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  • 1
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    Moisture sources and synoptic to seasonal variability of North Atlantic water vapor isotopic composition (2015)
    Wiley
    Details
    Publication Date: 2015-05-23
    Description: The isotopic composition of near surface (or planetary boundary layer) water vapor on the south coast of Iceland (63.83°N, 21.47°W) has been monitored in situ between November 2011 and April 2013. The calibrated dataset documents seasonal variations in the relationship between δ 18 O and local humidity (ppmv), and between deuterium excess and δ 18 O. These seasonal variations are attributed to seasonal changes in atmospheric transport. A strong linear relationship is observed between deuterium excess and atmospheric relative humidity calculated at regional sea surface temperature. Surprisingly, we find a similar relationship between deuterium excess and relative humidity as observed in the Bermuda Islands. During days with low amount of isotopic depletion (more enriched values), our data significantly deviate from the global meteoric water line. This feature can be explained by a supply of an evaporative flux into the planetary boundary layer above the ocean, which we show using a 1-d box model. Based on the close relationship identified between moisture origin and deuterium excess, we combine deuterium excess measurements performed in Iceland and south Greenland with moisture source diagnostics based on back-trajectory calculations to establish the distribution of d-excess moisture uptake values across the North Atlantic. We map high deuterium excess in the Arctic, and low deuterium excess for vapor in the subtropics and mid-latitudes. This confirms the role of North Atlantic water vapor isotopes as moisture origin tracers.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Modern solar maximum forced late 20th century Greenland cooling (2015)
    Wiley
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    Publication Date: 2015-06-27
    Description: The abrupt Northern Hemispheric (NH) warming at the end of the 20 th century has been attributed to an enhanced greenhouse effect. Yet, Greenland and surrounding subpolar North Atlantic remained anomalously cold in 1970s- early 1990s. Here, we reconstructed robust Greenland temperature records (NGRIP and GISP2) over the past 2100 years using argon and nitrogen isotopes in air trapped within ice cores, and show that this cold anomaly was part of a recursive pattern of antiphase Greenland temperature responses to solar variability with a possible multidecadal lag. We hypothesize that high solar activity during the modern solar maximum (ca. 1950s-1980s) resulted in a cooling over Greenland and surrounding subpolar North Atlantic through the slow-down of Atlantic Meridional Overturning Circulation (AMOC) with atmospheric feedback processes.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Variations in atmospheric N2O concentration during abrupt climatic changes (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-07-10
    Description: Nitrous oxide (N2O) is an important greenhouse gas that is presently increasing at a rate of 0.25 percent per year. Records measured along two ice cores from Summit in Central Greenland provide information about variations in atmospheric N2O concentration in the past. The record covering the past millennium reduces the uncertainty regarding the preindustrial concentration. Records covering the last glacial-interglacial transition and a fast climatic change during the last ice age show that the N2O concentration changed in parallel with fast temperature variations in the Northern Hemisphere. This provides important information about the response of the environment to global climatic changes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fluckiger -- Dallenbach -- Blunier -- Stauffer -- Stocker -- Raynaud -- Barnola -- New York, N.Y. -- Science. 1999 Jul 9;285(5425):227-30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. CNRS Laboratoire de Glaciologie et Geophysique de l'Environnement (LGGE), Boite Postale 96, 38402 St Martin d'Heres Cedex, Gr.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10398593" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Timing of millennial-scale climate change in Antarctica and Greenland during the last glacial period (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-01-06
