Snow/Firn Densification in Polar Ice Sheets

Snow/Firn Densification in Polar Ice Sheets
复制标题

极地冰盖中的雪/冷杉致密化

DOI：
--
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
T. Hondoh
T. Hondoh
中科院分区：
--
文献类型：
--
作者：
A. Salamatin;V. Lipenkov;J. Barnola;A. Hori;P. Duval;T. Hondoh

文献摘要

被引文献

相似文献

提出了一个复杂的物理模型的干雪/积雪致密化过程中冰盖。在宏观上，雪和雪经历非零偏应力和应变率的垂直单轴压缩。目前的致密化的数学描述包括雪中的粘性和“力链”效应，并发展了以前的概念，即在上覆压力下由晶界滑动和幂律蠕变烧结引起的冰粒重排。这两种致密化机制一起工作，在第一个雪阶段，直到最紧密的包装的冰粒达到临界密度为0.7-0.76和积雪阶段仅由位错蠕变控制seton. In除了冰粒配位数和径向分布函数的斜率，一个新的结构参数被引入到考虑颗粒粘结（团聚）的影响。该模型受到冰芯结构的直接体视学观测和一组代表性的雪/积雪密度深度剖面的约束和验证，这些剖面涵盖了当今广泛的气候条件（−57.5至−10 °C和每年2.15至330厘米的冰积累）。推导出了预测积雪孔隙闭合深度和闭合时的冰期的简单方程。模拟和讨论了东南极东方站准定常密度-深度剖面的古气候演变和封闭特征。
A 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 densification includes dilatancy and "force-chain" effects in snow and develops previous concepts of ice-particle rearrangement by grainboundary 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 densitydepth profiles covering a wide range of present-day climatic conditions (−57.5 to −10 °C and ice accumulation at 2.15 to 330 cm yr). 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.