Validierung von altimetrischen Meereisdickenmessungen mit einem helikopter-basierten elektromagnetischen Induktionsverfahren: 3D Finite-Elemente Simulation des Induktionsverfahrens und Vergleich mit Freibordmessungen von Laser- und Radaraltimetern in der Arktis

Abstract

Satellite platforms utilize altimeters to estimate the elevation of sea ice (freeboard) above the ocean surface, which can be converted into ice thickness. This work analyzes the characteristics and accuracy of these measurements. As a reference, ice thickness can be measured with helicopter-based electromagnetic induction sounding directly. This method assumes, that sea ice can be described as a level plate. Case studies of different types of ice deformations, using a 3D EM forward model, show a local underestimation of true thickness between 40 and 80%, but only a neglible error of mean ice thickness, when using this 1D approach. The comparisons of radar and laser freeboard data show varying penetration depths of radar waves into the snow layer of arctic sea ice. A parametric snow depth is used for the freeboard to thickness conversion, where the difference of laser and radar altimeter did not yield the thickness of the snow layer. The error of mean ice thickness is generally lower than 20% compared to results of the induction method. Spatial averaging of freeboard values at different scales resulted in an insignificant change of the freeboard to ice thickness ratio.