Intensification of southwestern Indonesian rainfall over the past millennium

Modern precipitation in Indonesia is strongly correlated to variations in the Asian/Australasian monsoons, the Walker circulation, and migrations of the Intertropical Convergence Zone (ITCZ), but controls on multidecadal to millennial rainfall variations are less clear. We present a new, highresolution, precipitation proxy reconstruction from Lake Lading (8°S, 113°E), Java, from 850 Common Era (C.E.) to present, based on the δD of terrestrial plant waxes. We find that rainfall has steadily increased in Java over the past millennium. This increase persists into the twentieth century despite evidence from other tropical proxy records for a northward ITCZ migration during the last two centuries, which should introduce drier conditions to Java. Aspects of this long-term increase in rainfall resemble records from the Northern Hemisphere, tropical Indo-Pacific, suggesting that strengthening Walker circulation played an important role in this long-term increase in rainfall and decrease in the δD of precipitation, while ITCZ variations may have been important to climate variations on multidecadal to centennial timescales.