Long-term fluctuation of Earth’s surface heat flux by the supercontinent cycle

Abstract

The heat released from the Earth’s interior to the surface has a significant impact on the future of our planet. Owing to the secular cooling of Earth, surface heat flux has gradually decreased throughout Earth’s history. The average surface heat flux would be subject to fluctuations in accordance with the supercontinent cycle on the order of 100 million years because the average age of the oceanic plate changes with time. Based on the half-space cooling model, a decrease in average plate age was associated with a decrease in bathymetry and an increase in average surface heat flux. However, the relationship between surface heat flux and bathymetry on Earth is not straightforward. A conceptual model proposed that the asymptotic bathymetry resulting from the plate flattening effect of oceanic plates is important for recovering sea level fluctuations that are comparable to those of the past Earth. The purpose of this study was to investigate temporal changes in long-term surface heat flux during the supercontinental cycle using a conceptual model. The results demonstrate that surface heat flux fluctuated between −10 % and +25 % during the supercontinent cycle, compared to surface heat flux at the time of supercontinental formation. In contrast, the parameterized convection theory for Earth’s thermal budget suggests that the rate of secular cooling due to decay of radioactive elements was reduced by approximately 15 % over the same period. These results imply that the effect of the supercontinental cycle on surface heat flux is comparable to or larger than secular cooling of the Earth.