    Description: A precise relative chronology for Greenland and West Antarctic paleotemperature is extended to 90,000 years ago, based on correlation of atmospheric methane records from the Greenland Ice Sheet Project 2 and Byrd ice cores. Over this period, the onset of seven major millennial-scale warmings in Antarctica preceded the onset of Greenland warmings by 1500 to 3000 years. In general, Antarctic temperatures increased gradually while Greenland temperatures were decreasing or constant, and the termination of Antarctic warming was apparently coincident with the onset of rapid warming in Greenland. This pattern provides further evidence for the operation of a "bipolar see-saw" in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Blunier, T -- Brook, E J -- New York, N.Y. -- Science. 2001 Jan 5;291(5501):109-12.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geosciences, Guyot Hall, Princeton University, Princeton, NJ 08544, USA. blunier@princeton.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11141558" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-05-16
    Description: Atmospheric methane is an important greenhouse gas and a sensitive indicator of climate change and millennial-scale temperature variability. Its concentrations over the past 650,000 years have varied between approximately 350 and approximately 800 parts per 10(9) by volume (p.p.b.v.) during glacial and interglacial periods, respectively. In comparison, present-day methane levels of approximately 1,770 p.p.b.v. have been reported. Insights into the external forcing factors and internal feedbacks controlling atmospheric methane are essential for predicting the methane budget in a warmer world. Here we present a detailed atmospheric methane record from the EPICA Dome C ice core that extends the history of this greenhouse gas to 800,000 yr before present. The average time resolution of the new data is approximately 380 yr and permits the identification of orbital and millennial-scale features. Spectral analyses indicate that the long-term variability in atmospheric methane levels is dominated by approximately 100,000 yr glacial-interglacial cycles up to approximately 400,000 yr ago with an increasing contribution of the precessional component during the four more recent climatic cycles. We suggest that changes in the strength of tropical methane sources and sinks (wetlands, atmospheric oxidation), possibly influenced by changes in monsoon systems and the position of the intertropical convergence zone, controlled the atmospheric methane budget, with an additional source input during major terminations as the retreat of the northern ice sheet allowed higher methane emissions from extending periglacial wetlands. Millennial-scale changes in methane levels identified in our record as being associated with Antarctic isotope maxima events are indicative of ubiquitous millennial-scale temperature variability during the past eight glacial cycles.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Loulergue, Laetitia -- Schilt, Adrian -- Spahni, Renato -- Masson-Delmotte, Valerie -- Blunier, Thomas -- Lemieux, Benedicte -- Barnola, Jean-Marc -- Raynaud, Dominique -- Stocker, Thomas F -- Chappellaz, Jerome -- England -- Nature. 2008 May 15;453(7193):383-6. doi: 10.1038/nature06950.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS-Universite Joseph Fourier Grenoble, 54 Rue Moliere, 38402 St Martin d'Heres, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18480822" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/*chemistry ; Greenhouse Effect ; History, Ancient ; Ice Cover ; Methane/*analysis ; Temperature ; Time Factors ; Tropical Climate ; Wetlands
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 6
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    High-resolution carbon dioxide concentration record 650,000-800,000 years before present (2008)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2008-05-16
    Description: Changes in past atmospheric carbon dioxide concentrations can be determined by measuring the composition of air trapped in ice cores from Antarctica. So far, the Antarctic Vostok and EPICA Dome C ice cores have provided a composite record of atmospheric carbon dioxide levels over the past 650,000 years. Here we present results of the lowest 200 m of the Dome C ice core, extending the record of atmospheric carbon dioxide concentration by two complete glacial cycles to 800,000 yr before present. From previously published data and the present work, we find that atmospheric carbon dioxide is strongly correlated with Antarctic temperature throughout eight glacial cycles but with significantly lower concentrations between 650,000 and 750,000 yr before present. Carbon dioxide levels are below 180 parts per million by volume (p.p.m.v.) for a period of 3,000 yr during Marine Isotope Stage 16, possibly reflecting more pronounced oceanic carbon storage. We report the lowest carbon dioxide concentration measured in an ice core, which extends the pre-industrial range of carbon dioxide concentrations during the late Quaternary by about 10 p.p.m.v. to 172-300 p.p.m.v.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Luthi, Dieter -- Le Floch, Martine -- Bereiter, Bernhard -- Blunier, Thomas -- Barnola, Jean-Marc -- Siegenthaler, Urs -- Raynaud, Dominique -- Jouzel, Jean -- Fischer, Hubertus -- Kawamura, Kenji -- Stocker, Thomas F -- England -- Nature. 2008 May 15;453(7193):379-82. doi: 10.1038/nature06949.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. luethi@climate.unibe.ch〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18480821" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 7
