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    Snow grain-size measurements in Antarctica (2002)
    Cambridge University Press
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    Publication Date: 2002-01-01
    Description: Grain-size is an important but not well-known characteristic of snow at the surface of Antarctica. In the past, grain-size has been reported using various methods, the reliability, reproducibility and intercomparability of which is not warranted. In this paper, we present and recommend, depending on available logistical support, three techniques of snow-grain sampling and/or imaging in the field as well as an original digital image-processing method, which we have proved provides reproducible and intercomparable measures of a snow grain-size parameter, the mean convex radius. Results from more than 500 samples and 3000 images of snow grains are presented, which yield a still spatially limited yet unprecedentedly wide picture of near-surface snow grain-size distribution from fieldwork in Antarctica. In particular, except at sites affected by a very particular meteorology, surface grains in the interior of the ice sheet are uniformly small (0.1–0.2 mm). The climate-related increase of grain-size with depth through metamorphism is, as expected, not spatially uniform. Our Antarctic snow grain-size database will continue to grow as field investigations bring new samples, images and measures of snow grain.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 2
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    Numerical simulations of Greenland snowpack and comparison with passive microwave spectral signatures (2001)
    Cambridge University Press
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    Publication Date: 2001-01-01
    Description: In this paper, we show that a detailed snow model (here, the Crocus model) may help to validate large-scale inferred meteorological datasets (e.g. from climate models or analyses) over the data-sparse ice sheets. Two series of snow simulations are carried out with two different meteorological datasets in input to the snow model. Both datasets are extracted from the European Center for Medium-range Weather Forecasts meteorological analyses and forecast archives. First, the microwave signatures of the surface of central Greenland from the Scanning Multichannel Microwave Radiometer (SMMR) are compared with the simulated density, grain-size and stratigraphy. The annual mean gradient ratio and polarization ratio, which are related to the emissivity of snow, are found to correlate spatially with these snow structural parameters. The sensitivity of the snow structure to differences in the two meteorological sets is then examined. It is found to be high for temperature and infrared radiation, precipitation and surface wind. The quantitative value of this result is limited by a still limited snow model validation over Greenland. Also, an optimal use of satellite data and a snow model for meteorological validation would require physically based translation of the simulated snow parameters into radiative properties, i. e radiation transfer modeling.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 3
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    Space–time Antarctic surface mass-balance variability from climate models (2004)
    Cambridge University Press
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    Publication Date: 2004-01-01
    Description: The interannual to interdecadal variability and space–time statistics (including radius of decorrelation) of the Antarctic surface mass balance (SMB) are evaluated from climate models and meteorological analyses. At model resolution scales (〉100 km), the interannual relative standard deviation of precipitation ranges from ∼5% (remotest interior) to ∼40% and possibly more. Time variability is spatially coherent at distances of ∼500km on average, less than 300 km in the interior near ridges, but in excess of 700 km in some regions. As far as spatial distributions are concerned, interannual statistics can be broadly transposed to interdecadal time-scales. The amplitude of variability may also be extrapolated across time-scales, using a ‘white’ spectrum hypothesis according to one coupled ocean– atmosphere model, but a significantly ‘red’ spectrum hypothesis according to another. Surface sublimation and blowing-snow processes are estimated to have limited contributions to the statistics of the SMB at model-resolved scales. Precipitation statistics can thus largely be transposed to SMB. The information reported here is expected to be useful for defining the details of field programmes such as the International Trans-Antarctic Scientific Expedition (ITASE), for extrapolating the spatial significance of field SMB data and for better interpreting Antarctic ice-sheet surface elevation changes from satellite altimetry.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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