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  • 1
    Journal cover
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    Copernicus
    Online: 1.2014 –
    Publisher: Copernicus
    Topics: Physics
    Keywords: Astronomie, Astrophysik
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  • 2
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2001 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1680-7367
    Electronic ISSN: 1680-7375
    Topics: Geosciences
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  • 3
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2004 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1726-4170
    Electronic ISSN: 1726-4189
    Topics: Biology , Geosciences
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  • 4
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    Delft University of Technology | Copernicus
    Online: 1.2008 –
    Publisher: Delft University of Technology , Copernicus
    Print ISSN: 1996-9473
    Electronic ISSN: 1996-9481
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 5
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2006 – 4.2009
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1815-3836
    Electronic ISSN: 1815-3844
    Topics: Geosciences
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  • 6
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    Copernicus
    Online: 1.2013 –
    Publisher: Copernicus
    Print ISSN: 2195-4771
    Electronic ISSN: 2195-478X
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Keywords: Geothermie
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  • 7
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2001 –
    Print: 1.2001 – 10.2010 (Location: A17, Kompaktmagazin, 48/6-7)
    Publisher: European Geosciences Union (EGU) , Copernicus
    Corporation: European Geosciences Union, EGU
    Print ISSN: 1561-8633
    Electronic ISSN: 1684-9981
    Topics: Geography , Geosciences
    Acronym: NHESS
    Abbreviation: Nat Haz Earth Syst Sci
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  • 8
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    Copernicus
    Online: 1.2009 –
    Publisher: Copernicus
    Electronic ISSN: 1869-9537
    Topics: Geosciences
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  • 9
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    Copernicus
    Online: 1.2016 –
    Publisher: Copernicus
    Corporation: European Academy of Wind Energy, EAWE
    Electronic ISSN: 2366-7621
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Keywords: Windenergie ; Erneuerbare Energien
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  • 10
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    U.R.S.I.-Landesausschuss in der Bundesrepublik Deutschland e.V. | Copernicus
    Online: 1.2003 –
    Formerly as: Kleinheubacher Berichte  (1963–2001)
    Publisher: U.R.S.I.-Landesausschuss in der Bundesrepublik Deutschland e.V. , Copernicus
    Print ISSN: 1684-9965
    Electronic ISSN: 1684-9973
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 11
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2006 – 5.2010
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1815-381X
    Electronic ISSN: 1815-3828
    Topics: Geosciences
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  • 12
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    Copernicus | European Geosciences Union
    Online: 1.2019 –
    Publisher: Copernicus , European Geosciences Union
    Corporation: European Geosciences Union (EGU)
    Description: Geochronology (GChron) is a not-for-profit open-access open-review journal providing a unified outlet for high-quality basic and applied research in geochronology, independent of technique used or timescale considered. Geochronology publishes research in all aspects of geoscience that aim to determine times or rates of geologic events and processes: basic research into fundamental physics and chemistry of geologic dating methods; novel applications across the full range of geosciences; and developments in standardization and intercomparison, statistical methods, data management, and computational infrastructure. Geochronology aims to encourage and sustain innovation in geochronology by providing a centralized communication platform that transcends specific fields of application and focuses on the common theme of quantifying geologic time.
    Print ISSN: 2628-3697
    Electronic ISSN: 2628-3719
    Topics: Geosciences
    Acronym: GChron
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  • 13
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2008 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1991-9611
    Electronic ISSN: 1991-962X
    Topics: Geosciences
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  • 14
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2008 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1991-959X
    Electronic ISSN: 1991-9603
    Topics: Geosciences
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  • 15
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    Copernicus
    Online: 1(1).1982 –
    Publisher: Copernicus
    Print ISSN: 0262-821X
    Electronic ISSN: 2041-4978
    Topics: Geosciences
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  • 16
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    Copernicus
    Online: 1.2013 –
    Publisher: Copernicus
    Corporation: European Geosciences Union, EGU
    Electronic ISSN: 2195-9269
    Topics: Geography , Geosciences
    Keywords: Meteorologie, Klimaänderung, Geodynamik
    Acronym: NHESSD
    Abbreviation: Nat Haz Earth Syst Sci Discuss
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  • 17
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2005 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1812-0784
    Electronic ISSN: 1812-0792
    Topics: Geosciences
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  • 18
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2004 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1812-0806
    Electronic ISSN: 1812-0822
    Topics: Geosciences
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  • 19
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    Copernicus | Integrated Ocean Drilling Program
    Online: 1.2005 –
    Print: 1.2005 – (Location: A17, Kompaktmagazin, 64/6)
    Publisher: Copernicus , Integrated Ocean Drilling Program
    Corporation: German Research Centre for Geosciences, GFZ , Integrated Ocean Drilling Program, IODP
    Print ISSN: 1816-8957
    Electronic ISSN: 1816-3459
    Topics: Geosciences
    Keywords: Meeresgeologie, Tiefseeforschung
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  • 20
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    Copernicus
    Online: 1.2002 –
    Publisher: Copernicus
    Print ISSN: 1868-4556
    Electronic ISSN: 1868-4564
    Topics: Geosciences
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  • 21
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2003 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1680-7340
    Electronic ISSN: 1680-7359
    Topics: Geosciences
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  • 22
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    Copernicus
    Online: 1.2007 –
    Publisher: Copernicus
    Print ISSN: 1992-0628
    Electronic ISSN: 1992-0636
    Topics: Natural Sciences in General
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  • 23
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    Copernicus
    Online: 1.2015 –
    Publisher: Copernicus
    Print ISSN: 2364-3579
    Electronic ISSN: 2364-3587
    Topics: Geosciences , Physics
    Keywords: Ozeanographie ; Klimatologie ; Meteorologie
    Acronym: ASCMO
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  • 24
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    European Geosciences Union (EGU) | Copernicus
    Online: 14(10).1996 –
    Print: 1.1983 - 2.1984; 9(1).1991; 10.1992 – 28.2010 (Location: A17, Kompaktmagazin, 5/2-4)
    Formerly as: Annales de Géophysique  (1944–1982)
    Publisher: European Geosciences Union (EGU) , Copernicus
    Corporation: European Geophysical Society
    Print ISSN: 0992-7689
    Electronic ISSN: 1432-0576
    Topics: Geosciences , Physics
    Acronym: ANGEO
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  • 25
