Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Abteilungen OPUS4-51386 Review Fritz, Michael Andre; Rosa, Stefanie; Sicard, Adrien Mechanisms Underlying the Environmentally Induced Plasticity of Leaf Morphology The primary function of leaves is to provide an interface between plants and their environment for gas exchange, light exposure and thermoregulation. Leaves have, therefore a central contribution to plant fitness by allowing an efficient absorption of sunlight energy through photosynthesis to ensure an optimal growth. Their final geometry will result from a balance between the need to maximize energy uptake while minimizing the damage caused by environmental stresses. This intimate relationship between leaf and its surroundings has led to an enormous diversification in leaf forms. Leaf shape varies between species, populations, individuals or even within identical genotypes when those are subjected to different environmental conditions. For instance, the extent of leaf margin dissection has, for long, been found to inversely correlate with the mean annual temperature, such that Paleobotanists have used models based on leaf shape to predict the paleoclimate from fossil flora. Leaf growth is not only dependent on temperature but is also regulated by many other environmental factors such as light quality and intensity or ambient humidity. This raises the question of how the different signals can be integrated at the molecular level and converted into clear developmental decisions. Several recent studies have started to shed the light on the molecular mechanisms that connect the environmental sensing with organ-growth and patterning. In this review, we discuss the current knowledge on the influence of different environmental signals on leaf size and shape, their integration as well as their importance for plant adaptation. Lausanne Frontiers Research Foundation 2018 25 Frontiers in genetics 9 10.3389/fgene.2018.00478 Institut für Biochemie und Biologie OPUS4-53037 Wissenschaftlicher Artikel Streubel, Susanna; Fritz, Michael Andre; Teltow, Melanie; Kappel, Christian; Sicard, Adrien Successive duplication-divergence mechanisms at the RCO locus contributed to leaf shape diversity in the Brassicaceae Gene duplication is a major driver for the increase of biological complexity. The divergence of newly duplicated paralogs may allow novel functions to evolve, while maintaining the ancestral one. Alternatively, partitioning the ancestral function among paralogs may allow parts of that role to follow independent evolutionary trajectories. We studied the REDUCED COMPLEXITY (RCO) locus, which contains three paralogs that have evolved through two independent events of gene duplication, and which underlies repeated events of leaf shape evolution within the Brassicaceae. In particular, we took advantage of the presence of three potentially functional paralogs in Capsella to investigate the extent of functional divergence among them. We demonstrate that the RCO copies control growth in different areas of the leaf. Consequently, the copies that are retained active in the different Brassicaceae lineages contribute to define the leaf dissection pattern. Our results further illustrate how successive gene duplication events and subsequent functional divergence can increase trait evolvability by providing independent evolutionary trajectories to specialized functions that have an additive effect on a given trait. Cambridge Company of Biologists 2018 10 Development : Company of Biologists 145 8 10.1242/dev.164301 Institut für Biochemie und Biologie OPUS4-52618 Wissenschaftlicher Artikel Wetterich, Sebastian; Schirrmeiste, Lutz; Nazarova, Larisa B.; Palagushkina, Olga; Bobrov, Anatoly; Pogosyan, Lilit; Savelieva, Larisa; Syrykh, Liudmila; Matthes, Heidrun; Fritz, Michael; Günther, Frank; Opel, Thomas; Meyer, Hanno Holocene thermokarst and pingo development in the Kolyma Lowland (NE Siberia) Ground ice and sedimentary records of a pingo exposure reveal insights into Holocene permafrost, landscape and climate dynamics. Early to mid-Holocene thermokarst lake deposits contain rich floral and faunal paleoassemblages, which indicate lake shrinkage and decreasing summer temperatures (chironomid-based T-July) from 10.5 to 3.5 cal kyr BP with the warmest period between 10.5 and 8 cal kyr BP. Talik refreezing and pingo growth started about 3.5 cal kyr BP after disappearance of the lake. The isotopic composition of the pingo ice (delta O-18 - 17.1 +/- 0.6 parts per thousand, delta D -144.5 +/- 3.4 parts per thousand, slope 5.85, deuterium excess -7.7 +/- 1.5 parts per thousand) point to the initial stage of closed-system freezing captured in the record. A differing isotopic composition within the massive ice body was found (delta O-18 - 21.3 +/- 1.4 parts per thousand, delta D -165 +/- 11.5 parts per thousand, slope 8.13, deuterium excess 4.9 +/- 3.2 parts per thousand), probably related to the infill of dilation cracks by surface water with quasi-meteoric signature. Currently inactive syngenetic ice wedges formed in the thermokarst basin after lake drainage. The pingo preserves traces of permafrost response to climate variations in terms of ground-ice degradation (thermokarst) during the early and mid-Holocene, and