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Orbital Forcing and Evolution of the Southern African Monsoon From Late Miocene to Early Pliocene
Ist Teil von
Paleoceanography and paleoclimatology, 2023-09, Vol.38 (9)
Ort / Verlag
Hoboken: Blackwell Publishing Ltd
Erscheinungsjahr
2023
Quelle
Wiley Online Library
Beschreibungen/Notizen
Abstract
The late Miocene‐early Pliocene (7.4‐4.5 Ma) is a key interval in Earth's history where intense reorganization of atmospheric and ocean circulation occurred within a global cooling scenario. The Southern African monsoon (SAFM) potentially played an important role in climate systems variability during this interval. However, the dynamics of this important atmospheric system is poorly understood due to the scarcity of continuous records. Here, we present an exceptional continuous late Miocene to early Pliocene reconstruction of SAFM based on elemental geochemistry (Ca/Ti and Si/K ratios), stable isotope geochemistry (δ
18
O and δ
13
C recorded in the planktonic foraminifera
Orbulina universa
), and marine sediment grain size data from the International Ocean Discovery Program (IODP) Site U1476 located at the entrance of the Mozambique Channel. Spectral characteristics of the Si/K ratio (fluvial input) was used to identify the main orbital forcing controlling SAFM. Precession cycles governed precipitation from 7.4 to ∼6.9 Ma and during the early Pliocene. From ∼6.9 to ∼5.9 Ma, the precession and long eccentricity cycles drove the SAFM. The major Antarctic ice sheet expansion across this interval appear to influence the isotopic records of
O. universa
imprinting its long‐term variability signal as a response to the ocean and atmospheric reorganization. Precession cycles markedly weakened from 5.9 to 5.3 Ma, almost the same period when the Mediterranean Outflow Water ceased. These findings highlight important teleconnections among the SAFM, Mediterranean Sea, and other tropical regions.
Key Points
From 7.4 to 4.5 Ma, the Southern African Monsoon (SAFM) was driven by precession and the long eccentricity cycles related to internal feedbacks
Weak Northern African monsoon was coeval with intense SAFM during the acme of the Messinian Salinity Crisis
The SAFM intensity and
Orbulina universa
responded to changes in the Antarctic ice sheet during the latest Miocene