Spatial and temporal variation in dynamic mantle support of the Antarctic plate: Implications for ice sheet evolution

Accurately constraining past and future ice sheet evolution requires a quantitative understanding of key boundary conditions in ice sheet models, including topography and heat flux. Both of these conditions are in part moderated by spatially and temporally variable mantle dynamics. This study exploits an interdisciplinary approach to probe the mantle beneath Antarctica to better understand sub-crustal processes. First, observed bathymetry and topography are corrected for isostatic effects to isolate the residual topographic signal, a proxy for dynamic mantle support. In this way, a comprehensive suite of oceanic residual depth (n = 1120) and continental residual elevation (n = 237) spot measurements are calculated. Secondly, basaltic rare earth element concentrations acquired from an augmented database of Neogene volcanic samples (n = 264) are inversely modelled to determine melt fraction as a function of depth. Thus, we constrain mantle potential temperature and depth to the top of the melting column (i.e. lithospheric thickness). Finally, results from these approaches are interpreted alongside other geological and geophysical data, including free air gravity anomalies and mantle tomographic models to understand present day mantle-lithosphere interactions. Sequence stratigraphic analysis along continental margins (e.g. offshore from Dronning Maud Land and the Wilkes and Aurora Subglacial Basins) is also used to constrain temporal changes in mantle-induced vertical plate motion. Robust observations in the oceanic realm evidence dynamic support beneath the central Scotia Sea, the Marie Byrd Seamounts, in the vicinity of the Astrid Ridge, and beneath the Emerald Fracture Zone. Residual topography measurements define the extent to which these dynamic swells continue onto the continent, with 1-2 km of mantle support throughout West Antarctica, the Transantarctic Mountains, and the Gamburtsev Subglacial Mountains. Collectively, these results highlight considerable spatial and temporal variation in dynamic mantle support throughout Antarctica, making it imperative to account for such mantle-lithosphere interactions when modelling the onset and evolution of glaciation.