aggradation (wedge-ice and pingo-ice growth) during the late Holocene. Hoboken Wiley 2018 17 Permafrost and Periglacial Processes 29 3 182 198 10.1002/ppp.1979 Institut für Physik und Astronomie OPUS4-33308 Dissertation Fritz, Michael Late quaternary environmental dynamics of the western canadian artic : permafrost and lake sediment archives at the easter beringian edge Potsdam 2011 119 S. Institut für Geowissenschaften OPUS4-40809 misc Fritz, Michael; Deshpande, B. N.; Bouchard, F.; Högström, E.; Malenfant-Lepage, J.; Morgenstern, Anne; Nieuwendam, A.; Oliva, M.; Paquette, M.; Rudy, A. C. A.; Siewert, M. B.; Sjöberg, Y.; Weege, Stefanie Brief communication Accelerating climate change and increased economic and environmental interests in permafrost-affected regions have resulted in an acute need for more directed permafrost research. In June 2014, 88 early career researchers convened to identify future priorities for permafrost research. This multidisciplinary forum concluded that five research topics deserve greatest attention: permafrost landscape dynamics, permafrost thermal modeling, integration of traditional knowledge, spatial distribution of ground ice, and engineering issues. These topics underline the need for integrated research across a spectrum of permafrost-related domains and constitute a contribution to the Third International Conference on Arctic Research Planning (ICARP III). 2015 6 Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe 490 urn:nbn:de:kobv:517-opus4-408096 10.25932/publishup-40809 Mathematisch-Naturwissenschaftliche Fakultät OPUS4-48828 Wissenschaftlicher Artikel Tanski, George; Bergstedt, Helena; Bevington, Alexandre; Bonnaventure, Philip; Bouchard, Frederic; Coch, Caroline; Dumais, Simon; Evgrafova, Alevtina; Frauenfeld, Oliver W.; Frederick, Jennifer; Fritz, Michael; Frolov, Denis; Harder, Silvie; Hartmeyer, Ingo; Heslop, Joanne; Hoegstroem, Elin; Johansson, Margareta; Kraev, Gleb; Kuznetsova, Elena; Lenz, Josefine; Lupachev, Alexey; Magnin, Florence; Martens, Jannik; Maslakov, Alexey; Morgenstern, Anne; Nieuwendam, Alexandre; Oliva, Marc; Radosavljevi, Boris; Ramage, Justine Lucille; Schneider, Andrea; Stanilovskaya, Julia; Strauss, Jens; Trochim, Erin; Vecellio, Daniel J.; Weber, Samuel; Lantuit, Hugues The Permafrost Young Researchers Network (PYRN) is getting older 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. New York Cambridge Univ. Press 2019 4 Polar record 55 4 216 219 10.1017/S0032247418000645 Institut für Umweltwissenschaften und Geographie OPUS4-52686 Wissenschaftlicher Artikel Wolter, Juliane; Lantuit, Hugues; Wetterich, Sebastian; Rethemeyer, J.; Fritz, Michael Climatic, geomorphologic and hydrologic perturbations as drivers for mid- to late Holocene development of ice-wedge polygons in the western Canadian Arctic Ice-wedge polygons are widespread periglacial features and influence landscape hydrology and carbon storage. The influence of climate and topography on polygon development is not entirely clear, however, giving high uncertainties to projections of permafrost development. We studied the mid- to late Holocene development of modern ice-wedge polygon sites to explore drivers of change and reasons for long-term stability. We analyzed organic carbon, total nitrogen, stable carbon isotopes, grain size composition and plant macrofossils in six cores from three polygons. We found that ail sites developed from aquatic to wetland conditions. In the mid-Holocene, shallow lakes and partly submerged ice-wedge polygons existed at the studied sites. An erosional hiatus of ca 5000 years followed, and ice-wedge polygons re-initiated within the last millennium. Ice-wedge melt and surface drying during the last century were linked to climatic warming. The influence of climate on ice-wedge polygon development was outweighed by geomorphology during most of the late Holocene. Recent warming, however, caused ice-wedge degradation at all sites. Our study showed that where waterlogged ground was maintained, low-centered polygons persisted for millennia. Ice-wedge melt and increased drainage through geomorphic disturbance, however, triggered conversion into high-centered polygons and may lead to self-enhancing degradation under continued warming. Hoboken Wiley 2018 18 Permafrost and Periglacial Processes 29 3 164 181 10.1002/ppp.1977 Institut für Umweltwissenschaften und Geographie OPUS4-52942 Wissenschaftlicher Artikel Fritz, Michael; Unkel, Ingmar; Lenz, Josefine; Gajewski, Konrad; Frenzel, Peter; Paquette, Nathalie; Lantuit, Hugues; Körte, Lisa; Wetterich, Sebastian Regional environmental change versus local signal preservation in Holocene thermokarst lake sediments Thermokarst lakes cover nearly one fourth of ice-rich permafrost lowlands in the Arctic. Sediments from an athalassic subsaline thermokarst lake on Herschel Island (69°36′N; 139°04′W, Canadian Arctic) were used to understand regional changes in climate and in sediment transport, hydrology, nutrient availability and permafrost disturbance. The sediment record spans the last ~ 11,700 years and the basal date is in good agreement with the Holocene onset of thermokarst initiation in the region. Electrical conductivity in pore water continuously decreases, thus indicating desalinization and