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15 results on '"Dansgaard-Oeschger cycle"'

1. Changes in Atmospheric Dynamics Over Dansgaard‐Oeschger Climate Oscillations Around 40 ka and Their Impact on Europe.

Author

Stadelmaier, Kim H., Ludwig, Patrick, Pinto, Joaquim G., and Újvári, Gábor

Subjects
ATMOSPHERIC models, ICE cores, GLACIAL Epoch, OXYGEN isotopes, MARINE sediments
Abstract

Dansgaard‐Oeschger (D‐O) climate variability during the last glaciation was first evidenced in ice cores and marine sediments, and is also recorded in various terrestrial paleoclimate archives in Europe. The relative synchronicity across Greenland, the North Atlantic and Europe implies a tight and fast coupling between those regions, most probably effectuated by an atmospheric transmission mechanism. In this study, we investigated the atmospheric changes during Greenland interstadial (GI) and stadial (GS) phases based on regional climate model simulations using two specific periods, GI‐10 and GS‐9 both around 40 ka, as boundary conditions. Our simulations accurately capture the changes in temperature and precipitation as reconstructed by the available proxy data. Moreover, the simulations depict an intensified and southward shifted eddy‐driven jet during the stadial period. Ultimately, this affects the near‐surface circulation toward more southwesterly and cyclonic flow in western Europe during the stadial period, explaining much of the seasonal climate variability recorded by the proxy data, including oxygen isotopes, at the considered proxy sites. Plain Language Summary: The climate during the last ice age varied between colder and warmer periods on timescales ranging from hundreds to thousands of years. This variability was first detected in Greenland ice cores and marine sediment cores of the North Atlantic, as well as in continental geological records in Europe. The variation between the colder and warmer periods occur mostly simultaneously in Greenland and in Europe, which is why the atmosphere is assumed to have an important role in transferring the climate signals. We simulated two different periods of the last ice age, one colder and one warmer around 40,000 years ago, using a regional climate model. The aim was to study how the climate and atmospheric circulation changed during these two periods. We find the eddy‐driven jet over the North Atlantic intensified and shifted southward during the colder period. The jet influences the near‐surface atmospheric circulation and leads to more southwesterly and cyclonic flow in western Europe. Oxygen isotope variations observed in western European paleoclimate records may be partly explained by different, more southern moisture sources on top of changes in seasonal temperatures. Key Points: Simulated temperatures agree with proxy data; precipitation is biased but GI‐10 versus GS‐9 differences are well capturedThe stadial winter jet stream is intensified and shifted southward, consistent with dominant southwesterly/cyclonic flow in western EuropeOxygen isotope signal changes at western European proxy sites may be explained not only by temperature but also by varying moisture sources [ABSTRACT FROM AUTHOR]

Published
2024
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2. 临汾盆地黄土沉积记录的末次冰期 千年尺度气候事件.

Author

田庆春, 石小静, and 郝晓龙

Subjects
CLIMATE change, THERMOLUMINESCENCE dating, WESTERLIES, MAGNETIC susceptibility, ICE cores, MONSOONS, GEOGRAPHY
Abstract

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Published
2022
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3. Orbital insolation variations, intrinsic climate variability, and Quaternary glaciations

Author

Keno Riechers, Takahito Mitsui, Niklas Boers, and Michael Ghil

Subjects
Insolation, El Nino-Southern Oscillation, climate variability, Global and Planetary Change, Milankovitch cycles, Orbital forcing, orbital forcing, Stratigraphy, glaciation, Paleontology, Forcing (mathematics), Random dynamical systems, climate variation, Physics::Geophysics, Climatology, paleoclimatic past, 500 Naturwissenschaften und Mathematik::550 Geowissenschaften, Geologie::550 Geowissenschaften, Glacial period, Dansgaard-Oeschger cycle, intrinsic variability, Quaternary, external forcing, Geology, Physics::Atmospheric and Oceanic Physics
Abstract

The relative role of external forcing and of intrinsic variability is a key question of climate variability in general and of our planet's paleoclimatic past in particular. Over the last 100 years since Milankovic's contributions, the importance of orbital forcing has been established for the period covering the last 2.6 Myr and the Quaternary glaciation cycles that took place during that time. A convincing case has also been made for the role of several internal mechanisms that are active on timescales both shorter and longer than the orbital ones. Such mechanisms clearly have a causal role in Dansgaard–Oeschger and Heinrich events, as well as in the mid-Pleistocene transition. We introduce herein a unified framework for the understanding of the orbital forcing's effects on the climate system's internal variability on timescales from thousands to millions of years. This framework relies on the fairly recent theory of non-autonomous and random dynamical systems, and it has so far been successfully applied in the climate sciences for problems like the El Niño–Southern Oscillation, the oceans' wind-driven circulation, and other problems on interannual to interdecadal timescales. Finally, we provide further examples of climate applications and present preliminary results of interest for the Quaternary glaciation cycles in general and the mid-Pleistocene transition in particular.

