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Your search keyword '"Chappellaz, Jérôme"' showing total 101 results
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101 results on '"Chappellaz, Jérôme"'

1. Antarctic surface temperature and elevation during the Last Glacial Maximum

Author

Buizert, Christo, Fudge, TJ, Roberts, William HG, Steig, Eric J, Sherriff-Tadano, Sam, Ritz, Catherine, Lefebvre, Eric, Edwards, Jon, Kawamura, Kenji, Oyabu, Ikumi, Motoyama, Hideaki, Kahle, Emma C, Jones, Tyler R, Abe-Ouchi, Ayako, Obase, Takashi, Martin, Carlos, Corr, Hugh, Severinghaus, Jeffrey P, Beaudette, Ross, Epifanio, Jenna A, Brook, Edward J, Martin, Kaden, Chappellaz, Jérôme, Aoki, Shuji, Nakazawa, Takakiyo, Sowers, Todd A, Alley, Richard B, Ahn, Jinho, Sigl, Michael, Severi, Mirko, Dunbar, Nelia W, Svensson, Anders, Fegyveresi, John M, He, Chengfei, Liu, Zhengyu, Zhu, Jiang, Otto-Bliesner, Bette L, Lipenkov, Vladimir Y, Kageyama, Masa, and Schwander, Jakob

Subjects
Climate Action, General Science & Technology
Abstract

Water-stable isotopes in polar ice cores are a widely used temperature proxy in paleoclimate reconstruction, yet calibration remains challenging in East Antarctica. Here, we reconstruct the magnitude and spatial pattern of Last Glacial Maximum surface cooling in Antarctica using borehole thermometry and firn properties in seven ice cores. West Antarctic sites cooled ~10°C relative to the preindustrial period. East Antarctic sites show a range from ~4° to ~7°C cooling, which is consistent with the results of global climate models when the effects of topographic changes indicated with ice core air-content data are included, but less than those indicated with the use of water-stable isotopes calibrated against modern spatial gradients. An altered Antarctic temperature inversion during the glacial reconciles our estimates with water-isotope observations.

Published
2021

2. Comparative carbon cycle dynamics of the present and last interglacial

Author

Brovkin, Victor, Brücher, Tim, Kleinen, Thomas, Zaehle, Sönke, Joos, Fortunat, Roth, Raphael, Spahni, Renato, Schmitt, Jochen, Fischer, Hubertus, Leuenberger, Markus, Stone, Emma J, Ridgwell, Andy, Chappellaz, Jérôme, Kehrwald, Natalie, Barbante, Carlo, Blunier, Thomas, and Jensen, Dorthe Dahl

Subjects
Life on Land, Carbon cycle, Climate, Models, interglacials, The Holocene, The Eemian, Peatland, Fire, Coral reef, Earth Sciences, History and Archaeology, Paleontology
Abstract

Changes in temperature and carbon dioxide during glacial cycles recorded in Antarctic ice cores are tightly coupled. However, this relationship does not hold for interglacials. While climate cooled towards the end of both the last (Eemian) and present (Holocene) interglacials, CO2 remained stable during the Eemian while rising in the Holocene. We identify and review twelve biogeochemical mechanisms of terrestrial (vegetation dynamics and CO2 fertilization, land use, wildfire, accumulation of peat, changes in permafrost carbon, subaerial volcanic outgassing) and marine origin (changes in sea surface temperature, carbonate compensation to deglaciation and terrestrial biosphere regrowth, shallow-water carbonate sedimentation, changes in the soft tissue pump, and methane hydrates), which potentially may have contributed to the CO2 dynamics during interglacials but which remain not well quantified. We use three Earth System Models (ESMs) of intermediate complexity to compare effects of selected mechanisms on the interglacial CO2 and δ13CO2 changes, focusing on those with substantial potential impacts: namely carbonate sedimentation in shallow waters, peat growth, and (in the case of the Holocene) human land use. A set of specified carbon cycle forcings could qualitatively explain atmospheric CO2 dynamics from 8 ka BP to the pre-industrial. However, when applied to Eemian boundary conditions from 126 to 115 ka BP, the same set of forcings led to disagreement with the observed direction of CO2 changes after 122 ka BP. This failure to simulate late-Eemian CO2 dynamics could be a result of the imposed forcings such as prescribed CaCO3 accumulation and/or an incorrect response of simulated terrestrial carbon to the surface cooling at the end of the interglacial. These experiments also reveal that key natural processes of interglacial CO2 dynamics - shallow water CaCO3 accumulation, peat and permafrost carbon dynamics - are not well represented in the current ESMs. Global-scale modeling of these long-term carbon cycle components started only in the last decade, and uncertainty in parameterization of these mechanisms is a main limitation in the successful modeling of interglacial CO2 dynamics.

