Every summer, one third of the world’s population receives rainfall from the East Asian monsoon. Variations in monsoon behavior can pose flood or drought risk, so understanding how it has changed over time could help clarify future risks. Wei et al. now provide new insights into 47,000 years of East Asian monsoon history.
The new research addresses a lack of long-term, high-resolution data on past monsoon variability from southern China. To help fill this gap, the researchers collected an 8.6-meter-long sediment core from Dahu Swamp in the Nanling Mountains of southern China; the region’s topography makes it particularly sensitive to shifts in monsoon rainfall patterns.
The research team took samples of material every 2 centimeters along the length of the core and analyzed each sample’s magnetic properties to produce snapshots of mineral composition in the swamp at different time periods. These snapshots provided clues to the hydrologic and climatic processes in play when the materials were deposited.
Findings from the mineral-magnetic analysis enabled the scientists to reconstruct patterns of fluctuation between relatively wet and dry periods in the region over the past 47,000 years. These monsoonal rainfall patterns are consistent with data from northern China and are in line with past climate changes resulting from gradual shifts in Earth’s orbit and orientation.
The results also add to mounting evidence against a traditional view that climate processes at high latitudes were the primary driver of paleoclimate monsoon trends. The new findings suggest that tropical climate patterns associated with the El Niño–Southern Oscillation have played an important role in driving long-term monsoon rainfall patterns.
This research could help refine climate models and improve predictions of future shifts in monsoon rainfall patterns as climate change progresses. (Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2019PA003796, 2020)
—Sarah Stanley, Freelance Writer