Precipitation variability within the West Pacific Warm Pool over the past 120 ka: Evidence from the Davao Gulf, southern Philippines

Abstract

AbstractProxy records of hydrologic variability in the West Pacific Warm Pool (WPWP) have revealed wide‐scale changes in past convective activity in response to orbital and suborbital climate forcings. However, attributing proxy responses to regional changes in WPWP hydrology versus local variations in precipitation requires independent records linking the terrestrial and marine realms. We present high‐resolution stable isotope, UK′37 sea surface temperature, X‐ray fluorescence (XRF) core scanning, and coccolithophore‐derived paleoproductivity records covering the past 120 ka from International Marine Global Change (IMAGES) Program Core MD06‐3075 (6°29′N, 125°50′E, water depth 1878 m), situated in the Davao Gulf on the southern side of Mindanao. XRF‐derived log(Fe/Ca) records provide a robust proxy for runoff‐driven sedimentary discharge from Mindanao, while past changes in local productivity are associated with variable freshwater runoff and stratification of the surface layer. Significant precessional‐scale variability in sedimentary discharge occurred during marine isotope stage (MIS) 5, with peaks in discharge contemporaneous with Northern Hemisphere summer insolation minima. We attribute these changes to the latitudinal migration of the Intertropical Convergence Zone (ITCZ) over the WPWP together with variability in the strength of the Walker circulation acting on precessional timescales. Between 60 and 15 ka sedimentary discharge at Mindanao was muted, displaying little orbital‐ or millennial‐scale variability, likely in response to weakened precessional insolation forcing and lower sea level driving increased subsidence of air masses over the exposed Sunda Shelf. These results highlight the high degree of local variability in the precipitation response to past climate changes in the WPWP.