Airborne Electromagnetics as a Method for Arctic Wide Sea Ice Thickness Retrieval

Abstract

The purpose of this thesis was to mount Airborne Electromagnetic (AEM) sensors for sea-ice thickness retrieval under the wings of long range airplanes and to quantify existing noise sources. Another aim was to determine and to characterise thickness distribution functions of several regions in the central Arctic. The accuracy of a prototype aeroplane EM system was found to be /- 0.5 m. The accuracy was reduced due to wing flexure, which produces noise of equal amplitude as the wanted ocean signal. Other noise sources are inductive ocean-aeroplane coupling and pitch which may disturb the measurements by another 10 percent of the signal. It is suggested to take the 90° out of phase response signal, since wing flexure noise mainly is 180° out of phase. On transects in the central Arctic mean thickness standard errors as low as 0.2 m could be obtained for 10 km long profiles in less deformed ice independently of the age of the ice regime. In a deformed multi year ice (MYI) regime standard errors of 0.2 m were obtained on transects as long as 100 km. These results show that a reduction of central Arctic mean sea-ice thickness by 1.8 between 1991 and 2007 was higher than typical spatial variability.