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  • 1. Abbasi, R.
    et al.
    Abdou, Y.
    Abu-Zayyad, T.
    Ackermann, M.
    Adams, J.
    Aguilar, J. A.
    Ahlers, M.
    Altmann, D.
    Andeen, K.
    Auffenberg, J.
    Bai, X.
    Baker, M.
    Barwick, S. W.
    Bay, R.
    Alba, J. L. B.
    Beattie, K.
    Beatty, J. J.
    Bechet, S.
    Becker, J. K.
    Becker, K. H.
    Bell, M.
    Benabderrahmane, M. L.
    BenZvi, S.
    Berdermann, J.
    Berghaus, P.
    Berley, D.
    Bernardini, E.
    Bertrand, D.
    Besson, D. Z.
    Bindig, D.
    Bissok, M.
    Blaufuss, E.
    Blumenthal, J.
    Boersma, D. J.
    Bohm, C.
    Bose, D.
    Boser, S.
    Botner, O.
    Brayeur, L.
    Brown, A. M.
    Buitink, S.
    Caballero-Mora, K. S.
    Carson, M.
    Casier, M.
    Chirkin, D.
    Christy, B.
    Clevermann, F.
    Cohen, S.
    Colnard, C.
    Cowen, D. F.
    Silva, A. H. C.
    D'Agostino, M. V.
    Danninger, M.
    Daughhetee, J.
    Davis, J. C.
    DeClercq, C.
    Degner, T.
    Descamps, F.
    Desiati, P.
    de Vries-Uiterweerd, G.
    DeYoung, T.
    Diaz-Velez, J. C.
    Dierckxsens, M.
    Dreyer, J.
    Dumm, J. P.
    Dunkman, M.
    Eisch, J.
    Ellsworth, R. W.
    Engdegard, O.
    Euler, S.
    Evenson, P. A.
    Fadiran, O.
    Fazely, A. R.
    Fedynitch, A.
    Feintzeig, J.
    Feusels, T.
    Filimonov, K.
    Finley, C.
    Fischer-Wasels, T.
    Flis, S.
    Franckowiak, A.
    Franke, R.
    Gaisser, T. K.
    Gallagher, J.
    Gerhardt, L.
    Gladstone, L.
    Glusenkamp, T.
    Goldschmidt, A.
    Goodman, J. A.
    Gora, D.
    Grant, D.
    Griesel, T.
    Gross, A.
    Grullon, S.
    Gurtner, M.
    Ha, C.
    Ismail, A. H.
    Hallgren, A.
    Halzen, F.
    Han, K.
    Hanson, K.
    Heereman, D.
    Heinen, D.
    Helbing, K.
    Hellauer, R.
    Hickford, S.
    Hill, G. C.
    Hoffman, K. D.
    Hoffmann, B.
    Homeier, A.
    Hoshina, K.
    Huelsnitz, W.
    Hulss, J. P.
    Hulth, P. O.
    Hultqvist, K.
    Hussain, S.
    Ishihara, A.
    Jacobi, E.
    Jacobsen, J.
    Japaridze, S.
    Johansson, H.
    Kappes, A.
    Karg, T.
    Karle, A.
    Kiryluk, J.
    Kislat, F.
    Klein, S. R.
    Kohne, J. H.
    Kohnen, G.
    Kolanoski, H.
    Kopke, L.
    Kopper, S.
    Koskinen, D. J.
    Kowalski, M.
    Kowarik, T.