Published
2022
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4. North Andean environmental and climatic change at orbital to submillennial time-scales: Vegetation, water-levels and sedimentary regimes from Lake Fúquene between 284 and 130 ka.

Author

Bogotá-A., R.G., Hooghiemstra, H., and Berrio, J.C.

Subjects
*SEDIMENTATION & deposition, *CLIMATE change, *POLLEN, *WATER levels
Abstract

We present a record of environmental and climatic changes in the northern Andes during the penultimate interglacial–glacial cycle based on integrated information from pollen and grain size distributions (GSDs). The record reflects the 58.33–26.21 m interval of a new sediment core from Lake Fúquene (2540 m elevation; 5°N) in the Colombian Andes. The age model is mainly based on cyclostyratigraphy and shows that this core interval reflects the period from 284 to 130 ka. The 1 cm sample increments yield a resolution of ~ 60 yr. In 2553 samples we analyzed 66 selected pollen and spore taxa with the best known ecological ranges. We reconstructed upper forest line (UFL) positions between ~ 2000 and ~ 3400 m elevation and the most abrupt temperature shifts ranged up to 10 °C/100 yr at Terminations II and III. Regional vegetation change is mainly driven by eccentricity (100 kyr) and obliquity (41 kyr) cycles, while changes in local aquatic vegetation show variability in the obliquity and precession (21 kyr) bands. Millennial-scale climate variability reflecting Dansgaard–Oeschger (DO) climate cycles in the upper part of the record, continues in this penultimate intergalcial–glacial cycle strongly suggesting that this variability has a persistent character in Pleistocene vegetation and climate dynamics. Short-lived upslope excursions of the UFL reflect 20 DO-style cycles during marine isotope stages (MIS) 7 and 6. Changes in species composition of montane forest are evident, and trees with most pioneer qualities ( Alnus , Morella , Quercus and Weinmannia ) migrated at the forefront. Other arboreal taxa like Podocarpus , Miconia , and Hedyosmum mostly followed later. Changes in regional vegetation distribution and forest composition, as well as in local aquatic vegetation and GSD of sediments supplied to the lake, allowed the development of an integrated reconstruction of the biotic and abiotic environments in the drainage basin. [ABSTRACT FROM AUTHOR]

Published
2016
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5. Millennial-scale tropical atmospheric and Atlantic Ocean circulation change from the Last Glacial Maximum and Marine Isotope Stage 3.

Author

IIThem, T.R., Schmidt, M.W., and Lynch-Stieglitz, J.

Subjects
*ATMOSPHERIC circulation, *OCEAN circulation, *LAST Glacial Maximum, *CLIMATE change, *MERIDIONAL overturning circulation
Abstract

Abrupt, millennial-scale climate oscillations, known as Dansgaard–Oeschger (D–O) cycles, characterized the climate system of the last glacial period. Although proxy evidence shows that D–O cycles resulted in large-scale changes in atmospheric circulation patterns around the planet, an understanding of how Atlantic Meridional Overturning Circulation (AMOC) varied across these events remains unclear. Here, we take advantage of the fact that both tropical atmospheric circulation changes corresponding to north–south shifts in the Intertropical Convergence Zone (ITCZ) and large-scale changes in ocean circulation associated with AMOC variability can be reconstructed in the same sediment core from the Florida Straits to examine the relationship between atmospheric and ocean circulation changes across D–O events. To reconstruct surface water conditions, Mg/Ca-paleothermometry and stable isotope measurements were combined on the planktonic foraminifera Globigerinoides ruber (white variety) from sediment core KNR166-2 JPC26 (24°19.61′N, 83°15.14′W; 546 m depth) to reconstruct a high-resolution record of sea surface temperature and δ O seawater 18 (a proxy for upper mixed layer salinity) during Marine Isotope Stages (MIS) 2 and 3 from 20–35 ka BP. As an additional proxy for upper water column salinity change, we also generate a faunal abundance record of the salinity-sensitive planktonic foraminifera Neogloboquadrina dutertrei . Our results suggest that rapid reductions in sea surface salinity occurred at the onset of D–O interstadials, while stadials are characterized by increased surface salinities. The most likely cause of these salinity changes was variation in the strength and position of the ITCZ across D–O events. Finally, we examine the relationship between millennial-scale atmospheric circulation changes recorded in the planktonic records and ocean circulation changes inferred from the benthic δ O 18 record from our core. Our results provide some of the first evidence that AMOC strength did vary across at least one of the millennial-scale D–O cycles of MIS 3. [ABSTRACT FROM AUTHOR]

