CHAMP Gravity Anomalies over Antarctica

Summary

Before CHAMP, the Antarctic gravity field was constrained predominantly by satellite altimetry-derived gravity measurements over the oceans and the variations in satellite orbits at altitudes of about 700 km and higher. CHAMP free-air gravity estimates at 400 km altitude suggest that previous gravity models may have regionally overestimated the anomaly field of Antarctica by roughly 5 mGals. The free-air anomalies can be separated into terrain-correlated and terrain-decorrelated components using the correlation spectrum with the computed terrain gravity effects. Analysis of the terrain-correlated anomalies together with the terrain effects reveals anomalously thinned crust beneath East Antarctica between the Gamburtsev and Transantarctic Mountains that includes Wilkes Land. These results suggest tectonically extended crust for roughly a third of East Antarctica as important new constraints on Gondwana dynamics. Additionally, the terrain-decorrelated free-air anomalies reveal mass variations of the mantle and core to constrain the thermodynamics of the subcrust, the origin of the geomagnetic field, and standard precession and nutation models. With CHAMP, we also have for the first time co-registered complementary magnetic and gravity observations. Hence, we can identify and study regionally correlative lithospheric mass and magnetization variations via Poisson’s relationship for new constraints on regional petrological, structural, and thermal variations of the Antarctic lithosphere.