Published
2016

3. Southern Hemisphere atmospheric history of carbon monoxide over the late Holocene reconstructed from multiple Antarctic ice archives

Author

Faïn, Xavier, primary, Etheridge, David M., additional, Fourteau, Kévin, additional, Martinerie, Patricia, additional, Trudinger, Cathy M., additional, Rhodes, Rachael H., additional, Chellman, Nathan J., additional, Langenfelds, Ray L., additional, McConnell, Joseph R., additional, Curran, Mark A. J., additional, Brook, Edward J., additional, Blunier, Thomas, additional, Teste, Grégory, additional, Grilli, Roberto, additional, Lemoine, Anthony, additional, Sturges, William T., additional, Vannière, Boris, additional, Freitag, Johannes, additional, and Chappellaz, Jérôme, additional

Published
2023
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4. Contributors

Author

Antoniades, Dermot, primary, Biersma, Elisabeth M., additional, Bockheim, James, additional, Cannone, Nicoletta, additional, Casanova-Katny, Angelica, additional, Chappellaz, Jérôme, additional, Chowdhry Beeman, Jai, additional, Clem, Kyle R., additional, Convey, Peter, additional, Fogt, Ryan L., additional, Giralt, Santiago, additional, Glasser, Neil F., additional, Granados, Ignacio, additional, Guglielmin, Mauro, additional, Hernández, Armand, additional, Hobbs, William R., additional, Hocking, Emma, additional, Hodgson, Dominic A., additional, López-Martínez, Jerónimo, additional, Marshall, Gareth J., additional, Maturana, Claudia S., additional, Nývlt, Daniel, additional, Olalla-Tárraga, Miguel Ángel, additional, Oliva, Marc, additional, Parrenin, Frédéric, additional, Pearson, Michael, additional, Pla-Rabes, Sergi, additional, Raphael, Marilyn N., additional, Raynaud, Dominique, additional, Roberts, Stephen J., additional, Roman, Matěj, additional, Salerno, Melisa A., additional, Shin, Jinhwa, additional, Smellie, John L., additional, Stammerjohn, Sharon E., additional, Stenni, Barbara, additional, Toro, Manuel, additional, Vega, Greta C., additional, Verleyen, Elie, additional, Vyverman, Wim, additional, and Zarankin, Andres, additional

Published
2020
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8. A 2000-year temperature reconstruction on the East Antarctic plateau from argon–nitrogen and water stable isotopes in the Aurora Basin North ice core

Author

Servettaz, Aymeric P. M., primary, Orsi, Anaïs J., additional, Curran, Mark A. J., additional, Moy, Andrew D., additional, Landais, Amaelle, additional, McConnell, Joseph R., additional, Popp, Trevor J., additional, Le Meur, Emmanuel, additional, Faïn, Xavier, additional, and Chappellaz, Jérôme, additional

Published
2023
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9. Supplementary material to "Southern Hemisphere atmospheric history of carbon monoxide over the late Holocene reconstructed from multiple Antarctic ice archives"

Author

Faïn, Xavier, primary, Etheridge, David M., additional, Fourteau, Kévin, additional, Martinerie, Patricia, additional, Trudinger, Cathy M., additional, Rhodes, Rachael H., additional, Chellman, Nathan J., additional, Langenfelds, Ray L., additional, McConnell, Joseph R., additional, Curran, Mark A. J., additional, Brook, Edward J., additional, Blunier, Thomas, additional, Teste, Grégory, additional, Grilli, Roberto, additional, Lemoine, Anthony, additional, Sturges, William T., additional, Vannière, Boris, additional, Freitag, Johannes, additional, and Chappellaz, Jérôme, additional

Published
2023
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10. A 2000-year temperature reconstruction on the East Antarctic plateau from argon–nitrogen and water stable isotopes in the Aurora Basin North ice core

Author

Servettaz, Aymeric P. M., Orsi, Anaïs J., Curran, Mark A. J., Moy, Andrew D., Landais, Amaelle, Mcconnell, Joseph R., Popp, Trevor J., Le Meur, Emmanuel, Faïn, Xavier, Chappellaz, Jérôme, Servettaz, Aymeric P. M., Orsi, Anaïs J., Curran, Mark A. J., Moy, Andrew D., Landais, Amaelle, Mcconnell, Joseph R., Popp, Trevor J., Le Meur, Emmanuel, Faïn, Xavier, and Chappellaz, Jérôme

Published
2023

11. Southern Hemisphere atmospheric history of carbon monoxide over the late Holocene reconstructed from multiple Antarctic ice archives

Author

Faïn, Xavier, Etheridge, David M., Fourteau, Kévin, Martinerie, Patricia, Trudinger, Cathy M., Rhodes, Rachael H., Chellman, Nathan J., Langenfelds, Ray L., Mcconnell, Joseph R., Curran, Mark A. J., Brook, Edward J., Blunier, Thomas, Teste, Grégory, Grilli, Roberto, Lemoine, Anthony, Sturges, William T., Vannière, Boris, Freitag, Johannes, Chappellaz, Jérôme, Faïn, Xavier, Etheridge, David M., Fourteau, Kévin, Martinerie, Patricia, Trudinger, Cathy M., Rhodes, Rachael H., Chellman, Nathan J., Langenfelds, Ray L., Mcconnell, Joseph R., Curran, Mark A. J., Brook, Edward J., Blunier, Thomas, Teste, Grégory, Grilli, Roberto, Lemoine, Anthony, Sturges, William T., Vannière, Boris, Freitag, Johannes, and Chappellaz, Jérôme

Published
2023

13. Northern Hemisphere atmospheric history of carbon monoxide since preindustrial times reconstructed from multiple Greenland ice cores

Author

Faïn, Xavier, primary, Rhodes, Rachael H., additional, Place, Philip, additional, Petrenko, Vasilii V., additional, Fourteau, Kévin, additional, Chellman, Nathan, additional, Crosier, Edward, additional, McConnell, Joseph R., additional, Brook, Edward J., additional, Blunier, Thomas, additional, Legrand, Michel, additional, and Chappellaz, Jérôme, additional

Published
2022
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15. Northern Hemisphere atmospheric history of carbon monoxide since preindustrial times reconstructed from multiple Greenland ice cores

