Impact of surface-water temperature on South American Summer Monsoon dynamics during the past ~850 kyrs
Final Report Abstract
The South American Monsoonal System (SAMS) is an important atmospheric feature in subtropical South America that has significant socio-economic and ecological importance. However, its response to external factors such as greenhouse gas concentrations is not well understood because numerical models are not yet able to accurately represent the SAMS' spatiotemporal variability. To improve our understanding of the mechanisms and feedbacks that govern the SAMS, this project uses two sediment cores retrieved from eastern Brazil that provide insights into the continental hydroclimate over the past approximately 850,000 years. This time frame extends our current knowledge of SAMS variability by more than 650,000 years compared to previous continuous records and allows us to investigate the influence of various parameters, such as changes in insolation or atmospheric greenhouse gas concentrations, under different boundary conditions. Our results (based on XRF-core scanning, foraminiferal stable isotope and trace element data, as well as mineralogical and lipid biomarkers) show that the strength of the SAMS was primarily influenced by changes in insolation due to precession, with the exception of the penultimate glacial period (MIS 6). In addition, increased greenhouse gas concentrations seem to have an indirect effect on SAMS intensity through their dampening effect on inter- and intrahemispheric sea surface temperature gradients, which reduces moisture advection into the continent. If greenhouse gas emissions continue to increase, these results suggest that already dry eastern South America will experience even less precipitation, which will present significant socio-economic challenges. During MIS 6, an anomalously strong warming in the western tropical Atlantic facilitated moisture transport towards eastern Brazil, possibly due to increased sea ice extension and northward frontal shifts in the Southern Ocean. Coastal precipitation in eastern Brazil exhibits an unexpectedly strong influence of orbital obliquity, documenting a previously unknown strong influence of high northern latitude processes on tropical precipitation. A close relationship with deep ocean circulation changes suggests that this high-latitude influence is largely transferred to the tropical realm by oceanic processes. Interestingly, the Mid-Brunhes Event (MBE) at around 400 ka, a major shift in global climate, coincides with increased suborbital scale variability in coastal precipitation. Our data thus points at an increased sensitivity of the tropical hydroclimate to climate disturbances originating in the high northern latitudes around the MBE which puts a new perspective on the mechanisms underlying this event.
Publications
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Effects of tropical precipitation variability on the composition of fluvial sediments from SE Brazil in glacial and interglacial times (MIS 6-5). (2020, 3, 23). American Geophysical Union (AGU).
Arndt, Iris; Voigt, Silke; Petschick, Rainer; Bahr, André; Hou, Alicia & Raddatz, Jacek
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Forcing of western tropical South Atlantic sea surface temperature across three glacial-interglacial cycles. Global and Planetary Change, 188, 103150.
Hou, Alicia; Bahr, André; Schmidt, Stefan; Strebl, Cornelia; Albuquerque, Ana Luiza; Chiessi, Cristiano M. & Friedrich, Oliver
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Insolation and Greenhouse Gas Forcing of the South American Monsoon System Across Three Glacial‐Interglacial Cycles. Geophysical Research Letters, 47(14).
Hou, Alicia; Bahr, André; Raddatz, Jacek; Voigt, Silke; Greule, Markus; Albuquerque, Ana Luiza; Chiessi, Cristiano M. & Friedrich, Oliver
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Orbitally-paced South American Summer Monsoon variability during the mid- to late-Pleistocene. (2020, 3, 23). American Geophysical Union (AGU).
Hou, Alicia Meng Xiao; Bahr, André; Raddatz, Jacek; Voigt, Silke; Albuquerque, Ana Luiza; Chiessi, Cristiano M. & Friedrich, Oliver
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Obliquity Influence on Low‐Latitude Coastal Precipitation in Eastern Brazil During the Past ∼850 kyr. Paleoceanography and Paleoclimatology, 37(2).
Hou, Alicia; Bahr, André; Chiessi, Cristiano M.; Jaeschke, Andrea; Albuquerque, Ana Luiza S.; Pross, Jörg; Koutsodendris, Andreas & Friedrich, Oliver
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Spatiotemporal Discharge Variability of the Doce River in SE Brazil During MIS 6 and 5. Frontiers in Earth Science, 10 (2022, 6, 6).
Arndt, Iris; Voigt, Silke; Petschick, Rainer; Hou, Alicia; Raddatz, Jacek; Albuquerque, Ana Luiza S. & Bahr, André
