Crustal thickness in Antarctica from CHAMP gravimetry

• Main Authors: M. Llubes A, N. Florsch B, B. Legresy A, J. -m. Lemoine C, S. Loyer C
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: gravimetry from satellite; Antarctic; crust thickness; The Antarctic; Antarc*; Antarctica
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.584.5956; http://etienne.berthier.free.fr/ftp/32-llubes-epsl2003l.pdf

CHAMP, flying at an altitude of about 400 km, is the first of a new generation of satellites dedicated to Earth gravity field observation. The high-quality data have generated new gravity field models: EIGEN-1S in 2001, and EIGEN-2S more recently. The gravitational potential is decomposed into spherical harmonic coefficients and in this study we use the free air gravity anomalies reconstituted up to degree 60, at zero altitude. The anomalies for the Antarctic continent range from 357 to 65 mGal. We have modeled the gravity effect from the ice, the ocean and the bedrock, using a 666 km cut-off filter to simulate the resolution obtained by CHAMP. Computing the differences between this terrain effect and the CHAMP map provides a map of the Bouguer anomalies. Because of the dominant influence of the crust, we first used a crustal thickness model from seismology. This gives a map of the mantle Bouguer anomalies, the range of which is still large (between 3255 and 216 mGal) indicating imperfections in the crust model. By appealing to isostasy we then imposed the condition that this mantle Bouguer anomaly should vanish and therefore solve for a new resulting crustal thickness. This gravity-based crust model gives thicknesses from 8.5 to 42.6 km in the zone of interest. There is a good general agreement with seismological models, but our models shows more detail, particularly in the western part of the continent. These details are in agreement with geological studies.