Author

Faïn, Xavier, Rhodes, Rachael H., Philip, Place, Petrenko, Vasilii V., Fourteau, Kévin, Chellman, Nathan, Crosier, Edward, McConnell, Joseph R., Brook, Edward J., Blunier, Thomas, Legrand, Michel, Chappellaz, Jérôme, Faïn, Xavier, Rhodes, Rachael H., Philip, Place, Petrenko, Vasilii V., Fourteau, Kévin, Chellman, Nathan, Crosier, Edward, McConnell, Joseph R., Brook, Edward J., Blunier, Thomas, Legrand, Michel, and Chappellaz, Jérôme

Published
2021

16. Millennial-scale atmospheric CO2 variations during the Marine Isotope Stage 6 period (190–135 ka)

Author

Shin, Jinhwa, Nehrbass-Ahles, Christoph, Grilli, Roberto, Chowdhry Beeman, Jai, Parrenin, Frédéric, Teste, Grégory, Landais, Amaelle, Schmidely, Loïc, Silva, Lucas, Schmitt, Jochen, Bereiter, Bernhard, Stocker, Thomas F., Fischer, Hubertus, and Chappellaz, Jérôme

Abstract

Using new and previously published CO2 data from the EPICA Dome C ice core (EDC), we reconstruct a new high-resolution record of atmospheric CO2 during Marine Isotope Stage (MIS) 6 (190 to 135 ka)  the penultimate glacial period. Similar to the last glacial cycle, where high-resolution data already exists, our record shows that during longer North Atlantic (NA) stadials, millennial CO2 variations during MIS 6 are clearly coincident with the bipolar seesaw signal in the Antarctic temperature record. However, during one short stadial in the NA, atmospheric CO2 variation is small (∼5 ppm) and the relationship between temperature variations in EDC and atmospheric CO2 is unclear. The magnitude of CO2 increase during Carbon Dioxide Maxima (CDM) is closely related to the NA stadial duration in both MIS 6 and MIS 3 (60–27 ka). This observation implies that during the last two glacials the overall bipolar seesaw coupling of climate and atmospheric CO2 operated similarly. In addition, similar to the last glacial period, CDM during the earliest MIS 6 show different lags with respect to the corresponding abrupt CH4 rises, the latter reflecting rapid warming in the Northern Hemisphere (NH). During MIS 6i at around 181.5±0.3 ka, CDM 6i lags the abrupt warming in the NH by only 240±320 years. However, during CDM 6iv (171.1±0.2 ka) and CDM 6iii (175.4±0.4 ka) the lag is much longer: 1290±540 years on average. We speculate that the size of this lag may be related to a larger expansion of carbon-rich, southern-sourced waters into the Northern Hemisphere in MIS 6, providing a larger carbon reservoir that requires more time to be depleted.

Published
2020

17. Supplementary material to "Northern Hemisphere atmospheric history of carbon monoxide since preindustrial times reconstructed from multiple Greenland ice cores"

Author

Faïn, Xavier, primary, Rhodes, Rachael H., additional, Philip, Place, additional, Petrenko, Vasilii V., additional, Fourteau, Kévin, additional, Chellman, Nathan, additional, Crosier, Edward, additional, McConnell, Joseph R., additional, Brook, Edward J., additional, Blunier, Thomas, additional, Legrand, Michel, additional, and Chappellaz, Jérôme, additional

Published
2021
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18. Northern Hemisphere atmospheric history of carbon monoxide since preindustrial times reconstructed from multiple Greenland ice cores

Author

Faïn, Xavier, primary, Rhodes, Rachael H., additional, Philip, Place, additional, Petrenko, Vasilii V., additional, Fourteau, Kévin, additional, Chellman, Nathan, additional, Crosier, Edward, additional, McConnell, Joseph R., additional, Brook, Edward J., additional, Blunier, Thomas, additional, Legrand, Michel, additional, and Chappellaz, Jérôme, additional

Published
2021
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19. Ice Memory

Author

Ginot, Patrick, primary, Chappellaz, Jérôme, additional, Barbante, Carlo, additional, Schwikowski, Margit, additional, and Ohlmann, Anne-Catherine, additional

Published
2021
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20. Atmospheric history of carbon monoxide since preindustrial times reconstructed from multiple Greenland ice cores

Author

Faïn, Xavier, primary, Rhodes, Rachael, additional, Place, Philip, additional, Petrenko, Vasilii, additional, Fourteau, Kévin, additional, Chellman, Nathan, additional, Crosier, Edward, additional, McConnell, Joe, additional, Brook, Edward, additional, Blunier, Thomas, additional, Legrand, Michel, additional, Szopa, Sophie, additional, Tsigaridis, Kostas, additional, Naik, Vaishali, additional, and Chappellaz, Jérôme, additional

Published
2021
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21. Millennial-scale atmospheric CO2 variations during the Marine Isotope Stage 6 period (190–135 kyr BP)

Author

Shin, Jinhwa, Nehrbass-Ahles, Christoph, Grilli, Roberto, Chowdhry Beeman, Jai, Parrenin, Frédéric, Teste, Grégory, Landais, Amaelle, Schmidely, Loïc, Schmitt, Jochen, Stocker, Thomas F., Fischer, Hubertus, and Chappellaz, Jérôme