continuous increase of lake size and water level. The inc/coh ratio of XRF scans provides a high-resolution organic-carbon proxy which correlates with TOC measurements. XRF-derived Mn/Fe ratios indicate aerobic versus anaerobic conditions which moderate the preservation potential of organic matter in lake sediments. The coexistence of marine, brackish and freshwater ostracods and foraminifera is explained by (1) oligohaline to mesohaline water chemistry of the past lake and (2) redeposition of Pleistocene specimens found within upthrusted marine sediments around the lake. Episodes of catchment disturbance are identified when calcareous fossils and allochthonous material were transported into the lake by thermokarst processes such as active-layer detachments, slumping and erosion of ice-rich shores. The pollen record does not show major variations and the pollen-based climate record does not match well with other summer air temperature reconstructions from this region. Local vegetation patterns in small catchments are strongly linked to morphology and sub-surface permafrost conditions rather than to climate. Multidisciplinary studies can identify the onset and life cycle of thermokarst lakes as they play a crucial role in Arctic freshwater ecosystems and in the global carbon cycle of the past, present and future. Dordrecht Springer 2018 20 Journal of paleolimnolog 60 1 77 96 10.1007/s10933-018-0025-0 Institut für Umweltwissenschaften und Geographie OPUS4-45736 Wissenschaftlicher Artikel Obu, Jaroslav; Lantuit, Hugues; Fritz, Michael; Pollard, Wayne H.; Sachs, Torsten; Guenther, Frank Relation between planimetric and volumetric measurements of permafrost coast erosion: a case study from Herschel Island, western Canadian Arctic Ice-rich permafrost coasts often undergo rapid erosion, which results in land loss and release of considerable amounts of sediment, organic carbon and nutrients, impacting the near-shore ecosystems. Because of the lack of volumetric erosion data, Arctic coastal erosion studies typically report on planimetric erosion. Our aim is to explore the relationship between planimetric and volumetric coastal erosion measurements and to update the coastal erosion rates on Herschel Island in the Canadian Arctic. We used high-resolution digital elevation models to compute sediment release and compare volumetric data to planimetric estimations of coastline movements digitized from satellite imagery. Our results show that volumetric erosion is locally less variable and likely corresponds better with environmental forcing than planimetric erosion. Average sediment release volumes are in the same range as sediment release volumes calculated from coastline movements combined with cliff height. However, the differences between these estimates are significant for small coastal sections. We attribute the differences between planimetric and volumetric coastal erosion measurements to mass wasting, which is abundant along the coasts of Herschel Island. The average recorded coastline retreat on Herschel Island was 0.68m a(-1) for the period 2000-2011. Erosion rates increased by more than 50% in comparison with the period 1970-2000, which is in accordance with a recently observed increase along the Alaskan Beaufort Sea. The estimated annual sediment release was 28.2 m(3) m(-1) with resulting fluxes of 590 kg C m(-1) and 104 kg N m(-1). Jarfalla Co-Action Publ. 2016 13 Polar research : a Norwegian journal of Polar research 35 57 99 10.3402/polar.v35.30313 Institut für Geowissenschaften OPUS4-53732 Wissenschaftlicher Artikel Couture, Nicole J.; Irrgang, Anna Maria; Pollard, Wayne; Lantuit, Hugues; Fritz, Michael Coastal erosion of permafrost soils along the yukon coastal plain and fluxes of organic carbon to the canadian beaufort sea Reducing uncertainties about carbon cycling is important in the Arctic where rapid environmental changes contribute to enhanced mobilization of carbon. Here we quantify soil organic carbon (SOC) contents of permafrost soils along the Yukon Coastal Plain and determine the annual fluxes from coastal erosion. Different terrain units were assessed based on surficial geology, morphology, and ground ice conditions. To account for the volume of wedge ice and massive ice in a unit, SOC contents were reduced by 19% and sediment contents by 16%. The SOC content in a 1m(2) column of soil varied according to the height of the bluff, ranging from 30 to 662kg, with a mean value of 183kg. Forty-four per cent of the SOC was within the top 1m of soil and values varied based on surficial materials, ranging from 30 to 53kg C/m(3), with a mean of 41kg. Eighty per cent of the shoreline was erosive with a mean annual rate of change of -0.7m/yr. This resulted in a SOC flux per meter of shoreline of 132kg C/m/yr, and a total flux for the entire 282km of the Yukon coast of 35.5 x 10(6) kg C/yr (0.036 Tg C/yr). The mean flux of sediment per meter of shoreline was 5.3 x 10(3) kg/m/yr, with a total flux of 1,832 x 10(6)kg/yr (1.832 Tg/yr). Sedimentation rates indicate that approximately 13% of the eroded carbon was sequestered in nearshore sediments, where the overwhelming majority of organic carbon was of terrestrial origin. Plain Language Summary The oceans help slow the buildup of carbon dioxide (CO2) because they absorb much of this greenhouse gas. However, if carbon from other sources is added to the oceans, it can affect their ability to absorb atmospheric CO2. Our study examines the organic carbon added to the Canadian Beaufort Sea from eroding permafrost along the Yukon coast, a region quite vulnerable to erosion. Understanding carbon cycling in this area is important because environmental changes in the Arctic such as longer open water seasons, rising sea levels, and warmer air, water and soil temperatures are likely to increase coastal erosion and, thus, carbon fluxes to the sea. We measured the carbon in different types of permafrost soils and applied corrections to account for the volume taken up by various types of ground ice. By determining how quickly the shoreline is eroding, we assessed how much organic carbon is being transferred to the ocean each year. Our results show that 36 x 10(6) kg of carbon is added annually from this section of the coast. If we extrapolate these results to other coastal areas along the Canadian Beaufort Sea, the flux of organic carbon is nearly 3 times what was previously thought. Washington American Geophysical Union 2018 17 Journal of geophysical research : Biogeosciences 123 2 406 422 10.1002/2017JG004166 Institut für Geowissenschaften OPUS4-35559 Wissenschaftlicher Artikel Fritz, Michael; Herzschuh, Ulrike; Wetterich, Sebastian; Lantuit, Hugues; De Pascale, Gregory P.; Pollard, Wayne H.; Schirrmeister, Lutz Late glacial and holocene sedimentation, vegetation, and climate history from easternmost Beringia (northern Yukon Territory, Canada) Beringian climate and environmental history are poorly characterized at its easternmost edge. Lake sediments from the northern Yukon Territory have recorded sedimentation, vegetation, summer temperature and precipitation changes since similar to 16 cal ka BP. Herb-dominated tundra persisted until similar to 14.7 cal ka BP with mean July air temperatures <= 5 degrees C colder and annual precipitation 50 to 120 mm lower than today. Temperatures rapidly increased during the Bolling/Allerod interstadial towards modern conditions, favoring establishment of Betula-Salix shrub tundra. Pollen-inferred temperature reconstructions recorded a pronounced Younger Dryas stadial in east Beringia with a temperature drop of similar to 1.5 degrees C (similar to 2.5 to 3.0 degrees C below modern conditions) and low net precipitation (90 to 170 mm) but show little evidence of an early Holocene thermal maximum in the pollen record. Sustained low net precipitation and increased evaporation during early Holocene warming suggest a moisture-limited spread of vegetation and an obscured summer temperature maximum. Northern Yukon Holocene moisture availability increased in response to a retreating Laurentide Ice Sheet, postglacial sea level rise, and decreasing summer insolation that in turn led to establishment of Alnus-Berula shrub tundra from similar to 5 cal ka BP until present, and conversion of a continental climate into a coastal-maritime climate near the Beaufort Sea. San Diego Elsevier 2012 12 Quaternary research : an interdisciplinary journal 78 3 549 560 10.1016/j.yqres.2012.07.007 Institut für Geowissenschaften OPUS4-43227 misc Radosavljevic, Boris; Lantuit, Hugues; Pollard, Wayne; Overduin, Pier Paul; Couture, Nicole; Sachs, Torsten; Helm, Veit; Fritz, Michael Erosion and flooding-threats to coastal Infrastructure in the Arctic Arctic coastal infrastructure and cultural and archeological sites are increasingly vulnerable to erosion and flooding due to amplified warming of the Arctic, sea level rise, lengthening of open water periods, and a predicted increase in frequency of major storms. Mitigating these hazards necessitates decision-making tools at an appropriate scale. The objectives of this paper are to provide such a tool by assessing potential erosion and flood hazards at Herschel Island, a UNESCO World Heritage candidate site. This study focused on Simpson Point and the adjacent coastal sections because of their archeological, historical, and cultural significance. Shoreline movement was analyzed using the Digital Shoreline Analysis System (DSAS) after digitizing shorelines from 1952, 1970, 2000, and 2011. For purposes of this analysis, the coast was divided in seven coastal reaches (CRs) reflecting different morphologies and/or exposures. Using linear regression rates obtained from these data, projections of shoreline position were made for 20 and 50 years into the future. Flood hazard was assessed using a least cost path analysis based on a high-resolution light detection and ranging (LiDAR) dataset and current Intergovernmental Panel on Climate Change sea level estimates. Widespread erosion characterizes the study area. The rate of shoreline movement in different periods of the study ranges from −5.5 to 2.7 m·a⁻¹ (mean −0.6 m·a⁻¹). Mean coastal retreat decreased from −0.6 m·a⁻¹ to −0.5 m·a⁻¹, for 1952-1970 and 1970-2000, respectively, and increased to −1.3 m·a⁻¹ in the period 2000-2011. Ice-rich coastal sections most exposed to wave attack exhibited the highest rates of coastal retreat. The geohazard map combines shoreline projections and flood hazard analyses to show that most of the spit area has extreme or very high flood hazard potential, and some buildings are vulnerable to coastal erosion. This study demonstrates that transgressive forcing may provide ample sediment for the expansion of depositional landforms, while growing more susceptible to overwash and flooding. 