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  • 1
    Publication Date: 2018-02-16
    Description: The shelf zone of the Laptev Sea and the Lena Delta in particular, has shown pronounced changes over the last 100 years. Despite growing interest into the region, the still insufficient amount of observational data as well as the lack of modeling efforts with fine resolution over the shelf leaves many challenging questions. Certain observational evidence has, however, already accumulated, leading to valuable insights about dynamics in the current region. We collected the data about temperature and salinity profiles, dissolved oxygen and pH for the Lena Delta region of the Laptev Sea for different years. Additionally, the newly organized expedition to the Lena Delta allowed collecting the particulate carbon content and chemical composition in the main Lena freshwater channels. Based on these data, the dominant environmental factors driving the biological system were established. Given the large territory, the direct measurement data have to be supplemented by a hydrodynamical and bio-optical analysis via remote sensing and modeling. The goal of our modeling approach is to simulate the shelf circulation dynamics under the action of varying atmospheric forcing, Lena runoff and tidal forcing, and their impact on ecosystem dynamics.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 2
    Publication Date: 2015-05-06
    Description: Although a subsurface phenomenon, permafrost creates distinct features on the land surface which can be observed using remote sensing data. This is especially true for the East Siberian Arctic where ice-rich permafrost is abundant in the geological subsurface and only protected by a thin layer of organic soils. In the Lena River Delta, deeper seasonal thaw during increasingly frequent warm summers does not only result in irreversible loss of ground ice and subsequent land subsidence, but also in discharge of soil organic carbon that was previously fixed in permafrost. To characterize the dynamics of thawing permafrost and its impacts on landscapes, hydrology, and emission of methane and carbon dioxide we analyse optical remote sensing time series from various sensors. Local field measurements (meteorology, ground temperature, geodetic surveys) during several recent Russian-German Arctic expeditions complement our remote sensing studies and help differentiating factors causing relief and land cover changes. While previous studies concentrated on general inventory of thermokarst landforms, higher temporal resolution of contemporary image acquisitions provides unique information for the understanding of seasonal processes, such as ice-on and ice-off on thermokarst lakes, shore erosion on delta channels, water level changes and drainage events in lakes, and wettening/drying of thermokarst-affected areas. Ground truth data provides the basis for calibration and correction of 21 RapidEye scenes (level 1B) from 2014 using a bundle block adjustment procedure. Next steps will include extraction of seasonal variations of band metrics such as NDVI which we will compare to decadal Landsat time series of landcover change and multitemporal, photogrammetrically-derived digital elevation models in order to identify signatures and trends typical for permafrost thaw related processes on the surface. Our approach will allow assessment of rates and short-term changes in thermokarst dynamics and landscape evolution. In addition, the derived data will be valuable for permafrost-thaw model parameterization.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed , info:eu-repo/semantics/conferenceObject
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  • 3
    Publication Date: 2015-06-26
    Description: Submarine permafrost degradation has been invoked as a cause for recent observations of methane emissions from the seabed to the water column and atmosphere of the East Siberian shelf. Sediment drilled 52 m down from the sea ice in Buor Khaya Bay, central Laptev Sea revealed unfrozen sediment overlying ice-bonded permafrost. Methane concentrations in the overlying unfrozen sediment were low (mean 20 µM) but higher in the underlying ice-bonded submarine permafrost (mean 380 µM). In contrast, sulfate concentrations were substantially higher in the unfrozen sediment (mean 2.5 mM) than in the underlying submarine permafrost (mean 0.1 mM). Using deduced permafrost degradation rates, we calculate potential mean methane efflux from degrading permafrost of 120 mg m−2 yr−1 at this site. However, a drop of methane concentrations from 190 µM to 19 µM and a concomitant increase of methane δ13C from −63‰ to −35‰ directly above the ice-bonded permafrost suggest that methane is effectively oxidized within the overlying unfrozen sediment before it reaches the water column. High rates of methane ebullition into the water column observed elsewhere are thus unlikely to have ice-bonded permafrost as their source.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 4
    Publication Date: 2015-11-18
    Description: Arctic coastal infrastructure, 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.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 5
    Publication Date: 2016-02-12
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 6
    Publication Date: 2016-07-19
