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Grenoble, France

Gilbert A.,IHH | Gilbert A.,British Petroleum | Wagnon P.,LGGE | Wagnon P.,British Petroleum | And 4 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2010

In June 1999, a deep (138.7 m) ice core was extracted from the summit glacier of Illimani, Bolivia (6340 m above sea level, 16°39'S, 67°47'W), and an englacial temperature profile was measured in the borehole. Using on-site and regional meteorological data as well as ice core stratigraphy, past surface temperatures were reconstructed with a heat flow model. The englacial temperature measurements exhibit a profile that is far from a steady state, reflecting an increasing atmospheric temperature over several years and nonstationary climatic conditions. Englacial temperature interpretation, using air temperature data, borehole temperature inversion, and melting rate quantification based on ice core density, shows two warming phases from 1900 to 1960 (+0.5 ± 0.3 K starting approximately in 1920-1930) and from 1985 to 1999 (+0.6 ± 0.2 K), corresponding to a mean atmospheric temperature rise of 1.1 ± 0.2 K over the 20th century. According to various climate change scenarios, the future evolution of englacial temperatures was simulated to estimate when and under what conditions this high-elevation site on the Illimani summit glacier could become temperate in the future. Results show that this glacier might remain cold for more than 90 years in the case of a +2 K rise over the 21st century but could become temperate in the first 20 m depth between 2050 and 2060 if warming reaches +5 K. Copyright 2010 by the American Geophysical Union. Source


Abe L.,University of Nice Sophia Antipolis | Epchtein N.,University of Nice Sophia Antipolis | Ansorge W.,RAMS CON Management Consultants | Argentini S.,CNR Institute of atmospheric Sciences and Climate | And 21 more authors.
Proceedings of the International Astronomical Union | Year: 2012

The Polar Large Telescope (PLT) project is primarily aimed at undertaking large, wide band synoptic astronomical surveys in the infrared in order to provide critical data to the forthcoming generation of observational facilities such as ALMA, JWST, LSST and the E-ELT, and to complement the observations obtained with them. Sensitive thermal IR surveys beyond 2.3 μm cannot be carried out from any existing ground based observatory and the Antarctic Plateau is the only place on the ground where it can be envisaged, thanks to its unique atmospheric and environmental properties, such as the turbulence profile (image quality), the low opacity and the reduced thermal background emission of the sky. These unique conditions enable high angular resolution wide field surveys in the near thermal infrared (2.3-5 μm). This spectral range is particularly well suited to tackling key astrophysical questions such as: i) investigating the nature of the distant universe, the first generation of stars and the latest stages of stellar evolution, ii) understanding transient phenomena such as gamma ray-bursts and Type Ia supernovae, iii) increasing our knowledge of extra-solar planets. Further instruments may broaden the expected science outcomes of such a 2-4 m class telescope especially for the characterization of galaxies at very large distance to provide new clues in the mysteries of dark matter and energy. Efforts will be made to merge this project with other comparable projects within an international consortium. Copyright © 2013 International Astronomical Union. Source


Reffray G.,Mercator Ocean | Bourdalle-Badie R.,Mercator Ocean | Calone C.,LGGE
Geoscientific Model Development | Year: 2015

Through two numerical experiments, a 1-D vertical model called NEMO1D was used to investigate physical and numerical turbulent-mixing behaviour. The results show that all the turbulent closures tested (k+l from Blanke and Delecluse, 1993, and two equation models: generic length scale closures from Umlauf and Burchard, 2003) are able to correctly reproduce the classical test of Kato and Phillips (1969) under favourable numerical conditions while some solutions may diverge depending on the degradation of the spatial and time discretization. The performances of turbulence models were then compared with data measured over a 1-year period (mid-2010 to mid-2011) at the PAPA station, located in the North Pacific Ocean. The modelled temperature and salinity were in good agreement with the observations, with a maximum temperature error between-2 and 2 °C during the stratified period (June to October). However, the results also depend on the numerical conditions. The vertical RMSE varied, for different turbulent closures, from 0.1 to 0.3 °C during the stratified period and from 0.03 to 0.15 °C during the homogeneous period. This 1-D configuration at the PAPA station (called PAPA1D) is now available in NEMO as a reference configuration including the input files and atmospheric forcing set described in this paper. Thus, all the results described can be recovered by downloading and launching PAPA1D. The configuration is described on the NEMO site (http://www.nemo-ocean.eu/Using-NEMO/Configurations/C1D-PAPA). This package is a good starting point for further investigation of vertical processes. © 2015 Author(s). Source


Legchenko A.,IRD LTHE | Descloitres M.,IRD LTHE | Guyard H.,IRD LTHE | Vincent C.,LGGE | And 3 more authors.
Near Surface 2010 - 16th European Meeting of Environmental and Engineering Geophysics | Year: 2010

Under mountain conditions accumulation of water in high reservoirs may present a natural hazard for local population and infrastructures. One of the possible water sources could be glaciers with melting ice. Examples of water accumulation that caused catastrophe events are known in history. The main objective of our study was to investigate the possibility of accumulation of non-frozen water within the Tête Rousse glacier (Massif of Mont Blanc, altitude of 3200 m). The fieldwork was carried out in September, 2009. For detecting bulk water we applied the Magnetic Resonance Sounding method MRS selectively sensitive to groundwater. We performed nine soundings with 80×80 m2 square loop that covered the major part of the glacier. MRS measurements allowed us to detect bulk water with a high degree of reliability and to locate the principal water storage area. The total volume of the water was estimated with MRS between 60000 and 70000 m3. This result will be verified during the summer 2010 by using additional geophysical measurements and boreholes. Source


Rabier F.,Meteo - France | Bouchard A.,Meteo - France | Brun E.,Meteo - France | Doerenbecher A.,Meteo - France | And 33 more authors.
Bulletin of the American Meteorological Society | Year: 2010

The Concordiasi project was undertaken in Antarctica to reduce uncertainties in diverse and complementary fields in Antarctica science. Some of the objectives of the project involved investigations of precipitation to constrain the mass budget over Antarctica and stratospheric ozone depletion. The project was a joint French-United States initiative that started during the International Polar Year (IPY). The project was undertaken over Antarctica during September-November, 2008, December, 2009, and was expected to continue between September-December, 2010. It was undertaken as part of the IPY-The Observing System Research and Predictability Experiment. Participants in the project included scientists from France, the US, Italy, and Australia, along with international organizations such as the European Center for Medium-Range Weather Forecasts (ECMWF). Source

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