2016 18 Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe 996 urn:nbn:de:kobv:517-opus4-432279 10.25932/publishup-43227 Mathematisch-Naturwissenschaftliche Fakultät OPUS4-61279 Wissenschaftlicher Artikel Radosavljevic, Boris; Lantuit, Hugues; Knoblauch, Christian; Couture, Nicole; Herzschuh, Ulrike; Fritz, Michael Arctic nearshore sediment dynamics - an example from Herschel Island - Qikiqtaruk, Canada Increasing arctic coastal erosion rates imply a greater release of sediments and organic matter into the coastal zone. With 213 sediment samples taken around Herschel Island-Qikiqtaruk, Canadian Beaufort Sea, we aimed to gain new insights on sediment dynamics and geochemical properties of a shallow arctic nearshore zone. Spatial characteristics of nearshore sediment texture (moderately to poorly sorted silt) are dictated by hydrodynamic processes, but ice-related processes also play a role. We determined organic matter (OM) distribution and inferred the origin and quality of organic carbon by C/N ratios and stable carbon isotopes delta C-13. The carbon content was higher offshore and in sheltered areas (mean: 1.0 wt.%., S.D.: 0.9) and the C/N ratios also showed a similar spatial pattern (mean: 11.1, S.D.: 3.1), while the delta C-13 (mean: -26.4 parts per thousand VPDB, S.D.: 0.4) distribution was more complex. We compared the geochemical parameters of our study with terrestrial and marine samples from other studies using a bootstrap approach. Sediments of the current study contained 6.5 times and 1.8 times less total organic carbon than undisturbed and disturbed terrestrial sediments, respectively. Therefore, degradation of OM and separation of carbon pools take place on land and continue in the nearshore zone, where OM is leached, mineralized, or transported beyond the study area. Basel MDPI 2022 18 Journal of marine science and engineering 10 11 10.3390/jmse10111589 Institut für Biochemie und Biologie OPUS4-40815 misc Fritz, Michael; Opel, Thomas; Tanski, George; Herzschuh, Ulrike; Meyer, Hanno; Eulenburg, A.; Lantuit, Hugues Dissolved organic carbon (DOC) in Arctic ground ice Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have accumulated in late Pleistocene and Holocene unconsolidated deposits. Permafrost vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change are largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements which are important for ecosystems and carbon cycling. Here we show, using biogeochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage, with a maximum of 28.6 mg L-1 (mean: 9.6 mg L-1). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg2+ and K+. DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly frozen and stored in ground ice, especially in ice wedges, even before further degradation. We found that ice wedges in the Yedoma region represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a freshwater reservoir of 4200 km(2). This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost car-bon pool for ecosystems and climate feedback upon mobilization. 2015 16 Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe 493 urn:nbn:de:kobv:517-opus4-408155 Mathematisch-Naturwissenschaftliche Fakultät OPUS4-39351 Wissenschaftlicher Artikel Fritz, Michael; Opel, Thomas; Tanski, George; Herzschuh, Ulrike; Meyer, H.; Eulenburg, A.; Lantuit, Hugues Dissolved organic carbon (DOC) in Arctic ground ice Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have accumulated in late Pleistocene and Holocene unconsolidated deposits. Permafrost vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change are largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements which are important for ecosystems and carbon cycling. Here we show, using biogeochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage, with a maximum of 28.6 mg L-1 (mean: 9.6 mg L-1). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg2+ and K+. DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly frozen and stored in ground ice, especially in ice wedges, even before further degradation. We found that ice wedges in the Yedoma region represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a freshwater reservoir of 4200 km(2). This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost car-bon pool for ecosystems and climate feedback upon mobilization. Göttingen Copernicus 2015 16 The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union 9 2 737 752 10.5194/tc-9-737-2015 Institut für Geowissenschaften OPUS4-47789 Wissenschaftlicher Artikel Coch, Caroline; Juhls, Bennet; Lamoureux, Scott F.; Lafreniere, Melissa J.; Fritz, Michael; Heim, Birgit; Lantuit, Hugues Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments Climate change is affecting the rate of carbon cycling, particularly in the Arctic. Permafrost degradation through deeper thaw and physical disturbances results in the release of carbon dioxide and methane to the atmosphere and to an increase in lateral dissolved organic matter (DOM) fluxes. Whereas