Monsoon Seasonality Advanced by Opposite‐Hemisphere Continental Drift

Abstract

AbstractCharacteristics of regional monsoons are largely determined by continental configuration. Motivated by the impacts of Australia on the East Asian monsoon, we investigate the modulation of the monsoon by opposite‐hemisphere continent using aquaplanet simulations with idealized continents. Simulation results show that the monsoon seasonality is advanced significantly by a near‐equator continent in the opposite‐hemisphere. In the early boreal summer, the rapid cooling of the Southern Hemisphere continents forms a high pressure on it, leading to enhanced cross‐equatorial flow and premoistening of the Northern Hemisphere monsoon, thus promoting the monsoon onset. This mechanism requires the opposite‐hemispheric continent to be within a 25° tropical belt to activate this mechanism. The results imply that the continental drift of Australia over the past 40 Ma might have shaped the seasonality of the East Asian monsoon over the geological timescale.