Climate and atmospheric history of the past 420,000 years from the Vostok ice core,

Antarctica has allowed the extension of the ice record of atmospheric composition and climate to the past four glacial-interglacial cycles. The succession of changes through each climate cycle and termination was similar, and atmospheric and climate properties oscillated between stable bounds. Interglacial periods differed in temporal evolution and duration. Atmospheric concentrations of carbon dioxide and methane correlate well with Antarctic air-temperature throughout the record. Present-day atmospheric burdens of these two important greenhouse gases seem to have been unprecedented during the past 420,000 years. The late Quaternary period (the past one million years) is punctuated by a series of large glacial-interglacial changes with cycles that last about 100,000 years (ref. 1). Glacial-interglacial climate changes are documented by complementary climate records 1,2 largely derived from deep sea sediments, continental deposits of flora, fauna and loess, and ice cores. These studies have documented the wide range of climate variability on Earth. They have shown that much of the variability occurs with periodicities corresponding to that of the precession, obliquity and eccentricity of the Earth's orbit 1,3 . But understanding how the climate system responds to this initial orbital forcing is still an important issue in palaeoclimatology, in particular for the generally strong ϳ100,000-year (100-kyr) cycle. Ice cores give access to palaeoclimate series that includes local temperature and precipitation rate, moisture source conditions, wind strength and aerosol fluxes of marine, volcanic, terrestrial, cosmogenic and anthropogenic origin. They are also unique with their entrapped air inclusions in providing direct records of past changes in atmospheric trace-gas composition. The ice-drilling project undertaken in the framework of a long-term collaboration between Russia, the United States and France at the Russian Vostok station in East Antarctica (78Њ S, 106Њ E, elevation 3,488 m, mean temperature −55 ЊC) has already provided a wealth of such information for the past two glacial-interglacial cycles [4][5][6][7][8][9] Here we present a series of detailed Vostok records covering this ϳ400-kyr period. We show that the main features of the more recent Vostok climate cycle resemble those observed in earlier cycles. In particular, we confirm the strong correlation between atmospheric greenhouse-gas concentrations and Antarctic temperature, as well as the strong imprint of obliquity and precession in most of the climate time series. Our records reveal both similarities and differences between the successive interglacial periods. They suggest the lead of Antarctic air temperature, and of atmospheric greenhousegas concentrations, with respect to global ice volume and Greenland air-temperature changes during glacial terminations. The ice record The data are shown in Figs 1, 2 and 3 (see Supplementary Information for the numerical data). They include the deuterium content of the ice (dD ice , a proxy of local temperature change), the dust content (desert aerosols), the concentration of sodium (marine aerosol), and from the entrapped air the greenhouse gases CO 2 and CH 4 , and the d 18 O are defined in the legends to Figs 1 and 2, respectively.) All these measurements have been performed using methods previously described except for slight modifications (see The detailed record of dD ic

Beyond equilibrium climate sensitivity

ISSN:1752-0908ISSN:1752-089

Le dernier cycle climatique (150 000 ans) à partir d'une carotte de glace de l'Antarctique

Pour la première fois, un carottage de 2 083 m récemment réalisé par les Expéditions Antarctiques Soviétiques à la Station Vostok permet de décrire l'évolution de l'environnement atmosphérique au cours de l'ensemble du dernier cycle climatique. L'échelle de temps établie à partir d'un modèle d'écoulement de la glace indique que la série obtenue couvre environ 150 000 ans. Cette échelle est pratiquement linéaire en fonction de la profondeur. Le profil isotopique (Ô18O) considéré comme indicateur de la température montre que l'Holocène a été précédé par une période glaciaire très longue dans laquelle on observe deux interstades relativement plus chauds. Le dernier interglaciaire, étudié de façon détaillée, apparaît plus chaud d'environ 3 °C que le climat actuel. La fin du précédent glaciaire présente les mêmes caractéristiques que le dernier maximum glaciaire, avec un climat plus froid d'environ 10°C que l'actuel.Lorius C., Jouzel J., Ritz C., Merlivat L., Barkov N. I., Korotkevich Y. S., Kotlyakov V. M. Le dernier cycle climatique (150 000 ans) à partir d'une carotte de glace de l'Antarctique . In: Bulletin de l'Association française pour l'étude du quaternaire, vol. 23, n°1-2, 1986. p. 28

A 150,000-year climatic record from Antarctic ice

International audienceDuring much of the Quaternary, the Earth's climate has undergone drastic changes most notably successive glacial and interglacial episodes. The past 150 kyr includes such a climatic cycle: the last interglacial, the last glacial and the present holocene interglacial. A new climatic–time series for this period has been obtained using δ18 O data from an Antarctic ice core

Evidence for an early Holocene climatic optimum in the Antarctic deep ice-core record

International audienc

A comparison of the Vostok ice deuterium record and series from Southern Ocean core MD 88-770 over the last two glacial-interglacial cycles

International audienceTaking advantage of the fact that the Vostok deuterium (δD) record now covers almost two entire climatic cycles, we have applied the orbital tuning approach to derive an age-depth relation for the Vostok ice core, which is consistent with the SPECMAP marine time scale. A second age-depth relation for Vostok was obtained by correlating the ice isotope content with estimates of sea surface temperature from Southern Ocean core MD 88-770. Both methods lead to a close correspondence between Vostok and MD 88-770 time series. However, the coherence between the correlated δD and insolation is much lower than between the orbitally tuned 8D and insolation. This reflects the lower accuracy of the correlation method with respect to direct orbital tuning. We compared the ice and marine records, set in a common temporal framework, in the time and frequency domains. Our results indicate that changes in the Antarctic air temperature quite clearly lead variations in global ice volume in the obliquity and precession frequency bands. Moreover, the average phase we estimated between the filtered δD and insolation signals at precessional frequencies indicates that variations in the southern high latitude surface temperature could be induced by changes in insolation taking place during a large period of the summer in northern low latitudes or winter in southern low latitudes. The relatively large lag found between Vostok δD variations and obliquity-driven changes in insolation suggests that variations in the local radiative balance are not the only mechanism responsible for the variability in surface temperature at those frequencies. Finally, in contrast to the cross-spectral analysis method used in previous studies, the method we use here to estimate the phases can reveal errors in cross-correlations with orbitally tuned chronologies