Moving perihelion reshape the low-latitude hydrological cycle and weathering

Geologic evidence reveals that the Earth's orbit change has significant impact on the global carbon cycle. However, the mechanism is still not fully understood. In this study, we present numerical experiment and geologic records to show that the low-latitude hydrological cycle and weathering are affected by moving perihelion. More specifically, precession of the Earth’s rotation axis alters the occurrence season and latitude of perihelion. When perihelion occurs, increasing insolation raises the moist static energy over land faster than over ocean due to differing thermal inertia. This thermodynamically moves the tropical convergence precipitation from the ocean to the land, contributing to enhancing the terrestrial precipitation and weathering over the latitudinal rain belt. Our results suggests that the insolation in individual seasons is equally important in shaping the orbital scale climate changes at low-latitude. This provides new insight on the Milankovitch theory which highlights the role of summer isolation in driving the astronomical climate change.