Assessment of Electromagnetic Absorption of Ice From Ice Core Measurements

Ice core drillings have been performed in various zones in Antarctica and Greenland to obtain climatological information, study ice properties, or analyze air and dust encapsulated in the ice during the quaternary period. During these procedures, a set of measurements to characterize the ice and to evaluate its physical and chemical properties are usually performed in situ. In particular, using known temperature and dielectric profiles (DEP measurements), it is possible to evaluate the ice electromagnetic power absorption profile, valid at the drilling site. In the last decades, bedrock characterization through radio echo sounding surveys has been improved by the analysis of the power of radar echoes. This way, analysis of the electromagnetic properties of bedrock interfaces makes it possible to assess the physical characteristics and to distinguish between wet and dry conditions. Power variation of the received echoes also depends on ice absorption and on bedrock reflectivity due to specific physical conditions of the ice. In this paper, the propagation of electromagnetic waves through the ice sheet is examined, and in particular, a new method for establishing the electromagnetic absorption profile for ice from core drilling measurements is proposed and discussed. Variation in the ice absorption is deduced, starting from the analysis of ice core data from the European Project for Ice Coring in Antarctica (EPICA) at the Concordia station (Antarctica) and from the Greenland Ice Core Project (GRIP) site (Greenland). This direct method of measurement is proposed with the aim of defining common characteristics of the ice absorption rate that are valid both in Antarctica and in Greenland.