Published
2015
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6. Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions

Author

Kévin Fourteau, Xavier Faïn, Patricia Martinerie, Amaëlle Landais, Alexey A. Ekaykin, Vladimir Ya. Lipenkov, Jérôme Chappellaz, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Arctic and Antarctic Research Institute (AARI), Russian Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
lcsh:GE1-350, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, paleoenvironment, lcsh:Environmental protection, methane, plateau, numerical method, analytical method, smoothing, atmospheric modeling, East Antarctica, low temperature, carbon monoxide, climate variation, mixing ratio, lcsh:Environmental pollution, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, lcsh:TD172-193.5, Antarctica, lcsh:TD169-171.8, Dansgaard-Oeschger cycle, ice core, lcsh:Environmental sciences
Abstract

We investigate for the first time the loss and alteration of past atmospheric information from air trapping mechanisms under low-accumulation conditions through continuous CH4 (and CO) measurements. Methane concentration changes were measured over the Dansgaard-Oeschger event 17 (DO-17, ĝ1/4 ĝ€†60ĝ€†000ĝ€†yrĝ€†BP) in the Antarctic Vostok 4G-2 ice core. Measurements were performed using continuous-flow analysis combined with laser spectroscopy. The results highlight many anomalous layers at the centimeter scale that are unevenly distributed along the ice core. The anomalous methane mixing ratios differ from those in the immediate surrounding layers by up to 50ĝ€†ppbv. This phenomenon can be theoretically reproduced by a simple layered trapping model, creating very localized gas age scale inversions. We propose a method for cleaning the record of anomalous values that aims at minimizing the bias in the overall signal. Once the layered-trapping-induced anomalies are removed from the record, DO-17 appears to be smoother than its equivalent record from the high-accumulation WAIS Divide ice core. This is expected due to the slower sinking and densification speeds of firn layers at lower accumulation. However, the degree of smoothing appears surprisingly similar between modern and DO-17 conditions at Vostok. This suggests that glacial records of trace gases from low-accumulation sites in the East Antarctic plateau can provide a better time resolution of past atmospheric composition changes than previously expected. We also developed a numerical method to extract the gas age distributions in ice layers after the removal of the anomalous layers based on comparison with a weakly smoothed record. It is particularly adapted for the conditions of the East Antarctic plateau, as it helps to characterize smoothing for a large range of very low-temperature and low-accumulation conditions. © Author(s) 2017.

Published
2017

8. The response of atmospheric nitrous oxide to climate variations during the last glacial period

Author

Schilt A., Baumgartner M., Eicher O., Chappellaz J., Schwander J., Fischer H., and Stocker T. F.

Subjects
glacial, Nitrous oxide, Atmospheric chemistry, concentration (composition), Holocene, Last Glacial, 530 Physics, glacial-interglacial cycle, Heinrich Events, Ice core, GRIP, Heinrich event, Salinity measurement, NGRIP, climate variation, Greenhouse gases, greenhouse gas, Climate change, Dansgaard-Oeschger cycle, Nitrogen oxides
Abstract

Detailed insight into natural variations of the greenhouse gas nitrous oxide (N2O) in response to changes in the Earth's climate system is provided by new measurements along the ice core of the North Greenland Ice Core Project (NGRIP). The presented record reaches from the early Holocene back into the previous interglacial with a mean time resolution of about 75years. Between 11 and 120kyrBP, atmospheric N2O concentrations react substantially to the last glacial-interglacial transition (Termination 1) and millennial time scale climate variations of the last glacial period. For long-lasting Dansgaard/Oeschger (DO) events, the N2O increase precedes Greenland temperature change by several hundred years with an increase rate of about 0.8-1.3ppbv/century, which accelerates to about 3.8-10.7ppbv/century at the time of the rapid warming in Greenland. Within each bundle of DO events, the new record further reveals particularly low N2O concentrations at the approximate time of Heinrich events. This suggests that the response of marine and/or terrestrial N2O emissions on a global scale are different for stadials with and without Heinrich events. Key Points High-resolution record of atmospheric N2O from 11 to 120 kyr BPSubstantial N2O response to the last glacial-interglacial transition (T1)DO and Heinrich event cycles visible in the atmospheric N2O concentration ©2013. American Geophysical Union. All Rights Reserved.

