Weisen Shen1,2, Douglas Wiens2, Richard Aster3, Andrew Nyblade4, Terry Wilson5
1Stony Brook University, Stony Brook, United States, 2Washington University in St Louis, St Louis, United States, 3Colorado State University, Fort Collins, United States, 4Penn State University, University Park, United States, 5Ohio State University, Columbus, United States
Investigating the thermal state of the Antarctic lithosphere plays an important role for understanding the history and future of the West Antarctic Ice Sheet (WAIS), at least from two perspectives: 1) Surface heat flow imposes a key boundary condition for ice sheet dynamics modeling; 2) Mantle viscosity and lithospheric thickness are important parameters for glacial isostatic adjustment calculation. However, because of its remoteness and lack of direct measurements, the lithosphere’s thermal state is not completely understood. Here we discuss a most recent effort that produces a thermal model for the Antarctic lithosphere using the seismic data collected in the past two decades.
By processing over 15-year seismic data recorded across Antarctica, we obtain a seismic velocity model for the crust and uppermost mantle from a Bayesian Monte Carlo inversion of Rayleigh waves from earthquakes, ambient noise, and receiver functions. After fixing crustal thickness, we further invert the seismic data for thermal structure employing experimental results relating mantle shear velocity variations to temperature, with a range of acceptable crustal heat generation values as prior constraints. We solve for the best fitting conductive geotherm through a thermodynamic inversion, thus providing estimates of surface heat flow and the thermal lithospheric thickness. The resulting seismic and thermal models reveal a highly heterogeneous mantle lithospheric thermal structure. In particular, thinner lithosphere and higher estimated geothermal heat flow (70-100 mW/m2) are found beneath the West Antarctic Rift system, Marie Byrd Land, Ellsworth-Whitmore Mountains, and southern Transantarctic Mountains, while the East Antarctica has lower heat flow (40-60mW/m2). Notably, an anomalously thin lithosphere with high surface heat flow is identified in the vicinity of the Thwaites Glacier, indicating a mantle source that may facilitate the future instability of the WAIS in that area.