Linking upwelling intensity and orbital-scale climate variability in South Africa's winter rainfall zone: Insights from a ca. 70,000-year hyrax midden record

• Published in: Quaternary Science Advances
• Main Authors: Chase, Brian, M, Carr, Andrew, S, Boom, Arnoud, Tyrrell, Genevieve, Reimer, Paula, J
• Other Authors: Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École Pratique des Hautes Études (EPHE), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Institut de recherche pour le développement IRD : UR226-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), University of Cape Town, University of Leicester, Queen's University Belfast (QUB)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: Late Quaternary; Benguela upwelling; Rainfall seasonality; Palaeoclimate; Rock hyrax middens; Stable isotopes; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Antarc*; Antarctic; Sea ice
• Online Access: https://cnrs.hal.science/hal-04180429; https://cnrs.hal.science/hal-04180429/document; https://cnrs.hal.science/hal-04180429/file/Chase%20et%20al%202023_QSA_70%20kyr%20Groenfontein%20upwelling%20%26%20WRZ.pdf; https://doi.org/10.1016/j.qsa.2023.100110

International audience The climate of Africa's southwestern Cape is characterised by a strongly seasonal winter precipitation regime, with late Quaternary climate variability generally considered to have been driven by the position of the southern westerlies. This paper presents a unique ~70,000 year-long palaeoclimatic record from a rock hyrax midden from South Africa's winter rainfall zone, enabling the analysis of regional climate systems since the beginning of marine isotope stage 4. The data suggest that the last glacial period was relatively humid compared to the Holocene, likely due to cooler temperatures, more extensive Antarctic sea-ice extent and an equatorward displacement of the westerly storm track. However, orbital-scale climate variability associated with the 23 kyr precessional cycle primarily correlates with changes in upwelling intensity in the Benguela system, implying an important role for the blocking of tropical easterly flow in driving long-term climatic variability. These factors combined during glacial periods to significantly amplify rainfall seasonality in the southwestern Cape, bringing more winter rainfall via mid-latitude frontal systems, while reducing the proportion of summer rainfall, particularly during the glacial periods of the late Quaternary. The results therefore highlight the need to consider a complex suite of circulation systems and dynamics when inferring drivers of long-term environmental change in the region.