    Krasberg, M.
    Kroll, G.
    Kunnen, J.
    Kurahashi, N.
    Kuwabara, T.
    Labare, M.
    Laihem, K.
    Landsman, H.
    Larson, M. J.
    Lauer, R.
    Lunemann, J.
    Madsen, J.
    Marotta, A.
    Maruyama, R.
    Mase, K.
    Matis, H. S.
    Meagher, K.
    Merck, M.
    Meszaros, P.
    Meures, T.
    Miarecki, S.
    Middell, E.
    Milke, N.
    Miller, J.
    Montaruli, T.
    Morse, R.
    Movit, S. M.
    Nahnhauer, R.
    Nam, J. W.
    Naumann, U.
    Nowicki, S. C.
    Nygren, D. R.
    Odrowski, S.
    Olivas, A.
    Olivo, M.
    O'Murchadha, A.
    Panknin, S.
    Paul, L.
    de los Heros, C. P.
    Piegsa, A.
    Pieloth, D.
    Posselt, J.
    Price, P. B.
    Przybylski, G. T.
    Rawlins, K.
    Redl, P.
    Resconi, E.
    Rhode, W.
    Ribordy, M.
    Richman, M.
    Riedel, B.
    Rizzo, A.
    Rodrigues, J. P.
    Rothmaier, F.
    Rott, C.
    Ruhe, T.
    Rutledge, D.
    Ruzybayev, B.
    Ryckbosch, D.
    Sander, H. G.
    Santander, M.
    Sarkar, S.
    Schatto, K.
    Schmidt, T.
    Schoneberg, S.
    Schonwald, A.
    Schukraft, A.
    Schulte, L.
    Schultes, A.
    Schulz, O.
    Schunck, M.
    Seckel, D.
    Semburg, B.
    Seo, S. H.
    Sestayo, Y.
    Seunarine, S.
    Silvestri, A.
    Smith, M. W. E.
    Spiczak, G. M.
    Spiering, C.
    Stamatikos, M.
    Stanev, T.
    Stezelberger, T.
    Stokstad, R. G.
    Stossl, A.
    Strahler, E. A.
    Strom, R.
    Stuer, M.
    Sullivan, G. W.
    Taavola, H.
    Taboada, I.
    Tamburro, A.
    Ter-Antonyan, S.
    Tilav, S.
    Toale, P. A.
    Toscano, S.
    Tosi, D.
    van Eijndhoven, N.
    Van Overloop, A.
    van Santen, J.
    Vehring, M.
    Voge, M.
    Walck, C.
    Waldenmaier, T.
    Wallraff, M.
    Walter, M.
    Wasserman, R.
    Weaver, C.
    Wendt, C.
    Westerhoff, S.
    Whitehorn, N.
    Wiebe, K.
    Wiebusch, C. H.
    Williams, D. R.
    Wischnewski, R.
    Wissing, H.
    Wolf, M.
    Wood, T. R.
    Woschnagg, K.
    Xu, C.
    Xu, D. L.
    Xu, X. W.
    Yanez, J. P.
    Yodh, G.
    Yoshida, S.
    Zarzhitsky, P.
    Zoll, M.
    IceCube, Collaboration
    An absence of neutrinos associated with cosmic-ray acceleration in gamma-ray bursts2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 484Article in journal (Refereed)
    Abstract [en]

