HR: 0800h
AN: NS11A-0152    [Abstracts]
TI: Development and First Results of a new Airplane Based Fixed Wing Electromagnetic Induction Sea Ice Thickness Sounder
AU: * Rabenstein, L
EM: lrabenstein@awi.de
AF: Alfred-Wegener Institut, Busse Str. 24, Bremerhaven, 27570, Germany
AU: Lobach, J
EM: ferra@sympatico.ca
AU: Haas, C
EM: chaas@awi.de
AF: Alfred-Wegener Institut, Busse Str. 24, Bremerhaven, 27570, Germany
AB: Regular observation of Arctic and Antarctic sea ice thickness is of high importance for a better understanding of processes of climate change in polar regions. For regular and accurate observations of polar sea ice thickness a long range airborne device is necessary. Airborne electromagnetic induction (AEM) sounding was found to be an ideal method for accurate and wide area sea ice thickness measurements. As a consequence of five years of successful helicopter electromagnetic (HEM) sea ice thickness measurements and to overcome helicopter range restrictions, the Alfred Wegener Institute (AWI) constructed a new airplane based fixed wing EM system. The first test flights were carried out in 2006 over the North Sea and in April 2007 in Svalbard, where the system's performance was proven under arctic conditions. The system operates in frequency domain with 1990 Hz and a vertical coplanar coil configuration. Thus the system produces a horizontal dipole. The coils are mounted beneath the wings with a separation of 11.6 meters. The airplane, a Dornier 228, is also equipped with a laser altimeter to determine the altitude of the instrument with an accuracy of 2cm. The compensation of the transmitter signal at the receiver coil is done electronically. Flights over open sea are used for the calibration of the system, because the ocean functions as a homogeneous half space with well known conductivity. A data acquisition computer records four voltages with a sample rate of 10 Hz. These are the reference voltage of the transmitter, the compensated and raw receiver voltages and the compensation signal. The laser height is recorded with a sample rate of 100 Hz to account for surface roughness. EM instruments for sea ice thickness sounding should have a vertical resolution of 10cm but due to the electrical noise caused by the airplane engines this was not easy to achieve. To account for the noise a time average filter is used. Alternatively, in order to keep the original horizontal resolution a correction with the reference voltage, which includes the noise but not the ocean’s EM signal, is applied.
DE: 0750 Sea ice (4540)
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting