Satellite Gravity Constraints on the Antarctic Moho and Its Potential Isostatic Adjustments

Abstract

We investigate the impact of combining Gravity Field and Steady-state Ocean Circulation Explorer (GOCE) satellite gravity anomaly and Bedmap2 terrain relief data to enhance Antarctic seismic Moho estimates over the satellite's coverage region south of latitude 60°S. The study considers improving the seismic surface wave-inferred AN1 Moho (An et al., 2015a, https://doi.org/10.1002/2014JB011332) from misfits of the gravitational effects of the terrain and the seismic Moho computed at 250 km altitude. The updates also relate the GOCE gravity anomalies that correlate directly and inversely with the terrain's gravity effects as isostatic anomalies of the uncompensated mantle relief. These terrain-correlated effects infer potential isostatic adjustments of the Moho that may help constrain the crust's stress field, track the Gamburtsev Subglacial Mountains to the Kerguelen mantle hotspot, and further test the putative Wilkes Land impact basin for its crustal attributes. Analysis of the gravity-updated seismic AN1 Moho (sAMoho) estimates suggests that most are within the seismic errors of several kilometers or less. However, the gravity-updated estimates that are deeper than the sAMoho estimates tend to characterize anomalously hot upper mantle where the assumed mantle-to-crust density contrast may be too low. These Moho difference estimates discern elevated heat flow for the Maud Rise, Kerguelen Plateau, Pacific-Antarctic Ridge, and most of western Antarctica extending from the Pacific-Antarctic Ridge along the Transantarctic Mountains and across the Ross Sea through Marie Byrd Land and the western margin of the Antarctic Peninsula Microplate to the Scotia Ridge. The methodology of this study also is effective in updating any Moho model for improved gravity and terrain data.