    Very energetic astrophysical events are required to accelerate cosmic rays to above 10(18) electronvolts. GRBs (c-ray bursts) have been proposed as possible candidate sources(1-3). In the GRB 'fireball' model, cosmic-ray acceleration should be accompanied by neutrinos produced in the decay of charged pions created in interactions between the high-energy cosmic-ray protons and gamma-rays(4). Previous searches for such neutrinos found none, but the constraints were weak because the sensitivity was at best approximately equal to the predicted flux(5-7). Here we report an upper limit on the flux of energetic neutrinos associated with GRBs that is at least a factor of 3.7 below the predictions(4,8-10). This implies either that GRBs are not the only sources of cosmic rays with energies exceeding 10(18) electronvolts or that the efficiency of neutrino production is much lower than has been predicted.

  • 2. Andersen, K. K
    et al.
    and NGRIP members,
    High-resolution record of Northern hemisphere climate extending into the last interglacial period2004In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 431, p. 147-151Article in journal (Refereed)
  • 3. Bjorkman, Anne D.
    et al.
    Myers-Smith, Isla H.
    Elmendorf, Sarah C.
    Normand, Signe
    Rüger, Nadja
    Beck, Pieter S. A.
    Blach-Overgaard, Anne
    Blok, Daan
    Cornelissen, J. Hans C.
    Forbes, Bruce C.
    Georges, Damien
    Goetz, Scott J.
    Guay, Kevin C.
    Henry, Gregory H. R.
    HilleRisLambers, Janneke
    Hollister, Robert D.
    Karger, Dirk N.
    Kattge, Jens
    Manning, Peter
    Prevéy, Janet S.
    Rixen, Christian
    Schaepman-Strub, Gabriela
    Thomas, Haydn J. D.
    Vellend, Mark
    Wilmking, Martin
    Wipf, Sonja
    Carbognani, Michele
    Hermanutz, Luise
    Lévesque, Esther
    Molau, Ulf
    Petraglia, Alessandro
    Soudzilovskaia, Nadejda A.
    Spasojevic, Marko J.
    Tomaselli, Marcello
    Vowles, Tage
    Alatalo, Juha M.
    Alexander, Heather D.
    Anadon-Rosell, Alba
    Angers-Blondin, Sandra
    Beest, Mariska te
    Berner, Logan
    Björk, Robert G.
    Buchwal, Agata
    Buras, Allan
    Christie, Katherine
    Cooper, Elisabeth J.
    Dullinger, Stefan
    Elberling, Bo
    Eskelinen, Anu
    Frei, Esther R.
    Grau, Oriol
    Grogan, Paul
    Hallinger, Martin
    Harper, Karen A.
    Heijmans, Monique M. P. D.
    Hudson, James
    Hülber, Karl
    Iturrate-Garcia, Maitane
    Iversen, Colleen M.
    Jaroszynska, Francesca
    Johnstone, Jill F.
    Jørgensen, Rasmus Halfdan
    Kaarlejärvi, Elina
    Klady, Rebecca
    Kuleza, Sara
    Kulonen, Aino
    Lamarque, Laurent J.
    Lantz, Trevor
    Little, Chelsea J.
    Speed, James D. M.
    Michelsen, Anders
    Milbau, Ann
    Nabe-Nielsen, Jacob
    Nielsen, Sigrid Schøler
    Ninot, Josep M.
    Oberbauer, Steven F.
    Olofsson, Johan
    Onipchenko, Vladimir G.
    Rumpf, Sabine B.
    Semenchuk, Philipp
    Shetti, Rohan
    Collier, Laura Siegwart
    Street, Lorna E.
    Suding, Katharine N.
    Tape, Ken D.
    Trant, Andrew
    Treier, Urs A.
    Tremblay, Jean-Pierre
    Tremblay, Maxime
    Venn, Susanna
    Weijers, Stef
    Zamin, Tara
    Boulanger-Lapointe, Noémie
    Gould, William A.
    Hik, David S.
    Hofgaard, Annika
    Jónsdóttir, Ingibjörg S.
    Jorgenson, Janet
    Klein, Julia
    Magnusson, Borgthor
    Tweedie, Craig
    Wookey, Philip A.
    Bahn, Michael
    Blonder, Benjamin
    van Bodegom, Peter M.
    Bond-Lamberty, Benjamin
    Campetella, Giandiego
    Cerabolini, Bruno E. L.
    Chapin, F. Stuart
    Cornwell, William K.
    Craine, Joseph
    Dainese, Matteo
    de Vries, Franciska T.
    Díaz, Sandra
    Enquist, Brian J.
    Green, Walton
    Milla, Ruben
    Niinemets, Ülo
    Onoda, Yusuke
    Ordoñez, Jenny C.
    Ozinga, Wim A.
    Penuelas, Josep
    Poorter, Hendrik
    Poschlod, Peter
    Reich, Peter B.
    Sandel, Brody
    Schamp, Brandon
    Sheremetev, Serge
    Weiher, Evan
    Plant functional trait change across a warming tundra biome2018In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 562, no 7725, p. 57-62Article in journal (Refereed)
    Abstract [en]

    The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature–trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.

  • 4. Brinkhuis, H
    et al.
    Schouten, S
    Collinson, M E
    Sluijs, A
    Damste, J S S
    Dickens, G R
    Huber, M
    Cronin, T M
    Onodera, J
    Takahashi, K
    Bujak, J P
    Stein, R
    van der Burgh, J
    Eldrett, J S
    Harding, I C
    Lotter, A F
    Sangiorgi, F
    Cittert, H V V
    de Leeuw, J W
    Matthiessen, J
    Backman, J
    Moran, K
    Jakobsson, M
    Episodic fresh surface waters in the Eocene Arctic Ocean2006In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 441, no 7093, p. 606-609Article in journal (Refereed)
    Abstract [en]

