Southeast Asia typically evokes rich and wet tropical forests. So, the discovery of a drought more than 1,000 years long beginning about 5,000 years ago was an unexpected outcome from research started by the Penn Museum’s Joyce White nearly two decades ago. She and colleagues from the University of California, Irvine; William Paterson University; the University of Quebec; and more published these findings in the journal Nature Communications.
Evidence for the megadrought came from Laos’ Luang Prabang Province, where White has worked since 2001. A Henry Luce Foundation grant enabled the research program to expand starting in 2008, and a paleoclimate team that included William Paterson’s Michael Griffiths and Kathleen Johnson of UCI, co-lead authors on the latest paper, joined in 2010. Some of their work included collecting stalagmite samples from the Tham Doun Mai cave along the Ou River.
Much like tree rings, stalagmites have rings that contain datable signs of changing climate. As rainwater drips through cracks in a cave’s roof, it interacts with a mineral called calcite to form stalactites on the cave’s ceiling. As that water-mineral mixture drips from the stalactite, stalagmites form on the floor below, building over time, layer by layer.
“From those rings, we can interpret the occurrence of various climate events,” says White, who directs the Penn Museum’s Middle Mekong Archaeological Project and is an adjunct professor in Penn’s Department of Anthropology. “In this case, two of the stalagmites stopped growing for several hundred years, then started to grow again.” Chemical analyses confirmed that a prolonged drought lasting more than 1,000 years caused the cessation.
When combined with climate modeling, the cave evidence seems connected to changes in vegetation and dust in northern Africa that happened around the same time—right around when the Sahara transitioned from forest to desert. The modeling also showed how such changes in northern Africa could affect rainfall across Southeast Asia. Penn Today talked with White about what the discovery means, plus the work that led to it.
Funding for this research came from the Henry Luce Foundation, Swedish Research Council, National Geographic Society, and National Science Foundation (grants 1405472, 1603056, 1404932, and 1602947).
Joyce White is a consulting scholar and principal investigator of the Middle Mekong Archaeological Project at the University of Pennsylvania Museum of Archaeology and Anthropology, director of the Ban Chiang Project also at the Penn Museum, executive director of the Institute for Southeast Asian Archaeology, and an adjunct professor in the Department of Anthropology in the School of Arts & Sciences at the University of Pennsylvania.