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2004 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
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  • 26
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    European Geosciences Union (EGU) | Copernicus
    Online: 1(1).2005 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1814-9340
    Electronic ISSN: 1814-9359
    Topics: Geosciences
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  • 27
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2007 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1994-0432
    Electronic ISSN: 1994-0440
    Topics: Geography , Geosciences
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  • 28
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2007 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1994-0416
    Electronic ISSN: 1994-0424
    Topics: Geography , Geosciences
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  • 29
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    Delft University of Technology | Copernicus
    Online: 1.2008 –
    Publisher: Delft University of Technology , Copernicus
    Print ISSN: 1996-9457
    Electronic ISSN: 1996-9465
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 30
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    Copernicus
    Online: 1.2010 –
    Publisher: Copernicus
    Electronic ISSN: 2190-4995
    Topics: Geosciences
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  • 31
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    Copernicus
    Online: 1.2009 –
    Publisher: Copernicus
    Print ISSN: 1866-3508
    Electronic ISSN: 1866-3516
    Topics: Geosciences
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  • 32
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    European Geosciences Union (EGU) | Copernicus
    Online: 7.2005 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1029-7006
    Electronic ISSN: 1607-7962
    Topics: Geosciences
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  • 33
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    American Geophysical Union (AGU) | European Geosciences Union (EGU) | Copernicus
    Online: 1.1994 –
    Print: 1.1994 – 17.2010 (Location: A17, Kompaktmagazin, 54/1)
    Publisher: American Geophysical Union (AGU) , European Geosciences Union (EGU) , Copernicus
    Corporation: European Geosciences Union, EGU
    Print ISSN: 1023-5809
    Electronic ISSN: 1607-7946
    Topics: Geosciences , Physics
    Keywords: Geophysik, Meteorologie, Ozeanographie
    Acronym: NPG
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  • 34
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    Copernicus
    Online: 1.2014 –
    Publisher: Copernicus
    Corporation: European Geosciences Union, EGU
    Electronic ISSN: 2198-5634
    Topics: Geosciences , Physics
    Keywords: Geophysik, Meteorologie, Ozeanographie
    Acronym: NPGD
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  • 35
    Publisher: Copernicus
    Corporation: International Association of Hydrological Sciences, IAHS
    Print ISSN: 2199-8981
    Electronic ISSN: 2199-899X
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Keywords: Hydrologie
    Acronym: PIAHS
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  • 36
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    Copernicus
    Online: 1.2005 – 8.2012
    Publisher: Copernicus
    Print ISSN: 1816-1499
    Electronic ISSN: 1816-1502
    Topics: Geography
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  • 37
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    Copernicus | European Geosciences Union (EGU)
    Online: 1.2014 –
    Publisher: Copernicus , European Geosciences Union (EGU)
    Electronic ISSN: 2199-3998
    Topics: Geosciences
    Keywords: Bodenkunde, Pedologie
    Acronym: SOILD
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  • 38
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2018 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Electronic ISSN: 2568-6402
    Topics: Geosciences , Physics
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  • 39
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    Arbeitsgemeinschaft Extraterrestrische Forschung e. V. (AEF) | Copernicus
    Online: 1.2004 – 8(1).2012
    Publisher: Arbeitsgemeinschaft Extraterrestrische Forschung e. V. (AEF) , Copernicus
    Print ISSN: 1810-6528
    Electronic ISSN: 1810-6536
    Topics: Physics
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  • 40
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2001 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1680-7316
    Electronic ISSN: 1680-7324
    Topics: Geosciences
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  • 41
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.2005 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1814-9324
    Electronic ISSN: 1814-9332
    Topics: Geosciences
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  • 42
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    Copernicus
    Online: 1.2010 –
    Publisher: Copernicus
    Print ISSN: 2190-4979
    Electronic ISSN: 2190-4987
    Topics: Geosciences
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  • 43
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    Copernicus
    Online: 1.2008 –
    Publisher: Copernicus
    Electronic ISSN: 1866-3591
    Topics: Geosciences
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  • 44
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    Copernicus
    Online: 1.1998 –
    Publisher: Copernicus
    Corporation: Museum für Naturkunde Berlin
    Print ISSN: 2193-0066
    Electronic ISSN: 2193-0074
    Topics: Geosciences
    Keywords: Paläontologie
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  • 45
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    Copernicus
    Online: 1.2010 –
    Publisher: Copernicus
    Print ISSN: 2190-5010
    Electronic ISSN: 2190-5029
    Topics: Geosciences
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  • 46
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    European Geosciences Union (EGU) | Copernicus
    Online: 1.1997 –
    Print: 1.1997 – 14.2010 (Location: A17, Kompaktmagazin, 33/5-6)
    Publisher: European Geosciences Union (EGU) , Copernicus
    Corporation: European Geosciences Union, EGU
    Print ISSN: 1027-5606
    Electronic ISSN: 1607-7938
    Topics: Geography , Geosciences
    Acronym: HESS
    Abbreviation: Hydrol Earth Syst Sci
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  • 47
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    European Geosciences Union (EGU) | Copernicus
    Online: 1(1).2004 –
    Publisher: European Geosciences Union (EGU) , Copernicus
    Print ISSN: 1812-2108
    Electronic ISSN: 1812-2116
    Topics: Geography , Geosciences
    Acronym: HESSD
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  • 48
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    Copernicus
    Online: 1.2010 –
    Publisher: Copernicus
    Print ISSN: 2191-9151
    Electronic ISSN: 2191-916X
    Topics: Physics
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  • 49
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    Copernicus
    Online: 1(1).2014 –
    Publisher: Copernicus
    Print ISSN: 2363-4707
    Electronic ISSN: 2363-4715
    Topics: Biology
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  • 50
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    Copernicus
    Online: 1.2010 –
    Publisher: Copernicus
    Print ISSN: 1869-9510
    Electronic ISSN: 1869-9529
    Topics: Geosciences
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  • 51
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    Copernicus
    Online: 1.2005 – 7.2012
    Publisher: Copernicus
    Print ISSN: 1729-4274
    Electronic ISSN: 1729-4312
    Topics: Geography
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  • 52
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    Copernicus
    Online: 1.2016 –
    Publisher: Copernicus
    Corporation: European Academy of Wind Energy, EAWE
    Print ISSN: 2366-7443
    Electronic ISSN: 2366-7451
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Keywords: Windenergie ; Erneuerbare Energien
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  • 53
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    Copernicus
    In:  Climate of the Past Discussions . pp. 1-51.