    It has been suggested, on the basis of modern hydrology and fully coupled palaeoclimate simulations, that the warm greenhouse conditions(1) that characterized the early Palaeogene period (55-45 Myr ago) probably induced an intensified hydrological cycle(2) with precipitation exceeding evaporation at high latitudes(3). Little field evidence, however, has been available to constrain oceanic conditions in the Arctic during this period. Here we analyse Palaeogene sediments obtained during the Arctic Coring Expedition, showing that large quantities of the free-floating fern Azolla grew and reproduced in the Arctic Ocean by the onset of the middle Eocene epoch (similar to 50 Myr ago). The Azolla and accompanying abundant freshwater organic and siliceous microfossils indicate an episodic freshening of Arctic surface waters during an similar to 800,000-year interval. The abundant remains of Azolla that characterize basal middle Eocene marine deposits of all Nordic seas(4-7) probably represent transported assemblages resulting from freshwater spills from the Arctic Ocean that reached as far south as the North Sea(8). The termination of the Azolla phase in the Arctic coincides with a local sea surface temperature rise from similar to 10 degrees C to 13 degrees C, pointing to simultaneous increases in salt and heat supply owing to the influx of waters from adjacent oceans. We suggest that onset and termination of the Azolla phase depended on the degree of oceanic exchange between Arctic Ocean and adjacent seas.

  • 5. Cressey, Daniel
    Geology: The next land rush2008In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 451, no 7174, p. 12-15Article in journal (Refereed)
  • 6. Ingall, Ellery D.
    et al.
    Diaz, Julia M.
    Longo, Amelia F.
    Oakes, Michelle
    Finney, Lydia
    Vogt, Stefan
    Lai, Barry
    Yager, Patricia L.
    Twining, Benjamin
    Brandes, Jay A.
    Role of biogenic silica in the removal of iron from the Antarctic seas2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 4, no 1981, p. 1-6Article in journal (Refereed)
  • 7. Jakobsson, Martin
    et al.
    Backman, Jan
    Rudels, Bert
    Nycander, Jonas
    Frank, Martin
    Mayer, Larry
    Jokat, Wilfried
    Sangiorgi, Francesca
    O’Regan, Matthew
    Brinkhuis, Henk
    King, John
    Moran, Kathryn
    The early Miocene onset of a ventilated circulation regime in the Arctic Ocean2007In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 447, no 7147, p. 986-990Article in journal (Refereed)
    Abstract [en]

    Deep-water formation in the northern North Atlantic Ocean and the Arctic Ocean is a key driver of the global thermohaline circulation and hence also of global climate(1). Deciphering the history of the circulation regime in the Arctic Ocean has long been prevented by the lack of data from cores of Cenozoic sediments from the Arctic’s deep-sea floor. Similarly, the timing of the opening of a connection between the northern North Atlantic and the Arctic Ocean, permitting deep-water exchange, has been poorly constrained. This situation changed when the first drill cores were recovered from the central Arctic Ocean(2). Here we use these cores to show that the transition from poorly oxygenated to fully oxygenated (’ventilated’) conditions in the Arctic Ocean occurred during the later part of early Miocene times. We attribute this pronounced change in ventilation regime to the opening of the Fram Strait. A palaeo-geographic and palaeo-bathymetric reconstruction of the Arctic Ocean, together with a physical oceanographic analysis of the evolving strait and sill conditions in the Fram Strait, suggests that the Arctic Ocean went from an oxygen-poor ‘lake stage’, to a transitional ‘estuarine sea’ phase with variable ventilation, and finally to the fully ventilated ‘ocean’ phase 17.5 Myr ago. The timing of this palaeo-oceanographic change coincides with the onset of the middle Miocene climatic optimum(3), although it remains unclear if there is a causal relationship between these two events.

  • 8. Moran, Kathryn
    et al.
    Backman, Jan
    Brinkhuis, Henk
    Clemens, Steven C.
    Cronin, Thomas
    Dickens, Gerald R.
    Eynaud, Frederique
    Gattacceca, Jerome
    Jakobsson, Martin
    Jordan, Richard W.
    Kaminski, Michael
    King, John
    Koc, Nalan
    Krylov, Alexey
    Martinez, Nahysa
    Matthiessen, Jens
    McInroy, David
    Moore, Theodore C.
    Onodera, Jonaotaro
    O’Regan, Matthew
    Palike, Heiko
    Rea, Brice
    Rio, Domenico
    Sakamoto, Tatsuhiko
    Smith, David C.
    Stein, Ruediger
    St John, Kristen
    Suto, Itsuki
    Suzuki, Noritoshi
    Takahashi, Kozo
    Watanabe, Mahito
    Yamamoto, Masanobu
    Farrell, John
    Frank, Martin
    Kubik, Peter
    Jokat, Wilfried
    Kristoffersen, Yngve
    The Cenozoic palaeoenvironment of the Arctic Ocean2006In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 441, no 7093, p. 601-605Article in journal (Refereed)
    Abstract [en]

