Tropical convection variability in the West Pacific Warm Pool over the past 120kyr

The West Pacific Warm Pool is a major centre of tropical convection, playing a key role in the transfer of heat and moisture to the mid and high latitudes. We present high-resolution stable isotope, X-ray fluorescence (XRF) core scanning and palaeoproductivity records from IMAGES Core MD06-3075 (6°29 N, 125°50 E, water depth 1878m) recovered in the Davao Gulf on the southern edge of Mindanao aboard the R/V Marion Dufresne. This location is ideal to capture precipitation driven runoff from Mindanao, linked to oscillations in the mean position of the Intertropical Convergence Zone and variability in the El Niño Southern Oscillation. Initial XRF results show a decrease in all major terrigenous flux proxies (Log(Fe/Ca), Log(Al/Ca), Log(Ti/Ca)), indicative of reduced precipitation and runoff during the globally colder period between MIS 2 and MIS 4. In contrast, wetter conditions were prevalent during MIS 5 and over the Holocene. Coccolithophore based palaeoproductivity records indicate reduced primary productivity during intervals of enhanced surface ocean stratification due to increased freshwater runoff. Our palaeoproductivity records corroborate the XRF data, showing low productivity during MIS 5 and the Holocene, when terrigenous runoff was high. During MIS 5, enhanced runoff follows northern hemisphere summer insolation minima, suggesting a more prolonged period of convective rain over Mindanao due to a southward shift of the boreal summer ITCZ position. However, little correlation with insolation is seen in the long dry period between 60 and 20 ka. Permanent dry conditions may indicate a shift to more permanent El Niño type conditions, which would move the centre of tropical convection towards the central Pacific.