    Publication Date: 2018-09-05
    Description: Dynamic vegetation models simulate global vegetation in terms of fractional coverages of a few plant functional types (PFTs). Although these models often share the same concept, they differ with respect to the number and kind of PFTs, complicating the comparability of simulated vegetation distributions. Pollen-based reconstructions are initially only available in form of time-series of individual taxa that are not distinguished in the models. Thus, to evaluate simulated vegetation distributions, the modelling results and pollen-based reconstructions have to be converted into a comparable format. The classical approach is the method of biomisation, but hitherto, PFT-based biomisation methods were only available for individual models. We introduce and evaluate a simple, universally applicable technique to harmonize PFT-distributions by assigning them into nine mega-biomes that follow the definitions commonly used for vegetation reconstructions. The method works well for all state-of the art dynamic vegetation models, independent of the spatial resolution or the complexity of the models. Large biome belts (such as tropical forest) are well represented, but regionally confined biomes (warm-mixed forest, Savanna) are only partly captured. Overall, the PFT-based biomisation is able to keep up with the conventional biomisation approach of forcing biome models (here: BIOME1) with the background climate states. The new method has, however, the advantage that it allows a more direct comparison and evaluation of the vegetation distributions simulated by Earth System Models. Thereby, the new method provides a powerful tool for the evaluation of Earth System Models in general.
    Type: Article , NonPeerReviewed
    Format: text
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  • 54
    Publication Date: 2018-09-12
    Description: In this study, we propose a statistical method to validate sea-level reconstructions using geological records known as sea-level indicators (SLIs). SLIs are often the only available data to retrace late-glacial relative sea level (RSL). Determining the RSL from SLI height is not straight forward, the elevation at which an SLI was found usually does not represent the past RSL. In contrast, it has to be related to past RSL by investigating sample’s type, habitat and deposition conditions. For instance, water distribution at which a specific specimen is found today can be related to the indicator's depositional height range. Furthermore, the precision of dating varies between geological samples, and, in case of radiocarbon dating, the age has to be calibrated using a non-linear calibration curve. To avoid an a-priori assumption like normal-distributed uncertainties, we define likelihood functions which take into account the indicative meaning’s available error information and calibration statistics represented by joint probabilities. For this conceptional study, we restrict ourselves to one type of indicators, shallow-water shells, which are usually considered as low-grade samples giving only a lower limit of former sea level, as the depth range in which they live spreads over several tens of meters, and does not follow a normal distribution. The presented method is aimed to serve as a strategy for glacial isostatic adjustment reconstructions, in this case for the German Paleo-Climate Modelling Initiative PalMod (https://www.palmod.de/en) and by extending it to other SLI types.
    Type: Article , NonPeerReviewed
    Format: text
    Format: text
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  • 55
    Publication Date: 2018-02-16
    Description: The Lena Delta in Northern Siberia is one of the largest river deltas in the world. During peak discharge, after the ice melt in spring, it delivers between 60–8000 m3 s−1 of water and sediment into the Arctic Ocean. The Lena Delta and the Laptev Sea coast also constitute a continuous permafrost region. Ongoing climate change, which is particularly pronounced in the Arctic, is leading to increased rates of permafrost thaw. This has already profoundly altered the discharge rates of the Lena River. But the chemistry of the river waters which are discharged into the coastal Laptev Sea have also been hypothesized to undergo considerable compositional changes, e.g. by increasing concentrations of inorganic nutrients such as dissolved organic carbon (DOC) and methane. These physical and chemical changes will also affect the composition of the phytoplankton communities. However, before potential consequences of climate change for coastal arctic phytoplankton communities can be judged, the inherent status of the diversity and food web interactions within the delta have to be established. In 2010, as part of the AWI Lena Delta programme, the phyto- and microzooplankton community in three river channels of the delta (Trofimov, Bykov and Olenek) as well as four coastal transects were investigated to capture the typical river phytoplankton communities and the transitional zone of brackish/marine conditions. Most CTD profiles from 23 coastal stations showed very strong stratification. The only exception to this was a small, shallow and mixed area running from the outflow of Bykov channel in a northerly direction parallel to the shore. Of the five stations in this area, three had a salinity of close to zero. Two further stations had salinities of around 2 and 5 throughout the water column. In the remaining transects, on the other hand, salinities varied between 5 and 30 with depth. Phytoplankton counts from the outflow from the Lena were dominated by diatoms (Aulacoseira species) cyanobacteria (Aphanizomenon, Pseudanabaena) and chlorophytes. In contrast, in the stratified stations the plankton was mostly dominated by dinoflagellates, ciliates and nanoflagellates, with only an insignificant diatom component from the genera Chaetoceros and Thalassiosira (brackish as opposed to freshwater species). Ciliate abundance was significantly coupled with the abundance of total flagellates. A pronounced partitioning in the phytoplankton community was also discernible with depth, with a different community composition and abundance above and below the thermocline in the stratified sites. This work is a first analysis of the phytoplankton community structure in the region where Lena River discharge enters the Laptev Sea.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 56
    Publication Date: 2014-11-28
    Description: The reconstruction of the stable carbon isotope evolution in atmospheric CO2 (δ13Catm), as archived in Antarctic ice cores, bears the potential to disentangle the contributions of the different carbon cycle fluxes causing past CO2 variations. Here we present a new record of δ13Catm before, during and after the Marine Isotope Stage 5.5 (155 000 to 105 000 yr BP). The dataset is archived on the data repository PANGEA® (www.pangea.de) under 10.1594/PANGAEA.817041. The record was derived with a well established sublimation method using ice from the EPICA Dome C (EDC) and the Talos Dome ice cores in East Antarctica. We find a 0.4‰ shift to heavier values between the mean δ13Catm level in the Penultimate (~ 140 000 yr BP) and Last Glacial Maximum (~ 22 000 yr BP), which can be explained by either (i) changes in the isotopic composition or (ii) intensity of the carbon input fluxes to the combined ocean/atmosphere carbon reservoir or (iii) by long-term peat buildup. Our isotopic data suggest that the carbon cycle evolution along Termination II and the subsequent interglacial was controlled by essentially the same processes as during the last 24 000 yr, but with different phasing and magnitudes. Furthermore, a 5000 yr lag in the CO2 decline relative to EDC temperatures is confirmed during the glacial inception at the end of MIS5.5 (120 000 yr BP). Based on our isotopic data this lag can be explained by terrestrial carbon release and carbonate compensation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