    The history of the Arctic Ocean during the Cenozoic era ( 0 - 65 million years ago) is largely unknown from direct evidence. Here we present a Cenozoic palaeoceanographic record constructed from >400 m of sediment core from a recent drilling expedition to the Lomonosov ridge in the Arctic Ocean. Our record shows a palaeoenvironmental transition from a warm ‘greenhouse’ world, during the late Palaeocene and early Eocene epochs, to a colder ‘icehouse’ world influenced by sea ice and icebergs from the middle Eocene epoch to the present. For the most recent similar to 14 Myr, we find sedimentation rates of 1 - 2 cm per thousand years, in stark contrast to the substantially lower rates proposed in earlier studies; this record of the Neogene reveals cooling of the Arctic that was synchronous with the expansion of Greenland ice (similar to 3.2 Myr ago) and East Antarctic ice (similar to 14 Myr ago). We find evidence for the first occurrence of ice-rafted debris in the middle Eocene epoch (similar to 45 Myr ago), some 35 Myr earlier than previously thought; fresh surface waters were present at,49 Myr ago, before the onset of ice-rafted debris. Also, the temperatures of surface waters during the Palaeocene/Eocene thermal maximum (similar to 55 Myr ago) appear to have been substantially warmer than previously estimated. The revised timing of the earliest Arctic cooling events coincides with those from Antarctica, supporting arguments for bipolar symmetry in climate change.

  • 9. Pagani, Mark
    et al.
    Pedentchouk, Nikolai
    Huber, Matthew
    Sluijs, Appy
    Schouten, Stefan
    Brinkhuis, Henk
    Damste, Jaap S. Sinninghe
    Dickens, Gerald R.
    Scientists, Expedit 302
    Arctic hydrology during global warming at the Palaeocene/Eocene thermal maximum2006In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 442, no 7103, p. 671-675Article in journal (Refereed)
    Abstract [en]

    The Palaeocene/ Eocene thermal maximum represents a period of rapid, extreme global warming similar to 55 million years ago, superimposed on an already warm world(1-3). This warming is associated with a severe shoaling of the ocean calcite compensation depth(4) and a > 2.5 per mil negative carbon isotope excursion in marine and soil carbonates(1-4). Together these observations indicate a massive release of C-13- depleted carbon(4) and greenhouse- gas-induced warming. Recently, sediments were recovered from the central Arctic Ocean(5), providing the first opportunity to evaluate the environmental response at the North Pole at this time. Here we present stable hydrogen and carbon isotope measurements of terrestrial- plant- and aquatic- derived n- alkanes that record changes in hydrology, including surface water salinity and precipitation, and the global carbon cycle. Hydrogen isotope records are interpreted as documenting decreased rainout during moisture transport from lower latitudes and increased moisture delivery to the Arctic at the onset of the Palaeocene/ Eocene thermal maximum, consistent with predictions of poleward storm track migrations during global warming(6). The terrestrial- plant carbon isotope excursion ( about -4.5 to -6 per mil) is substantially larger than those of marine carbonates. Previously, this offset was explained by the physiological response of plants to increases in surface humidity(2). But this mechanism is not an effective explanation in this wet Arctic setting, leading us to hypothesize that the true magnitude of the excursion - and associated carbon input was greater than originally surmised. Greater carbon release and strong hydrological cycle feedbacks may help explain the maintenance of this unprecedented warmth.

  • 10. Qiu, J
    Flight of the navigators2005In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 437, no 7060, p. 804-806Article in journal (Refereed)
    Abstract [en]

    The Arctic is a unique testing ground for studying how birds navigate long distances, one of ornithology’s greatest mysteries. Birds use a number of different navigational cues, the Earth’s magnetic field, the landscape and the position of the Sun and stars. Studies on bird navigation will have implications forpreventing or containing animal based epidemics such as avian influenza.

