Reply to comment on: “Estimates of heat flow from Cenozoic seafloor using global depth and age data”

Fig. 1. The original purpose of our paper (Wei and Sandwell, 2006) was to provide an estimate of the global Cenozoic heat flow that was largely independent of the sometimesbiased conductive heat flow measurements (Hofmeister and Criss, 2005). The increasing seafloor depth with increasing age is one of the most obvious signals of global plate tectonics. Global mantle convection with thin surface plates provides an efficient mechanism for transferring heat out of the mantle. The objective of our study was to use this obvious depth signal to place bounds on global heat flow from the Earth. We developed a new method of estimating heat flow using depth and age grids and applied it to a Cenozoic seafloor. However, the fundamental equation relating depth and heat flow was derived at least three times previously (Parsons and McKenzie, 1978; O'Connell and Hager, 1980; Doin and Fleitout, 1996). Our contribution was basically to use the new global estimates of depth and heat flow to estimate the Earth's heat output. Hofmeister and Criss [comment] claim that there are errors in our derivation and also that some of our assumptions may not be valid. We believe that the derivation and final equation are correct but rather than spend time addressing each of their objections, we will re-derive the fundamental result from first principles and highlight the assumptions and approximations. The basic equation in question relates the subsidence rate to the surface heat flow