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	Author	Savarino, J.; Bekki, S.; Cole-Dai, J.; Thiemens, M.H.
	Title	Evidence from sulfate mass independent oxygen isotopic compositions of dramatic changes in atmospheric oxidation following massive volcanic eruptions			Type	Journal Article
	Year	2003	Publication	Journal of geophysical research-atmospheres	Abbreviated Journal	J. Geophys. Res.
	Volume	108	Issue		Pages
	Keywords	0340 Atmospheric Composition and Structure: Middle atmosphere—composition and chemistry; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0370 Atmospheric Composition and Structure: Volcanic effects; 1040 Geochemistry: Isotopic composition/chemistry; 1863 Hydrology: Snow and ice
	Abstract	Oxygen isotopic ratio measurements (?17O and ?18O) of background and volcanic sulfate preserved in South Pole snow and ice were used to investigate the impact on the oxidation state of the atmosphere by explosive volcanic eruptions. By comparing different paleovolcanic events, we observe a difference in the SO2 oxidation pathway between moderate (tens of teragrams (Tg) of SO2) and massive (hundreds of Tg) eruptions. Both isotopic data and numerical simulations suggest the shutdown of stratospheric OH chemistry and the opening of unaccounted oxidation channels for SO2, such as the reaction with O(3P) atoms when hundreds of Tg of SO2 are injected into the stratosphere. It is very likely that oxidation rates and pathways and concentrations of most traces gases are also dramatically affected, with potentially important implications for climate forcing.
	Programme	457
	Campaign
	Address
	Corporate Author				Thesis
	Publisher	American Geophysical Union	Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0148-0227	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	yes
	Call Number	IPEV @ Thierry.Lemaire @			Serial	5589
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	Author	Frezzotti, M.; Gandolfi, S.; Urbini, S.
	Title	Snow megadunes in Antarctica: Sedimentary structure and genesis			Type	Journal Article
	Year	2002	Publication	Journal of geophysical research-atmospheres	Abbreviated Journal	J. Geophys. Res.
	Volume	107	Issue		Pages
	Keywords	1827 Hydrology: Glaciology; 1863 Hydrology: Snow and ice; 1894 Hydrology: Instruments and techniques; 3322 Meteorology and Atmospheric Dynamics: Land/atmosphere interactions; 5470 Planetology: Solid Surface Planets: Surface materials and properties
	Abstract	Megadune fields occupy large areas in the interior of the East Antarctic ice sheet and are the result of unusual snow accumulation and redistribution processes. They therefore are important to surface mass balance and ice core interpretation. Field observations (GPS, GPR, and surface measurements) have provided a detailed description of megadune sedimentation and morphology over a 70 km2 area, located 200 km east of Dome C. A combination of remote sensing analysis (using Landsat and satellite radar altimetry) and field measurements indicate that slope in the prevailing wind direction (SPWD) and climatic conditions play a crucial role in megadune genesis. The megadune areas tend to be characterized by slightly steeper regional slope and the presence of highly persistent katabatic winds. The megadunes represent 2 to 4 m amplitude waves of 2 to 5 km wavelength formed by variable net accumulation, ranging between 25% (leeward faces) to 120% (windward faces) of the accumulation in adjacent nonmegadune areas. Leeward faces are characterized by glazed, sastrugi-free surfaces and extensive depth hoar formation. Windward faces are covered by large rough sastrugi up to 1.5 m in height.
	Programme	961
	Campaign
	Address
	Corporate Author				Thesis
	Publisher	American Geophysical Union	Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0148-0227	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	yes
	Call Number	IPEV @ Thierry.Lemaire @			Serial	5631
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	Author	Goujon, C.; Barnola, J.-M.; Ritz, C.
	Title	Modeling the densification of polar firn including heat diffusion: Application to close-off characteristics and gas isotopic fractionation for Antarctica and Greenland sites			Type	Journal Article
	Year	2003	Publication	Journal of geophysical research-atmospheres	Abbreviated Journal	J. Geophys. Res.
