2024-03-28T12:40:13Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/454492022-11-17T02:08:08Zhdl_2115_45402hdl_2115_8305hdl_2115_147Snow/Firn Densification in Polar Ice SheetsSalamatin, Andrey N.Lipenkov, Vladimir Ya.Barnola, Jean MarcHori, AkiraDuval, PaulHondoh, Takeoice sheetsnow/firn densificationphysical modelpaleoclimatic implication400A sophisticated physical model of the dry snow/firn densification process in ice sheets is proposed. Macroscopically, snow and firn undergo vertical uniaxial compression with non-zero deviatoric stresses and strain rates. The present mathematical description of densificntion includes dilatancy and "force-chain" effects in snow and develops previous concepts of ice-particle rearrangement by grain-boundary sliding and sintering by power-law creep under overburden pressure. Both densification mechanisms work together during the first snow stage until the closest packing of ice grains is reached at critical densities of 0.7-0.76 and the firn stage controlled only by the dislocation creep sets on. In addition to the ice-grain coordination number and the slope of the radial distribution function, a new structural parameter is introduced to account for grain bonding (agglomeration) effects. The model is constrained and validated on direct stereological observations of ice core structures and a representative set of snow/firn density-depth profiles covering a wide range of present-day climatic conditions (-57.5 to -10℃ and ice accumulation at 2.15 to 330 cm yr^[-1] ). Simple equations are derived for predicting the depth of pore closure in firn and the ice age at close-off. The paleoclimatic evolution of quasi-stationary density-depth profiles and close-off characteristics at Vostok Station (East Antarctica) are simulated and discussed.Physics of Ice Core Records II : Papers collected after the 2nd International Workshop on Physics of Ice Core Records, held in Sapporo, Japan, 2-6 February 2007. Edited by Takeo HondohInstitute of Low Temperature Science, Hokkaido UniversityDepartmental Bulletin Paperapplication/pdfhttp://hdl.handle.net/2115/45449https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/45449/1/LTS68suppl_016.pdf1880-7593低温科学68Supplement1952222009-12engpublisher