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    Changing boreal methane sources and constant biomass burning during the last termination (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-04-19
    Description: Past atmospheric methane concentrations show strong fluctuations in parallel to rapid glacial climate changes in the Northern Hemisphere superimposed on a glacial-interglacial doubling of methane concentrations. The processes driving the observed fluctuations remain uncertain but can be constrained using methane isotopic information from ice cores. Here we present an ice core record of carbon isotopic ratios in methane over the entire last glacial-interglacial transition. Our data show that the carbon in atmospheric methane was isotopically much heavier in cold climate periods. With the help of a box model constrained by the present data and previously published results, we are able to estimate the magnitude of past individual methane emission sources and the atmospheric lifetime of methane. We find that methane emissions due to biomass burning were about 45 Tg methane per year, and that these remained roughly constant throughout the glacial termination. The atmospheric lifetime of methane is reduced during cold climate periods. We also show that boreal wetlands are an important source of methane during warm events, but their methane emissions are essentially shut down during cold climate conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fischer, Hubertus -- Behrens, Melanie -- Bock, Michael -- Richter, Ulrike -- Schmitt, Jochen -- Loulergue, Laetitia -- Chappellaz, Jerome -- Spahni, Renato -- Blunier, Thomas -- Leuenberger, Markus -- Stocker, Thomas F -- England -- Nature. 2008 Apr 17;452(7189):864-7. doi: 10.1038/nature06825.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Alfred Wegener Institute for Polar and Marine Research, Columbusstrasse, 27568 Bremerhaven, Germany. hubertus.fischer@awi.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18421351" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/chemistry ; *Biomass ; Carbon/analysis ; Carbon Isotopes ; Cold Climate ; Fires/*statistics & numerical data ; Greenland ; History, Ancient ; Hydrogen/analysis ; *Ice Cover ; Methane/*analysis/*chemistry/metabolism ; Monte Carlo Method ; *Temperature ; Trees/*metabolism ; Wetlands
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 8
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    Holocene thinning of the Greenland ice sheet (2009)
    Nature Publishing Group (NPG)
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    Publication Date: 2009-09-18
    Description: On entering an era of global warming, the stability of the Greenland ice sheet (GIS) is an important concern, especially in the light of new evidence of rapidly changing flow and melt conditions at the GIS margins. Studying the response of the GIS to past climatic change may help to advance our understanding of GIS dynamics. The previous interpretation of evidence from stable isotopes (delta(18)O) in water from GIS ice cores was that Holocene climate variability on the GIS differed spatially and that a consistent Holocene climate optimum-the unusually warm period from about 9,000 to 6,000 years ago found in many northern-latitude palaeoclimate records-did not exist. Here we extract both the Greenland Holocene temperature history and the evolution of GIS surface elevation at four GIS locations. We achieve this by comparing delta(18)O from GIS ice cores with delta(18)O from ice cores from small marginal icecaps. Contrary to the earlier interpretation of delta(18)O evidence from ice cores, our new temperature history reveals a pronounced Holocene climatic optimum in Greenland coinciding with maximum thinning near the GIS margins. Our delta(18)O-based results are corroborated by the air content of ice cores, a proxy for surface elevation. State-of-the-art ice sheet models are generally found to be underestimating the extent and changes in GIS elevation and area; our findings may help to improve the ability of models to reproduce the GIS response to Holocene climate.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Vinther, B M -- Buchardt, S L -- Clausen, H B -- Dahl-Jensen, D -- Johnsen, S J -- Fisher, D A -- Koerner, R M -- Raynaud, D -- Lipenkov, V -- Andersen, K K -- Blunier, T -- Rasmussen, S O -- Steffensen, J P -- Svensson, A M -- England -- Nature. 2009 Sep 17;461(7262):385-8. doi: 10.1038/nature08355.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Oe, Denmark. bo@gfy.ku.dk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19759618" target="_blank"〉PubMed〈/a〉