  • 11. Sluijs, A
    et al.
    Schouten, S
    Pagani, M
    Woltering, M
    Brinkhuis, H
    Damste, J S S
    Dickens, G R
    Huber, M
    Reichart, G J
    Stein, R
    Matthiessen, J
    Lourens, L J
    Pedentchouk, N
    Backman, J
    Moran, K
    Scientists, Expedition 302
    Subtropical arctic ocean temperatures during the Palaeocene/Eocene thermal maximum2006In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 441, no 7093, p. 610-613Article in journal (Refereed)
    Abstract [en]

    The Palaeocene/Eocene thermal maximum, similar to 55 million years ago, was a brief period of widespread, extreme climatic warming(1-3), that was associated with massive atmospheric greenhouse gas input(4). Although aspects of the resulting environmental changes are well documented at low latitudes, no data were available to quantify simultaneous changes in the Arctic region. Here we identify the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence obtained during the Arctic Coring Expedition(5). We show that sea surface temperatures near the North Pole increased from similar to 18 degrees C to over 23 degrees C during this event. Such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. At the same time, sea level rose while anoxic and euxinic conditions developed in the ocean’s bottom waters and photic zone, respectively. Increasing temperature and sea level match expectations based on palaeoclimate model simulations(6), but the absolute polar temperatures that we derive before, during and after the event are more than 10 degrees C warmer than those model-predicted. This suggests that higher-than-modern greenhouse gas concentrations must have operated in conjunction with other feedback mechanisms - perhaps polar stratospheric clouds(7) or hurricane-induced ocean mixing(8) - to amplify early Palaeogene polar temperatures.

  • 12.
    Sohn, Robert A.
    et al.
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Willis, Claire
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Humphris, Susan
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Shank, Timothy M.
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Singh, Hanumant
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Edmonds, Henrietta N.
    Univ Texas Austin, Inst Marine Sci, Port Aransas, TX 78373 USA..
    Kunz, Clayton
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Hedman, Ulf
    Swedish Polar Secretariat, S-10405 Stockholm, Sweden..
    Helmke, Elisabeth
    Alfred Wegener Inst Polar & Marine Res, D-27570 Bremerhaven, Germany..
    Jakuba, Michael
    Johns Hopkins Univ, Baltimore, MD 21218 USA..
    Liljebladh, Bengt
    Univ Gothenburg, S-40530 Gothenburg, Sweden..
    Linder, Julia
    Alfred Wegener Inst Polar & Marine Res, D-27570 Bremerhaven, Germany..
    Murphy, Christopher
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Nakamura, Ko-ichi
    AIST, Higashi, Tokyo, Japan..
    Sato, Taichi
    Univ Tokyo, Ocean Res Inst, Tokyo 1648639, Japan..
    Schlindwein, Vera
    Alfred Wegener Inst Polar & Marine Res, D-27570 Bremerhaven, Germany..
    Stranne, Christian
    Univ Gothenburg, S-40530 Gothenburg, Sweden..
    Tausenfreund, Maria
    Alfred Wegener Inst Polar & Marine Res, D-27570 Bremerhaven, Germany..
    Upchurch, Lucia
    Univ Texas Austin, Inst Marine Sci, Port Aransas, TX 78373 USA..
    Winsor, Peter
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol & Geochem, S-10691 Stockholm, Sweden..
    Soule, Adam
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Explosive volcanism on the ultraslow-spreading Gakkel ridge, Arctic Ocean2008In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 453, no 7199, p. 1236-1238Article in journal (Refereed)
    Abstract [en]

    Roughly 60% of the Earth's outer surface is composed of oceanic crust formed by volcanic processes at mid- ocean ridges. Although only a small fraction of this vast volcanic terrain has been visually surveyed or sampled, the available evidence suggests that explosive eruptions are rare on mid- ocean ridges, particularly at depths below the critical point for seawater ( 3,000 m)(1). A pyroclastic deposit has never been observed on the sea floor below 3,000 m, presumably because the volatile content of mid- ocean- ridge basalts is generally too low to produce the gas fractions required for fragmenting a magma at such high hydrostatic pressure. We employed new deep submergence technologies during an International Polar Year expedition to the Gakkel ridge in the Arctic Basin at 856 E, to acquire photographic and video images of 'zero- age' volcanic terrain on this remote, ice- covered ridge. Here we present images revealing that the axial valley at 4,000 m water depth is blanketed with unconsolidated pyroclastic deposits, including bubble wall fragments (limu o Pele)(2), covering a large ( > 10 km(2)) area. At least 13.5 wt% CO(2) is necessary to fragment magma at these depths(3), which is about tenfold the highest values previously measured in a mid- ocean- ridge basalt(4). These observations raise important questions about the accumulation and discharge of magmatic volatiles at ultraslow spreading rates on the Gakkel ridge(5) and demonstrate that large- scale pyroclastic activity is possible along even the deepest portions of the global mid- ocean ridge volcanic system.