riverine DOM fluxes of the large Arctic rivers are well assessed, knowledge is limited with regard to small catchments that cover more than 40% of the Arctic drainage basin. Here, we use absorption measurements to characterize changes in DOM quantity and quality in a low Arctic (Herschel Island, Yukon, Canada) and a high Arctic (Cape Bounty, Melville Island, Nunavut, Canada) setting with regard to geographical differences, impacts of permafrost degradation, and rainfall events. We find that DOM quantity and quality is controlled by differences in vegetation cover and soil organic carbon content (SOCC). The low Arctic site has higher SOCC and greater abundance of plant material resulting in higher chromophoric dissolved organic matter (cDOM) and dissolved organic carbon (DOC) than in the high Arctic. DOC concentration and cDOM in surface waters at both sites show strong linear relationships similar to the one for the great Arctic rivers. We used the optical characteristics of DOM such as cDOM absorption, specific ultraviolet absorbance (SUVA), ultraviolet (UV) spectral slopes (S275-295), and slope ratio (SR) for assessing quality changes downstream, at base flow and storm flow conditions, and in relation to permafrost disturbance. DOM in streams at both sites demonstrated optical signatures indicative of photodegradation downstream processes, even over short distances of 2000 m. Flow pathways and the connected hydrological residence time control DOM quality. Deeper flow pathways allow the export of permafrost-derived DOM (i.e. from deeper in the active layer), whereas shallow pathways with shorter residence times lead to the export of fresh surface- and near-surface-derived DOM. Compared to the large Arctic rivers, DOM quality exported from the small catchments studied here is much fresher and therefore prone to degradation. Assessing optical properties of DOM and linking them to catchment properties will be a useful tool for understanding changing DOM fluxes and quality at a pan-Arctic scale. Göttingen Copernicus 2019 19 Biogeosciences 16 23 4535 4553 10.5194/bg-16-4535-2019 Institut für Geowissenschaften OPUS4-45156 Wissenschaftlicher Artikel Tanski, George; Couture, Nicole; Lantuit, Hugues; Eulenburg, Antje; Fritz, Michael Eroding permafrost coasts release low amounts of dissolved organic carbon (DOC) from ground ice into the nearshore zone of the Arctic Ocean Ice-rich permafrost coasts in the Arctic are highly sensitive to climate warming and erode at a pace that exceeds the global average. Permafrost coasts deliver vast amounts of organic carbon into the nearshore zone of the Arctic Ocean. Numbers on flux exist for particulate organic carbon (POC) and total or soil organic carbon (TOC, SOC). However, they do not exist for dissolved organic carbon (DOC), which is known to be highly bioavailable. This study aims to estimate DOC stocks in coastal permafrost as well as the annual flux into the ocean. DOC concentrations in ground ice were analyzed along the ice-rich Yukon coast (YC) in the western Canadian Arctic. The annual DOC flux was estimated using available numbers for coast length, cliff height, annual erosion rate, and volumetric ice content in different stratigraphic horizons. Our results showed that DOC concentrations in ground ice range between 0.3 and 347.0mgL(-1) with an estimated stock of 13.63.0gm(-3) along the YC. An annual DOC flux of 54.90.9Mgyr(-1) was computed. These DOC fluxes are low compared to POC and SOC fluxes from coastal erosion or POC and DOC fluxes from Arctic rivers. We conclude that DOC fluxes from permafrost coasts play a secondary role in the Arctic carbon budget. However, this DOC is assumed to be highly bioavailable. We hypothesize that DOC from coastal erosion is important for ecosystems in the Arctic nearshore zones, particularly in summer when river discharge is low, and in areas where rivers are absent. Cambridge American Geophysical Union 2016 15 Global biogeochemical cycles 30 1054 1068 10.1002/2015GB005337 Institut für Biochemie und Biologie OPUS4-46137 Wissenschaftlicher Artikel Wolter, Juliane; Lantuit, Hugues; Herzschuh, Ulrike; Stettner, Samuel; Fritz, Michael Tundra vegetation stability versus lake-basin variability on the Yukon Coastal Plain (NW Canada) during the past three centuries London Sage Publ. 2017 13 The Holocene : an interdisciplinary journal focusing on recent environmental change 27 1846 1858 10.1177/0959683617708441 Institut für Geowissenschaften OPUS4-45204 misc Radosavljevic, Boris; Lantuit, Hugues; Pollard, Wayne; Overduin, Pier Paul; Couture, Nicole; Sachs, Torsten; Helm, Veit; Fritz, Michael Erosion and Flooding - Threats to Coastal Infrastructure in the Arctic: A Case Study from Herschel Island, Yukon Territory, Canada (vol 39, pg 900, 2016) New York Springer 2016 2 Estuaries and coasts : journal of the Estuarine Research Federation 39 1294 1295 10.1007/s12237-016-0115-z Institut für Geowissenschaften OPUS4-48002 Wissenschaftlicher Artikel Tanski, Georg; Wagner, Dirk; Knoblauch, Christian; Fritz, Michael; Sachs, Torsten; Lantuit, Hugues Rapid CO2 Release From Eroding Permafrost in Seawater Washington American Geophysical Union 2019 9 Geophysical research letters 46 20 11244 11252 10.1029/2019GL084303 Institut für Geowissenschaften