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Author |
Rousseau, D.-D.; Duzer, D.; Etienne, J.-L.; Cambon, G.; Jolly, D.; Ferrier, J.; Schevin, P. |
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Title |
Pollen record of rapidly changing air trajectories to the North Pole |
Type |
Journal Article |
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Year |
2004 |
Publication |
Journal of geophysical research-atmospheres |
Abbreviated Journal |
J. Geophys. Res. |
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Volume |
109 |
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Keywords |
0305 Atmospheric Composition and Structure: Aerosols and particles; 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 1620 Global Change: Climate dynamics; 3322 Meteorology and Atmospheric Dynamics: Land/atmosphere interactions |
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Abstract |
Tracing modern atmospheric dynamics is important for constraining models used in past climate reconstruction. However, these models must be verified by modern observations. We present the rapid changeover of two different air trajectories to the North Pole determined by studying the long distance transport of pollen. Samples were collected on a manned floating capsule drifting southward on the sea ice from the North Pole in 2002. It was observed that an air mass at 3000 m altitude transported birch and pine pollen released in Western Europe during week 22 (May 27). Two weeks later, during week 24 (June 10), alder, birch and willow pollen from eastern Siberia reached the drifting station with an air mass at 1000 m altitude. These particular patterns support independent investigations of air trajectories in the Arctic, especially the transport of anthropogenic pollutants such as sulfate and nitrate. |
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349 |
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American Geophysical Union |
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0148-0227 |
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yes |
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Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
5621 |
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Author |
Legrand, M.; Preunkert, S.; Jourdain, B.; Aumont, B. |
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Title |
Year-round records of gas and particulate formic and acetic acids in the boundary layer at Dumont d'Urville, coastal Antarctica |
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Journal Article |
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Year |
2004 |
Publication |
Journal of geophysical research-atmospheres |
Abbreviated Journal |
J. Geophys. Res. |
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Volume |
109 |
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414 |
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American Geophysical Union |
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0148-0227 |
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yes |
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IPEV @ Thierry.Lemaire @ |
Serial |
5536 |
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Author |
Savarino, J.; Bekki, S.; Cole-Dai, J.; Thiemens, M.H. |
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Title |
Evidence from sulfate mass independent oxygen isotopic compositions of dramatic changes in atmospheric oxidation following massive volcanic eruptions |
Type |
Journal Article |
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Year |
2003 |
Publication |
Journal of geophysical research-atmospheres |
Abbreviated Journal |
J. Geophys. Res. |
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Volume |
108 |
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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. |
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457 |
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American Geophysical Union |
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0148-0227 |
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yes |
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Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
5589 |
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Author |
Park, Y.-H. |
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Title |
Determination of the surface geostrophic velocity field from satellite altimetry |
Type |
Journal Article |
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Year |
2004 |
Publication |
Journal of geophysical research-atmospheres |
Abbreviated Journal |
J. Geophys. Res. |
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Volume |
109 |
Issue |
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Pages |
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Keywords |
4512 Oceanography: Physical: Currents; 4528 Oceanography: Physical: Fronts and jets; 4556 Oceanography: Physical: Sea level variations |
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Abstract |
Presently available marine geoid models are not accurate enough to extract the mean surface circulation directly from satellite altimetry. A novel method for estimating the mean velocity field of major ocean current systems is derived from the free surface boundary condition. With a given quasi-geostrophic balance for the horizontal surface flow, a scaling analysis of this boundary condition indicates that although the vertical velocity w is mostly balanced by the local change of the free surface, ???/?t, useful information on the mean current ($\overline{u}$, $\overline{v}$) is contained in a small ageostrophic departure (???/?t ? w). Our method consists in the development of a simple algebraic equation with two unknowns ($\overline{u}$, $\overline{v}$) and an adjustable parameter $\widetilde{\alpha}$ associated with ???/?t, assuming that the latter is proportional to (???/?t ? w). Most interestingly, ???/?t and all other coefficients of the equation can be determined from altimetry. The altimeter data used is combined TOPEX/Poseidon-ERS gridded data, and the solution is obtained by least squares, minimizing the contribution from the time-variable part of the parameter $\widetilde{\alpha}$ and prescribing the zonal direction of the mean current. The method, which is found to be particularly useful for quasi-zonal high-energy current systems, has been validated against direct observations in the Gulf Stream and Southern Ocean. Comparisons with direct observations and Monte Carlo experiments suggest an overall solution error of about 10 cm s?1. Once calibrated against regional velocity statistics, this method will be able to determine from altimetry the mean or instantaneous surface velocity field down to the frontal scale, with a realism that has been inaccessible because of the geoid constraint. |
