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

Abstract

The western equatorial Pacific (WEP) plays an important role on global climate. Many studies have reported the classical orbital cycles in the WEP temperature variations, but the half-precession (~10-kyr) cycle, despite its uniqueness in the equatorial insolation, is paid less attention. Here, a systematic study on the half-precession cycle in the WEP temperature is performed based on the analysis of transient climate simulations covering the past 800,000 years, combined with high-resolution temperature reconstructions. The results show that the half-precession cycle is a significant signal in the WEP temperature. The model simulations show that in response to astronomical forcing, the half-precession cycle in the WEP surface and upper subsurface temperatures is driven by maximum equatorial insolation, while it is driven by bi-hemisphere maximum insolation in the lower subsurface temperature. The different forcing mechanisms at different depths are related to distinct local ocean circulation patterns. The astronomically-induced half-precession cycles are modulated by eccentricity, CO₂ and ice sheets. Given the importance of WEP on global climate, the half-precession cycle in the WEP temperature may contribute to the half-precession signal recorded in other regions.