USAP-DC

Non-Technical abstract The physical state of the mantle beneath the Antarctic Ice Sheet plays a key role in the interaction between the Antarctic ice cover and the solid earth, strongly influencing the glacial system's evolution. Generally, mantle temperature profiles are determined by analyzing rock samples from the mantle to determine pressure-temperature conditions, and/or by conversion of seismic velocity anomalies to temperature anomalies. However, mantle rocks have been found only in a very few places in Antarctica, and seismic anomalies reflect not only thermal anomalies but also compositional variations. In this project, the investigators will (1) use the most recent geophysical datasets sensitive to temperature and composition (high-resolution seismic velocity model, topography, satellite gravity), (2) Combine the sensitivity of these datasets in a to retrieve the most reliable model of thermal and compositional structure, (3) translate the results into 2-dimensional maps of temperature slices and the composition of iron in the mantle,(4) compare the results with results from other continents to better understand Antarctic geological history, and (5) use the new thermal model along with established rock relationships to estimate mantle viscosity. Technical abstract The thermochemical structure of the lithosphere beneath Antarctica is fundamental for understanding the geological evolution of the continent and its relationship to surrounding Gondwana continents. In addition, the thermal structure controls the solid earth response to glacial unloading, with important implications for ice sheet models and the future of the West Antarctic Ice Sheet. However, it is challenging to get an accurate picture of temperature and composition from only sparse petrological/geochemical analysis, and most previous attempts to solve this problem geophysically have relied on seismic or gravity data alone. Here, we propose to use a probabilistic joint inversion (high resolution regional seismic data, satellite gravity data, topography) and petrological modelling approach to determine the 3D thermochemical structure of the mantle. The inversion will be carried out using a Markov-chain Bayesian Monte Carlo methodology, providing quantitative estimates of uncertainties. Mapping the 3-dimensional thermochemical structure (thermal and composition) will provide a comprehensive view of the horizontal (50-100 km resolution) and vertical (from the surface down to 380 km) variations. This new model will give us the temperature variation from the surface down to 380 km and the degree of depletion of the lithospheric mantle and the sub-lithospheric mantle. This new model will also be compared to recent models of Gondwana terranes 200 Myrs to build a new model of the thermochemical evolution of the cratonic mantle. The new thermal and chemical structures can be used to better understand the geothermal heat flux beneath the ice sheet as well as improve glacial isostatic adjustment and ice sheet models. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Person	Role
Ben-Mansour, Walid	Investigator and contact
Wiens, Douglas	Co-Investigator

Antarctic Earth Sciences

Award # 2203487

USAP-2203487_1

None in the Database