The Response of East Asian Monsoon to the Precessional Cycle: A New Study Using the Geophysical Fluid Dynamics Laboratory Model Geophysical Research Letters

Speleothem oxygen isotopes have been shown to exhibit a close relationship with summer insolation in the Northern Hemisphere, leading to the hypothesis that East Asian monsoon intensity is proportional to the summer insolation. This hypothesis, however, has been questioned because previous climate model simulations have been unable to simulate the observed large variation in precipitation or the precipitation isotope values, about a half of the variation in the entire modern tropical regions, in response to the insolation change due to the precession cycle. Here we show new results, using the fully coupled Geophysical Fluid Dynamics Laboratory model, that it is dynamically possible to have much higher precipitation during the high summer insolation period compared with the low summer insolation period in the East Asian monsoon region. We conclude that past East Asian monsoon intensity probably increased with increasing northern hemispheric insolation, given a large change in speleothem oxygen isotopes.