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

Abstract

The sensitivity of pressure‐ and temperature‐dependent thermal conductivity (k: W/m/K) and the thermal expansivity (α:1/K) on the thermal structure of the oceanic plate is investigated parametrically by comparing the ocean floor depth and heat flux calculated by one‐dimensional conduction model with those of GDH1, a theoretical thermal model of the oceanic lithosphere. We find that an optimum fit is obtained, when the value of thermal expansivity is ∼ 3 × 10−5, while those associated with the thermal conductivity have many possibilities. The estimates, which give an equally good fit to the GDH1 model, of the plate thickness D (km) and the temperature at the base of the plate Tm (°C) may be given by Tm ∼ 1450‐(k0−4.5) × 100‐(α−3.0 × 10−5) × 105×100, D ∼ 90 + (k0−4.5) × 20 ‐ (α−3.0 × 10−5) × 105 × 20 where k0 (W/m/K) is the lattice thermal conductivity at the ocean floor. A similar relation is obtained for constant thermal conductivity.