电磁感应技术在波罗的海海冰厚度探测中的应用研究

APPLICATION OF ELECTROMAGNETIC-INDUCTION IN THE BALTIC SEA ICE THICKNESS MEASUREMENT

海冰作为冰雪圈的重要组成部分,对气候变化十分敏感,海冰物理过程研究需要得到精确的海冰厚度。本文介绍一种能够高效探测海冰厚度的电磁感应方法及其在波罗的海(Baltic Sea)的成功应用。该技术方法针对海冰和海水的电特性,利用电磁感应原理精确探测仪器至冰水交界面的距离,以实现海冰厚度的测定。通过电磁感应(EM)仪直接观测的视电导率与同点位钻孔测量数据对比分析,获得视电导率与海冰厚度的转换关系式,并对通过该关系式计算出的海冰厚度进行验证,表明电磁感应技术能够获得可靠的海冰厚度数据,平均相对误差仅为12%。对波西尼亚海湾(Bothnian Bay)海冰厚度探测剖面的统计结果表明,2007年春季该区域平整冰厚度范围在0.4—0.6m之间。

Sea ice, as a component of the cryosphere, is very sensitive to the climate change. Study of sea ice physics needs accurate sea ice thickness data. This paper presents an electromagnetic-induction （EM） technique which can be used to measure the sea ice thickness distribution efficiently, and its successful application in Baltic Sea. Based on the electromagnetic field theory and by applying the electrical properties of sea ice and seawater, this technique can detect the distance between the EM instrument and the ice/water interface accurately, so the sea ice thickness can be obtained. Contrastive analysis of the apparent conductivity data obtained by EM and the value of drill-hole at the same position allows a construction of the transformable formula of the apparent conductivity and sea ice thickness, and the verification of the sea ice thickness calculated by this formula indicates that electromagnetic-induction technique is able to measure sea ice thickness with good accuracy. The average relative error between EM measurements and drill holes data was 12%. The statistic of all ice thickness profiles shows the distribution of smooth surface ice in the Bay of Bothnian was 0.4-0.6 m. This result is in consistent with the EM-bird measurement.