	Volume	108	Issue		Pages
	Keywords	1827 Hydrology: Glaciology; 1863 Hydrology: Snow and ice; 3344 Meteorology and Atmospheric Dynamics: Paleoclimatology
	Abstract	Modeling the densification of polar firn is essential to estimate variations of close-off characteristics (density, close-off depth, delta age) in relation with past climate parameters (temperature and accumulation rates). Furthermore, the air composition in the firn is modified by gravitational and thermal fractionation, and stable isotope measurements of permanent gases like nitrogen or argon can provide information on the amplitude of these fractionations. In this work, we propose a new model coupling firn densification and heat diffusion. In addition to the determination of the firn thickness and gas-ice age differences, the model allows a reconstruction of the time evolution of the temperature for different sites in Antarctica (Vostok) and Greenland (GISP2) and therefore the evolution of gravitational and thermal isotopic fractionations in firn. Under present-day conditions, the modeled profiles are in good agreement with the available temperature measurements in firn. For sites with low accumulation rates such as Vostok, the results show the existence of temperature gradients in the firn column even when no rapid climatic changes occur. The comparison of the modeled ?15N results to measurements allows to better constrain the ?18O-temperature relationship, used to infer the surface temperature history, and for GISP2, the model validates the long-term borehole-based temperature.
	Programme	902
	Campaign
	Address
	Corporate Author				Thesis
	Publisher	American Geophysical Union	Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0148-0227	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	yes
	Call Number	IPEV @ Thierry.Lemaire @			Serial	5616
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	Author	Bouruet-Aubertot, P.; Mercier, H.; Gaillard, F.; Lherminier, P.
	Title	Evidence of strong inertia-gravity wave activity during the POMME experiment			Type	Journal Article
	Year	2005	Publication	Journal of geophysical research-atmospheres	Abbreviated Journal	J. Geophys. Res.
	Volume	110	Issue		Pages
	Keywords	inertia-gravity waves, turbulent mixing; 4544 Oceanography: Physical: Internal and inertial waves; 4568 Oceanography: Physical: Turbulence, diffusion, and mixing processes; 4572 Oceanography: Physical: Upper ocean and mixed layer processes
	Abstract	The purpose of this paper is to characterize inertia-gravity waves (IGW) activity and to investigate the variability of these waves in relationship to atmospheric forcing and larger-scale motions. To this aim, we analyzed Eulerian measurements of horizontal currents and temperature collected over 1 year during the Programme Océan Multidisciplinaire Méso Echelle (POMME). We focused on the main frequency components of the IGW spectrum, namely the inertial frequency f and the semidiurnal frequency M2. Time evolution of the relative energy of these two components gave evidence of isolated events of high intensity. We performed a detailed analysis of these events and identified mechanisms of generation of these waves. Localized spots of intense, near-inertial IGW were observed in winter. During the mixed layer deepening, one event was correlated with plume-like structures resulting from peaks of intense surface cooling. This suggests a local generation process driven by strong downward vertical motions. Instead, other events of strong IGW could be related to submesoscale features, characteristic of a frontal region, in particular, wave trapping within anticyclonic eddies. In contrast, a downward energy propagation down to about 500 m below the mixed layer was isolated after a stormy period. Eventually, internal tidal beams, possibly generated at a nearby seamount, intermittently crossed the mooring, though less energetically than the previous events. Last, we estimated the eddy diffusivity from the velocity vertical shear. Large variations were obtained, from 10?6 m2/s up to 10?3 m2/s, consistent with the intense events previously isolated.
	Programme	417
	Campaign
	Address
	Corporate Author				Thesis
	Publisher	American Geophysical Union	Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0148-0227	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	yes
	Call Number	IPEV @ Thierry.Lemaire @			Serial	5590
Permanent link to this record



	Author	Savarino, J.; Romero, A.; Cole-Dai, J.; Bekki, S.; Thiemens, M.H.
	Title	UV induced mass-independent sulfur isotope fractionation in stratospheric volcanic sulfate			Type	Journal Article
	Year	2003	Publication	Geophysical research letters	Abbreviated Journal
	Volume	30	Issue		Pages
	Keywords	0340 Atmospheric Composition and Structure: Middle atmosphere—composition and chemistry; 0370 Atmospheric Composition and Structure: Volcanic effects; 1040 Geochemistry: Isotopic composition/chemistry; 1827 Hydrology: Glaciology
	Abstract	Sulfuric acid aerosols produced in the stratosphere following massive volcanic eruptions possess a mass-independent sulfur isotopic signature, acquired when volcanic SO2 experiences UV photooxidation. The volcanic data are consistent with laboratory SO2 photooxidation experiments using UV light at 248 nm (maximum absorption of ozone), whereas sulfur isotopic anomalies previously observed in Archean samples are consistent with photodissociation at 190–220 nm. A mechanism of SO2 photooxidation, occurring in the early stage of a stratospheric volcanic plume, in the range of 220–320 nm (weak band absorption of SO2), is also proposed. Since mass-independent sulfur isotope anomalies in stratospheric volcanic sulfate appear to depend on the exposure of SO2 to UV radiation, their measurements might therefore offer the possibility to determine the degree of UV penetration in the ozone-absorption window for the present and past atmospheres. They can also be used to determine the stratospheric or tropospheric nature of volcanic eruptions preserved in glaciological records, offering the possibility to reassess the climatic impact of past volcanic eruptions.