    Format: application/pdf
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  • 57
    Publication Date: 2018-02-16
    Description: Bio-optical measurements and sampling were carried out in the delta of the Lena River (northern Siberia, Russia) between 26 June and 4 July 2011. The aim of this study was to determine the inherent optical properties of the Lena water, i.e., absorption, attenuation, and scattering coefficients, during the period of maximum runoff. This aimed to contribute to the development of a bio-optical model for use as the basis for optical remote sensing of coastal water of the Arctic. In this context the absorption by CDOM (colored dissolved organic matter) and particles, and the concentrations of total suspended matter, phytoplankton-pigments, and carbon were measured. CDOM was found to be the most dominant parameter affecting the optical properties of the river, with an absorption coefficient of 4.5–5 m−1 at 442 nm, which was almost four times higher than total particle absorption values at visible wavelength range. The wavelenght-dependence of absorption of the different water constituents was chracterized by determining the semi logarithmic spectral slope. Mean CDOM, and detritus slopes were 0.0149 nm−1(standard deviation (stdev) = 0.0003, n = 18), and 0.0057 nm−1 (stdev = 0.0017, n = 19), respectively, values which are typical for water bodies with high concentrations of dissolved and particulate carbon. Mean chlorophyll a and total suspended matter were 1.8 mg m−3 (stdev = 0.734 n = 18) and 31.9 g m−3 (stdev = 19.94, n = 27), respectively. DOC (dissolved organic carbon) was in the range 8–10 g m−3 and the total particulate carbon (PC) in the range 0.25–1.5 g m−3. The light penetration depth (Secchi disc depth) was in the range 30–90 cm and was highly correlated with the suspended matter concentration. The period of maximum river runoff in June was chosen to obtain bio-optical data when maximum water constituents are transported into the Laptev Sea. However, we are aware that more data from other seasons and other years need to be collected to establish a general bio-optical model of the Lena water and conclusively characterize the light climate with respect to primary production.
    Repository Name: EPIC Alfred Wegener Institut
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  • 58
    Publication Date: 2015-03-19
    Description: The Surface Ocean CO2 Atlas (SOCAT), an activity of the international marine carbon research community, provides access to synthesis and gridded fCO2 (fugacity of carbon dioxide) products for the surface oceans. Version 2 of SOCAT is an update of the previous release (version 1) with more data (increased from 6.3 million to 10.1 million surface water fCO2 values) and extended data coverage (from 1968–2007 to 1968–2011). The quality control criteria, while identical in both versions, have been applied more strictly in version 2 than in version 1. The SOCAT website (http://www.socat.info/) has links to quality control comments, metadata, individual data set files, and synthesis and gridded data products. Interactive online tools allow visitors to explore the richness of the data. Applications of SOCAT include process studies, quantification of the ocean carbon sink and its spatial, seasonal, year-to-year and longerterm variation, as well as initialisation or validation of ocean carbon models and coupled climate-carbon models.
    Repository Name: EPIC Alfred Wegener Institut
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  • 59
    Publication Date: 2014-06-02
    Description: Following the launch of ESA's Soil Moisture and Ocean Salinity (SMOS) mission, it has been shown that brightness temperatures at a low microwave frequency of 1.4 GHz (L-band) are sensitive to sea ice properties. In the first demonstration study, sea ice thickness up to 50 cm has been derived using a semi-empirical algorithm with constant tie-points. Here, we introduce a novel iterative retrieval algorithm that is based on a thermodynamic sea ice model and a three-layer radiative transfer model, which explicitly takes variations of ice temperature and ice salinity into account. In addition, ice thickness variations within the SMOS spatial resolution are considered through a statistical thickness distribution function derived from high-resolution ice thickness measurements from NASA's Operation IceBridge campaign. This new algorithm has been used for the continuous operational production of a SMOS-based sea ice thickness data set from 2010 on. The data set is compared to and validated with estimates from assimilation systems, remote sensing data, and airborne electromagnetic sounding data. The comparisons show that the new retrieval algorithm has a considerably better agreement with the validation data and delivers a more realistic Arctic-wide ice thickness distribution than the algorithm used in the previous study (Kaleschke et al., 2012).
    Repository Name: EPIC Alfred Wegener Institut
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  • 60
    Publication Date: 2015-05-11
    Description: The ice sheets in Greenland and Antarctica contain a significant amount of air within their upper approximately thousand meters and air hydrates below. While this air is still in exchange with the atmosphere in the permeable firn, the gas is entrapped at the firn-ice transition at 60 – 120 m depth. Understanding the dominant deformation mechanisms is essential to interpret paleo-atmosphere records and to allow a more realistic model of ice sheet dynamics. Recent research shows how the presence of air bubbles can significantly influence microdynamical processes such as grain growth and grain boundary migration (Azuma et al., 2012, Roessiger et al., 2014). Therefore, numerical modelling was performed focussing on the mechanical properties of ice with air inclusions and the implications of the presence of bubbles on recrystallisation. The full-field crystal plasticity code of Lebensohn (2001), using a Fast Fourier Transform (FFT), was coupled to the 2D numerical microstructural modelling platform Elle, following the approach by Griera et al. (2013), and used to simulate dynamic recrystallization of pure ice (Montagnat et al., 2013). FFT calculates the viscoplastic response of polycrystalline and polyphase materials that deform by dislocation glide, takes into account the mechanical anisotropy of ice and calculates dislocation densities using the local gradient of the strain-rate field. Incorporating a code for polyphase grain boundary migration driven by surface and internal strain energy reduction, based on the methodology of Becker et al. (2008) and Roessiger et al. (2014), now also enables us to model deformation of ice with air bubbles. The presence of bubbles leads to an increase in strain localization, which reduces the bulk strength of the bubbly ice. In the absence of dynamic recrystallisation, air bubbles quickly collapse at low strains and spherical to elliptical bubble shapes are only maintained when recrystallisation is activated. Our modelling confirms that strain-induced grain boundary migration already occurs in the uppermost levels of ice sheets (Kipfstuhl et al. 2009, Weikusat et al. 2009).