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335 |
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American Geophysical Union |
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ISSN |
0148-0227 |
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yes |
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Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
5582 |
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Author |
Debayle, E.; Sambridge, M. |
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Title |
Inversion of massive surface wave data sets: Model construction and resolution assessment |
Type |
Journal Article |
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Year |
2004 |
Publication |
Journal of geophysical research-atmospheres |
Abbreviated Journal |
J. Geophys. Res. |
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Volume |
109 |
Issue |
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Pages |
B02316 |
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Keywords |
7218 Seismology: Lithosphere and upper mantle; 7255 Seismology: Surface waves and free oscillations; 7260 Seismology: Theory and modeling; 8180 Tectonophysics: Tomography |
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Abstract |
A new scheme is proposed for the inversion of surface waves using a continuous formulation of the inverse problem and the least squares criterion. Like some earlier schemes a Gaussian a priori covariance function controls the horizontal degree of smoothing in the inverted model, which minimizes some artifacts observed with spherical harmonic parameterizations. Unlike earlier schemes the new approach incorporates some sophisticated geometrical algorithms which dramatically increase computational efficiency and render possible the inversion of several tens of thousands of seismograms in few hours on a typical workstation. The new algorithm is also highly suited to parallelization which makes practical the inversion of data sets with more than 50,000 ray paths. The constraint on structural and anisotropic parameters is assessed using a new geometric approach based on Voronoi diagrams, polygonal cells covering the Earth's surface. The size of the Voronoi cells is used to give an indication of the length scale of the structures that can be resolved, while their shape provides information on the variation of azimuthal resolution. The efficiency of the scheme is illustrated with realistic uneven ray path configurations. A preliminary global tomographic model has been built for SV wave heterogeneities and azimuthal variations through the inversion of 24,124 fundamental and higher-mode Rayleigh waveforms. Our results suggest that the use of relatively short paths (<10,000 km) in a global inversion should minimize multipathing, or focusing/defocusing effects and provide lateral resolution of a few hundred kilometers across the globe. |
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133;906 |
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Publisher |
American Geophysical Union |
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ISSN |
0148-0227 |
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yes |
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Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
5607 |
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Author |
Yagova, N.V.; Pilipenko, V.A.; Lanzerotti, L.J.; Engebretson, M.J.; Rodger, A.S.; Lepidi, S.; Papitashvili, V.O. |
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Title |
Two-dimensional structure of long-period pulsations at polar latitudes in Antarctica |
Type |
Journal Article |
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Year |
2004 |
Publication |
Journal of geophysical research-atmospheres |
Abbreviated Journal |
J. Geophys. Res. |
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Volume |
109 |
Issue |
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Pages |
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Keywords |
2776 Magnetospheric Physics: Polar cap phenomena; 2752 Magnetospheric Physics: MHD waves and instabilities; 2744 Magnetospheric Physics: Magnetotail; 2724 Magnetospheric Physics: Magnetopause, cusp, and boundary layers |
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Abstract |
Two-dimensional (2-D) statistical distributions of spectral power and coherence of polar geomagnetic variations with quasi-periods about 10 min are analyzed using data from magnetometer arrays in Antarctica. Examination of the 2-D patterns of spectral power and coherence shows the occurrence of significant variations in geomagnetic power levels but with low spatial coherence near the cusp projection and in the auroral region. At the same time, low-amplitude pulsations, which we coin Pi cap
3 pulsations, are very coherent throughout the polar cap. The region occupied by coherent Pi cap