    Keywords: Altitude ; *Greenhouse Effect ; Greenland ; History, Ancient ; *Ice Cover ; Oxygen/analysis ; Oxygen Isotopes ; Temperature
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 9
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    Natural and anthropogenic variations in methane sources during the past two millennia (2012)
    Nature Publishing Group (NPG)
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    Publication Date: 2012-10-06
    Description: Methane is an important greenhouse gas that is emitted from multiple natural and anthropogenic sources. Atmospheric methane concentrations have varied on a number of timescales in the past, but what has caused these variations is not always well understood. The different sources and sinks of methane have specific isotopic signatures, and the isotopic composition of methane can therefore help to identify the environmental drivers of variations in atmospheric methane concentrations. Here we present high-resolution carbon isotope data (delta(13)C content) for methane from two ice cores from Greenland for the past two millennia. We find that the delta(13)C content underwent pronounced centennial-scale variations between 100 BC and AD 1600. With the help of two-box model calculations, we show that the centennial-scale variations in isotope ratios can be attributed to changes in pyrogenic and biogenic sources. We find correlations between these source changes and both natural climate variability--such as the Medieval Climate Anomaly and the Little Ice Age--and changes in human population and land use, such as the decline of the Roman empire and the Han dynasty, and the population expansion during the medieval period.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sapart, C J -- Monteil, G -- Prokopiou, M -- van de Wal, R S W -- Kaplan, J O -- Sperlich, P -- Krumhardt, K M -- van der Veen, C -- Houweling, S -- Krol, M C -- Blunier, T -- Sowers, T -- Martinerie, P -- Witrant, E -- Dahl-Jensen, D -- Rockmann, T -- England -- Nature. 2012 Oct 4;490(7418):85-8. doi: 10.1038/nature11461.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Princetonplein 5, 3584CC Utrecht, The Netherlands. c.j.sapart@uu.nl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23038470" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/chemistry ; Biomass ; Carbon Isotopes ; Climate Change/history ; Fires/*history ; Greenland ; History, 15th Century ; History, 16th Century ; History, 17th Century ; History, 18th Century ; History, 19th Century ; History, 20th Century ; History, Ancient ; History, Medieval ; Holy Roman Empire ; Human Activities/*history ; Ice/analysis ; Methane/analysis/*history/*metabolism ; Population Dynamics ; Roman World/history
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 10
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    Hydrogen isotopes preclude marine hydrate CH4 emissions at the onset of Dansgaard-Oeschger events (2010)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2010-06-26
    Description: The causes of past changes in the global methane cycle and especially the role of marine methane hydrate (clathrate) destabilization events are a matter of debate. Here we present evidence from the North Greenland Ice Core Project ice core based on the hydrogen isotopic composition of methane [deltaD(CH4)] that clathrates did not cause atmospheric methane concentration to rise at the onset of Dansgaard-Oeschger (DO) events 7 and 8. Box modeling supports boreal wetland emissions as the most likely explanation for the interstadial increase. Moreover, our data show that deltaD(CH4) dropped 500 years before the onset of DO 8, with CH4 concentration rising only slightly. This can be explained by an early climate response of boreal wetlands, which carry the strongly depleted isotopic signature of high-latitude precipitation at that time.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bock, Michael -- Schmitt, Jochen -- Moller, Lars -- Spahni, Renato -- Blunier, Thomas -- Fischer, Hubertus -- New York, N.Y. -- Science. 2010 Jun 25;328(5986):1686-9. doi: 10.1126/science.1187651.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Climate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland. bock@climate.unibe.ch〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20576890" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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