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  • 61
    Publication Date: 2015-05-11
    Description: Deformation of ice in continental sized ice sheets determines the flow behavior of ice towards the sea. Basal dislocation glide is assumed to be the dominant deformation mechanism in the creep deformation of natural ice, but non-basal glide is active as well. Knowledge of what types of deformation mechanisms are active in polar ice is critical in predicting the response of ice sheets in future warmer climates and its contribution to sea level rise, because the activity of deformation mechanisms depends critically on deformation conditions (such as temperature) as well as on the material properties (such as grain size). One of the methods to study the deformation mechanisms in natural materials is Electron Backscattered Diffraction (EBSD). We obtained ca. 50 EBSD maps of five different depths from a Greenlandic ice core (NEEM). The step size varied between 8 and 25 micron depending on the size of the deformation features. The size of the maps varied from 2000 to 10000 grid point. Indexing rates were up to 95%, partially by saving and reanalyzing the EBSP patterns. With this method we can characterize subgrain boundaries and determine the lattice rotation configurations of each individual subgrain. Combining these observations with arrangement/geometry of subgrain boundaries the dislocation types can be determined, which form these boundaries. Three main types of subgrain boundaries have been recognized in Antarctic (EDML) ice core (Weikusat et al. 2010, 2011). Here, we present the first results obtained from EBSD measurements performed on the NEEM ice core samples from the last glacial period, focusing on the relevance of dislocation activity of the possible slip systems. Preliminary results show that all three subgrain types, recognized in the EDML core, occur in the NEEM samples. In addition to the classical boundaries made up of basal dislocations, subgrain boundaries made of non-basal dislocations are also common.
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  • 62
    Publication Date: 2015-05-11
    Description: Ice is a common mineral at the Earth’s surface. How much ice is stored in the Greenland and Antarctic ice sheets depends on its mechanical properties. Therefore properties of ice directly impact on human society through its role in controlling sea level. The bulk behaviour of large ice masses is the result of the behaviour of the ensemble of individual ice grains. This is strongly influenced by the viscoplastic anisotropy of these grains and their lattice orientation. Numerical modelling provides a better insight into the mechanics of ice from the micro to the ice sheet scale. We present numerical simulations that predict the microstructural evolution of an aggregate of pure ice grains at different strain rates. We simulate co-axial deformation and dynamic recrystallization up to large strain using a full-field approach. The crystal plasticity code (Lebensohn et al., 2009) is used to calculate the response of a polycrystalline aggregate that deforms by purely dislocation glide, applying a Fast Fourier Transform (FFT). This code is coupled with the ELLE microstructural modelling platform to include intracrystalline recovery, as well as grain boundary migration driven by the reduction of surface and strain energies. The results show a strong effect of recrystallization on the final microstructure, producing larger and more equiaxed grains, with smooth boundaries. This effect does not significantly modify the single-maximum pattern of c-axes that are distributed at a low angle to the shortening direction. However, in experiments with significant recrystallization the a-axes rotate towards the elongation axis at the same time as the c-axes rotate towards the compression axis. If slip systems on prismatic and/or pyramidal planes are active, it is thought that a-axes gradually concentrate with depth (Miyamoto, 2005). The bulk activity of the slip systems is different depending on the relative activity of deformation versus recrystallization: the non-basal slip systems are more active at high strain in experiments with dynamic recrystallization compared to those experiments with low recrystallization activity.
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  • 63
    Publication Date: 2015-05-11
    Description: Ice cores are the only climate archives incorporating paleo-atmosphere as individual gas inclusions, enabling the extraction and analysis of the contained gasses. A firm understanding of the processes involved is mandatory for a reliable interpretation of the gas records. One prominent process is the transition from air bubbles to crystalline air hydrates, which is known to influence, at least temporarily, the gas mixing ratios by diffusion and fractionation. This transition is still not understood completely and the existing theories do not explain the large diversity of observed hydrate morphologies. Raman tomographic measurements using the AWI cryo-Raman system provide 3D reconstructions of air hydrate morphologies. The results show complex growth structures that emphasize the importance of crystallography, microstructure and ice rheology for the hydrate formation process. Accurate hydrate volumes can be calculated from the 3D objects, improving the estimates of total gas contents.
    Repository Name: EPIC Alfred Wegener Institut
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  • 64
    Publication Date: 2015-05-11
    Description: The Asian monsoon system is an important tipping element in Earth's climate with a large impact on human societies in the past and present. In light of the potentially severe impacts of present and future anthropogenic climate change on Asian hydrology, it is vital to understand the forcing mechanisms of past climatic regime shifts in the Asian monsoon domain. Here we use novel recurrence network analysis techniques for detecting episodes with pronounced non-linear changes in Holocene Asian monsoon dynamics recorded in speleothems from caves distributed throughout the major branches of the Asian monsoon system. A newly developed multi-proxy methodology explicitly considers dating uncertainties with the COPRA (COnstructing Proxy Records from Age models) approach and allows for detection of continental-scale regime shifts in the complexity of monsoon dynamics. Several epochs are characterised by non-linear regime shifts in Asian monsoon variability, including the periods around 8.5–7.9, 5.7–5.0, 4.1–3.7, and 3.0–2.4 ka BP. The timing of these regime shifts is consistent with known episodes of Holocene rapid climate change (RCC) and high-latitude Bond events. Additionally, we observe a previously rarely reported non-linear regime shift around 7.3 ka BP, a timing that matches the typical 1.0–1.5 ky return intervals of Bond events. A detailed review of previously suggested links between Holocene climatic changes in the Asian monsoon domain and the archaeological record indicates that, in addition to previously considered longer-term changes in mean monsoon intensity and other climatic parameters, regime shifts in monsoon complexity might have played an important role as drivers of migration, pronounced cultural changes, and the collapse of ancient human societies.
    Repository Name: EPIC Alfred Wegener Institut
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  • 65
    Publication Date: 2015-04-20
    Description: A still open question is how equilibrium warming in response to increasing radiative forcing (equilibrium climate sensitivity S) is depending on background climate. We here bring paleo-data based evidence on the state-dependency of S by using CO2 proxy data together with model-based reconstruction of land ice albedo over the last 5 million years. We find that the land-ice albedo forcing depends non-linearly on the background climate, while any non-linearity of CO2 radiative forcings depends on the CO2 data set used. Over the last 2 million years the combined S_[CO2,LI] from CO2 and land-ice albedo forcing is state-dependent and during interglacials at least twice as high as during glacials, thus CO2 doubling leads to an interglacial warming of 5 K. In the Pliocene data uncertainties prevents a well-supported calculation, but our analysis suggests that S_[CO2,LI] during a land-ice free northern hemisphere was smaller than during interglacials of the Pleistocene.
