A Simple Conduction-Advection Model of the Lithosphere and Possible Demise of the Hypothesis of Regional Hydrothermal Circulation in the Ocean Crust

Reply to comments by Henry N. Pollack and David S. Chapman on “Spherical harmonic analysis of Earth’s conductive heat flow”

“…Recently Cardoso and Hamza (2007) and Hamza et al (2007b) argued, based on analogy with studies of heat transfer in channel flow (see for example, Olsen and Singer 1985), that upwelling magma flow in the rift zone of oceanic spreading centers would be characterized by higher temperatures in their central parts relative to the borders. It seems reasonable that lateral temperature variations in the uprising limb of the asthenospheric material play a decisive role in determining the temperature structure of the basal part of the boundary layer in the region of the central rift zone.…”

“…Examples were presented for continental areas of Australia and South America (Cardoso and Hamza 2005) and also for the equatorial region of the Atlantic Ocean (Cardoso and Hamza 2006). The procedures employed in maps derived using automatic contouring techniques are equivalent to the use of orthogonal polynomials, mentioned in the comments of P&C. The coefficients (weights) of numerical representations are derived entirely from interpolations of raw data within the region of interest, in contrast to the contentions of P&C.…”

“…In these regions the thermal Fig. 1 a Illustration of artificial temperature discontinuity implied in the GDH model for bathymetry (adapted from Cardoso et al 2007). b Illustration of artificial temperature discontinuity implied in the GDH model for heat flow (adapted from Cardoso et al 2007) contraction is the dominant process that determines the vertical movement of the upper surface of the lithosphere.…”

“…1 a Illustration of artificial temperature discontinuity implied in the GDH model for bathymetry (adapted from Cardoso et al 2007). b Illustration of artificial temperature discontinuity implied in the GDH model for heat flow (adapted from Cardoso et al 2007) contraction is the dominant process that determines the vertical movement of the upper surface of the lithosphere. Evidence for the occurrence of such a change in the mechanism of the lithosphere buoyancy can be found in the results of ocean floor bathymetry data reported by Sclater and Francheteau (1970) and Parsons and Sclater (1977).…”

“…As mentioned earlier, the ocean floor bathymetry is controlled by two distinct mechanisms. According to Cardoso et al (2007) variation of bathymetry at young ages (about 20 m.y.) is determined by the rate at which the lithosphere thickens as it moves away from the spreading center.…”