Interplay of variable thermal conductivity and expansivity on the thermal structure of oceanic lithosphere II

We have extended our previous analysis of the effects of constant vs. variable, i.e., pressure and temperature dependent thermal conductivity (κ) and constant thermal expansivity (α) on the thermal structure of the oceanic lithosphere. We apply our analysis to the actual data set including information on the geoid slope. The heat flow and ocean floor depth data constrain the thermal expansivity (α ≈ 3 × 10^-5 1/°C). Including geoid slope data may loosely constrain both the thermal expansivity and the thermal conductivity. The probable value of thermal conductivity is ≈ 3 W/m/ °C for the constant κ case and ≈ 4 W/m/°C (at ambient conditions) for the variable κ case. These α and κ are generally consistent with laboratory data of appropriate lithospheric materials. Our analysis supports the plate model with thin lithosphere and high bottom temperature, such as GDHI (95 km; 1450°C). Variable κ case requires slightly thinner and higher temperature lithosphere (≈ 85 km and ≈ 1500°C and gives a slightly better fit to the geoid slope data.