    Description: Palaeotemperature reconstructions play an important role as palaeoclimate records, for our understanding of the climate system behavior as such, as well as being the basis for models identifying the impact of these climate conditions on specific processes in the past and future. Temperature records reconstructed from borehole logs have a more direct relationship to the historic temperature history than other proxy-based reconstructions such as tree-rings, pollen or isotope ratios in ice cores, which can include influences from other independent factors on those proxies. At larger depths borehole temperatures are dominated by the geothermal heat flux and a rather uniform geothermal gradient in the profile. At shallower levels temperature variations at the surface propagate as heat waves into the ground. The further down, the more the temperature reflects influences of longer periods of surface variations due to the Earth’s damping higher angular frequency periods first. This study uses two inversion optimization methods previously applied to ice core sites (Roberts et al., 2013) to reconstruct the local surface temperature history at two shallow (100m and 65m deep) permafrost borehole sites: Sardakh Island in the Lena-Delta and Cape Mamontov Klyk in the Western Laptev Sea, Russia (Fig. 1). We employed a flux-conserving finite volume numerical soil model to calculate temperature-depth-profiles from surface temperature histories. Thermal properties of the sites were retrieved from either the observed temperature field or the sediment composition analysis of the borehole. Two inversion schemes that employ the forward soil model to optimize surface temperature history in a least square sense were used in the reconstruction: (i) the least square QR (LSQR) method and (ii) the particle swarm optimization (PSO) method. The latter resembles a Monte Carlo based approach (Ebbesen et al., 2012), the former is based on a generalized least-square solution of a linearized version of the problem as utilized by Orsi et al. (2012). Recoverable time length for the surface temperature histories for the two borehole sites were found to be well above 400 years in both cases by frequency-dependent heat wave damping analysis. The local surface soil temperature reconstructions for the two boreholes are discussed in comparison to other local as well as larger scale global temperature reconstructions to highlight important local and regional deviations. Additionally, the reconstructions of both sites are compared on the basis that one (Mamontov Klyk) is situated away from any major river systems and the other (Sardakh) is situated in the Lena River Delta, possibly showing thermal influence by the river. The local surface temperature history is important as a driving input factor in local permafrost models that assess the evolution, degradation and impact of permafrost in the high latitudes in the future climate system. References: Roberts JL, Moy AD, van Ommen TD, Curran MAJ, Worby AP, Goodwin ID, Inoue M. 2013. Borehole temperatures reveal a changed energy budget at Mill Island, East Antarctica, over recent decades. The Cryosphere 7: 263-273 Ebbesen S, Kiwitz P, Guzzella L. 2012. A generic particle swarm optimization Matlab function. American Control Conference (ACC); 1519-1524 Orsi A, Cornuelle B, Severinghaus J. 2012. Little Ice Age cold interval in West Antarctica: Evidence from borehole temperature at the West Antarctic Ice Sheet (WAIS) Divide. Geophys. Res. Lett. 39: L09710. DOI: 10.1029/2012GL051260
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 7
    Publication Date: 2017-10-17
    Description: Arctic coastal infrastructure, 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 study were to assess potential erosion and flood hazards at Herschel Island, a UNESCO World Heritage candidate site, and produce a map to be used as a decision making tool. The 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.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 8
    Publication Date: 2017-01-20
    Description: The effect of climate warming on the degradation of permafrost in Arctic coastal lowlands and associated hydrological and biogeochemical processes varies between different types of permafrost deposits. The Lena River Delta consists of three geomorphological main terraces that differ in their genesis and stratigraphic, cryological, geomorphological and hydrological characteristics. The third terrace was formed during the late Pleistocene and consists mainly of Yedoma-type Ice Complex deposits, whereas the first terrace has formed during the Holocene by deltaic processes. Permafrost degradation on both terraces releases dissolved organic carbon (DOC) to thermokarst lakes and via streams DOC gets transported to the Lena River channels and the Arctic Ocean. This presentation shows 1. differences in the surface water chemistry between the first terrace and the Yedoma Ice Complex and their landforms, 2. analyses of the temporal variability of DOC during the summer, and 3. an estimation of summer DOC flux for the considered catchment of about 6.45 km2. Between June and September 2013 and 2014, respectively summer surface water and soil water samples were collected in a small catchment in the south of Kurungnakh Island in the central Lena River Delta. This catchment covers the first terrace as well as the Yedoma Ice Complex and is characterized by thermokarst lakes and streams on both terraces. Two weirs were installed in the main stream along the drainage flow path to continuously measure discharge during summer 2013. We divided the study area into landscape units and compared pH, electrical conductivity, stable isotopic composition and DOC concentrations between units and between terraces. The considered landscape units are streams and thermokarst lakes on Yedoma Ice Complex and on the first terrace, Yedoma uplands, streams, which