基于冰内孔隙率的冰中声速经验公式的研究

Porosity based ice sound velocity model and its empirical formula

冰介质中的声速特性受温度、盐度、密度等因素影响,是一个随时间和空间变化的不稳定值。研究了冰介质中温度、盐度、密度三个物理量在垂直方向上的变化特性,引入孔隙率作为冰中声速特性的表征因子,利用孔隙率与温度、盐度、密度已有的函数关系,通过大量天然冰的实验数据,得到淡水冰中声速关于温度、盐度和密度的经验公式。进行了河冰声速测量的外场试验,验证了淡水冰中声速的经验公式的有效性,并利用该声速经验公式研究了淡水冰垂直方向上的声速剖面。文中所做的相关研究可为以后研究利用冰介质中的声速特性提供借鉴,为以后利用声学方法,在极地或我国北方高纬度地区进行冰层厚度监测,了解寒地冰层的更替、演化以及气候变迁等工作奠定研究基础。

The sound velocity of ice is affected by temperature, salinity and density, so it is a unstable value that varies with time and space. The three main factors affecting ice sound velocity are analyzed in this paper, and a practicable sound velocity modeling method is proposed as follows: taking porosity as the best characterization factor of ice sound velocity, analyzing a large amount of experimental data on natural ice to establish the mathematic model of the ice sound velocity about porosity first, then using the existed function relationship of porosity with temperature, salinity and density to put forward the ice sound velocity model expressed by temperature, salinity and density. Based on the proposed method, a complete sound velocity model of freshwater ice is established and a corresponding empirical formula is obtained. The river ice sound velocity experiment is conducted to verify the effectiveness of the freshwater ice's sound velocity model. And based on this model, the vertical velocity profile of freshwater ice is studied in this paper. What we have done in this paper would provide a theoretical basis for using acoustic techniques to monitor the thickness of ice and understand the evolution of cold ice layers and the climate change in the polar region and the high latitudes in northern China.