Passive seismic insights into the subglacial environment, crustal architecture, and dynamic topography of the northern Transantarctic Mountains

The Transantarctic Mountains, a major escarpment separating East and West Antarctica, are of enigmatic origin. The component of their topography which arises due to transient mantle processes (dynamic topography) can be constrained by quantifying and removing the isostatic contribution to topography to define residual elevation. In this way, insight into shaping of the Transantarctic Mountains by mantle processes can be gained. This method is dependent on accurately constraining the thickness and density of the crust and overlying ice in order to sufficiently account for isostatic loading. The TAMNNET seismic network offers an opportunity to study the crustal architecture of the northern Transantarctic Mountains using passive seismic techniques. Autocorrelations of spectrally whitened P-wave coda signals and high frequency (2 - 4 Hz) P-S receiver functions utilise ice sheet reverberations to forward model properties and thicknesses of the ice and subglacial layer. This new method allows for the presence and extent of subglacial sediment to be assessed, characterisation of the subglacial geology and hydrology based on seismic velocities and Vp/Vs ratio, and insight into the temperature of the ice sheet, all of which have important implications for ice sheet dynamics.  Crustal architecture is modelled using lower frequency (0.5 - 2 Hz) receiver functions and empirical relationships between seismic velocity, density and pressure. Using these results to correct for isostatic topography and ice loading yields residual elevations of 1 - 2 km, consistent with the presence of Neogene volcanism in the region, mantle upwellings imaged in tomographic models, and thinned lithosphere identified through rare-earth element modelling of basalts from the Erebus and Hallett Volcanic Provinces. Collectively, these observations imply that dynamic mantle convective processes are integral to the origin and evolution of the northern Transantarctic Mountains, shedding light on the interplay between tectonic processes in the West Antarctic Rift System and the margin of the East Antarctic Craton.