V.N. Petrov's research while affiliated with Arctic and Antarctic Research Institute and other places

We have studied the distribution of 327 clay mineral particles retrieved from four Antaretic ice smaples corresponding to present and Last Glacial Maximum (LGM) climate conditions. Illite, chlorite, smectite and kaolinite were identified in all samples. Focusing on kaolinite, because of its use as a possible tracer of low latitude soils, we find a significantly smaller amount for LGM samples while the dust concentration in snow during the LGM was about 30 times higher than for present climate conditions. This can be interpreted as change in the contribution of the Australian source with climate. A second approach was based on the modeling of the desert dust cycle using an Atmospheric General Circulation Model (AGCM) under both present-day and ice age conditions. Unlike mineralogical results, the model suggests the prevalence of the Australian dust source in the deposits over East Antarctica under both present-day and LGM climate conditions. However the model fails to reproduce the strong increase in dust deposits during the LGM. This discrepancy could be partly due to the lack of a higher latitude dust source in the model. The stronger dust input recorded in ice cores for the LGM could be related to an additional active high latitude source (possibly close to South America) overlapping the atmospheric background coming from low latitude areas.

Depth profiles along the Vostok ice core of methanesulfonate and non-seasalt sulfate are presented which provide the first historical record of biogenic sulfur emissions from the Southern Hemisphere oceans over a complete glacial-interglacial cycle. Those measurements confirm and extend some previous observations made on a very limited data set from the Dome C ice core in Antarctica, which indicated increased oceanic emissions of dimethylsulfide during the later stages of the glacial period, compared with the present day. The observed glacial-interglacial variations in methanesulfonate and non-seasalt sulfate confirm that the ocean-atmosphere sulfur cycle is extremely sensitive to climate change.

The study of ice cores provides the opportunity of access to numerous parameters which are related to climate or environmental changes. Many of these variables are of regional or even global geographical significance. There are now several ice cores which penetrate into ice which has formed at the surface of polar ice sheets during the last ice age and the recently obtained Vostok (Antarctica) record provides detailed information over the last climatic cycle (160 ka).In comparison with current Holocene conditions, the Last Glacial Maximum (20 ka BP) is characterized by much colder conditions (up to 10°C) and reduced precipitation (× ). A large increase of continental and marine aerosols is explained by a more vigorous large scale atmospheric circulation associated with changing continental deserts and shelves as well as changes in sea ice extent. The drastic climatic change occurring at the last glacial termination is correlated with a large increase of atmospheric CO2 (from about 200 to 270 ppmv).The isotopic temperature record from the Vostok ice core depicts two drastic glacial-interglacial terminations (around 15 and 140 ka BP) and a long glacial period (110-15 ka BP) which includes two interstadials. Full glacial stages are characterized by larger aerosol loadings. The CO2 record of global significance is well correlated with the isotope temperature profile with high (270 ppmv) during interglacials and low (200 ppmv) during full glacial conditions.Spectral analysis of the Yostok temperature record supports the existence of a relationship between the Pleistocene climate and orbital forcing. On the other hand, the existence of a CO2-climate correlation suggests that CO2 changes have had an important climatic role in amplifying the relatively weak orbital forcing.

Mineralogical characterisation of insoluble microparticles entrapped in ice layers successively deposited on the Antarctic continent is a useful tool for paleoclimate reconstruction. Indeed, it is likely to provide information on the distribution of potential source areas and of climatic conditions prevailing over different time periods. A first study, covering the last 30 kyr and including the end of the last glacial age, has shown that, over central East Antarctica, continental input was soil derived and originated probably from South America. In this work, the time period covered is l60 kyrs which includes a complete climate cycle. Clay species and particle size considerations suggest that local sources and Australia have been of minor importance for the studied area over the last 160 kyr. They support the hypothesis of colder and drier conditions prevailing over the source areas during glacial extrema. Lastly the predominance of illite, feldspar and quartz in association with presumably weathered volcanic products is consistent with a continental input originating from South America for the East Antarctic area, but is not in complete agreement with the results of general circulation models.

