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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of dynamics and differential equations 6 (1994), S. 613-629 
    ISSN: 1572-9222
    Keywords: nonlocal reaction-diffusion equations ; stationary solutions ; bifurcation from simple eigenvalues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The stability of stationary solutions of nonlocal reaction-diffusion equations on a bounded intervalJ of the real line with homogeneous Dirichlet boundary conditions is studied. It is shown that it is possible to have stable stationary solutions which change sign once onJ in the case of constant diffusion when the reaction term does not depend explicitly on the space variable. The problem of the possible types of stable solutions that may exist is considered. It is also shown that Matano's result on the lap-number is still true in the case of nonlocal problems.
    Type of Medium: Electronic Resource
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  • 2
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    Arctic Observing Summit
    In:  EPIC3Arctic Observing Summit, online, 2020-03-31-2020-04-02Arctic Observing Summit
    Publication Date: 2020-11-26
    Description: Arctic permafrost coasts are major carbon (Schuur et al., 2015) and mercury pools (Schuster et al., 2018). They represent about 34% of the Earth’s coastline, with long sections affected by high erosion rates (Fritz et al, 2017), increasingly threatening coastal communities. 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 from 43 to 94% in September and from 8 to 34% in February (IPCC, 2014). An increase of the sea-ice free season leads to a longer exposure of coasts to wave action. Further, climate warming is also expected to modify the contribution of terrestrial erosion (Fritz et al., 2015, Ramage et al., 2018, Irrgang et al., 2018). Within the project EU Horizon2020 project NUNATARYUK, we are updating the mapping of the Arctic coast, with the Canadian Beaufort coast as a case-study. The surveying methodology includes: i. a high resolution update of the coastline mapping and change rates using Pleiades (CNES) satellite acquisitions from 2018, ii. a survey using RTK-UAV aerial imagery of long-term monitoring sites from the Canada-US border to King Point, and iii. the experimental use of TerraSAR-X staring spotlight scenes at key sites to monitor intraseasonal dynamics of cliff edge retreat. This research is funded by the EC H2020 Project NUNATARYUK. Support on remote sensing imagery access by the WMO Polar Space Task Group.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev , info:eu-repo/semantics/conferenceObject
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  • 3
    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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  • 4
    Publication Date: 2021-02-28
    Description: Permafrost coasts make up roughly one third of all coasts worldwide. Their erosion leads to the release of previously locked organic carbon, changes in ecosystems and the destruction of cultural heritage, infrastructure and whole communities. Since rapid environmental changes lead to an intensification of Arctic coastal dynamics, it is of great importance to adequately quantify current and future coastal changes. However, the remoteness of the Arctic and scarcity of data limit our understanding of coastal dynamics at a pan-Arctic scale and prohibit us from getting a complete picture of the diversity of impacts on the human and natural environment. In a joint effort of the EU project NUNATARYUK and the NSF project PerCS-Net, we seek to close this knowledge gap by collecting and analyzing all accessible high-resolution shoreline position data for the Arctic coastline. These datasets include geographical coordinates combined with coastal positions derived from archived data, surveying data, air and space born remote sensing products, or LiDAR products. The compilation of this unique dataset will enable us to reach unprecedented data coverage and will allow us a first insight into the magnitude and trends of shoreline changes on a pan-Arctic scale with locally highly resolved temporal and spatial changes in shoreline dynamics. By comparing consistently derived shoreline change data from all over the Arctic we expect that the trajectory of coastal change in the Arctic becomes evident. A synthesis of some initial results will be presented in the 2020 Arctic Report Card on Arctic Coastal Dynamics. This initiative is an ongoing effort – new data contributions are welcome!
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 5
    Publication Date: 2020-11-26
    Description: 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 high erosion rates (Fritz et al, 2017), increasingly affecting coastal communities. 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 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 further expose coasts to wave action, with changing climate also modifying the contribution of terrestrial erosion (Fritz et al., 2015, Ramage et al 2018, Irrgang et al 2018). Within the project NUNATARYUK, we are updating the mapping of the Arctic coast and assessing the hazard exposure of communities, with the Beaufort Sea as a case-study. The surveying methodology includes: i. a high resolution update of the coastline mapping and change rates using Pleiades (CNES) satellite acquisitions from 2018, ii. a survey using RTK-UAV aerial imagery of long-term monitoring sites from the CanadaUS border to King Point, as well as sites in Amundsen Bay, and iii. ultra high-resolution surveys of coastal settlements using RTK-UAV in collaboration with communities aiming at improving coastal hazard assessment (e.g. Tuktoyaktuk and Paulatuk). This presentation shows the updates from this integrated coastal assessment with the field data from the summer of 2019.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev , info:eu-repo/semantics/conferenceObject
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  • 6
    Publication Date: 2023-07-13
    Description: Soft sediment permafrost coasts are well known for their very dynamic nature. In some places their erosion can reach tens of meters, even though the erosion time is restricted to the short open water season of three to four months per year. Due to its high ground ice content, the Yukon coast in the western Canadian Arctic is particularly prone to erosion. Building on results from Irrgang et al., 2018, we continued analyzing shoreline movements along the Yukon Coast using Pleiades satellite imagery covering the whole Yukon Coast from 2018 and 2022, as well as very highly resolved data from UAV overflights covering long term monitoring sites in 2019 and 2022. Using the Digital Shoreline Analysis System (DSAS) Esri ArcMap extension tool, we quantified shoreline movements for the time periods 2011-2018, and 2018-2022 for the entire coastline and for 2015-2019 and 2019- 2022 for long term monitoring sites. We used the same transects and shoreline proxies as in Irrgang et al., 2018, to ensure comparability of our results and elongate our observation series. We will show how recent shoreline position changes differ from past ones and will provide possible reasoning for these detected changes. We are using our multi-time-step shoreline change rate dataset of the Yukon Coast for training and validation purposes within the Earth Observation for Permafrost Coasts (EO4PAC) project. The increasing usage of machine learning approaches for automated shoreline delineation and shoreline change rate retrieval opens up new pathways – especially if it comes to exploring large and remote areas. Such datasets which contain on site derived shoreline change rates and manually derived shorelines from (very) high resolution airborne and spaceborne data are crucial for training algorithms, validation of results and thus for the quality improvement of machine learning techniques.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 7
    Publication Date: 2015-01-01
    Print ISSN: 0960-1481
    Electronic ISSN: 1879-0682
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Elsevier
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  • 8
    Publication Date: 2004-01-01
    Print ISSN: 0024-3795
    Electronic ISSN: 1873-1856
    Topics: Mathematics
    Published by Elsevier
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  • 9
    Publication Date: 2004-01-01
    Print ISSN: 0024-3795
    Electronic ISSN: 1873-1856
    Topics: Mathematics
    Published by Elsevier
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  • 10
    Publication Date: 2015-06-23
    Print ISSN: 0095-4616
    Electronic ISSN: 1432-0606
    Topics: Mathematics
    Published by Springer
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