Steady subtropical terrestrial aridity since Pangea

Modern terrestrial aridity affects billions of peoples’ lives and is projected to be severe in a warming future. Former works concentrated on aridity changes in the future, while deep-time paleoclimate simulations and proxies provide a new perspective for us to fully understand the evolution of terrestrial aridity. Distributions of arid and humid regions have strong implications for the existence of geological proxies, such as evaporites and coals. A systematic study of the land-sea distribution and aridity evolution has strong benefits to both science and industry. Here, we use Community Earth System Model version 1.2.2 (CESM 1.2.2) to investigate the evolution of terrestrial aridity since the supercontinent Pangea period. Simulation results show that the terrestrial arid regions are always concentrated in the subtropics, and the larger the subtropical land, the larger the arid region. During the Cretaceous when the Pangea breaks up completely, the arid/semi-arid area decreases evidently. The semi-arid area is proven to significantly expand under CO₂-induced global warming, which is due to the dominant contribution from enhanced potential evapotranspiration. It is concluded that the geologic evolution of terrestrial aridity is dominated by subtropical land area, then by land fragmentation and CO₂ concentrations.