	Programme	457
	Campaign
	Address
	Corporate Author				Thesis
	Publisher	American Geophysical Union	Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0094-8276	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	yes
	Call Number	IPEV @ Thierry.Lemaire @			Serial	5537
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	Author	Legagneux, L.; Domine, F.
	Title	A mean field model of the decrease of the specific surface area of dry snow during isothermal metamorphism			Type	Journal Article
	Year	2005	Publication	Journal of geophysical research-atmospheres	Abbreviated Journal	J. Geophys. Res.
	Volume	110	Issue		Pages
	Keywords	model; isothermal snow metamorphism; Ostwald ripening; 0736 Cryosphere: Snow; 3947 Mineral Physics: Surfaces and interfaces; 1847 Hydrology: Modeling; 5112 Physical Properties of Rocks: Microstructure
	Abstract	The surface area of snow that is accessible to gases is an essential parameter for quantifying the exchange of trace gases between the snowpack and the atmosphere and is called the specific surface area (SSA). Snow SSA decreases during metamorphism, but this is not described in current snow models owing to the complexity of the physics and geometry of snow. In this paper, we test whether it is possible to model snow SSA changes during isothermal metamorphism without accounting for all the complexity of the three-dimensional (3-D) structure of real snow. We have developed a mean field model of snow metamorphism under isothermal conditions, grounded in the theoretical framework of transient Ostwald ripening and representing snow as a distribution of spherical particles. Analytical expressions of the growth rates of these spheres are obtained, and the evolution of two measurable parameters that characterize snow geometry, the SSA and the distribution of radii of curvature (DRC), are simulated and compared to experimental data obtained by X-ray tomography. The qualitative effects of temperature, snow density, and the condensation coefficient on the rate of SSA decrease are examined. The model predicts very well the rate of evolution of the particle size distribution, which validates our physical description of isothermal metamorphism. In particular, we find that vapor phase diffusion is rate limiting. However, the calculation of the SSA from the DRC appears delicate and evidences too crude approximations in our description of the 3-D geometry of snow. Finally, it is stressed that the initial DRC can greatly influence the rate of SSA decrease, while experimental measurements of the rate of SSA decrease suggest that all snow types evolve in a similar way. It is thus proposed that most natural fresh snows have similar DRCs.
	Programme	437
	Campaign
	Address
	Corporate Author				Thesis
	Publisher	American Geophysical Union	Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0148-0227	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	yes
	Call Number	IPEV @ Thierry.Lemaire @			Serial	5650
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	Author	Monnin, E.; Indermuhle, A.; Dallenbach, A.; Fluckiger, J.; Stauffer, B.; Stocker, T.F.; Raynaud, D.; Barnola, J.-M.
	Title	Atmospheric CO2 Concentrations over the Last Glacial Termination			Type	Journal Article
	Year	2001	Publication	Science	Abbreviated Journal	Science
	Volume	291	Issue	5501	Pages	112-114
	Keywords
	Abstract	A record of atmospheric carbon dioxide (CO2) concentration during the transition from the Last Glacial Maximum to the Holocene, obtained from the Dome Concordia, Antarctica, ice core, reveals that an increase of 76 parts per million by volume occurred over a period of 6000 years in four clearly distinguishable intervals. The close correlation between CO2 concentration and Antarctic temperature indicates that the Southern Ocean played an important role in causing the CO2 increase. However, the similarity of changes in CO2 concentration and variations of atmospheric methane concentration suggests that processes in the tropics and in the Northern Hemisphere, where the main sources for methane are located, also had substantial effects on atmospheric CO2 concentrations
	Programme	960
	Campaign
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0036-8075	ISBN		Medium
	Area		Expedition		Conference
	Notes	10.1126/science.291.5501.112			Approved	yes
	Call Number	IPEV @ Thierry.Lemaire @			Serial	5574
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	Author	Simpson, W.R.; Alvarez-Aviles, L.; Douglas, T.A.; Sturm, M.; Domine, F.
