Sea level rise and extreme climate events are two global climate issues currently faced by humanity under the background of global warming. However, the climate feedbacks in tropical Southeast Asia remain unknown, although portions of this region are now densely populated.
Recently, the research team led by Prof. WAN Shiming from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) identified their sedimentary responses to sea level change and palaeoflood activities over the past 40,000 years by studying the time series evolution of terrigenous composition and mass accumulation rate in the core CG18 from the Northwest (NW) Borneo Trough, and further revealed the response mechanism of tropical Southeast Asia to abrupt climate changes in the high-latitude Northern Hemisphere.
The study was published in Geophysical Research Letters on Dec. 12.
Sr–Nd isotopic results indicate that the terrigenous sediments in core CG18 mainly originated from NW Borneo. Despite Borneo's narrow shelf, the results suggest that sea level change is the primary control governing sediment deposition in the NW Borneo Trough at orbital timescales. Furthermore, the terrigenous mean grain size and mass accumulation rate results from core CG18 show that the lowest sea level drop occurred around 21,000 years ago, and there were three rapid sea level rise events during the last deglaciation, corresponding to three meltwater pulse events (MWP-19 ka, MWP-1A, and MWP-1B).
Both modern observations and palaeoproxy records in this study indicate that northern high-latitude cooling could lead to the outbreak of floods in NW Borneo by influencing the East Asian winter monsoon (EAWM) and/or the Intertropical Convergence Zone (ITCZ), resulting in enhanced orography-induced convection in NW Borneo and/or a contracted ITCZ rain belt in the northern low latitudes.
"Additionally, our new records suggest that a stronger EAWM during cold stadials could have transported high levels of northerly moisture to NW Borneo, resulting in relatively higher speleothem δ18O values in NW Borneo," said HUANG Jie, first and corresponding author of the study. "Here changes in speleothem δ18O in NW Borneo during cold stadials may not reflect local rainfall variability but instead reflect changes in moisture source."
The various findings presented in this study tend to indicate that abrupt climate variations in the high-latitude Northern Hemisphere can translate to climate swings in tropical Southeast Asia through effects on sea level, the EAWM and the ITCZ.
"Such information is critical to correctly assessing future sea level rise and flood risks in tropical Southeast Asia," added Prof. WAN.
Atmospheric circulation, rainfall, geologic setting, and relevant study sites in the study area
Huang, J.*, Wan, S., Chang, F., Liu J., Yang, Z., Sun, H., Ma, X., Li, A., & Li, T. (2023). Rapid climate links between high northern latitudes and tropical Southeast Asia over the last 40 ka. Geophysical Research Letters, 50, e2023GL107171.
(Text by HUANG Jie)
Media Contact:
ZHANG Yiyi
Institute of Oceanology
E-mail: zhangyiyi@qdio.ac.cn
(Editor: ZHANG Yiyi)