On the Rates of Growth of Grains and Crystals in South Polar Firn
On the Rates of Growth of Grains and Crystals in South Polar Firn
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DOI：
10.3189/s0022143000031233
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发表时间：
1969
影响因子：
3.4
通讯作者：
A. Gow
中科院分区：
文献类型：
--
作者：
A. Gow
在南极49米深的薄切片中，研究了作为年龄函数的积雪晶体的大小。颗粒横截面的尺寸从0.1 m深度的0.24 mm 2增加到10 m深度的0.63 mm 2。与晶粒不同的是，晶体的尺寸在相同的时间间隔内从0.18毫米增加到0.43毫米，这意味着晶粒通常只由一个或两个晶体组成，而不是像人们经常争论的那样由几个晶体组成。平均晶体横截面随着积雪年龄的增加而线性增加，速率为0.0006 mm 2/年;在49 m处388年的积雪中，晶体尺寸为0.63 mm 2。对来自南极洲和格陵兰岛其他地区的晶体生长数据的分析也揭示了晶体的平均横截面弧长（D2）（单位：mm 2）与其年龄（t）之间的强烈线性关系，即。晶体生长速率K与温度的关系可以用K = K 0 exp（E/RT）的形式表示，这一事实证实了下述预言：在雪中晶体生长基本上类似于在金属和陶瓷烧结体中的晶粒生长。对现有数据的外推表明，在−60° C至−15°C的温度范围内，干雪中的晶体生长速率预计会有两个数量级的变化（0.0003至0.03 mm 2年−1）。利用晶体生长的年平均温度数据，以确定在雪中的积累率的方法进行了论证。
The size of firn crystals as a function of age has been investigated in thin sections to a depth of 49 m at the South Pole. Grain cross-sections increased in size from 0.24 mm2 at 0.1 m depth to 0.63 mm2 at 10 m. Crystals, as distinct from grains, increased in size from 0.18 to 0.43 mm2 over the same interval, implying that grains are generally composed of just one or two crystals rather than several as is frequently contended. The mean crystal cross-section increased linearly with the age of the firn at a rate of 0.0006 mm2 year−1; in 388 year old firn at 49 m the crystal size measured 0.63 mm2. Analysis of crystal-growth data from other locations in Antarctica and Greenland also revealed a strong linear relationship between the mean cross-sectional arcas (D 2) of crystals (in mm2) and their ages in years (t), i.e. . The fact that the temperature dependence of the crystal growth rate K can be expressed very satisfactorily in an equation of the form K = K 0 exp (E/RT) confirms predictions that crystal growth in firn is essentially analogous to grain growth in metallic and ceramic sinters. An extrapolation of available data indicates that crystal growth rates in dry firn could be expected to vary by two orders of magnitude (0.0003 to 0.03 mm2 year−1) over the temperature range −60° to −15°C. A method of utilizing crystal growth-mean annual temperature data to determine accumulation rates in snow is demonstrated.