Airborne Gravity Analysis of Hypothesized Subglacial Volcanic Edifice in West Antarctica

Abstract:

Subglacial volcanoes provide insight into Antarctic geothermal flux, a critical parameter for understanding ice sheet stability. Behrendt and others have identified a region in the West Antarctic Rift System that they hypothesize to be volcanic in nature. Here, a combined airborne gravity/radar analysis of data collected during 1994/1996 and 2004/2005 surveys is applied to test the region of interest's proposed volcanic origin. The reprocessed gravity disturbance more accurately accounts for aircraft dynamics and cross seasonal differences, producing improved resolution of the gravity field. Likewise, the new bed simulation created by Goff et al. 2014 (Journal of Glaciology) represents a significant advancement over previous interpolations of the surveyed region. We add supplementary radar data to further improve this model and maintain the continuity of additional recognizable topographic features.

2 1/2 and 3D forward modeling of Behrendt's “caldera-like” model and hypothesized volcano Mt. Thiel, constrained by the bed topography, produces an inferred gravity field to be compared with the observed gravity field. Although other influences on the gravitational field, such as isostatic compensation, cannot be definitively ruled out without additional constraining information, the results are consistent with a volcanic province as hypothesized. This type of gravity/radar analysis represents a valuable approach that can be used elsewhere to characterize the distribution of volcanic edifices that can be sources of heterogeneous heat flux, allowing for the better understanding of ice sheet basal conditions and their implications for ice sheet evolution and potential instability.