scispace - formally typeset
Search or ask a question
Author

Kenji Kawamura

Bio: Kenji Kawamura is an academic researcher from National Institute of Polar Research. The author has contributed to research in topics: Ice core & Ice sheet. The author has an hindex of 39, co-authored 105 publications receiving 8498 citations. Previous affiliations of Kenji Kawamura include University of California, San Diego & Graduate University for Advanced Studies.
Topics: Ice core, Ice sheet, Firn, Glacial period, Geology


Papers
More filters
Journal ArticleDOI
15 May 2008-Nature
TL;DR: It is found that atmospheric carbon dioxide is strongly correlated with Antarctic temperature throughout eight glacial cycles but with significantly lower concentrations between 650,000 and 750,000 yr before present, which extends the pre-industrial range of carbon dioxide concentrations during the late Quaternary by about 10 p.p.m.v.
Abstract: Changes in past atmospheric carbon dioxide concentrations can be determined by measuring the composition of air trapped in ice cores from Antarctica. So far, the Antarctic Vostok and EPICA Dome C ice cores have provided a composite record of atmospheric carbon dioxide levels over the past 650,000 years. Here we present results of the lowest 200 m of the Dome C ice core, extending the record of atmospheric carbon dioxide concentration by two complete glacial cycles to 800,000 yr before present. From previously published data and the present work, we find that atmospheric carbon dioxide is strongly correlated with Antarctic temperature throughout eight glacial cycles but with significantly lower concentrations between 650,000 and 750,000 yr before present. Carbon dioxide levels are below 180 parts per million by volume (p.p.m.v.) for a period of 3,000 yr during Marine Isotope Stage 16, possibly reflecting more pronounced oceanic carbon storage. We report the lowest carbon dioxide concentration measured in an ice core, which extends the pre-industrial range of carbon dioxide concentrations during the late Quaternary by about 10 p.p.m.v. to 172-300 p.p.m.v.

1,977 citations

Journal ArticleDOI
TL;DR: In this article, the isotopic abundances of atmospheric Ar were determined using a dynamically operated isotope ratio mass spectrometer with minor modifications and special gas handling techniques to avoid fractionation.

908 citations

Journal ArticleDOI
Dorthe Dahl-Jensen, Mary R. Albert1, Ala Aldahan2, Nobuhiko Azuma3, David Balslev-Clausen4, Matthias Baumgartner, Ann-Marie Berggren2, Matthias Bigler, Tobias Binder5, Thomas Blunier, J. C. Bourgeois6, Edward J. Brook7, Susanne L Buchardt4, Christo Buizert, Emilie Capron, Jérôme A Chappellaz8, J. Chung9, Henrik Clausen4, Ivana Cvijanovic4, Siwan M. Davies10, Peter D. Ditlevsen4, Olivier Eicher11, Hubertus Fischer11, David A. Fisher6, L. G. Fleet12, Gideon Gfeller11, Vasileios Gkinis4, Sivaprasad Gogineni13, Kumiko Goto-Azuma14, Aslak Grinsted4, H. Gudlaugsdottir15, Myriam Guillevic4, S. B. Hansen4, Martin Hansson16, Motohiro Hirabayashi14, S. Hong, S. D. Hur9, Philippe Huybrechts17, Christine S. Hvidberg4, Yoshinori Iizuka16, Theo M. Jenk4, Sigfus J Johnsen4, Tyler R. Jones18, Jean Jouzel, Nanna B. Karlsson4, Kenji Kawamura14, Kaitlin M. Keegan1, E. Kettner4, Sepp Kipfstuhl19, Helle Astrid Kjær4, Michelle Koutnik20, Takayuki Kuramoto14, Peter Köhler19, Thomas Laepple19, Amaelle Landais, Peter L. Langen4, L. B. Larsen4, Daiana Leuenberger11, Markus Leuenberger, Carl Leuschen13, J. Li13, Vladimir Ya. Lipenkov21, Patricia Martinerie8, Olivia J. Maselli22, Valérie Masson-Delmotte, Joseph R. McConnell22, Heinrich Miller19, Olivia Mini11, A. Miyamoto23, M. Montagnat-Rentier24, Robert Mulvaney12, Raimund Muscheler, Anais Orsi25, John Paden13, Christian Panton4, Frank Pattyn26, Jean-Robert Petit8, K. Pol, Trevor Popp, G. Possnert, Frédéric Prié, M. Prokopiou, Aurélien Quiquet24, Sune Olander Rasmussen4, Dominique Raynaud8, J. Ren, C. Reutenauer4, Catherine Ritz8, Thomas Röckmann, Jean Rosen7, Mauro Rubino, Oleg Rybak19, Denis Samyn2, Célia Sapart27, Adrian Schilt28, A. Schmidt4, Jakob Schwander11, Simon Schüpbach, Inger K Seierstad, Jeffrey P. Severinghaus25, Simon G. Sheldon4, Sebastian B. Simonsen4, Jesper Sjolte, Anne M. Solgaard4, Todd Sowers, Peter Sperlich, Hans Christian Steen-Larsen29, Konrad Steffen30, J. P. Steffensen31, Daniel Steinhage19, Thomas F. Stocker, C. Stowasser18, A. S. Sturevik32, W. T. Sturges33, Arny E. Sveinbjörnsdottir29, A. Svensson30, Jean-Louis Tison31, J. Uetake34, Paul Vallelonga, R. S. W. van de Wal19, G. van der Wel11, Bruce H. Vaughn4, Bo Møllesøe Vinther2, E. Waddington35, Anna Wegner, Ilka Weikusat19, James W. C. White26, Frank Wilhelms19, Mai Winstrup4, Emmanuel Witrant, Eric W. Wolff11, C. Xiao, J. Zheng36 
24 Jan 2013-Nature
TL;DR: In this paper, the North Greenland Eemian Ice Drilling (NEEM) ice core was extracted from folded Greenland ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records.
Abstract: Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 +/- 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 +/- 250 metres, reaching surface elevations 122,000 years ago of 130 +/- 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.

