Core-scale radioscopic imaging: A new method reveals density-calcium link in Antarctic firn

Abstract

A new radioscopic imaging technique has been developed to measure firn density in unprecedented resolution and accuracy even when the porosity is low or the geometry of a core or piece of core is not perfect. The technique is based on an X-ray microfocus computer tomograph (ICE-CT) designed especially for ice-core applications. Applied on an archive piece of the Antarctic firn core B32 drilled in Dronning Maud Land in 1998, the obtained density profile shows a strong correlation with the calcium ion concentration as found previously in Greenland. Given the impurity-density relationship found previously in Greenland, our result suggests both improved accuracy of the new density measurements and an impurity-density relationship with a similar magnitude in Greenland to that on the Antarctic plateau. Our measurements provide first evidence that the impurity-density relationship is a universal feature of polar firn and that the calcium ion concentration can serve as a proxy to describe quantitatively the effect of the impurities on densification. © 2014 Publishing Technology.