Abstract

Understanding natural carbon cycle/climate feedbacks on various time scales is highly relevant to reliably predict future climate changes. During the last two glacial periods, climate variations on millennial time scales were observed but the background conditions and duration of climate variations are different. Here we make use of contrasting climatic boundary conditions during the last two glacial periods to gain insight into the co-occurring carbon cycle changes. We reconstruct a new high-resolution record of atmospheric CO2 from the EPICA Dome C (EDC) ice core during Marine Isotope Stage (MIS) 6 (190 to 135 kyr BP). During long stadials in the North Atlantic (NA) region, atmospheric CO2 appears to be associated with the coeval Antarctic temperature changes at millennial time scale connected to the bipolar seesaw process. However, during one short stadial in the NA, atmospheric CO2 variation is negligible and the relationship between temperature variation in EDC and atmospheric CO2 is unclear. We suggest that the amplitude of CO2 variation may be affected by the duration of perturbations of the Atlantic Meridional Overturning Circulation (AMOC). In addition, similar to the last glacial period, in the earliest MIS 6 (MIS 6e and 6d, corresponding to 189 to 169 kyr BP), Carbon Dioxide Maxima (CDM) show different lags with respect to the corresponding abrupt CH4 jumps, the latter reflecting rapid warming in the Northern Hemisphere (NH). During MIS 6e at around 181.5 ± 0.3 kyr BP, CDM 6e.2 lags abrupt warming in the NH by only 200 ± 360 yrs. During MIS 6d which corresponds to CDM 6d.1 (171.1 ±0.2 kyr BP) and CDM 6d.2 (175.4 ± 0.4 kyr BP), the lag is much longer, i.e., 1,400 ± 375 yrs on average. The timing of CO2 variations with respect to abrupt warming in the NH may be affected by a major change in the organization of the AMOC from MIS 6e to MIS 6d.

Published
2019

22. Millennial-scale atmospheric CO<sub>2</sub> variations during the Marine Isotope Stage 6 period (190–135 ka)

Author

Shin, Jinhwa, primary, Nehrbass-Ahles, Christoph, additional, Grilli, Roberto, additional, Chowdhry Beeman, Jai, additional, Parrenin, Frédéric, additional, Teste, Grégory, additional, Landais, Amaelle, additional, Schmidely, Loïc, additional, Silva, Lucas, additional, Schmitt, Jochen, additional, Bereiter, Bernhard, additional, Stocker, Thomas F., additional, Fischer, Hubertus, additional, and Chappellaz, Jérôme, additional

Published
2020
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23. CH4 and N2O fluctuations during the penultimate deglaciation

Author

Schmidely, Loïc, primary, Nehrbass-Ahles, Christoph, additional, Schmitt, Jochen, additional, Han, Juhyeong, additional, Silva, Lucas, additional, Shin, Jinwha, additional, Joos, Fortunat, additional, Chappellaz, Jérôme, additional, Fischer, Hubertus, additional, and Stocker, Thomas F., additional

Published
2020
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27. Millennial-scale atmospheric CO2 variations during the Marine Isotope Stage 6 period (190–135 kyr BP)

Author

Shin, Jinhwa, primary, Nehrbass-Ahles, Christoph, additional, Grilli, Roberto, additional, Chowdhry Beeman, Jai, additional, Parrenin, Frédéric, additional, Teste, Grégory, additional, Landais, Amaelle, additional, Schmidely, Loïc, additional, Schmitt, Jochen, additional, Stocker, Thomas F., additional, Fischer, Hubertus, additional, and Chappellaz, Jérôme, additional

Published
2019
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28. Supplementary material to "Millennial-scale atmospheric CO2 variations during the Marine Isotope Stage 6 period (190–135 kyr BP)"

Author

Shin, Jinhwa, primary, Nehrbass-Ahles, Christoph, additional, Grilli, Roberto, additional, Chowdhry Beeman, Jai, additional, Parrenin, Frédéric, additional, Teste, Grégory, additional, Landais, Amaelle, additional, Schmidely, Loïc, additional, Schmitt, Jochen, additional, Stocker, Thomas F., additional, Fischer, Hubertus, additional, and Chappellaz, Jérôme, additional

Published
2019
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33. Simultaneous detection of C<sub>2</sub>H<sub>6</sub>, CH<sub>4</sub>, and <i>δ</i><sup>13</sup>C-CH<sub>4</sub> using optical feedback cavity-enhanced absorption spectroscopy in the mid-infrared region: towards application for dissolved gas measurements

Author

Lechevallier, Loic, primary, Grilli, Roberto, additional, Kerstel, Erik, additional, Romanini, Daniele, additional, and Chappellaz, Jérôme, additional

Published
2019
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36. Le climat à découvert