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  • 66
    Publication Date: 2015-05-28
    Description: Thermokarst lakes are important emitters of methane, a potent greenhouse gas. However, accurate estimation of methane flux from thermokarst lakes is difficult due to their remoteness and observational challenges associated with the heterogeneous nature of ebullition (bubbling). We used multi-temporal high-resolution (9–11 cm) aerial images of an interior Alaskan thermokarst lake, Goldstream Lake, acquired 2 and 4 days following freeze-up in 2011 and 2012, respectively, to characterize methane ebullition seeps and to estimate whole-lake ebullition. Bubbles impeded by the lake ice sheet form distinct white patches as a function of bubbling rate vs. time as ice thickens. Our aerial imagery thus captured in a single snapshot the ebullition events that occurred before the image acquisition. Image analysis showed that low-flux A- and B-type seeps are associated with low brightness patches and are statistically distinct from high-flux C-type and Hotspot seeps associated with high brightness patches. Mean whole-lake ebullition based on optical image analysis in combination with bubble-trap flux measurements was estimated to be 174 ± 28 and 216 ± 33 mL gas m−2 d−1 for the years 2011 and 2012, respectively. A large number of seeps demonstrated spatio-temporal stability over our two-year study period. A strong inverse exponential relationship (R2 ≥ 0.79) was found between percent surface area of lake ice covered with bubble patches and distance from the active thermokarst lake margin. Our study shows that optical remote sensing is a powerful tool to map ebullition seeps on lake ice, to identify their relative strength of ebullition and to assess their spatio-temporal variability.
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  • 67
    Publication Date: 2015-12-22
    Description: Whereas ice cores from high-accumulation sites in coastal Antarctica clearly demonstrate annual layering, it is debated whether a seasonal signal is also preserved in ice cores from lower-accumulation sites further inland and particularly on the East Antarctic Plateau. In this study, we examine 5 m of early Holocene ice from the Dome Fuji (DF) ice core at a high temporal resolution by continuous flow analysis. The ice was continuously analysed for concentrations of dust, sodium, ammonium, liquid conductivity, and water isotopic composition. Furthermore, a dielectric profiling was performed on the solid ice. In most of the analysed ice, the multi-parameter impurity data set appears to resolve the seasonal variability although the identification of annual layers is not always unambiguous. The study thus provides information on the snow accumulation process in central East Antarctica. A layer counting based on the same principles as those previously applied to the NGRIP (North Greenland Ice core Project) and the Antarctic EPICA (European Project for Ice Coring in Antarctica) Dronning Maud Land (EDML) ice cores leads to a mean annual layer thickness for the DF ice of 3.0 ± 0.3 cm that compares well to existing estimates. The measured DF section is linked to the EDML ice core through a characteristic pattern of three significant acidity peaks that are present in both cores. The corresponding section of the EDML ice core has recently been dated by annual layer counting and the number of years identified independently in the two cores agree within error estimates. We therefore conclude that, to first order, the annual signal is preserved in this section of the DF core. This case study demonstrates the feasibility of determining annually deposited strata on the central East Antarctic Plateau. It also opens the possibility of resolving annual layers in the Eemian section of Antarctic ice cores where the accumulation is estimated to have been greater than in the Holocene. © Author(s) 2015.
    Repository Name: EPIC Alfred Wegener Institut
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  • 68
    Publication Date: 2016-11-16
    Description: Permafrost presence is determined by a complex interaction of climatic, topographic, and ecological conditions operating over long time scales. In particular, vegetation and organic layer characteristics may act to protect permafrost in regions with a mean annual air temperature (MAAT) above 0°C. In this study, we document the presence of residual permafrost plateaus in the western Kenai Peninsula lowlands of south-central Alaska, a region with a MAAT of 1.5+/-1 °C (1981–2010). Continuous ground temperature measurements between 16 September 2012 and 15 September 2015, using calibrated thermistor strings, documented the presence of warm permafrost (-0.04 to -0.08 °C). Field measurements (probing) on several plateau features during the fall of 2015 showed that the depth to the permafrost table averaged 1.48m but at some locations was as shallow as 0.53 m. Late winter surveys (augering, coring, and GPR) in 2016 showed that the average seasonally frozen ground thickness was 0.45 m, overlying a talik above the permafrost table. Measured permafrost thickness ranged from 0.33 to 〉6.90 m. Manual interpretation of historic aerial photography acquired in 1950 indicates that residual permafrost plateaus covered 920 ha as mapped across portions of four wetland complexes encompassing 4810 ha. However, between 1950 and ca. 2010, permafrost plateau extent decreased by 60.0 %, with lateral feature degradation accounting for 85.0% of the reduction in area. Permafrost loss on the Kenai Peninsula is likely associated with a warming climate, wildfires that remove the protective forest and organic layer cover, groundwater flow at depth, and lateral heat transfer from wetland surface waters in the summer. Better understanding the resilience and vulnerability of ecosystem-protected permafrost is critical for mapping and predicting future permafrost extent and degradation across all permafrost regions that are currently warming. Further work should focus on reconstructing permafrost history in south-central Alaska as well as additional contemporary observations of these ecosystem-protected permafrost sites south of the regions with relatively stable permafrost.
