My main scientific interests are polar ice geochemistry, paleoclimatology, geophysics, and glacio-biology. I am involved in the study of several deep Antarctic ice cores (Vostok, Epica Dome C, Droning Maud) through international collaboration (Europe, Federation of Russia) aiming to depict climate and environmental changes over the late Quaternary.

Currently, I am also involved in the search for life in ice and in subglacial lakes (the subglacial Lake Vostok), collaborating with molecular biologists from Russia and France (Universities of Brest and Lyon).

  Would you please sum up your 1999 Nature paper, "Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica"?

This paper presented the first long climatic record from the ice (420,000 years), providing a continuous record of the temperature and atmospheric composition (CO2 and CH4) along with the dust and sea salt aerosols and isotope composition of atmospheric oxygen.

The ice core was 3,350 m long and drilled at the top of the Antarctic ice sheet at the (Soviet, now Russian) station of Vostok (3,488 m above sea level, mean annual temperature -55C). The paper extended the previous Vostok record (150 kyrs) which was already a first, with three articles in Nature (1987) dealing with the same subject.

Extension of the ice core in depth (below 2.2 km—the ice thickness is 3.7 km at Vostok) was very slow and took almost 10 years because of the technical difficulties (the drill was lost) and the collapse of the Soviet Union led the Vostok station to close several times for winter. The international collaboration (France and the USA) was very useful and helped to resume the drilling, and the Russian drillers were able to continue in depth (3,350 m reached in 1998).

The article was co-signed by 18 authors from the three collaborative nations (Russia, USA, and France), and I got the honor to be the first author. The scientific merit of this work should be shared with my co-authors.

The new record depicted the last four climatic cycles and the succession of glacial-interglacial periods. Glacial periods represent more than 80% of the time of a climatic cycle (of about 100 kyrs). Interglacial periods display different patterns and they lasted variable (short) periods from 25,000 to 70,000 years. The transitions from interglacials to glacial climates appear slow while the reverse, the deglaciation (or termination) is rapid (5-10 kyrs). The present interglacial period (the Holocene), which started 11 kyrs ago, appears rather stable with respect to previous warm periods.

During glacial periods, the Antarctic temperature was about 10C lower, and the atmosphere contained more aerosols because of a drier and windy environment. More importantly, the air composition was different and contained lower concentrations of greenhouse gases (CO2 and CH4).

A salient correlation between greenhouse gases and temperature suggested from the 150-kyrs record was fully confirmed for the four climatic cycles with an almost perfect covariance between temperature and CO2.

All climatic records cited above contain periodicity at orbital frequencies (typically, 100, 40 and 20 kyrs), conforming with the marine records, as well as the astronomical theory of climate (Milankovich theory).

The data extracted from this ice core had implications throughout the fields of glaciology and paleoclimatology. The CO2 is mostly stored in the ocean, and the atmospheric content reflects an equilibrium. This has changed, and so has the carbon cycle. This implies that the ocean dynamic, ocean chemistry, biological activity (uptake), and terrestrial biology are involved.

Secondly, the greenhouse gases, by capturing the infrared waves emitted by earth, prevent cooling and will play the role of amplifier in the climate system. The effect of CO2 on Earth’s temperature was suggested first by Svante Arrhenuis.

Here, the Vostok data suggests a small variation (excess) of insulation (resulting from the long-term earth-sun position changes, the shortening/lengthening of the seasons) will likely warm the earth and the ocean which will release additional CO2 that in turn contributes again to an additional warming. CO2 is an important actor in the climate system.

With industrial development and anthropologic activity, massive burning of fossil carbon as well as intensification of agriculture released exponential amounts of CO2 and CH4 over the last 150 years. Present atmospheric composition well surpasses all maximum concentrations from the ice records over the last 420 kyrs (30% more CO2, 300% more CH4).

This makes a permanent atmospheric cover over the globe which prevents the natural cooling of the earth’s surface and making it so the heat is always "on." A new climate equilibrium is expected but we have no analog from the past climate (except maybe at the time of the dinosaurs!). This raises questions for the future climate and the consequences.

Due to the glacier dynamics, the deeper part of the Vostok ice record (below 3350m) is disturbed and more difficult to interpret.

Following Vostok, the scientific community conducted several deep-drilling projects in Greenland (GRIP, GISP2, NGRIP) as well as in Antarctica (European project of EPICA) with two deep-ice cores (Dome C and Droning Maud land). The Japanese also conducted a similar project at Dome F.

The EPICA Dome C provided the first results in 2004, with a 740 kyr climatic record (maybe up to 800 kyrs). The greenhouse gas record is available back to 650 kyrs and fully confirms the Vostok conclusions with the covariation between CO2 and temperature.

The Vostok record is now shown in schools and used by the Intergovernmental Panel on Climate Change to evaluate the complex consequences of future global warming.

I am involved in studies of new deep ice cores in Antarctica with the similar aims, as well as in the search for life in the ice. The deep drilling from Vostok, which was taken down to 3,650 m, penetrated through an ice massif which was formed from the refreezing of water from a giant underlying subglacial lake. This was a very nice surprise from Vostok. The accretion ice samples, which are now available, have opened an unexpected window to this unknown environment.