546 citations

Journal ArticleDOI
25 Nov 2005-Science
TL;DR: A combined record of CH4 measured along the Dome C and the Vostok ice cores demonstrates, within the resolution of the authors' measurements, that preindustrial concentrations over Antarctica have not exceeded 773 ± 15 ppbv during the past 650,000 years.
Abstract: The European Project for Ice Coring in Antarctica Dome C ice core enables us to extend existing records of atmospheric methane (CH4) and nitrous oxide (N2O) back to 650,000 years before the present. A combined record of CH4 measured along the Dome C and the Vostok ice cores demonstrates, within the resolution of our measurements, that preindustrial concentrations over Antarctica have not exceeded 773 ± 15 ppbv (parts per billion by volume) during the past 650,000 years. Before 420,000 years ago, when interglacials were cooler, maximum CH4 concentrations were only about 600 ppbv, similar to lower Holocene values. In contrast, the N2O record shows maximum concentrations of 278 ± 7 ppbv, slightly higher than early Holocene values.

484 citations

Journal ArticleDOI
23 Aug 2007-Nature
TL;DR: The results indicate that orbital-scale Antarctic climate change lags Northern Hemisphere insolation by a few millennia, and that the increases in Antarctic temperature and atmospheric carbon dioxide concentration during the last four terminations occurred within the rising phase of Northern Hemisphere summer insolation.
Abstract: The Milankovitch theory of climate change proposes that glacial–interglacial cycles are driven by changes in summer insolation at high northern latitudes. The timing of climate change in the Southern Hemisphere at glacial–interglacial transitions (which are known as terminations) relative to variations in summer insolation in the Northern Hemisphere is an important test of this hypothesis. So far, it has only been possible to apply this test to the most recent termination because the dating uncertainty associated with older terminations is too large to allow phase relationships to be determined. Here we present a new chronology of Antarctic climate change over the past 360,000 years that is based on the ratio of oxygen to nitrogen molecules in air trapped in the Dome Fuji and Vostok ice cores. This ratio is a proxy for local summer insolation5, and thus allows the chronology to be constructed by orbital tuning without the need to assume a lag between a climate record and an orbital parameter. The accuracy of the chronology allows us to examine the phase relationships between climate records from the ice cores and changes in insolation. Our results indicate that orbital-scale Antarctic climate change lags Northern Hemisphere insolation by a few millennia, and that the increases in Antarctic temperature and atmospheric carbon dioxide concentration during the last four terminations occurred within the rising phase of Northern Hemisphere summer insolation. These results support the Milankovitch theory that Northern Hemisphere summer insolation triggered the last four deglaciations

466 citations


Cited by
More filters
Journal ArticleDOI
03 Sep 2009-Nature
TL;DR: Work in different scientific fields is now suggesting the existence of generic early-warning signals that may indicate for a wide class of systems if a critical threshold is approaching.
Abstract: Complex dynamical systems, ranging from ecosystems to financial markets and the climate, can have tipping points at which a sudden shift to a contrasting dynamical regime may occur. Although predicting such critical points before they are reached is extremely difficult, work in different scientific fields is now suggesting the existence of generic early-warning signals that may indicate for a wide class of systems if a critical threshold is approaching.

3,450 citations

Journal ArticleDOI
TL;DR: The potential for marine organisms to adapt to increasing CO2 and broader implications for ocean ecosystems are not well known; both are high priorities for future research as mentioned in this paper, and both are only imperfect analogs to current conditions.
Abstract: Rising atmospheric carbon dioxide (CO2), primarily from human fossil fuel combustion, reduces ocean pH and causes wholesale shifts in seawater carbonate chemistry. The process of ocean acidification is well documented in field data, and the rate will accelerate over this century unless future CO2 emissions are curbed dramatically. Acidification alters seawater chemical speciation and biogeochemical cycles of many elements and compounds. One well-known effect is the lowering of calcium carbonate saturation states, which impacts shell-forming marine organisms from plankton to benthic molluscs, echinoderms, and corals. Many calcifying species exhibit reduced calcification and growth rates in laboratory experiments under high-CO2 conditions. Ocean acidification also causes an increase in carbon fixation rates in some photosynthetic organisms (both calcifying and noncalcifying). The potential for marine organisms to adapt to increasing CO2 and broader implications for ocean ecosystems are not well known; both are high priorities for future research. Although ocean pH has varied in the geological past, paleo-events may be only imperfect analogs to current conditions.

2,995 citations

Journal ArticleDOI
TL;DR: The 2010 self-consistent set of values of the basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use is presented in this article.
Abstract: This paper gives the 2010 self-consistent set of values of the basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use. The 2010 adjustment takes into account the data considered in the 2006 adjustment as well as the data that became available from 1 January 2007, after the closing date of that adjustment, until 31 December 2010, the closing date of the new adjustment. Further, it describes in detail the adjustment of the values of the constants, including the selection of the final set of input data based on the results of least-squares analyses. The 2010 set replaces the previously recommended 2006 CODATA set and may also be found on the World Wide Web at physics.nist.gov/constants.

2,770 citations

Journal ArticleDOI
17 Jan 2008-Nature
TL;DR: With humans having an increasing impact on the planet, the interactions between the nitrogen cycle, the carbon cycle and climate are expected to become an increasingly important determinant of the Earth system.
Abstract: With humans having an increasing impact on the planet, the interactions between the nitrogen cycle, the carbon cycle and climate are expected to become an increasingly important determinant of the Earth system.

2,668 citations