A 2083 m deep ice core from Vostok Station (East Antarctica) has been used for a comprehensive study of all major ions (i.e. Na+, NH4+, K+, Ca2+, Mg2+, H+, Cl−, NO3− and SO42− originating from aerosols deposited over the last climatic cycle (160,000 a), as depicted from the isotopic composition of the ice.For the first time in deep ice core studies, a good balance between anions and cations is obtained throughout the profile. This allows the clear identification of marine salts (i.e. sea salt and Na2SO4), terrestrial salts (calcium and magnesium associated with nitrates and sulfates) and strong mineral acids (HNO3, H2SO4 and HCl).Concentration profiles confirm that both marine and terrestrial aerosol inputs were higher during cold climatic conditions (from 110 to 15 ka B.P.) than during the Last Interglacial (centered around 130 ka B.P.) and the Holocene (the last 10,000 a) stages. High concentration peaks (up to 5 and 30 times the Holocene values of marine and terrestrial contents, respectively) are in particular observed during the very cold climate characterizing the end of the penultimate glacial age (⋍ 160 ka B.P.) and the Last Glacial Maximum which terminated around 15 ka B.P. These peaks reflect strengthened sources and transport during full glacial conditions, linked to higher wind speeds, more extensive arid areas on the continents and the greater exposure of continental shelves. More generally, marine and terrestrial aerosol concentrations measured in ice are strongly affected by climatic conditions of global (source strength and atmospheric transport efficiency) and local (rate of snow accumulation) concern.As opposed to marine and terrestrial inputs, acidic gas-derived impurity concentrations (HNO3, H2SO4) remain relatively stable over the whole climatic cycle. In particular there is no correlation between observed H2SO4 fluctuations and the isotope-temperature profile. This would indicate the absence of a long-term relationship between volcanism and climate.The mineral acid contribution represents a large part (over 50%) of ice impurities deposited during interglacial periods. For glacial ice the contribution of marine and terrestrial salts becomes preponderant (up to 75% of total soluble impurities).During interglacial stages and the relatively warm periods of the Last Glacial Age, significant quantities of either Na2SO4 or HCl are found, possibly resulting from marine aerosol alteration during atmospheric transport from sea sources towards Antarctica. On the other hand, the Cl/Nam ratio values indicate the presence of non-fractionated marine aerosols during full glacial conditions, confirming faster transport from sea sources towards Antarctica.

Concentrations of lead (Pb) have been measured by the ultra-clean isotope dilution mass spectrometry technique in various sections of the Antarctic Dome C and Vostok deep ice cores, whose ages range from 3.85 to 155 ka B.P., in order to assess the natural, pre-human, sources of this toxic heavy metal in the global troposphere. Pb concentrations were very low, as low as about 0.3 pg Pb/g during the Holocene and probably during the last interglacial and part of the last ice age. On the other hand, they were quite high, up to about 40 pg Pb/g, during the Last Glacial Maximum and at the end of the penultimate ice age. Wind-blown dust from crustal rock and soil appears to be the main natural source of Pb in the global troposphere. Pb contribution from volcanoes is significant during periods of low Pb only. Contribution from the oceans is insignificant.

Concentrations of lead (Pb) have been measured by the ultra-clean isotope dilution mass spectrometry technique in various sections of the Antarctic Dome C and Vostok deep ice cores, whose ages range from 3.85 to 155 ka B.P., in order to assess the natural, pre-human, sources of this toxic heavy metal in the global troposphere. Pb concentrations were very low, as low as about 0.3 pg Pb/g during the Holocene and probably during the last interglacial and part of the last ice age. On the other hand, they were quite high, up to about 40 pg Pb/g, during the Last Glacial Maximum and at the end of the penultimate ice age. Wind-blown dust from crustal rock and soil appears to be the main natural source of Pb in the global troposphere. Pb contribution from volcanoes is significant during periods of low Pb only. Contribution from the oceans is insignificant.