Author

Ablain, Michaël, Allard, Patrick, Anquetin, Sandrine, Balkanski, Yves, Bard, Édouard, Bekki, Slimane, Berthier, Étienne, Blamart, Dominique, Blard, Pierre-Henri, Blay, Michel, Blayo, Éric, Bony, Sandrine, Bopp, Laurent, Braconnot, Pascale, Brenguier, Jean-Louis, Bustarret, Étienne, Cadule, Patricia, Cassou, Christophe, Cazenave, Anny, Céron, Jean-Pierre, Chappellaz, Jérôme, Chauvaud, Laurent, Ciais, Philippe, Codron, Francis, Corrège, Thierry, Cortijo, Elsa, Cottet, Georges-Henri, Criqui, Patrick, Dandin, Philippe, Daux, Valérie, Davin, Édouard, Decharme, Bertrand, Delcroix, Thierry, Delecluse, Pascale, Delire, Christine, Déqué, Michel, de Marsily, Ghislain, de Noblet-Ducoudré, Nathalie, Donnadieu, Yannick, Douville, Hervé, Dubuisson, Philippe, Dudok de Wit, Thierry, Dufresne, Jean-Louis, Durand, Gaël, Féral, Jean-Pierre, Fluteau, Frédéric, France-Lanord, Christian, Friedlingstein, Pierre, Friess, Benjamin, Fuchs, Alain, Gaillardet, Jérôme, Garnier, Emmanuel, Genty, Dominique, Gerbeau, Jean-Frédéric, Goddéris, Yves, Grousset, Francis, Guillemot, Hélène, Guilyardi, Éric, Guimberteau, Matthieu, Guiot, Joël, Hall, Nick, Hourcade, Jean-Charles, Hourdin, Frédéric, Jeandel, Catherine, Joussaume, Sylvie, Jouzel, Jean, Kageyama, Masa, Khodri, Myriam, Klein, Patrice, Krinner, Gerhard, Laj, Paolo, Landais, Amaelle, Laval, Katia, Legras, Bernard, Le Bohec, Céline, Le Hir, Guillaume, Le Maho, Yvon, Le Treut, Hervé, Lilensten, Jean, Llovel, William, Lott, François, Maisonnave, Éric, Marchesiello, Patrick, Mascart, Patrick, Masson-Delmotte, Valérie, Mémery, Laurent, Metzl, Nicolas, Meurdesoif, Yann, Mignot, Juliette, Mosseri, Rémy, Naveau, Philippe, Petit, Jean-Robert, Peyron, Odile, Picon, Laurence, Pironneau, Olivier, Planton, Serge, Polcher, Jan, Pucéat, Emmanuelle, Rabatel, Antoine, Ramonet, Michel, Ramstein, Gilles, Reverdin, Gilles, Ribes, Aurélien, Roche, Didier, Roullet, Guillaume, Roux, Frank, Salas y Mélia, David, Sicre, Marie-Alexandrine, Swingedouw, Didier, Talagrand, Olivier, Tanré, Didier, Tatoni, Thierry, Thouret, Valérie, Thuillier, Gérard, Valcke, Sophie, Verron, Jacques, Vincent, Christian, Viovy, Nicolas, von Ballmoos, Peter, Wagnon, Patrick, Yiou, Pascal, GEOMAR LEGOS, Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Théorique de la Matière Condensée (LPTMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)

Subjects
effet de serre, climatologie, History & Philosophy Of Science, climat, [SDE.MCG]Environmental Sciences/Global Changes, SCI042000, météorologie, 01 natural sciences, 010305 fluids & plasmas, Outils et méthodes en recherche climatique, RBP, 0103 physical sciences, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 010306 general physics
Abstract

Qu'est ce que l'effet de serre ? Le rôle de l'homme sur le climat est-il détectable et comment ? Comment mesure-t-on la fonte de la banquise, le recul des glaciers de montagne ou bien encore l'élévation du niveau de la mer ? Comment les chercheurs font-ils pour modéliser un système aussi complexe que la planète terre ? Quelles données permettent de décrire et modéliser les climats passés ? Comment s'y prend-on pour prévoir l'évolution à venir du climat ? À l'écart de la polémique médiatique, Catherine Jeandel et Rémy Mosseri ont mobilisé plus d'une centaine de contributeurs qui livrent ici un panorama large des méthodes et outils mis en oeuvre pour étudier notre climat et son avenir. Ils montrent que, pour résoudre cette question extraordinairement complexe, une approche pluridisciplinaire est plus que jamais nécessaire, à la croisée de l'expérimentation, de l'observation, de la simulation et de la théorie. Un livre majeur.

Published
2017

37. 16. Inclusions minérales et gazeuses dans les glaces

Author

Chappellaz, Jérôme, Petit, Jean-Robert, Grousset, Francis, and Bard, Édouard

Abstract

Les gaz à effet de serre* (GES) et les poussières atmosphériques affectent le bilan radiatif terrestre (cf. II-2) tandis que l’activité solaire module le flux des rayons cosmiques qui interagit avec les hautes couches de l’atmosphère. Déterminer le rôle joué par ces facteurs sur la variabilité climatique* naturelle ou son évolution récente requiert de les reconstituer au cours du temps grâce notamment à l’analyse des glaces polaires : les couches de neige conservent les poussières éoliennes e...

Published
2017

38. Is there 1.5-million-year-old ice near Dome C, Antarctica?

Author

Parrenin, Frédéric, Cavitte, Marie G. P., Blankenship, Donald D., Chappellaz, Jérôme, Fischer, Hubertus, Gagliardini, Olivier, Masson-Delmotte, Valérie, Passalacqua, Olivier, Ritz, Catherine, Roberts, Jason, Siegert, Martin J., Young, Duncan A., Institut des Géosciences de l’Environnement (IGE), 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]), Institute for Geophysics, University of Texas at Dallas [Richardson] (UT Dallas), Observatoire des Sciences de l'Univers de Grenoble (OSUG ), 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 Grenoble Alpes [2016-2019] (UGA [2016-2019]), Abteilung Klinische Sozialmedizin, Berufs- und Umweltdermatologie, Universität Heidelberg [Heidelberg], 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 Queensland [Brisbane], 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 (UGA), CLIPS, 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)-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), 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 d'Informatique, Systèmes, Traitement de l'Information et de la Connaissance (LISTIC), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), EDGe, Universität Heidelberg [Heidelberg] = Heidelberg University, 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
[SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, ComputingMilieux_MISCELLANEOUS
Abstract