Published
2013

9. Regional imprints of millennial variability during the MIS 3 period around Antarctica

Author

Didier Swingedouw, Matthias Baumgartner, Valérie Masson-Delmotte, Bénédicte Lemieux-Dudon, Amaelle Landais, Adrian Schilt, Mattia Bonazza, Emilie Capron, Barbara Stenni, Mirko Severi, Frédéric Parrenin, Massimo Frezzotti, Roberto Udisti, Masa Kageyama, D. Buiron, Jérôme Chappellaz, Enricomaria Selmo, Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Dipartimento di Scienze Geologiche [Trieste], Università degli studi di Trieste, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), University of Bern, Italian National agency for new technologies, Energy and sustainable economic development [Frascati] (ENEA), Modélisation du climat (CLIM), Inria Grenoble - Rhône-Alpes, Institut National de Recherche en Informatique et en Automatique (Inria), Climate and Environmental Physics [Bern] (CEP), Physikalisches Institut [Bern], Universität Bern [Bern]-Universität Bern [Bern], University of Parma = Università degli studi di Parma [Parme, Italie], Università degli Studi di Firenze = University of Florence [Firenze] (UNIFI), Buiron, D., Stenni, Barbara, J., Chappellaz, A., Landai, M., Baumgartner, Bonazza, Mattia, E., Capron, M., Frezzotti, M., Kageyama, B., Lemieux Dudon, V., Masson Delmotte, F., Parrenin, A., Schilt, E., Selmo, M., Severi, D., Swingedouw, R., Udisti, Stenni, B., Chappellaz, J., Landais, A., Baumgartner, M., Bonazza, M., Capron, E., Frezzotti, M., Kageyama, M., Lemieux-Dudon, B., Masson-Delmotte, V., Parrenin, F., Schilt, A., Selmo, E., Severi, M., Swingedouw, D., Udisti, R., Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Università degli studi di Trieste = University of Trieste, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Universität Bern [Bern] (UNIBE)-Universität Bern [Bern] (UNIBE), Università degli studi di Parma = University of Parma (UNIPR), and Università degli Studi di Firenze = University of Florence (UniFI)

Subjects
Archeology, 010504 meteorology & atmospheric sciences, Paleoclimate, Global coupled model simulation, Greenland Ice Sheet, atmosphere-ocean coupling, Greenland, ice cores, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Arctic, Ice core, Millennial-scale variability, Ice age, stable isotope, Cryosphere, Climate change, Glacial period, Dansgaard-Oeschger cycle, Indian Sector, Global coupled model, sodium, deuterium, Talos Dome, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, geography.geographical_feature_category, teleconnection, Last Glacial, regional climate, Geology, Climatology, warming, millennial-scale variability, glacial period, global coupled model simulations, overturn, Paleoclimatology, freshwater input, paleoclimate, Paleoclimates, Southern Ocean, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, geography, Ice, marine isotope stage, East Antarctica, Arctic ice pack, Glacial geology, climate variation, Ice-sheet model, 13. Climate action, paleoceanography, coastal zone, meridional circulation, Antarctica, Ice sheet, ice core
Abstract

International audience; The climate of the last glacial Marine Isotopic Stage 3 (MIS3) period is characterized by strong millennial-scale variability with a succession of Dansgaard–Oeschger events first identified in Greenland ice cores and associated with variations of the Atlantic Meridional Overturning Circulation (AMOC). These abrupt events have a smooth and lagged counterpart in water stable isotopes from Antarctic ice cores. In this study we aim at depicting and understanding the circum-Antarctic expression of this millennial-scale variability. To illustrate the mechanisms potentially at work in the response of the southern high latitudes to an abrupt decrease of the AMOC, we first present results from experiments performed with the IPSL-CM4 atmosphere-ocean coupled model under glacial boundary conditions. When the AMOC is perturbed by imposing an additional freshwater flux in the North Atlantic, our model produces the classical bipolar seesaw mechanism generally invoked to explain the warming of the Southern Ocean/Antarctic region. However, this mechanism can be locally offset by faster atmospheric teleconnections originating from the tropics, even though the precise location of this fast response is not coherent among different climate models. Our model results are confronted with a synthesis of Antarctic records of ice core stable isotope and sea-salt sodium, including new data obtained on the TALDICE ice core. The IPSL-CM4 produces a dipole-like pattern around Antarctica, with warming in the Atlantic/Indian sectors contrasting with an unexpected cooling in the East-Pacific sector. The latter signal is not detected in our data synthesis. Both ice core data and simulations are consistent in depicting a more rapid response of the Atlantic sector compared to the Indian sector. This feature can be explained by the gradual impact of ocean transport on which faster atmospheric teleconnections are superimposed. Detailed investigations of the sequence of events between different proxies are conducted in three ice cores. Earlier shifts in deuterium excess and significant changes in sea-salt sodium fluxes in the most coastal sites (TALDICE and EDML) compared to EDC suggest reorganizations in local moisture sources, possibly linked with sea-ice cover. This study demonstrates the added value of circum-Antarctic ice core records to characterize the patterns and mechanisms of glacial climate variability.

