A paleolimnological record of rainfall and drought from East Java, Indonesia during the last 1,400 years

Abstract

Variations in the location and strength of convection in the Western Pacific Warm Pool (WPWP) have a profound impact on the distribution and amount of global rainfall. Much of the variability in WPWP convection is attributed to variations in the El Nino-Southern Oscillation, for which the long-term trends and forcing mechanisms remain poorly under- stood. Despite the importance of WPWP convection to global climate change, we have very few paleohydro- logical reconstructions from the region. Here we present a new paleolimnologic and paleohydrologic record spanning the past 1,400 years using a multi- proxy dataset from Lake Logung, located in East Java, Indonesia that provides insights into centennial-scale trends in warm pool hydrology. Organic matter d 13 C data indicate that East Java became wetter over the last millennium until ca. 1800 Common Era (CE), consis- tent with evidence for the southward migration of the Intertropical Convergence Zone (ITCZ) during this time. Superimposed on this long-term trend are four decade- to century-scale droughts, inferred from organic matter d 13 C and calcite abundance data. They are centered at 1030, 1550, 1830, and 1996 CE. The three more recent droughts correlate with hydrologic anomalies documented in other proxy records from the WPWP region on both sides of the equator, and the two most recent droughts correlate in time with historically documented periods of multiple, intense El Nino events. Thus, our record provides strong evidence that century-scale hydrologic variability in this region relates to changes in the Walker Circula- tion. Human activity within the lake catchment is apparent since 1860 CE.