are fed by the Ice Complex, a relict lake on the first terrace and the Olenyokskaya Channel, a main branch of the Lena River. DOC concentrations in the landscape units on Yedoma Ice Complex ranged between 3.5 mg L-1 (streams) and 52.5 mg L−1 (soilwater of Yedoma uplands) and on the first terrace between 2.8 mg L−1 (streams) and 15.6 mg L−1 (relict lake). The electrical conductivity on Yedoma Ice Complex ranged between 35 μS cm-1 (soilwater of Yedoma uplands) and 151 μS cm−1 (streams) and on the first terrace between 54 μS cm−1 (streams and relict lake) and 140 μS cm−1 (streams). δ18O values on Yedoma Ice Complex and first terrace ranged between -22.4 ‰ (soilwater of Yedoma uplands) and -16.4 ‰ (streams) and between -20.4 ‰and -14.7 ‰ (streams), respectively. δD ranged between -165.6 ‰ (soilwater of Yedoma uplands) and 125.5 ‰ (streams, which are fed by the Ice Complex) and between -160.8 ‰ and -119.4 ‰ (streams). Source waters on the Yedoma Ice Complex had higher DOC concentrations and lower electrical conductivity than Yedoma Ice Complex thermokarst lakes and the drainage flow path. This suggests that more labile organic carbon, perhaps derived from permafrost degradation on the Yedoma Ice Complex, enriches the lake but is removed from the lake, for example, by mineralization in the water column. Along the drainage flow path no further decrease of DOC concentration was observed, despite increasing discharge from weir 1 at the beginning of the flow path to almost two and a half times at weir 2 at the end of the flow path, and despite decreasing discharge during the measuring period from 1814 m3 d−1 in the end of July to 199 m3 d−1 in the end of August for weir 1 and from 2819 m3 d−1 in the end of July to 567 m3 d−1 in the end of August for weir 2. The temporal variability of DOC concentration during the sampling periods was low. In 2013 one sample site of soil water collection fluctuated slightly in August between 10.5 mg L−1 and 13.3 mg L−1, whereas the remaining landscape units showed no temporal variability. In 2014 the DOC concentration of the relict lake on the first terrace decreased from July (13.5 mg L−1) to September (11.1 mg L−1). Otherwise there were no changes in DOC concentration in the remaining landscape units. DOC measurements of the Olenyokskaya Channel show a decrease in DOC concentration from 12.4 mg L−1 in June to 7.6 mg L−1 in September. Using discharge data of 2013 a summer DOC flux of about 220 kg in 29 days for the study site above weir 2 with an area of 6.45 km2 was calculated.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 9
    Publication Date: 2018-05-27
    Description: Thawing submarine permafrost is a source of methane to the subsurface biosphere. Methane oxidation in submarine permafrost sediments has been proposed, but the responsible microorganisms remain uncharacterized. We analyzed archaeal communities and identified distinct anaerobic methanotrophic assemblages of marine and terrestrial origin (ANME-2a/b, ANME-2d) both in frozen and completely thawed submarine permafrost sediments. Besides archaea potentially involved in anaerobic oxidation of methane (AOM) we found a large diversity of archaea mainly belonging to Bathyarchaeota, Thaumarchaeota, and Euryarchaeota. Methane concentrations and δ13C-methane signatures distinguish horizons of potential AOM coupled either to sulfate reduction in a sulfate-methane transition zone (SMTZ) or to the reduction of other electron acceptors, such as iron, manganese or nitrate. Analysis of functional marker genes (mcrA) and fluorescence in situ hybridization (FISH) corroborate potential activity of AOM communities in submarine permafrost sediments at low temperatures. Modeled potential AOM consumes 72–100% of submarine permafrost methane and up to 1.2 Tg of carbon per year for the total expected area of submarine permafrost. This is comparable with AOM habitats such as cold seeps. We thus propose that AOM is active where submarine permafrost thaws, which should be included in global methane budgets.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 10
    Publication Date: 2018-08-24
    Description: The Circumpolar Arctic Coastal Communities Observatory Network (CACCON) functions as the Arctic Regional Engagement Network for Future Earth Coasts. In partnership with other Arctic knowledge networks and programs, including the Exchange for Local Observations and Knowledge of the Arctic (ELOKA) and Arctic-COAST, CACCON promotes consensus and collaboration to advance local knowledge availability and accessibility for adaptation planning and sustainable development in Arctic coastal communities and regions. Components of the CACCON agenda include: integrative analyses of sustainability challenges in Arctic coastal communities using co-developed situational and sustainability indicators; solutions-oriented research for actionable, proactive adaptation policies in Arctic coastal communities; sharing insights among existing community-based research and resilience programs; responding to community-based agendas and building resilience by growing local and regional knowledge co-production and dissemination capacity. These activities support the Global Coastal Futures initiative of Future Earth Coasts, rooted in the Future Earth principles of co-design and co-production of knowledge involving a broad cross-section of stakeholders and consensus-building on pathways for transformation to more sustainable strategies for enhanced present and future well-being on Arctic coasts.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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