    Repository Name: EPIC Alfred Wegener Institut
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  • 69
    Publication Date: 2017-12-19
    Description: Climate trends in the Antarctic region remain poorly characterized, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica2k working group, we build an enlarged database of ice core water stable isotope records from Antarctica, consisting of 112 records. We produce both unweighted and weighted isotopic (δ18O) composites and temperature reconstructions since 0 CE, binned at 5- and 10-year resolution, for seven climatically distinct regions covering the Antarctic continent. Following earlier work of the Antarctica2k working group, we also produce composites and reconstructions for the broader regions of East Antarctica, West Antarctica and the whole continent. We use three methods for our temperature reconstructions: (i) a temperature scaling based on the δ18O–temperature relationship output from an ECHAM5-wiso model simulation nudged to ERA-Interim atmospheric reanalyses from 1979 to 2013, and adjusted for the West Antarctic Ice Sheet region to borehole temperature data, (ii) a temperature scaling of the isotopic normalized anomalies to the variance of the regional reanalysis temperature and (iii) a composite-plus-scaling approach used in a previous continent-scale reconstruction of Antarctic temperature since 1 CE but applied to the new Antarctic ice core database. Our new reconstructions confirm a significant cooling trend from 0 to 1900 CE across all Antarctic regions where records extend back into the 1st millennium, with the exception of the Wilkes Land coast and Weddell Sea coast regions. Within this long-term cooling trend from 0 to 1900 CE, we find that the warmest period occurs between 300 and 1000 CE, and the coldest interval occurs from 1200 to 1900 CE. Since 1900 CE, significant warming trends are identified for the West Antarctic Ice Sheet, the Dronning Maud Land coast and the Antarctic Peninsula regions, and these trends are robust across the distribution of records that contribute to the unweighted isotopic composites and also significant in the weighted temperature reconstructions. Only for the Antarctic Peninsula is this most recent century-scale trend unusual in the context of natural variability over the last 2000 years. However, projected warming of the Antarctic continent during the 21st century may soon see significant and unusual warming develop across other parts of the Antarctic continent. The extended Antarctica2k ice core isotope database developed by this working group opens up many avenues for developing a deeper understanding of the response of Antarctic climate to natural and anthropogenic climate forcings. The first long-term quantification of regional climate in Antarctica presented herein is a basis for data–model comparison and assessments of past, present and future driving factors of Antarctic climate.
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  • 70
    Publication Date: 2018-08-20
    Description: To resolve the mechanisms behind the major climate reorganisation which occurred between 0.9 and 1.2Ma, the recovery of a suitable 1.5 million-year-old ice core is fundamental. The quest for such an Oldest Ice core requires a number of key boundary conditions, of which the poorly known basal geothermal heat flux (GHF) is lacking. We use a transient thermodynamical 1D vertical model that solves for the rate of change of temperature in the vertical, with surface temperature and modelled GHF as boundary conditions. For each point on the ice sheet, the model is forced with variations in atmospheric conditions over the last 2Ma, and modelled ice-thickness variations. The process is repeated for a range of GHF values to determine the value of GHF that marks the limit between frozen and melting conditions over the whole ice sheet, taking into account 2Ma of climate history. These threshold values of GHF are statistically compared to existing GHF data sets. The new probabilistic GHF fields obtained for the ice sheet thus provide the missing boundary conditions in the search for Oldest Ice. High spatial resolution radar data are examined locally in the Dome Fuji and Dome C regions, as these represent the ice core community's primary drilling sites. GHF, bedrock variability, ice thickness and other essential criteria combined highlight a dozen major potential Oldest Ice sites in the vicinity of Dome Fuji and Dome C, where GHF allows for Oldest Ice.
    Repository Name: EPIC Alfred Wegener Institut
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  • 71
    Publication Date: 2018-10-29
    Repository Name: EPIC Alfred Wegener Institut
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  • 72
    Publication Date: 2017-11-06
    Description: A suite of oxygenated volatile organic compounds (OVOCs – acetaldehyde, acetone, propanal, butanal and butanone) were measured concurrently in the surface water and atmosphere of the South China Sea and Sulu Sea in November 2011. A strong correlation was observed between all OVOC concentrations in the surface seawater along the entire cruise track, except for acetaldehyde, suggesting similar sources and sinks in the surface ocean. Additionally, several phytoplankton groups, such as haptophytes or pelagophytes, were also correlated to all OVOCs indicating that phytoplankton may be an important source for marine OVOCs in the South China and Sulu Seas. Humic and protein like fluorescent dissolved organic matter (FDOM) components seemed to be additional precursors for butanone and acetaldehyde. The atmospheric OVOC mixing ratios were relative high compared with literature values, suggesting the coastal region of North Borneo as a local hot spot for atmospheric OVOCs. The flux of atmospheric OVOCs was largely into the ocean for all 5 gases, with a few important exceptions near the coast of Borneo. The calculated amount of OVOCs entrained into the ocean seemed to be an important source of OVOCs to the surface ocean. When the fluxes were out of the ocean, marine OVOCs were found to be enough to control the local measured OVOC distribution in the atmosphere. Based on our model calculations, at least 0.4 ppb of marine derived acetone and butanone can reach the upper troposphere, where they may have an important influence on hydrogen oxide radical formation over the western Pacific Ocean.
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  • 73
    Publication Date: 2018-03-28
    Description: The Extrapolar SWIFT model is a fast ozone chemistry scheme for interactive calculation of the extrapolar stratospheric ozone layer in coupled general circulation models (GCMs). In contrast to the widely used prescribed ozone, the SWIFT ozone layer interacts with the model dynamics and can respond to atmospheric variability or climatological trends. The Extrapolar SWIFT model employs a repro-modelling approach, where algebraic functions are used to approximate the numerical output of a full stratospheric chemistry and transport model (ATLAS). The full model solves a coupled chemical differential equations system with 55 initial and boundary conditions (mixing ratio of various chemical species and atmospheric parameters). Hence the rate of change of ozone over 24  h is a function of 55 variables. Using covariances between these variables, we can find linear combinations in order to reduce the parameter space to the following nine basic variables: latitude, pressure altitude, temperature, local ozone column, mixing ratio of ozone and of the ozone depleting families (Cly, Bry, NOy and HOy). We will show that these 9 variables are sufficient to characterize the rate of change of ozone. An automated procedure fits a polynomial function of fourth degree to the rate of change of ozone obtained from several simulations with the ATLAS model. One polynomial function is determined per month which yields the rate of change of ozone over 24 h. A key aspect for the robustness of the Extrapolar SWIFT model is to include a wide range of stratospheric variability in the numerical output of the ATLAS model, also covering atmospheric states that will occur in a future climate (e.g. temperature and meridional circulation changes or reduction of stratospheric chlorine loading). For validation purposes, the Extrapolar SWIFT model has been integrated into the ATLAS model replacing the full stratospheric chemistry scheme. Simulations with SWIFT in ATLAS have proven that the systematic error is small and does not accumulate during the course of a simulation. In the context of a 10 year simulation, the ozone layer, simulated by SWIFT, shows a stable annual cycle, with inter-annual variations comparable to the ATLAS model. The application of Extrapolar SWIFT requires the evaluation of polynomial functions with 30–100 terms. Nowadays, computers can calculate such polynomial functions at thousands of model grid points in seconds. SWIFT provides the desired numerical efficiency and computes the ozone layer 104 times faster than the chemistry scheme in the ATLAS CTM.