Published
2012

10. A continuous record of temperature evolution over a sequence of Dansgaard-Oeschger events during Marine Isotopic Stage 4 (76 to 62 kyr BP)

Author

Landais, A., Barnola, J. M., Masson-Delmotte, Valérie, Jouzel, Jean, Chappellaz, J., Caillon, N., Huber, C., Leuenberger, M., Johnsen, S. J., Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Mathématiques Appliquées Paris 5 (MAP5 - UMR 8145), Université Paris Descartes - Paris 5 (UPD5)-Institut National des Sciences Mathématiques et de leurs Interactions (INSMI)-Centre National de la Recherche Scientifique (CNRS), Climate and Environmental Physics [Bern] (CEP), Physikalisches Institut [Bern], Universität Bern [Bern] (UNIBE)-Universität Bern [Bern] (UNIBE), Centre for Ice and Climate [Copenhagen], Niels Bohr Institute [Copenhagen] (NBI), Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH)-Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH), Institut Pierre-Simon-Laplace (IPSL), École normale supérieure - Paris (ENS Paris)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National d'Études Spatiales [Toulouse] (CNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Universität Bern [Bern]-Universität Bern [Bern], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU)-Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Mathématiques et de leurs Interactions (INSMI)-Université Paris Descartes - Paris 5 (UPD5), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Institut Pierre-Simon-Laplace ( IPSL ), Centre National de la Recherche Scientifique ( CNRS ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National d'Etudes Spatiales ( CNES ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -École normale supérieure - Paris ( ENS Paris ), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] ( LSCE ), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de glaciologie et géophysique de l'environnement ( LGGE ), Observatoire des Sciences de l'Univers de Grenoble ( OSUG ), Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ) -Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ) -Centre National de la Recherche Scientifique ( CNRS ), Mathématiques Appliquées à Paris 5 ( MAP5 - UMR 8145 ), Université Paris Descartes - Paris 5 ( UPD5 ) -Institut National des Sciences Mathématiques et de leurs Interactions-Centre National de la Recherche Scientifique ( CNRS ), Climate and Environmental Physics [Bern], University of Bern, and Niels Bohr Institute ( NBI ) -University of Copenhagen ( KU )

Subjects
Greenland, [ SDU.STU.GL ] Sciences of the Universe [physics]/Earth Sciences/Glaciology, Air isotopic measurements, Dansgaard-Oeschger events (DO), Thermal effects, Quaternary, Arctic, Isotopes, 3354 Meteorology and Atmospheric Dynamics: Precipitation (1854) Citation: Landais, paleoclimate, Dansgaard-Oeschger cycle, [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, ComputingMilieux_MISCELLANEOUS, Discharge (fluid mechanics), [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], [ PHYS.PHYS.PHYS-OPTICS ] Physics [physics]/Physics [physics]/Optics [physics.optics], World, Water, temperature, 3339 Meteorology and Atmospheric Dynamics: Ocean/atmosphere interactions (0312, marine isotope stage, Arctic and Antarctic, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, INDEX TERMS: 1040 Geochemistry: Isotopic composition/chemistry, Iceberg discharges, 4504), 3344 Meteorology and Atmospheric Dynamics: Paleoclimatology, [ SDU.STU.CL ] Sciences of the Universe [physics]/Earth Sciences/Climatology, Paleothermometry methods
Abstract

