Global Heat Flow: New Estimates Using Digital Maps and GIS Techniques
The digital geophysical maps and GIS (Geographic Information System) techniques have been employed in obtaining a better understanding of global heat flow. The starting point has been a system of 1o x 1o equal longitude grid consisting of 64800 cells. Superposed on this grid system are a set of 190 polygons that approximates boundaries of tectonic provinces and another set of 137 polygons that outlines age provinces. The area extents of these “tectonic polygons” were determined, and heat flow values calculated based on the empirical relation between heat flow and age of last thermos-tectonic event. Maps derived using such polygon representations reveal a pattern quite similar to that obtained in higher-degree spherical harmonic representations of global heat flow. In addition, an updated assessment of observational data has been carried out and estimated values assigned for cells where observational data are currently unavailable. This practice has been found to provide reasonable bounds in interpolations, leading to better representations of heat flow on a global scale. The mean global heat flow values obtained by this procedure is found to fall in the interval of 58 to 63mW/m². This estimate is lower than that reported in some of the previous studies in which use has been made of theoretical values derived from half-space cooling models as substitutes for experimental data. According to the results of the present work, based on reappraisal of global heat flow database and with due emphasis on observational data, the global conductive heat loss falls in the range of 28 to 35TW. This is nearly 22 to 35% less than those reported in earlier studies.