Ice sheets provide exceptional archives of past changes in polar climate, regional environment and global atmospheric composition. The oldest dated deep ice core drilled in Antarctica has been retrieved at EPICA Dome C (EDC), reaching ∼ 800 000 years. Obtaining an older paleoclimatic record from Antarctica is one of the greatest challenges of the ice core community. Here, we use internal isochrones, identified from airborne radar coupled to ice-flow modelling to estimate the age of basal ice along transects in the Dome C area. Three glaciological properties are inferred from isochrones: surface accumulation rate, geothermal flux and the exponent of the Lliboutry velocity profile. We find that old ice (> 1.5 Myr, 1.5 million years) likely exists in two regions: one ∼ 40 km south-west of Dome C along the ice divide to Vostok, close to a secondary dome that we name Little Dome C (LDC), and a second region named North Patch (NP) located 10–30 km north-east of Dome C, in a region where the geothermal flux is apparently relatively low. Our work demonstrates the value of combining radar observations with ice flow modelling to accurately represent the true nature of ice flow, and understand the formation of ice-sheet architecture, in the centre of large ice sheets.

Published
2017

39. CH4 and N2O fluctuations during the penultimate deglaciation.

Author

Schmidely, Loïc, Nehrbass-Ahles, Christoph, Schmitt, Jochen, Juhyeong Han, Silva, Lucas, Jinwha Shin, Joos, Fortunat, Chappellaz, Jérôme, Fischer, Hubertus, and Stocker, Thomas F.

Abstract

Deglaciations are characterized by the largest natural changes in methane (CH4) and nitrous oxide (N2O) concentrations of the past 800 thousand years. Reconstructions of millennial to centennial-scale variability within these periods are mostly restricted to the last deglaciation. In this study, we present composite records of CH4 and N2O concentrations from the EPICA Dome C ice core covering the penultimate deglaciation at temporal resolutions of about ~?100 years. Our data permit the identification of centennial-scale fluctuations standing out of the overall transition to interglacial levels. These features occurred in concert with reinvigorations of the Atlantic Meridional Overturning Circulation (AMOC) and northward shifts of the Intertropical Convergence Zone. The abrupt CH4 and N2O rises at about ~?134 and ~?128 thousand of years before present (hereafter ka?BP) are assimilated to the fluctuations accompanying the Dansgaard–Oeschger events of the last glacial period, while rising N2O levels at ~?130.5?ka?BP are assimilated to a pattern of increasing N2O concentrations that characterized the end of Heinrich stadials. We suggest the 130.5-ka event to be driven by a partial reinvigoration of the AMOC. Overall, the CH4 and N2O fluctuations during the penultimate deglaciation exhibit modes of variability that are also found during the last deglaciation. However, trace gas responses may differ for similar type of climatic events, as exemplified by the reduced amplitude and duration of the 134-ka event compared to the fluctuations of the Bølling–Allerød during the last deglaciation. [ABSTRACT FROM AUTHOR]

Published
2020

40. Millennial-scale atmospheric CO2 variations during the Marine Isotope Stage 6 period (190-135 kyr BP).

Author

Jinhwa Shin, Nehrbass-Ahles, Christoph, Grilli, Roberto, Beeman, Jai Chowdhry, Parrenin, Frédéric, Teste, Grégory, Landais, Amaelle, Schmidely, Loïc, Schmitt, Jochen, Stocker, Thomas F., Fischer, Hubertus, and Chappellaz, Jérôme

Abstract

Understanding natural carbon cycle/climate feedbacks on various time scales is highly relevant to reliably predict future climate changes. During the last two glacial periods, climate variations on millennial time scales were observed but the background conditions and duration of climate variations are different. Here we make use of contrasting climatic boundary conditions during the last two glacial periods to gain insight into the co-occurring carbon cycle changes. We reconstruct a new high-resolution record of atmospheric CO2 from the EPICA Dome C (EDC) ice core during Marine Isotope Stage (MIS) 6 (190 to 135 kyr BP). During long stadials in the North Atlantic (NA) region, atmospheric CO2 appears to be associated with the coeval Antarctic temperature changes at millennial time scale connected to the bipolar seesaw process. However, during one short stadial in the NA, atmospheric CO2 variation is negligible and the relationship between temperature variation in EDC and atmospheric CO2 is unclear. We suggest that the amplitude of CO2 variation may be affected by the duration of perturbations of the Atlantic Meridional Overturning Circulation (AMOC). In addition, similar to the last glacial period, in the earliest MIS 6 (MIS 6e and 6d, corresponding to 189 to 169 kyr BP), Carbon Dioxide Maxima (CDM) show different lags with respect to the corresponding abrupt CH4 jumps, the latter reflecting rapid warming in the Northern Hemisphere (NH). During MIS 6e at around 181.5 ± 0.3 kyr BP, CDM 6e.2 lags abrupt warming in the NH by only 200 ± 360 yrs. During MIS 6d which corresponds to CDM 6d.1 (171.1 ±0.2 kyr BP) and CDM 6d.2 (175.4 ± 0.4 kyr BP), the lag is much longer, i.e., 1,400 ± 375 yrs on average. The timing of CO2 variations with respect to abrupt warming in the NH may be affected by a major change in the organization of the AMOC from MIS 6e to MIS 6d. [ABSTRACT FROM AUTHOR]

Published
2020
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45. Estimation of gas record alteration in very low accumulation ice cores.