International audience; [1] Our knowledge of the temperature evolution over Greenland during Dansgaard-Oeschger events (DO) is currently qualitatively described through the water isotopic profile. Using two independent paleothermometry methods, one based on air isotopic measurements and the other on the combined measurements of water isotopes (dD and d 18 O), we show a complete and quantitative reconstruction of temperature at the NorthGRIP site over the period 76 to 62 kyr BP (DO 18, 19 and 20). We confirm that the associated warmings are larger than those conventionally depicted by the water isotopes (11°C, 16°C and 11°C for DO 18, 19 and 20). Secondly, we demonstrate that the relationship between temperature and d 18 O varies rapidly during the last glacial period, even over a DO. Finally, our temperature reconstruction over DO 19 agrees well with that predicted from simple climate models linking the DO to iceberg discharges. (2004), A continuous record of temperature evolution over a sequence of Dansgaard-Oeschger events during Marine Isotopic Stage 4 (76 to 62 kyr BP), Geophys. Res. Lett., 31, L22211, doi:10.1029/ 2004GL021193. [2] The last glacial cycle was characterized by millenial scale climate fluctuations that have been documented in the North Atlantic region through numerous marine and continental records [Bond et al., 1997; Genty et al., 2003]. The GRIP and GISP2 Summit ice cores [Dansgaard et al., 1993; Grootes et al., 1993] and the newly NorthGRIP [NorthGRIP Members, 2004] ice core exhibit 25 DO during the last glacial period. These events are characterized by rapid, e.g., in less than 100 years, and large, up to 16°C [Lang et al., 1999] warmings over Greenland. [3] Ice cores have already provided a wealth of information on DO in Greenland through the water isotopes for temperature changes, chemical records for atmospheric circulation and analysis of air bubbles for changes in greenhouse gases concentration. However, temperature reconstruction from water isotopes is subject to large biases mainly due to (i) the seasonality of the precipitation (i.e., periods without precipitation will not have their temperature recorded) [Fawcett et al., 1997] and (ii) changes in the oceanic source of Greenland snow [Boyle, 1997]. Whereas the latter can be estimated from the combined measurement of dD and d 18 O through the deuterium excess parameter (d = dD À 8 * d 18 O), we need additional information to account for the influence of seasonality and possible variation of the vertical atmospheric temperature profile (the isotopic composition of the snow depends on the condensation temperature). [4] One elegant way to overcome those difficulties is to use the isotopic composition of the air trapped in ice, a method based on the thermal diffusion of gases (nitrogen and argon), which allows estimates of the amplitude of rapid temperature increases [Severinghaus and Brook, 1999; Lang et al., 1999; Leuenberger et al., 1999]. This method gives directly access to the local mean surface temperature, and is therefore not affected by seasonality, the vertical temperature profile in the atmosphere, nor the source temperature of the precipitation. It confirms that the conventional temperature to water isotopes relationship, based on the spatial slope a s (the Dd 18 O ice /temperature slope calculated from present-day surface data) underestimates Greenland temperature change [Cuffey et al., 1995]. The temporal slope a t = Dd 18 O ice /DT (at a given site between two different climates) is lower than a s by up to a factor of 2. We have recently refined this approach, using a sophisticated firnification and heat diffusion model [Goujon et al., 2003] to quantify the temperature increase associated with large DO 12 [Landais et al., 2004]. [5] Here, we go beyond the simple quantification of the temperature increase. A detailed set of d 15 N and d 40 Ar measurements over DO 18, 19 and 20 provides us with strong constraints on the complete temperature scenario between 76 and 62 kyr BP. This period roughly corresponds to Marine Isotope Stage 4 with rapid ice sheet growth [Shackleton, 1987]. We have also measured a continuous dD profile in the ice that, combined with the existing d 18 O record, allows us to account for the source temperature effects. This complete study makes possible the precise estimation of the temperature change over a sequence of DO. [6] The d 15 N and d 40 Ar profiles (Figure 1) show a sharp peak corresponding to each warming. Rapid surface warm-GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L22211

Published
2004

11. Atmospheric methane during the last four glacial-interglacial cycles: Rapid changes and their link with Antarctic temperature

Author

J. M. Barnola, Céline Goujon, V. Lipenkov, Dominique Raynaud, Marc Delmotte, Pascal Yiou, Edward J. Brook, Jérôme A Chappellaz, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), ICOS-RAMCES (ICOS-RAMCES), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Washington State University (WSU), Extrèmes : Statistiques, Impacts et Régionalisation (ESTIMR), Arctic and Antarctic Research Institute (AARI), Russian Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Climate, Greenland, Soil Science, Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, atmospheric methane, Proxy (climate), Arctic, Ice core, Geochemistry and Petrology, atmospheric gas, Earth and Planetary Sciences (miscellaneous), Glacial period, Dansgaard-Oeschger cycle, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Ecology, biology, Atmospheric methane, glacial-interglacial cycle, methane, Paleontology, temperature, Forestry, biology.organism_classification, climate variation, Ice-sheet model, Geophysics, 13. Climate action, Space and Planetary Science, Climatology, Interglacial, Antarctica, Groenlandia, Quaternary, ice core, Geology
Abstract

Atmospheric methane (CH4) recorded in Antarctic ice cores represents the closest ice proxy available for Greenland temperature changes beyond times when Greenland climate records are available. The record over four climatic cycles from the Vostok ice core offers the opportunity to study the phase relationship between Greenland and Antarctic climate changes through detailed CH4 profiles. Combining American and French analytical efforts, we have improved the time resolution of the existing CH4 record from Petit et al [1999]. Spectral analyses reveal high- and low-frequency variability (including a strong precessional component). The phase relationship between CH4 and the Antarctic temperature proxy (δD) shows a systematic lag of CH4 versus temperature by 1100 ± 200 years, on long timescales (50-400 kyr) and a more complex behavior over shorter timescales (i.e., ≤25 kyr), suggesting that Dansgaard/Oeschger-type of climatic variability and associated interhemispheric linkage are robust features of late Quaternary climate. Copyright 2004 by the American Geophysical Union.

