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Macelloni Giovanni, Leduc-Leballeur Marion, Brogioni Marco, Ritz Catherine, Picard Ghislain, . (2016). Analyzing and modeling the SMOS spatial variations in the East Antarctic Plateau. REMOTE SENSING OF ENVIRONMENT, 180, 193–204.
Abstract: The SMOS brightness temperature (TB) collected on the East Antarctic Plateau revealed spatial signatures at L-band that have never before been observed when only higher-frequency passive microwave observations were available, and this has opened up a new field of research. Because of the much greater penetration depth, modeling the microwave ice sheet emission requires taking into account not only snow conditions on the surface, but should also include glaciological information. Even if the penetration depth of the L-band is not well known due to the uncertainty on the imaginary part of the ice permittivity, it is likely to be of the order of several hundreds of meters, which means that the temperature of the ice over a depth of nearly 1000 m influences the emission. Over such a depth, the temperature is related to both the surface conditions and to the ice sheet thickness, which in turn depends on the bedrock topography and on other glaciological variables. The present paper aims to provide a thorough theoretical explanation of the observed TB spatial variation close to the Brewster angle at vertical polarization, in order to limit the effect of surface and vertical density variability in the firn. In order to provide reliable inputs to the microwave emission models used for simulating TB data, an in-depth analysis of the temperature profiles was performed by means of glaciological models. The comparison between simulated and observed data over three transects totalling 2000 km in East Antarctica pointed out that, whereas the emission models are capable of explaining the TB spatial variations of several kelvins (0.7 and 2.9 K), they are unable to predict its absolute value correctly. This study also shows that the main limiting factor in simulating low-frequency microwave data is the uncertainty in the currently available imaginary part of the ice permittivity.
Keywords: Antarctica, Ice sheet temperature, Microwave emission model, SMOS,
Programme: 902,1110
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Caillon N., Severinghaus J.P., Jouzel J., Barnola J.M., Kang J. & Lipenkov V.Y. (2003). Timing of Atmospheric CO2 and Antarctic Temperature Changes across Termination III. Science, 299, 1728–1731.
Abstract: The analysis of air bubbles from ice cores has yielded a precise record of atmospheric greenhouse gas concentrations, but the timing of changes in these gases with respect to temperature is not accurately known because of uncertainty in the gas age-ice age difference. We have measured the isotopic composition of argon in air bubbles in the Vostok core during Termination III (~240,000 years before the present). This record most likely reflects the temperature and accumulation change, although the mechanism remains unclear. The sequence of events during Termination III suggests that the CO2 increase lagged Antarctic deglacial warming by 800 ± 200 years and preceded the Northern Hemisphere deglaciation.
Programme: 902
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Pourchet M., Magand M Frezzotti A A Ekaikin O. & Winther J.G. (2003). Radionuclides deposition over Antarctica. Journal of environmental radioactivity, 68, 137–158.
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Torinesi O., Fily M. & Genthon C. (2003). Variability and Trends of the Summer Melt Period of Antarctic Ice Margins since 1980 from Microwave Sensors. Journal of climate, 16, 1047–1060.
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Ekaikin A.A., Lipenkov V.Y., Barkov N.I., Petit J.R. & Masson Delmotte V. (2003). Spatial and temporal variability in isotope composition of recent snow in the vicinity of Vostok station, Antarctica : implications for ice-core record interpretation. Annals of glaciology, 35, 181–186.
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Genthon C., Krinner G. & Cosme E. (2002). Free and Laterally Nudged Antarctic Climate of an Atmospheric General Circulation Model. Monthly weather review, 130, 1601–1616.
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Morgan V.I., Delmotte M., van Ommen T.V., Jouzel J., Chappellaz J.,Woon S., Masson-Delmotte V. & Raynaud D. (2002). Relative Timing of Deglacial Climate Events in Antarctica and Greenland. Science, 297, 1862–1864.
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Basile I., Petit J.R., Touron S., Grousset F.E. & Barkov N.I. (2001). Volcanic layers in Antarctic (Vostok) ice-cores : source identification and atmospheric implications. J. Geophys. Res., 106(d23), 31915–31931.
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Braünlich M., Abbalin O., Marik T., Jöckel P., M Brenninkmeijer C.A., Chappellaz J., Barnola J.M., Mulvaney R. & Sturges W.T. (2001). Changes in the global atmospheric methane budget over the last decades inferred from 13C and D isotopic analysis of Antarctic firn air. J. Geophys. Res., 106(d17), 20465–20481.
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Caillon N., Severinghaus J.P., Barnola J.M., Chappellaz J., Jouzel J. & Parrenin F. (2001). Estimation of temperature change and of gas age – ice age difference, 108kyr BP, at Vostok, Antarctica. J. Geophys. Res., 106(d23), 31893–31902.
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