Pliocene dust storms across Asia as an analogue for future climate change?
Final Report Abstract
The proposed project aimed to reconstruct the frequency, intensity, and source regions of Asian dust storms during the mid-Pliocene Warm Period (mPWP; 3.264–3.025 Ma), and to identify the driving mechanisms involved. Because the mPWP was globally warmer and had a smaller Northern Hemisphere ice volume than today, it is an ideal template for dust-storm activity in a future warmer world. Understanding the factors that cause and modulate dust emissions, and foster long-range particle transport under warmer-than-today climate conditions, is therefore fundamentally important in order to forecast the impact of dust storms on the Earth system as a consequence of future global warming. To accomplish the above-mentioned aims, the project was composed of three work packages that applied a variety of geochemical and sedimentological proxies (oxygen and carbon isotopes as well as Mg/Ca ratios of planktic foraminifera, radiogenic neodymium [Nd] and lead [Pb] isotopes, and grain-size) to high-deposition-rate marine Core ORI-891-16-P2 from the South China Sea. Based on its position situated near the southern path of Asian dust storms, this core is exceptionally well suited to capture the occurrence of particularly potent dust storms. The generated datasets of elemental (XRF) and radiogenic isotope (Nd and Pb) compositions as well as grain-size variations allowed to reconstruct the occurrence and frequency of Asian dust storms across the middle to late Pliocene (3.69-2-96 Ma), documenting an increasing contribution of late Pliocene dust events to the sediments of Core ORI-891-16-P2. The new data show that the range and intensity of Asian dust storms increased substantially after the first strong northern hemisphere glaciation MIS M2, influencing even regions as far south as the SCS. We infer from these findings that an intensified Asian winter monsoon during the mPWP, accompanied by an increase in cold surges, was responsible for the efficient mobilization of dust particles. In a second part of the project, planktic foraminiferal δ18O and Mg/Ca records from Core ORI-891- 16-P2 have been generated. These proxy records are used to understand upper-ocean dynamics during late Pliocene glacials and interglacials in response to sea-level fluctuations across the above-mentioned intensification of Asian dust storms. The new records provide very light seawater δ18O values during the most severe late Pliocene glacials M2, KM2, and G20 while seasurface temperature stays surprisingly constant. The light intervals are therefore interpreted as time intervals of decreased surface-ocean salinity due to enhanced fresh-water runoff into the SCS coupled to the closure of important gateways connecting the SCS with the surrounding ocean basins due to glacial sea-level fall.
Publications
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Intensification of Asian dust storms during the Mid-Pliocene Warm Period (3.25–2.96 Ma) documented in a sediment core from the South China Sea. Quaternary Science Reviews, 292, 107669.
Süfke, Finn; Kaboth-Bahr, Stefanie; Wei, Kuo-Yen; Chuang, Chih-Kai; Gutjahr, Marcus; Pross, Jörg & Friedrich, Oliver