Published
2004

12. Evidence for an additional Heinrich event between H5 and H6 in the Labrador Sea

Author

Rashid, H, Hesse, R, Piper, Djw, Rashid, H, Hesse, R, and Piper, Djw

Abstract

An additional Heinrich ice-rafting event is identified between Heinrich events 5 and 6 in eight cores from the Labrador Sea and the northwest Atlantic Ocean. It is characterized by sediment rich in detrital carbonate (40% CaCO3) with high concentration of floating dropstones, high coarse-fraction (% > 150 mum) content, and has a sharp contact with the underlying but grades into the overlying hemipelagic sediment. It also shows lighter delta(18)O(Npl) values, indicating freshening due to iceberg rafting and/or meltwater discharge. This event is correlated with Dansgaard-Oeschger event 14 and interpreted as an additional Heinrich event, H5a. The thickness of H5a in the Labrador Sea reaches up to 220 cm. This additional Heinrich event has also been reported in cores PS2644 and SO82-5 from the northern North Atlantic. With the recognition of H5a the temporal spacing between Heinrich events 1 to 6 becomes more uniform ( similar to 7 ka).

Published
2003
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13. N2O and CH4 variations during the last glacial path epoch: Insight into global processes

Author

Flückiger, J., Blunier, T., Stauffer, B., Chappellaz, J., Spahni, R., Kawamura, K., Schwander, J., Stocker, T.F., and Dahl-Jensen, D.

Subjects
climate change, Arctic, nitrous oxide, greenhouse gas, Last Glacial, methane, Greenland, Dansgaard-Oeschger cycle, ice core
Abstract

Greenhouse gas measurements along polar ice cores provide important insight into the former composition of the atmosphere, its natural variations, and the responses to fast climatic changes in the past. We present high-resolution nitrous oxide (N2O) and methane (CH4) records measured along two ice cores from central Greenland covering part of Marine Isotope Stages 3 and 4 in the last glacial epoch. The N2O data confirm the hypothesis that N2O shows variations in phase to fast climatic changes observed in the Northern Hemisphere, the so-called Dansgaard-Oeschger (D-O) events. Variations exist not only for events with a long duration (1500 years and more) but also for the shorter ones. The comparison with CH4 unveils interesting differences between the response of CH4 and N2O to D-O events. While the average amplitudes of CH4 oscillations associated with D-O events are similar to those of the Northern Hemisphere summer insolation, the magnitude of the N2O concentration change instead correlates with the duration of the D-O events. The records give further insight into the timing of concentration changes at the beginning of D-O events. They show that for long-lasting events the N2O concentration starts to increase before both the sharp increase in the CH4 concentration and the temperature reconstructed for Greenland. Copyright 2004 by the American Geophysical Union.

14. Quantification of rapid temperature change during DO event 12 and phasing with methane inferred from air isotopic measurements

Author

Amaelle Landais, Jean Jouzel, Valérie Masson-Delmotte, Céline Goujon, Jérôme Chappellaz, Nicolas Caillon, J. M. Barnola, Markus Leuenberger, A.M. Grachev, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Scripps Institution of Oceanography (SIO), University of California [San Diego] (UC San Diego), University of California-University of California, Climate and Environmental Physics [Bern] (CEP), Physikalisches Institut [Bern], Universität Bern [Bern]-Universität Bern [Bern], Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Scripps Institution of Oceanography (SIO - UC San Diego), University of California (UC)-University of California (UC), and Universität Bern [Bern] (UNIBE)-Universität Bern [Bern] (UNIBE)

Subjects
010504 meteorology & atmospheric sciences, Greenland, 010502 geochemistry & geophysics, 01 natural sciences, Methane, Proxy (climate), chemistry.chemical_compound, Arctic, Ice core, Geochemistry and Petrology, paleoclimate, Earth and Planetary Sciences (miscellaneous), Glacial period, Dansgaard-Oeschger cycle, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, paleoatmosphere, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, geography, geography.geographical_feature_category, Last Glacial, methane, Firn, Arctic ice pack, Ice-sheet model, Pleistocene, Geophysics, chemistry, Greenland ice core project, 13. Climate action, Space and Planetary Science, Climatology, ice core, Geology
Abstract

The description of rapid climatic changes during the last glacial period at high northern latitudes has been largely documented through Greenland ice cores that are unique climatic and environmental records. However, Greenland ice isotopic records are biased temperature proxies and it is still a matter of debate whether changes in the high latitudes lead or lag rapid changes elsewhere. We focus here on the study of the mid-glacial Dansgaard Oeschger event 12 (45 ky BP) associated to a large d 18 Oice change in the GRIP (GReenland Ice core Project) ice core. We use combined measurements of CH4, d 15 N and d 40 Ar in entrapped air associated with a recently developed firn densification and heat diffusion model to infer (i) the phasing between methane and temperature increases and (ii) the amplitude of the temperature change. Our method enables us to overcome the difficulty linked with rapid accumulation change in quantifying the temperature change. We obtain a 12F2.5 8C temperature increase at the beginning of DO event 12 thus confirming that the conventional use of water isotopes in the Greenland ice cores largely underestimates the actual amplitude of rapid temperature change in central Greenland. In agreement with previous studies, methane and temperature increase are in phase at the sampling resolution of that part of our profile (90 years). D 2004 Elsevier B.V. All rights reserved.