OPUS4-55276 Wissenschaftlicher Artikel Tanski, George; Lantuit, Hugues; Ruttor, Saskia; Knoblauch, Christian; Radosavljevic, Boris; Strauß, Jens; Wolter, Juliane; Irrgang, Anna Maria; Ramage, Justine Lucille; Fritz, Michael Transformation of terrestrial organic matter along thermokarst-affected permafrost coasts in the Arctic 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. Amsterdam Elsevier Science 2017 14 The science of the total environment : an international journal for scientific research into the environment and its relationship with man 581 434 447 10.1016/j.scitotenv.2016.12.152 Institut für Umweltwissenschaften und Geographie OPUS4-45029 Wissenschaftlicher Artikel Fritz, Michael; Wolter, Juliane; Rudaya, Natalia; Palagushkina, Olga; Nazarova, Larisa B.; Obu, Jaroslav; Rethemeyer, Janet; Lantuit, Hugues; Wetterich, Sebastian Holocene ice-wedge polygon development in northern Yukon permafrost peatlands (Canada) Ice-wedge polygon (IWP) peatlands in the Arctic and Subarctic are extremely vulnerable to climatic and environmental change. We present the results of a multidisciplinary paleoenvironmental study on IWPs in the northern Yukon, Canada. High-resolution laboratory analyses were carried out on a permafrost core and the overlying seasonally thawed (active) layer, from an IWP located in a drained lake basin on Herschel Island. In relation to 14 Accelerator Mass Spectrometry (AMS) radiocarbon dates spanning the last 5000 years, we report sedimentary data including grain size distribution and biogeochemical parameters (organic carbon, nitrogen, C/N ratio, delta C-13), stable water isotopes (delta O-18, delta D), as well as fossil pollen, plant macrofossil and diatom assemblages. Three sediment units (SUS) correspond to the main stages of deposition (1) in a thermokarst lake (SW : 4950 to 3950 cal yrs BP), (2) during transition from lacustrine to palustrine conditions after lake drainage (SU2: 3950 to 3120 cal yrs BP), and (3) in palustrine conditions of the IWP field that developed after drainage (SU3: 3120 cal yrs BP to 2012 CE). The lacustrine phase (pre 3950 cal yrs BP) is characterized by planktonic-benthic and pioneer diatom species indicating circumneutral waters, and very few plant macrofossils. The pollen record has captured a regional signal of relatively stable vegetation composition and climate for the lacustrine stage of the record until 3950 cal yrs BP. Palustrine conditions with benthic and acidophilic diatom species characterize the peaty shallow-water environments of the low-centered IWP. The transition from lacustrine to palustrine conditions was accompanied by acidification and rapid revegetation of the lake bottom within about 100 years. Since the palustrine phase we consider the pollen record as a local vegetation proxy dominated by the plant communities growing in the IWP. Ice-wedge cracking in water-saturated sediments started immediately after lake drainage at about 3950 cal yrs BP and led to the formation of an IWP mire. Permafrost aggradation through downward closed-system freezing of the lake talik is indicated by the stable water isotope record. The originally submerged IWP center underwent gradual drying during the past 2000 years. This study highlights the sensitivity of permafrost landscapes to climate and environmental change throughout the Holocene. (C) 2016 Elsevier Ltd. All rights reserved. Oxford Elsevier 2016 19 Quaternary science reviews : the international multidisciplinary research and review journal 147 279 297 10.1016/j.quascirev.2016.02.008 Institut für Geowissenschaften OPUS4-45203 Wissenschaftlicher Artikel Radosavljevic, Boris; Lantuit, Hugues; Pollard, Wayne; Overduin, Pier Paul; Couture, Nicole; Sachs, Torsten; Helm, Veit; Fritz, Michael Erosion and Flooding-Threats to Coastal Infrastructure in the Arctic: A Case Study from Herschel Island, Yukon Territory, Canada Arctic coastal infrastructure and cultural and archeological sites are increasingly vulnerable to erosion and flooding due to amplified warming of the Arctic, sea level rise, lengthening of open water periods, and a predicted increase in frequency of major storms. Mitigating these hazards necessitates decision-making tools at an appropriate scale. The objectives of this paper are to provide such a tool by assessing potential erosion and flood hazards at Herschel Island, a UNESCO World Heritage candidate site. This study focused on Simpson Point and the adjacent coastal sections because of their archeological, historical, and cultural significance. Shoreline movement was analyzed using the Digital Shoreline Analysis System (DSAS) after digitizing shorelines from 1952, 1970, 2000, and 2011. For purposes of this analysis, the coast was divided in seven coastal reaches (CRs) reflecting different morphologies and/or exposures. Using linear regression rates obtained from these data, projections of shoreline position were made for 20 and 50 years into the future. Flood hazard was assessed using a least cost path analysis based on a high-resolution light detection and ranging (LiDAR) dataset and current Intergovernmental Panel on Climate Change sea level estimates. Widespread erosion characterizes the study area. The rate of shoreline movement in different periods of the