Author

Fourteau, Kévin, Martinerie, Patricia, Faïn, Xavier, Ekaykin, Alexey A., Chappellaz, Jérôme, and Lipenkov, Vladimir

Abstract

We measured the methane mixing ratios of enclosed air in five ice core sections drilled on the East Antarctic plateau. Our work aims to study two effects that affect the recorded gas concentrations in ice cores: layered gas trapping artifacts and firn smoothing. Layered gas trapping artifacts are due to the heterogeneous nature of polar firn, where some strata might close early and trap abnormally old gases that appear as spurious values during measurements. The smoothing is due to the combined effects of diffusive mixing in the firn and the progressive closure of bubbles at the bottom of the firn. Consequently, the gases trapped in a given ice layer span a distribution of ages. Concentration measurements thus only measure the average value in the ice layer, which removes the fast variability from the record. We focus on the study of East Antarctic plateau ice cores, as these low accumulation ice cores are particularly affected by both layering and smoothing. Our results suggest that the presence of layering artifacts in deep ice cores is linked with the chemical content of the ice. We use high-resolution methane data to parametrize a simple model reproducing the layered gas trapping artifacts for different accumulation conditions typical of the East Antarctic plateau. We also use the high-resolution methane measurements to estimate the gas age distributions of the enclosed air in the five newly measured ice core sections. It appears that for accumulations below 2 cm ie yr-1(ice equivalent) the gas records experience nearly the same degree of smoothing. We therefore propose to use a single gas age distribution to represent the firn smoothing observed in the glacial ice cores of the East Antarctic plateau. Finally, we used the layered gas trapping model and the estimation of glacial firn smoothing to estimate their potential impacts on a million-and-a-half years old ice core from the East Antarctic plateau. Our results indicate that layering artifacts are no longer individually resolved in the case of very thinned ice near the bedrock. They nonetheless contribute to slight biases of the measured signal (less than 10 ppbv and 0.5 ppmv in the case of methane and carbon dioxide). However, these biases are small compared to the dampening experienced by the record due to firn smoothing. [ABSTRACT FROM AUTHOR]

Published
2019
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46. Continuous In Situ Measurement of Dissolved Methane in Lake Kivu Using a Membrane Inlet Laser Spectrometer.

Author

Grilli, Roberto, Darchambeau, François, Chappellaz, Jérôme, Mugisha, Ange, Triest, Jack, and Umutoni, Augusta

Subjects
SPECTROMETERS, LAKES, WATER depth, METHANE, EXTRACTION techniques
Abstract

We report the first high resolution continuous profile of dissolved methane in the shallow water of Lake Kivu, Rwanda. The measurements were performed using an in situ dissolved gas sensor, called Sub-Ocean, based on a patented, membrane based extraction technique coupled with a highly sensitive optical spectrometer. The sensor was originally designed for ocean settings, but both the spectrometer and the extraction system were modified to extend the dynamical range up to six orders of magnitude with respect to the original prototype (from nmol L-1 to mmol L-1 detection) to fit the range of concentrations at lake Kivu. The accuracy of the instrument was estimated to ±22 % (2 s) from the standard deviation of eight profiles at 80 m of depth, corresponding to ±112 μBar of CH4 in water or ±160 nmol L-1 at 25 °C and 1 atm. The instrument was able to continuously measure the top 150 m of water depth within only 25 min. The maximum observed mixing ratio of CH4 in the gas phase concentration was 77 % at 150 m depth, which at this depth and thermal condition of the lake corresponds to 3.5 mmol L-1. At deeper depth, dissolved CH4 concentrations were too large for the methane absorption spectrum to be correctly retrieved. Results were in good agreement with discrete in situ measurements conducted with the commercial HydroC sensor. The fast profiling feature will be highly profitable for future monitoring of the lake, while the spectrometer could be replaced with a less sensitive analytical technique possibly including simultaneous detection of dissolved CO2 and which would allow to measure at higher concentrations of CH4. [ABSTRACT FROM AUTHOR]

Published
2019
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47. Simultaneous detection of C2H6, CH4, and δ13C-CH4 using optical feedback cavity-enhanced absorption spectroscopy in the mid-infrared region: towards application for dissolved gas measurements.

Author

Lechevallier, Loic, Grilli, Roberto, Kerstel, Erik, Romanini, Daniele, and Chappellaz, Jérôme

Subjects
OPTICAL feedback, SPECTRUM analysis, INFRARED absorption, OPTICAL resonators, ABSORPTION coefficients, ABSORPTION
Abstract

Simultaneous measurement of C2H6 and CH4 concentrations, and of the δ13C - CH4 isotope ratio is demonstrated using a cavity-enhanced absorption spectroscopy technique in the mid-IR region. The spectrometer is compact and has been designed for field operation. It relies on optical-feedback-assisted injection of 3.3 µ m radiation from an interband cascade laser (ICL) into a V-shaped high-finesse optical cavity. A minimum absorption coefficient of 2.8×10-9 cm -1 is obtained in a single scan (0.1 s) over 0.7 cm -1. Precisions of 3 ppbv, 11 ppbv, and 0.08 ‰ for C2H6 , CH4 , and δ13C - CH4 , respectively, are achieved after 400 s of integration time. Laboratory calibrations and tests of performance are reported here. They show the potential for the spectrometer to be embedded in a sensor probe for in situ measurements in ocean waters, which could have important applications for the understanding of the source and fate of hydrocarbons from the seabed and in the water column. [ABSTRACT FROM AUTHOR]

Published
2019
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48. High-resolution under-water laser spectrometer sensing provides new insights to methane distribution at an Arctic seepage site.