3 pulsations is shifted toward local MLT night from the geomagnetic pole and is decoupled from the regions of auroral and cusp ULF activity. The spectral power varies with time at polar latitudes in a manner different from that at auroral latitudes. Diurnal variations of power at different stations at the same geomagnetic latitude exhibit different behavior depending on the station's position relative to geomagnetic and geographic poles. This asymmetry is shown to be partly attributed to the variations of the ionospheric conductance. The primary source of polar pulsations is probably related to intermittent magnetosheath turbulence and tail lobe oscillations, though a particular propagation mechanism has not as yet been identified. |
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Programme |
905 |
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Publisher |
American Geophysical Union |
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0148-0227 |
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yes |
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Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
5539 |
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Author |
Ferrari, C.P.; Dommergue, A.; Boutron, C.F.; Jitaru, P.; Adams, F.C. |
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Title |
Profiles of Mercury in the snow pack at Station Nord, Greenland shortly after polar sunrise |
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Journal Article |
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Year |
2004 |
Publication |
Geophysical research letters |
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Volume |
31 |
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399 |
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American Geophysical Union |
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0094-8276 |
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yes |
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Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
5622 |
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Author |
Genthon, C.; Cosme, E. |
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Title |
Intermittent signature of ENSO in west-Antarctic precipitation |
Type |
Journal Article |
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Year |
2003 |
Publication |
Geophysical research letters |
Abbreviated Journal |
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Volume |
30 |
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Keywords |
3349 Meteorology and Atmospheric Dynamics: Polar meteorology; 3354 Meteorology and Atmospheric Dynamics: Precipitation; 1620 Global Change: Climate dynamics; 1655 Global Change: Water cycles; 9310 Information Related to Geographic Region: Antarctica |
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Abstract |
Precipitation data from the new ERA40 reanalyses and from a 200-year simulation confirm a robust main mode of precipitation variability in west Antarctica. An intermittently strong ENSO signature is found in this mode. However, high correlation with ENSO indices appears infrequent. Thus, the high correlation found in ERA40, and previously in other chronologically realistic data, in the late 1980s and the 1990s may not be expected to last. Unlike previously suggested by others, the sign of the correlation between ENSO indices and west Antarctic precipitation, when significant, does not appear to change in time: Precipitation variability at the ENSO pace in the Bellingshausen-Weddell (Ross-Amunsden) region is consistently in phase (phase opposition, respectively) with the Southern Oscillation Index. This is consistent with a tropospheric wave train connecting the tropical Pacific and west Antarctic regions, which modulates in phase opposition the advection of air and moisture in the 2 regions. |
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411 |
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American Geophysical Union |
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0094-8276 |
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yes |
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IPEV @ Thierry.Lemaire @ |
Serial |
5605 |
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Author |
Savarino, J.; Romero, A.; Cole-Dai, J.; Bekki, S.; Thiemens, M.H. |
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Title |
UV induced mass-independent sulfur isotope fractionation in stratospheric volcanic sulfate |
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Journal Article |
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2003 |
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Geophysical research letters |
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30 |
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457 |
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American Geophysical Union |
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0094-8276 |
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yes |
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IPEV @ Thierry.Lemaire @ |
Serial |
5537 |
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Author |
Caillon, N.; Jouzel, J.; Severinghaus, J.P.; Chappellaz, J.; Blunier, T. |
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Title |
A novel method to study the phase relationship between Antarctic and Greenland climate |
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Journal Article |
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2003 |
Publication |
Geophysical research letters |
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Volume |
30 |
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Keywords |
3344 Meteorology and Atmospheric Dynamics: Paleoclimatology; 4267 Oceanography: General: Paleoceanography; 1827 Hydrology: Glaciology; 4870 Oceanography: Biological and Chemical: Stable isotopes; 1620 Global Change: Climate dynamics |
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902 |
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American Geophysical Union |
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0094-8276 |
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yes |
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Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
5649 |
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