The Impact of Astronomical Forcing on Surface and Thermocline Variability Within the Western Pacific Warm Pool Over the Past 160 kyr

Abstract

AbstractThe Western Pacific Warm Pool (WPWP) constitutes an important component within the global climate system by providing an enormous amount of heat and moisture to the global atmosphere. Nevertheless, past variability of oceanography and climate across the WPWP is still debated. Here, we compile newly generated and published surface and thermocline temperature and seawater stable oxygen isotope (δ18OSW) records from the WPWP north and south of the equator to monitor its variability, particularly in response to astronomical forcing, over the last glacial‐interglacial cycle. We find a coherent first‐order variability in all records from the northern and southern WPWP sites over the past 160 kyr indicating a relatively stable WPWP spatial structure. The second‐order variability is modulated by regionally varying influences. Precipitation varied uniformly across the WPWP marine realm. Thermocline records illustrate the influence of both northern and southern Pacific waters on the WPWP. Differences between the thermocline temperature records are attributed to the differing effect of obliquity on the thermocline water masses influencing the individual sites. Precession exerts an influence on the thermocline at both northern and southern WPWP sites. Variations in thermocline conditions in the precession band are attributed to a combination of modifications in the thermocline source waters, changes in the regional atmospheric circulation and the El Niño‐Southern Oscillation regime.