  • 13. Vonk, J. E.
    et al.
    Sanchez-Garcia, L.
    van Dongen, B. E.
    Alling, V.
    Kosmach, D.
    Charkin, A.
    Semiletov, I. P.
    Dudarev, O. V.
    Shakhova, N.
    Roos, P.
    Eglinton, T. I.
    Andersson, A.
    Gustafsson, Ö.
    Activation of old carbon by erosion of coastal and subsea permafrost in Arctic Siberia2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 489Article in journal (Refereed)
    Abstract [en]

    The future trajectory of greenhouse gas concentrations depends on interactions between climate and the biogeosphere(1,2). Thawing of Arctic permafrost could release significant amounts of carbon into the atmosphere in this century(3). Ancient Ice Complex deposits outcropping along the similar to 7,000-kilometre-long coastline of the East Siberian Arctic Shelf (ESAS)(4,5), and associated shallow subsea permafrost(6,7), are two large pools of permafrost carbon(8), yet their vulnerabilities towards thawing and decomposition are largely unknown(9-11). Recent Arctic warming is stronger than has been predicted by several degrees, and is particularly pronounced over the coastal ESAS region(12,13). There is thus a pressing need to improve our understanding of the links between permafrost carbon and climate in this relatively inaccessible region. Here we show that extensive release of carbon from these Ice Complex deposits dominates (57 +/- 2 per cent) the sedimentary carbon budget of the ESAS, the world's largest continental shelf, overwhelming the marine and topsoil terrestrial components. Inverse modelling of the dual-carbon isotope composition of organic carbon accumulating in ESAS surface sediments, using Monte Carlo simulations to account for uncertainties, suggests that 44 +/- 10 teragrams of old carbon is activated annually from Ice Complex permafrost, an order of magnitude more than has been suggested by previous studies(14). We estimate that about two-thirds (66 +/- 16 per cent) of this old carbon escapes to the atmosphere as carbon dioxide, with the remainder being re-buried in shelf sediments. Thermal collapse and erosion of these carbon-rich Pleistocene coastline and seafloor deposits may accelerate with Arctic amplification of climate warming(2,13).

  • 14. Willerslev, E
    et al.
    Davison, J
    Moora, M
    Zobel, E
    Coissac, E
    Edwards, M E
    Lorenzen, E D
    Vestergård, M
    Gussarova, G
    Haile, J
    Craine, J
    Gielly, L
    Boessenkool, S
    Epp, L S
    Pearman, P B
    Cheddadi, R
    Murray, D
    Bråthen, K A
    Yoccoz, N
    Binney, H
    Crauaud, C
    Wincker, P
    Goslar, T
    Alsos, I G
    Bellemain, E
    Brysting, A K
    Elven, R
    Sønstebø, J H
    Murton, J
    Sher, A
    Rasmussen, M
    Rasmussen, R
    Mourier, T
    Cooper, A
    Austin, J
    Möller, Per
    Froese, D
    Zazula, G
    Pompanon, F
    Rioux, D
    Niderkorn, V
    Tikhonov, A
    Savvinov, G
    Roberts, R G
    MacPhee, R D E
    Gilbert, M T G
    Kjær, K H
    Orlando, L
    Brochmann, C
    Taberlet, P
    Fifty thousand years of arctic vegetation change and megafauna diet2014In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 506, no 7486, p. 47-+Article in journal (Refereed)
    Abstract [en]

    Although it is generally agreed that the Arctic flora is among the youngest and least diverse on Earth, the processes that shaped it are poorly understood. Here we present 50 thousand years (kyr) of Arctic vegetation history, derived from the first large-scale ancient DNA metabarcoding study of circumpolar plant diversity. For this interval we also explore nematode diversity as a proxy for modelling vegetation cover and soil quality, and diets of herbivorous megafaunal mammals, many of which became extinct around 10 kyr bp (before present). For much of the period investigated, Arctic vegetation consisted of dry steppe-tundra dominated by forbs (non-graminoid herbaceous vascular plants). During the Last Glacial Maximum (25–15 kyr bp), diversity declined markedly, although forbs remained dominant. Much changed after 10 kyr bp, with the appearance of moist tundra dominated by woody plants and graminoids. Our analyses indicate that both graminoids and forbs would have featured in megafaunal diets. As such, our findings question the predominance of a Late Quaternary graminoid-dominated Arctic mammoth steppe.

