Forcing mechanisms of the half-precession cycle in western tropical Pacific temperature

The western equatorial Pacific (WEP) plays an important role on global and regional climate. Its temperature reconstructions during the Quaternary display orbital-scale variations, containing major cycles of ~100, 40 and 20 kyr. In addition to these longer cycles, the half-precession cycle is also reported in a recent reconstruction, but the forcing mechanism deserves further study. Here we perform a systematic study on the half-precession cycle in the WEP temperature and related mechanisms. We first analyze existing temperature reconstructions to test whether there is robust half-precession cycle through time. We then use transient climate simulations to investigate its forcing mechanism. Our results show that the half-precession cycle is a robust feature in the long-term evolution of the WEP temperature, but its strength varies in time. Our model results further show that the half-precession cycle in the WEP temperature is mainly driven by maximum equatorial insolation, and its strength is modulated by eccentricity and the conditions of CO2 and ice sheets. Our simulated half-precession cycles in the WEP temperature provide a possible explanation for the half-precession signal recorded in proxy records.