Author

Jansson, Pär, Triest, Jack, Grilli, Roberto, Ferré, Bénédicte, Silyakova, Anna, Mienert, Jürgen, and Chappellaz, Jérôme

Subjects
WATER seepage, SPECTROMETERS, CONTINENTAL slopes, OCEAN acidification, MARINE sediments
Abstract

Methane (CH4) in marine sediments has the potential to contribute to changes in the ocean- and climate system. Physical and biochemical processes that are difficult to quantify with current standard methods such as acoustic surveys and discrete sampling govern the distribution of dissolved CH4 in oceans and lakes. Detailed observations of aquatic CH4 concentrations are required for a better understanding of CH4 dynamics in the water column, how it can affect lake- and ocean acidification, the chemosynthetic ecosystem, and mixing ratios of atmospheric climate gases. Here we present pioneering high-resolution in-situ measurements of dissolved CH4 throughout the water column over a 400 m deep CH4 seepage area at the continental slope west of Svalbard. A new fast-response under-water membrane-inlet laser spectrometer sensor demonstrates technological advances and breakthroughs for ocean measurements. We reveal decametre-scale variations of dissolved CH4 concentrations over the CH4 seepage zone. Previous studies could not resolve such heterogeneity in the area, assumed smoother distribution and therefore lacked both details and insights to ongoing processes. We show good repeatability of the instrument measurements, which are also in agreement with discrete sampling. New numerical models, based on acoustically evidenced free gas emissions from the seafloor, support the observed heterogeneity and CH4 inventory. We identified sources of CH4, undetectable with echosounder, and rapid diffusion of dissolved CH4 away from the sources. Results from the continuous ocean laser-spectrometer measurements, supported by modelling, improve our understanding of CH4 fluxes and related physical processes over Arctic CH4 degassing regions. [ABSTRACT FROM AUTHOR]

Published
2019
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49. Simultaneous Detection of C2H6, CH4 and δ13C-CH4 Using Optical Feedback Cavity Enhanced Absorption Spectroscopy in the Mid-Infrared Region: Towards Application for Dissolved Gas Measurements.

Author

Grilli, Roberto, Chappellaz, Jérôme, Lechevallier, Loic, Kerstel, Erik, and Romanini, Daniele

Subjects
*ISOTOPES, *SPECTROMETERS, *HYDROCARBONS
Abstract

Simultaneous measurement of C2H6 and CH4 concentrations, and of the δ13C-CH4 isotope ratio is demonstrated using a cavity enhanced absorption spectroscopy technique in the mid-IR region. The spectrometer is compact and has been designed for field operation. It relies on optical-feedback assisted injection of 3.3-μm radiation from an Interband Cascade Laser (ICL) into a V-shaped high-finesse optical cavity. A minimum absorption coefficient of 2.8×10−9cm−1 is obtained in a single scan (0.1s) over 0.7cm−1. Precisions of 3ppbv, 11ppbv, and 0.08‰ for C2H6, CH4, and δ13C-CH4, respectively, are achieved after 400s of integration time. Laboratory calibrations and tests of performance are reported here. They show the potential for the spectrometer to be embedded in a sensor probe for in situ measurements in ocean waters, which could have important applications for the understanding of the source and fate of hydrocarbons from the seabed and in the water column. [ABSTRACT FROM AUTHOR]

Published
2018
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50. Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation

Author

Rhodes, Rachael H., Faïn, Xavier, Brook, Edward J., McConnell, Joseph R., Maselli, Olivia J., Sigl, Michael, Edwards, Jon, Buizert, Christo, Blunier, Thomas, Chappellaz, Jérôme, Freitag, Johannes, Rhodes, Rachael H., Faïn, Xavier, Brook, Edward J., McConnell, Joseph R., Maselli, Olivia J., Sigl, Michael, Edwards, Jon, Buizert, Christo, Blunier, Thomas, Chappellaz, Jérôme, and Freitag, Johannes

Abstract

Advances in trace gas analysis allow localised, non-atmospheric features to be resolved in ice cores, superimposed on the coherent atmospheric signal. These highfrequency signals could not have survived the low-pass filter effect that gas diffusion in the firn exerts on the atmospheric history and therefore do not result from changes in the atmospheric composition at the ice sheet surface. Using continuous methane (CH4) records obtained from five polar ice cores, we characterise these non-atmospheric signals and explore their origin. Isolated samples, enriched in CH4 in the Tunu13 (Greenland) record are linked to the presence of melt layers. Melting can enrich the methane concentration due to a solubility effect, but we find that an additional in situ process is required to generate the full magnitude of these anomalies. Furthermore, in all the ice cores studied there is evidence of reproducible, decimetre-scale CH4 variability. Through a series of tests, we demonstrate that this is an artifact of layered bubble trapping in a heterogeneousdensity firn column; we use the term “trapping signal” for this phenomenon. The peak-to-peak amplitude of the trapping signal is typically 5 ppb, but may exceed 40 ppb. Signal magnitude increases with atmospheric CH4 growth rate and seasonal density contrast, and decreases with accumulation rate. Significant annual periodicity is present in the CH4 variability of two Greenland ice cores, suggesting that layered gas trapping at these sites is controlled by regular, seasonal variations in the physical properties of the firn. Future analytical campaigns should anticipate high-frequency artifacts at high-melt ice core sites or during time periods with high atmospheric CH4 growth rate in order to avoid misinterpretation of such features as past changes in atmospheric composition.

Published
2016

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