  • 15. Wolff, E W
    et al.
    Fischer, H
    Fundel, F
    Ruth, U
    Twarloh, B
    Littot, G C
    Mulvaney, R
    Rothlisberger, R
    de Angelis, M
    Boutron, C F
    Hansson, M
    Jonsell, U
    Hutterli, M A
    Lambert, F
    Kaufmann, P
    Stauffer, B
    Stocker, T F
    Steffensen, J P
    Bigler, M
    Siggaard-Andersen, M L
    Udisti, R
    Becagli, S
    Castellano, E
    Severi, M
    Wagenbach, D
    Barbante, C
    Gabrielli, P
    Gaspari, V
    Southern Ocean sea-ice extent, productivity and iron flux over the past eight glacial cycles2006In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 440, no 7083, p. 491-496Article in journal (Refereed)
    Abstract [en]

    Sea ice and dust flux increased greatly in the Southern Ocean during the last glacial period. Palaeorecords provide contradictory evidence about marine productivity in this region, but beyond one glacial cycle, data were sparse. Here we present continuous chemical proxy data spanning the last eight glacial cycles (740,000 years) from the Dome C Antarctic ice core. These data constrain winter sea-ice extent in the Indian Ocean, Southern Ocean biogenic productivity and Patagonian climatic conditions. We found that maximum sea-ice extent is closely tied to Antarctic temperature on multi-millennial timescales, but less so on shorter timescales. Biological dimethylsulphide emissions south of the polar front seem to have changed little with climate, suggesting that sulphur compounds were not active in climate regulation. We observe large glacial-interglacial contrasts in iron deposition, which we infer reflects strongly changing Patagonian conditions. During glacial terminations, changes in Patagonia apparently preceded sea-ice reduction, indicating that multiple mechanisms may be responsible for different phases of CO2 increase during glacial terminations. We observe no changes in internal climatic feedbacks that could have caused the change in amplitude of Antarctic temperature variations observed 440,000 years ago.

  • 16. Woodcroft, Ben J.
    et al.
    Singleton, Caitlin M.
    Boyd, Joel A.
    Evans, Paul N.
    Emerson, Joanne B.
    Zayed, Ahmed A. F.
    Hoelzle, Robert D.
    Lamberton, Timothy O.
    McCalley, Carmody K.
    Hodgkins, Suzanne B.
    Wilson, Rachel M.
    Purvine, Samuel O.
    Nicora, Carrie D.
    Li, Changsheng
    Frolking, Steve
    Chanton, Jeffrey P.
    Crill, Patrick M.
    Saleska, Scott R.
    Rich, Virginia I.
    Tyson, Gene W.
    Genome-centric view of carbon processing in thawing permafrost2018In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 560, no 7716, p. 49-54Article in journal (Refereed)
    Abstract [en]

    As global temperatures rise, large amounts of carbon sequestered in permafrost are becoming available for microbial degradation. Accurate prediction of carbon gas emissions from thawing permafrost is limited by our understanding of these microbial communities. Here we use metagenomic sequencing of 214 samples from a permafrost thaw gradient to recover 1,529 metagenome-assembled genomes, including many from phyla with poor genomic representation. These genomes reflect the diversity of this complex ecosystem, with genus-level representatives for more than sixty per cent of the community. Meta-omic analysis revealed key populations involved in the degradation of organic matter, including bacteria whose genomes encode a previously undescribed fungal pathway for xylose degradation. Microbial and geochemical data highlight lineages that correlate with the production of greenhouse gases and indicate novel syntrophic relationships. Our findings link changing biogeochemistry to specific microbial lineages involved in carbon processing, and provide key information for predicting the effects of climate change on permafrost systems.

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