NOAA/WDS Paleoclimatology - 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 multi-decadal to millennial rainfall variations are less clear. We present a new, high-resolution, precipitation proxy reconstruction from Lake Lading (8S, 113E), Java, from 850 C.E. to present, based on the dD of terrestrial plant waxes. We find that rainfall has steadily increased in Java over the past millennium. This increase persists into the 20th 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 dD of precipitation, while ITCZ variations may have been important to climate variations on multi-decadal to centennial timescales.