	Title	Halogens in the coastal snow pack near Barrow, Alaska: Evidence for active bromine air-snow chemistry during springtime			Type	Journal Article
	Year	2005	Publication	Geophysical research letters	Abbreviated Journal
	Volume	32	Issue		Pages
	Keywords	0312 Atmospheric Composition and Structure: Air/sea constituent fluxes; 0330 Atmospheric Composition and Structure: Geochemical cycles; 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere: constituent transport and chemistry; 1863 Hydrology: Snow and ice
	Abstract	We measured halide concentrations of snow and frost flowers in the vicinity of Barrow, Alaska. We find that the ratio of bromide to sodium in frost flowers is slightly enhanced (?10%) as compared to sea water. In contrast, the ratio of bromide to sodium in some snow samples is more than an order of magnitude enhanced, and in other samples is more than an order of magnitude depleted. We interpret the bromide depleted snow as having been processed by heterogeneous chemistry and providing reactive halogen compounds to the atmosphere. The eventual end product of reactive bromine chemistry is HBr that is then deposited over a wide region, enhancing bromide in inland snow samples. Although frost flowers or open leads are likely to be the original source of halides that become reactive halogen gases, we find that the bromide release often occurs subsequent to production of aerosol from marine sources.
	Programme	437
	Campaign
	Address
	Corporate Author				Thesis
	Publisher	American Geophysical Union	Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0094-8276	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	yes
	Call Number	IPEV @ Thierry.Lemaire @			Serial	5598
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	Author	Marchaudon, A.; Cerisier, J.-C.; Greenwald, R.A.; Sofko, G.J.
	Title	Electrodynamics of a flux transfer event: Experimental test of the Southwood model			Type	Journal Article
	Year	2004	Publication	Geophysical research letters	Abbreviated Journal
	Volume	31	Issue		Pages
	Keywords	2409 Ionosphere: Current systems; 2431 Ionosphere: Ionosphere/magnetosphere interactions; 2463 Ionosphere: Plasma convection; 2784 Magnetospheric Physics: Solar wind/magnetosphere interactions
	Abstract	On 12 September 1999, a conjunction between two SuperDARN radars and the Ørsted satellite gave, for the first time, simultaneous access to the ionospheric convection enhancement and the field-aligned currents (FACs) associated with a Flux Transfer Event. The radars observed an azimuthally elongated convection flow burst and the Ørsted satellite observed a series of successive small-scale parallel currents alternating between downward and upward. The most poleward pair of currents, whose directions were in agreement with the Southwood model, was observed when Ørsted crossed the front edge of the flow burst. A quantitative comparison of the current density of each FAC and of the Pedersen current density indicates that the closure current for this FACs pair occurred inside the flow burst, confirming the validity of the Southwood model. The Poynting flux carried by the parallel currents was less than 1% of the power carried by the solar wind plasma.
	Programme	312;911
	Campaign
	Address
	Corporate Author				Thesis
	Publisher	American Geophysical Union	Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0094-8276	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	yes
	Call Number	IPEV @ Thierry.Lemaire @			Serial	5587
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	Author	Thébault, E.; Mandea, M.; Schott, J.J.
	Title	Modeling the lithospheric magnetic field over France by means of revised spherical cap harmonic analysis (R-SCHA)			Type	Journal Article
	Year	2006	Publication	Journal of geophysical research-atmospheres	Abbreviated Journal	J. Geophys. Res.
	Volume	111	Issue		Pages
	Keywords	regional modeling; France; magnetic field; 1517 Geomagnetism and Paleomagnetism: Magnetic anomalies: modeling and interpretation; 1545 Geomagnetism and Paleomagnetism: Spatial variations: all harmonics and anomalies; 0545 Computational Geophysics: Modeling
	Abstract	We have recently proposed the revised spherical cap harmonic analysis (R-SCHA) modeling technique. The new mathematical functions represent faithfully the spatial variations of potential fields in a restricted area. In this paper, we tackle the inverse problem and outline the efficiency of the new basis functions with respect to real magnetic data. Processing simultaneously repeat stations, observatory, aeromagnetic, and CHAMP satellite data provides our first vector lithospheric field model over France, which extends from surface to 500 km of altitude. The magnetic field is represented with a minimum horizontal spatial representation of 40 km at the mean Earth radius. The magnetic lithospheric map consistency is confirmed with a comparison to known geological features. The model variation with altitude also suggests that the major French magnetic anomaly, the Paris basin anomaly, is produced by a deep-rooted geological structure. These results demonstrate the superiority of regional modeling over global modeling for delineating small-scale details in the lithospheric field. In view of forthcoming satellite missions, like Swarm, the revised spherical cap harmonic analysis method will help to accurately represent the lithospheric field for more detailed geological interpretations.
	Programme	905;139
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	Address
	Corporate Author				Thesis
	Publisher	American Geophysical Union	Place of Publication		Editor
	Language		Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0148-0227	ISBN		Medium
	Area		Expedition		Conference
	Notes				Approved	yes
	Call Number	IPEV @ Thierry.Lemaire @			Serial	5617
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