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. (2002). Highly deformed basal ice in the Vostok core, Antarctica. Geophysical research letters, 29.
Abstract: Our paper documents the build-up of a highly deformed basal ice layer in the basal part of the Vostok ice core. This is done mainly on the basis of an isotopic composition investigation of the ice. Complex deformation in the lower 228 m of the ice sheet has resulted in folding and intermixing of ice at a submetric scale and, for the upper part of this basal sequence, in interbedding of ice layers from distinct origins at a larger scale. This complex deformation occurred at a temperature largely below the pressure-melting point. The basal ice layer has built upwards and size-selective incorporation of bed material into the ice has taken place. The documentation of this complex basal deformation has implications for the maximum age of ice that will be useful in paleoclimate studies and for ice sheet dynamics.
Keywords: 1040 Geochemistry: Isotopic composition/chemistry; 1827 Hydrology: Glaciology; 4540 Oceanography: Physical: Ice mechanics and air/sea/ice exchange processes; 9310 Information Related to Geographic Region: Antarctica
Programme: 902
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. (2002). High-resolution Holocene N2O ice core record and its relationship with CH4 and CO2. Global biogeochemical cycles, 16.
Abstract: Nitrous oxide (N2O) concentration records exist for the last 1000 years and for time periods of rapid climatic changes like the transition from the last glacial to today's interglacial and for one of the fast climate variations during the last ice age. Little is known, however, about possible N2O variations during the more stable climate of the present interglacial (Holocene) spanning the last 11 thousand years. Here we fill this gap with a high-resolution N2O record measured along the European Project for Ice Coring in Antarctica (EPICA) Dome C Antarctic ice core. On the same ice we obtained high-resolution methane and carbon dioxide records. This provides the unique opportunity to compare variations of the three most important greenhouse gases (after water vapor) without any uncertainty in their relative timing. The CO2 and CH4 records are in good agreement with previous measurements on other ice cores. The N2O concentration started to decrease in the early Holocene and reached minimum values around 8 ka (<260 ppbv) before a slow increase to its preindustrial concentration of ?265 ppbv.
Programme: 960
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Legrand, M.; Sciare, J.; Jourdain, B.; Genthon, C. (2001). Subdaily variations of atmospheric dimethylsulfide, dimethylsulfoxide, methanesulfonate, and non-sea-salt sulfate aerosols in the atmospheric boundary layer at Dumont d'Urville (coastal Antarctica) during summer. J. Geophys. Res., 106.
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Reijmer, C.H.; Oerlemans, J. (2002). Temporal and spatial variability of the surface energy balance in Dronning Maud Land, East Antarctica. J. Geophys. Res., 107.
Abstract: We present data of nine Automatic Weather Stations (AWS), which are located in Dronning Maud Land (DML), East Antarctica, since the austral summer of 1997. Potential temperature and wind speed are maximum at the sites with the steepest surface slope, i.e., at the edge of the Antarctic plateau. Specific humidity and accumulation decrease with elevation and distance from the coast. The annual average energy gain at the surface from the downward sensible heat flux varies between ?3 W m?2 and ?25 W m?2, with the highest values at the sites with the largest surface inclination and wind speeds. The net radiative flux is negative and largely balances this sensible heat flux and ranges from ??2 W m?2 to ??28 W m?2; maximum values can be linked to maxima in surface slope and wind speed, and suggest a strong connection between the heat budget and the katabatic flow in DML. The average latent heat flux is generally small and negative (??1 W m?2) indicating a slight net mass loss through sublimation.
Keywords: 1827 Hydrology: Glaciology; 1863 Hydrology: Snow and ice; 3307 Meteorology and Atmospheric Dynamics: Boundary layer processes; 3349 Meteorology and Atmospheric Dynamics: Polar meteorology; 9310 Information Related to Geographic Region: Antarctica
Programme: 960
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. (2002). Effect of density on electrical conductivity of chemically laden polar ice. J. Geophys. Res., 107.
Abstract: Electrical conductivity measurements made using the dielectric profiling technique (DEP) are compared to chemical data from the top 350 m of the Dome C ice core in Antarctica. The chemical data are used to calculate the concentration of the major acidic impurities in the core: sulphuric acid and hydrochloric acid. The conductivity coefficients in solid ice for sulphuric acid (?H2SO4) and hydrochloric acid (?HCl) are found to be 4.9 and 4.5 S m?1M?1. These are consistent with previously found values for the acid conductivity coefficient at different sites and suggest that the same conductivity mechanisms are important in all polar ice. A method of rolling regression analysis is used to find the variation of the pure ice conductivity (?? pure) and the conductivity coefficient of sulphuric acid, ?H2SO4, with depth. Then ?? pure and ?H2SO4are assessed against changes in core density and hence volume fraction of ice, v, due to the inclusion of air bubbles in the firn. Looyenga's model for dielectric mixtures applied to conduction in firn broadly predicts the variation observed in ?? purebut does not fit well for ice above 110 m. A previous application of the theory of percolation in random lattices is used to model the conductivity coefficient in firn. The coefficient ?H2SO4 is linked to vby the power law: ?H2SO4(v) ? ?H2SO4(1) (v ? vc)t; where vc is a threshold volume fraction below which no conduction can take place and is related to the geometry of the conducting lattice being modeled. The value of the exponent tis also dependent on the structure of the lattice and is here found to be t = 2.5, which is slightly lower than the previously obtained value of t = 2.7 for a structure where each grain has between 14 and 16 nearest neighbors. This model is consistent with the concept of conduction, via liquid H2SO4, taking place at two grain boundaries for firn. The model does not, however, preclude conduction taking place via acid situated at three grain boundaries or in an interconnected vein network at densities above 640 kg m?3.
Keywords: 0634 Electromagnetics: Measurement and standards; 1863 Hydrology: Snow and ice; 1894 Hydrology: Instruments and techniques; 9310 Information Related to Geographic Region: Antarctica
Programme: 960
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Schwander, J.; Jouzel, J.; Hammer, C.U.; Petit, J.-R.; Udisti, R.; Wolff, E. (2001). A Tentative Chronology for the EPICA Dome Concordia Ice Core. Geophysical research letters, 28.
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Sciare, J.; Baboukas, E.; Kanakidou, M.; Krischke, U.; Belviso, S.; Bardouki, H.; Mihalopoulos, N. (2000). Spatial and temporal variability of atmospheric sulfur-containing gases and particles during the Albatross campaign. J. Geophys. Res., 105.
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. (1999). A 1500 year record of accumulation at Amundsenisen western Dronning Maud Land, Antarctica, derived from electrical and radioactive measurements on a 120 m ice core. J. Geophys. Res., 105.
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Bousquet, P.; Ciais, P.; Peylin, P.; Ramonet, M.; Monfray, P. (1999). Inverse modeling of annual atmospheric CO2 sources and sinks 1. Method and control inversion. J. Geophys. Res., 104(d21).
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Dommergue Aurelien, Larose Catherine, Fain Xavier, Clarisse Olivier, Foucher Delphine, Hintelmann Holger, Schneider Dominique, Ferrari Christophe P,. (2010). Environ. Sci. Technol., 44(3), 901–907.
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