study ranges from -5.5 to 2.7 mI double dagger a(-1) (mean -0.6 mI double dagger a(-1)). Mean coastal retreat decreased from -0.6 mI double dagger a(-1) to -0.5 mI double dagger a(-1), for 1952-1970 and 1970-2000, respectively, and increased to -1.3 mI double dagger a(-1) in the period 2000-2011. Ice-rich coastal sections most exposed to wave attack exhibited the highest rates of coastal retreat. The geohazard map combines shoreline projections and flood hazard analyses to show that most of the spit area has extreme or very high flood hazard potential, and some buildings are vulnerable to coastal erosion. This study demonstrates that transgressive forcing may provide ample sediment for the expansion of depositional landforms, while growing more susceptible to overwash and flooding. New York Springer 2016 16 Estuaries and coasts : journal of the Estuarine Research Federation 39 900 915 10.1007/s12237-015-0046-0 Institut für Geowissenschaften OPUS4-51134 Wissenschaftlicher Artikel Coch, Caroline; Lamoureux, Scott F.; Knoblauch, Christian; Eischeid, Isabell; Fritz, Michael; Obu, Jaroslav; Lantuit, Hugues Summer rainfall dissolved organic carbon, solute, and sediment fluxes in a small Arctic coastal catchment on Herschel Island (Yukon Territory, Canada) Coastal ecosystems in the Arctic are affected by climate change. As summer rainfall frequency and intensity are projected to increase in the future, more organic matter, nutrients and sediment could bemobilized and transported into the coastal nearshore zones. However, knowledge of current processes and future changes is limited. We investigated streamflow dynamics and the impacts of summer rainfall on lateral fluxes in a small coastal catchment on Herschel Island in the western Canadian Arctic. For the summer monitoring periods of 2014-2016, mean dissolved organic matter flux over 17 days amounted to 82.7 +/- 30.7 kg km(-2) and mean total dissolved solids flux to 5252 +/- 1224 kg km(-2). Flux of suspended sediment was 7245 kg km(-2) in 2015, and 369 kg km(-2) in 2016. We found that 2.0% of suspended sediment was composed of particulate organic carbon. Data and hysteresis analysis suggest a limited supply of sediments; their interannual variability is most likely caused by short-lived localized disturbances. In contrast, our results imply that dissolved organic carbon is widely available throughout the catchment and exhibits positive linear relationship with runoff. We hypothesize that increased projected rainfall in the future will result in a similar increase of dissolved organic carbon fluxes. Ottawa Canadian science publishing 2018 31 Artic science 4 4 750 780 10.1139/as-2018-0010 Institut für Geowissenschaften OPUS4-60737 Wissenschaftlicher Artikel Grotheer, Hendrik; Meyer, Vera; Riedel, Theran; Pfalz, Gregor; Mathieu, Lucie; Hefter, Jens H.; Gentz, Torben; Lantuit, Hugues; Mollennauer, Gesine; Fritz, Michael Burial and origin of permafrost-derived carbon in the nearshore zone of the southern Canadian Beaufort Sea Detailed organic geochemical and carbon isotopic (delta C-13 and Delta C-14) analyses are performed on permafrost deposits affected by coastal erosion (Herschel Island, Canadian Beaufort Sea) and adjacent marine sediments (Herschel Basin) to understand the fate of organic carbon in Arctic nearshore environments. We use an end-member model based on the carbon isotopic composition of bulk organic matter to identify sources of organic carbon. Monte Carlo simulations are applied to quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget. The models suggest that similar to 40% of all carbon released by local coastal permafrost erosion is efficiently trapped and sequestered in the nearshore zone. This highlights the importance of sedimentary traps in environments such as basins, lagoons, troughs, and canyons for the carbon sequestration in previously poorly investigated, nearshore areas. Plain Language Summary Increasing air and sea surface temperatures at high latitudes leads to accelerated thaw, destabilization, and erosion of perennially frozen soils (i.e., permafrost), which are often rich in organic carbon. Coastal erosion leads to an increased mobilization of organic carbon into the Arctic Ocean, which there can be converted into greenhouse gases and may therefore contribute to further warming. Carbon decomposition can be limited if organic matter is efficiently deposited on the seafloor, buried in marine sediments, and thus removed from the short-term carbon cycle. Basins, canyons, and troughs near the coastline can serve as sediment traps and potentially accommodate large quantities of organic carbon along the Arctic coast. Here we use biomarkers (source-specific molecules), stable carbon isotopes, and radiocarbon to identify the sources of organic carbon in the nearshore zone of the southern Canadian Beaufort Sea near Herschel Island. We quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget of the area and estimate that more than a third of all carbon released by local permafrost erosion is efficiently trapped in marine sediments. This highlights the importance of regional sediment traps for carbon sequestration. Hoboken, NJ Wiley 2020 11 Geophysical research letters 47 3 10.1029/2019GL085897 Institut für Geowissenschaften