds, n-alcohols). Our results show that OM significantly decreases after disturbance with a TOC and DOC loss of 77 and 55\% and a TN and DN loss of 53 and 48\%, respectively. C/N-ratios decrease significantly, whereas NH4-N concentrations slightly increase in freshly thawed material. In the nearshore zone, OM contents are comparable to the disturbed zone. We suggest that the strong decrease in OM is caused by initial dilution with melted massive ice and immediate offshore transport via the thaw stream. In the mudpool and thaw stream, OM is subject to degradation, whereas in the slump floor the nitrogen decrease is caused by recolonizing vegetation. Within the nearshore zone of the ocean, heavier portions of OM are directly buried in marine sediments close to shore. We conclude that RTS have profound impacts on coastal environments in the Arctic. They mobilize nutrients from permafrost, substantially decrease OM contents and provide fresh water and nutrients at a point source.}, language = {en} }