    Repository Name: EPIC Alfred Wegener Institut
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  • 74
    Publication Date: 2018-04-05
    Repository Name: EPIC Alfred Wegener Institut
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  • 75
    Publication Date: 2012-11-14
    Description: Earthquake history shows that the Sunda subduction zone of the Indonesian margin produces great earthquakes offshore Sumatra, whereas earthquakes of comparable magnitude are lacking offshore Java and the Lesser Sunda islands. Morphological structures from multibeam bathymetric data across the forearc relate with the extent of the seismogenic zone (SZ). Off Java and the Lesser Sunda islands the Indo-Australian plate subducts almost normal underneath the oceanic plate of the Indonesian archipelago. Landward of the trench, the outer wedge of the slope break is ~50 km uniformly wide with uniform bathymetric gradients. The slope of the outer wedge is locally cut by one/two steeper ridges of ~5 km extent. The sharp slope break corresponds to the updip limit of the SZ, which is also associated with the seawardmost part of the outer arc high. Landward of the slope break we find narrow, uniform outer arc ridges. The landward termination of these ridges coincides with the downdip limit of the SZ. The intersection of the shallow upper plate mantle with the subduction thrust fault marks the downdip limit of the SZ beneath the forearc. Off Sumatra the Indo-Australian plate subducts obliquely underneath the continental part of the Indonesian Sunda margin. Landward of the trench, the outer wedge varies, being mostly ~70 km wide, in some areas narrowing to 50 km width. The lower slope bathymetric gradients are steep. The outer wedge slope is made up of several steeper ridges of ~5 km extent. The slope break is only locally sharp, and corresponds to the updip limit of the SZ. The outer arc ridges off Sumatra are, in comparison with the forearc structures off Java and the Lesser Sunda islands, wider and partly elevated above sea level forming the Mentawai forearc islands. The downdip limit of the SZ coincides with the intersection of a deeper upper plate mantle with the subduction thrust fault beneath the forearc. Sunda Strait marks a transition zone between the Sumatra and Java margins. Seafloor morphology enables the identification of the seismogenic zone (SZ) across the entire Sunda margin. The SZ is uniformly wide for the Sumatra margin and narrows off Sunda Strait. Sunda Strait is the transition between the Sumatra margin and the uniformly narrow extent of the SZ of the Java/Lesser Sunda margin. Comparing the Java and Lesser Sunda islands with the Sumatra margin we find the differences along the Sunda margin, especially the wider extent of the SZ off Sumatra, producing larger earthquakes, to result from the combination of various causes: The sediment income on the oceanic incoming plate and the subduction direction; we attribute a major role to the continental/oceanic upper plate nature of Sumatra/Java influencing the composition and deformation style along the forearc and subduction fault. Off Sumatra the SZ is up to more than twice as wide as off Java/Lesser Sunda islands, enlarging the unstable regime off Sumatra and thus the risk of sudden stress release in a great earthquake.
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  • 76
    Publication Date: 2018-10-23
    Description: The current generation of marine biogeochemical modules in Earth system models (ESMs) considers mainly the effect of marine biota on the carbon cycle. We propose to also implement other biologically driven mechanisms in ESMs so that more climate-relevant feedbacks are captured. We classify these mechanisms in three categories according to their functional role in the Earth system: (1) "biogeochemical pumps", which affect the carbon cycling; (2) "biological gas and particle shuttles", which affect the atmospheric composition; and (3) "biogeophysical mechanisms", which affect the thermal, optical, and mechanical properties of the ocean. To resolve mechanisms from all three classes, we find it sufficient to include five functional groups: bulk phyto- and zooplankton, calcifiers, and coastal gas and surface mat producers. We strongly suggest to account for a larger mechanism diversity in ESMs in the future to improve the quality of climate projections.
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  • 77
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    Copernicus
    In:  Climate of the Past Discussions . pp. 1-18.
    Publication Date: 2018-09-11
    Description: Over the Last Glacial Maximum (LGM, ~21ka BP), the presence of vast Northern Hemisphere ice-sheets caused abrupt changes in surface topography and background climatic state. While the ice-sheet extent is well known, several conflicting ice-sheet topography reconstructions suggest that there is uncertainty in this boundary condition. The terrestrial and sea surface temperature (SST) of the LGM as simulated with six different Laurentide Ice Sheet (LIS) reconstructions in a fully coupled Earth System Model (COSMOS) have been compared with the subfossil pollen and plant macrofossil based and marine temperature proxies reconstruction. The terrestrial reconstruction shows a similar pattern and in good agreement with model data. The SST proxy dataset comprises a global compilation of planktonic foraminifera, diatoms, radiolarian, dinocyst, alkenones and planktonic foraminifera Mg/Ca-derived SST estimates. Significant mismatches between modeled and reconstructed SST have been observed. Among the six LIS reconstructions, Tarasov’s LIS reconstruction shows the highest correlation with reconstructed terrestrial and SST. In the case of radiolarian, Mg/Ca, diatoms and foraminifera show a positive correlation while dinocyst and alkenones show very low and negative correlation with the model. Dinocyst-based SST records are much warmer than reconstructed by other proxies as well as Pre-industrial (PI) temperature. However, there are large discrepancies between model temperatures and temperature recorded by different proxies. Eight different PMIP3 models also compared with temperature proxies reconstruction which show mismatches with the proxy records might be due to misinterpreted and/or biased proxy records. Therefore, it has been speculated that considering different habitat depths and growing seasons of the planktonic organisms used for SST reconstruction could provide a better agreement of proxy data with model results on a regional scale. Moreover, it can reduce model-data misfits. It is found that shifting in the habitat depth and living season can remove parts of the observed model-data mismatches in SST anomalies.
    Type: Article , NonPeerReviewed
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  • 78
    Publication Date: 2018-12-14
    Description: This paper describes ESM-SnowMIP, an international coordinated modelling effort to evaluate current snow schemes, including snow schemes that are included in Earth system models, in a wide variety of settings against local and global observations. The project aims to identify crucial processes and characteristics that need to be improved in snow models in the context of local- and global-scale modelling. A further objective of ESM-SnowMIP is to better quantify snow-related feedbacks in the Earth system. Although it is not part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6), ESM-SnowMIP is tightly linked to the CMIP6-endorsed Land Surface, Snow and Soil Moisture Model Intercomparison (LS3MIP).
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 79
    Publication Date: 2012-07-06
    Type: Conference or Workshop Item , NonPeerReviewed
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