15. High-resolution glacial and deglacial record of atmospheric methane by continuous-flow and laser spectrometer analysis along the NEEM ice core

Author

Xavier Faïn, O. Pascual, Logan Mitchell, D. Baslev-Clausen, Edward J. Brook, Jean Rosen, Jérôme A Chappellaz, Daniele Romanini, James E. Lee, Thomas Blunier, Simon Schüpbach, R. Dallmayr, Christopher Stowasser, Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Centre for Ice and Climate [Copenhagen], Niels Bohr Institute [Copenhagen] (NBI), Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU)-Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères] (LIPhy), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Joseph Fourier - Grenoble 1 (UJF), Archéologies, Cultures et Sociétés (ACS), Ministère de la Culture et de la Communication (MCC)-Université de Bourgogne (UB)-Centre National de la Recherche Scientifique (CNRS), Climate and Environmental Physics [Bern] (CEP), Physikalisches Institut [Bern], Universität Bern [Bern]-Universität Bern [Bern], Laboratoire de glaciologie et géophysique de l'environnement ( LGGE ), Observatoire des Sciences de l'Univers de Grenoble ( OSUG ), Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ) -Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ) -Centre National de la Recherche Scientifique ( CNRS ), Niels Bohr Institute ( NBI ) -University of Copenhagen ( KU ), Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères] ( LIPhy ), Université Joseph Fourier - Grenoble 1 ( UJF ) -Centre National de la Recherche Scientifique ( CNRS ), Archéologies, Cultures et Sociétés ( ACS ), Ministère de la Culture et de la Communication ( MCC ) -Université de Bourgogne ( UB ) -Centre National de la Recherche Scientifique ( CNRS ), Climate and Environmental Physics [Bern], University of Bern, Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Oregon State University (OSU), and The publication of this article isfinanced by CNRS-INSU

Subjects
Marine isotope stage, 010504 meteorology & atmospheric sciences, 530 Physics, lcsh:Environmental protection, Stratigraphy, Greenland Ice Sheet, Greenland, 010502 geochemistry & geophysics, Atmospheric sciences, deglaciation, 01 natural sciences, Proxy (climate), Methane, spectrometry, chemistry.chemical_compound, Arctic, lcsh:Environmental pollution, Ice core, glacial environment, interstadial, lcsh:TD169-171.8, Glacial period, Stadial, Dansgaard-Oeschger cycle, lcsh:Environmental sciences, 0105 earth and related environmental sciences, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], lcsh:GE1-350, Global and Planetary Change, Eemian, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], [ PHYS.PHYS.PHYS-OPTICS ] Physics [physics]/Physics [physics]/Optics [physics.optics], Atmospheric methane, methane, Paleontology, resolution, chemistry, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, 13. Climate action, Climatology, dissolved oxygen, lcsh:TD172-193.5, ice core, Geology
Abstract

The Greenland NEEM (North Greenland Eemian Ice Drilling) operation in 2010 provided the first opportunity to combine trace-gas measurements by laser spectroscopic instruments and continuous-flow analysis along a freshly drilled ice core in a field-based setting. We present the resulting atmospheric methane (CH4) record covering the time period from 107.7 to 9.5 ka b2k (thousand years before 2000 AD). Companion discrete CH4 measurements are required to transfer the laser spectroscopic data from a relative to an absolute scale. However, even on a relative scale, the high-resolution CH4 data set significantly improves our knowledge of past atmospheric methane concentration changes. New significant sub-millennial-scale features appear during interstadials and stadials, generally associated with similar changes in water isotopic ratios of the ice, a proxy for local temperature. In addition to the midpoint of Dansgaard–Oeschger (D/O) CH4 transitions usually used for cross-dating, sharp definition of the start and end of these events brings precise depth markers (with ±20 cm uncertainty) for further cross-dating with other palaeo- or ice core records, e.g. speleothems. The method also provides an estimate of CH4 rates of change. The onsets of D/O events in the methane signal show a more rapid rate of change than their endings. The rate of CH4 increase associated with the onsets of D/O events progressively declines from 1.7 to 0.6 ppbv yr−1 in the course of marine isotope stage 3. The largest observed rate of increase takes place at the onset of D/O event #21 and reaches 2.5 ppbv yr−1.

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