Inferring surface heat flux distributions guided by a global seismic model: particular application to Antarctica

Abstract

We present a method that uses a global seismic model of the crust and upper mantle to guide the extrapolation of existing heat-flow measurements to regions where such measurements are rare or absent. For any chosen spatial point on the globe, the procedure generates a histogram of heat-flow values determined from existing measurements obtained from regions that are structurally similar to the target point. The inferred histograms are based on a “structural similarity functional”, which is introduced to quantify the structural analogy between different regions. We apply this procedure world-wide using the global heat-flow data base of Pollack et al. [Rev. Geophys. 31 (1993) 267] guided by an update of the 3-D shear velocity model of the crust and uppermost mantle of Shapiro and Ritzwoller [Geophys. J. Int. 51 (2002) 88]. The method results in an inferred probability distribution for the heat flux for each geographical region of interest. These distributions are strongly non-Gaussian, but are well approximated by the log-logistic distribution which is completely specified by two parameters. The inferred distributions agree well with observed distributions of heat flux taken in 300-km radius circles regionally in numerous locations. Particular attention is drawn to the inferred surface heat flux distributions across Antarctica, where direct measurements are rare but information about heat flow may be needed to help understand the dynamics of the Antarctic ice sheets and ice streams. Mean heat flow in West Antarctica is expected to be nearly three times higher than in East Antarctica and much more variable. This high heat flow may affect the dynamics of West Antarctic ice streams and the stability of the West Antarctic Ice Sheet.